A beel thicky infested with water hyacinth

ECOLOGY AND FISHERIES 

OF BEELS 

IN ASSAM 

Central Inland Captun, Fisheries Research Instituta Barrackpore

Ecology and Fisheries of Beels 

in Assam 

Bull. No.104 November 2000 

Central Inland Capture Fisheries Research Institute 

(Indian council of Agricultural Research) 

Barrackpore-743 101 West Bengal

Ecology and fisheries of beels in Assam 

hdufrr.rol conrornrd rrr lhr, 8ull~~rrrr mrrv nor hr repro(l~r~rri m any form 

H I ~ ~ O N(he I pcrmrJ.\rov (!f rhc puhlr.\hrr 

( 'omp~ned at The Project Monitoring & 

Documentation Sectlon 

CIFRI. Barrackpore 

Ars~rtatr~c Scfall B~swas 

( o\rr dcs~gn P 1)asgupla 

Photographs V t Sugunan 

Publ~.ihcd 

by The Dlreclor, CIFRI, Barrackpore 

Prrnted st M'S Topans Prlvatc Ltd 

8 1 Dr B~rrsh Guha Smet 

Calcuna-700017

Fore word 

The State of hsam is endowed with copious aquatlc wealth tn the form of beek. 

swamos. ~onds and nv-. which bear rich DOtWIhal for Inland fish wodcllon Nevertheless. the 

Stale'sllll has a defctt of fish productm io the tune of 1 5 lakh t per year The floodplatn 

wetlands (beeis]. extending over one lakh ha, mstltute me most Important flshery resource of 

the State The tnvestlaatlons camed out bv the Central Inland Caolure Ftsherles Research 

lnstltute (CIFRI) have &ved mat the beefs &n produce much more fish than what they do at 

present Lack of technical adv~ce on utilization of this resource for fishery development has been 

one of the reasons for low vHtlds ClFRl has been investiaatlna the ecoloa~cal characlertst~cs 

of me beets of Assam tor me last two -es wtm a vlew I; develop guldelties for lhew Itsher). 

management Based on these extensive lnvestlgatlons some new Isghls nave beer) thrown on 

he ecology and fishery polenttal of the beels of Assam 

The lnstrtule has also been able to develop some broad gutdellnes for the management 

of culture-based and caDture fisherms of me beeh, whlch have been Dresented In th~s bulletln 

~b~t~re-baseo fssnery isc~~nates subslantsal tncrease In fish y.ela and productton wtltl rn nmtr 

monetary gnputs and environmental damage Development of heel fnsher es on the bass of 

culture-based fisheries IS also s~gnlfcant from a soclo-econom~c potnt of vtew Most of them are 

common properly resources managed under mperallve fold Thus beneftts accrued from the 

$"creased productlvlty 8s equttably d~strlbuted among the f~shers 

Thts bellettn IS the first ever anempt to provlde sc~entiflc advlce on ftshery management 

of flwdplatn wetlands of Assam, based on sc~enttfic prlnctples Even though tt 15 not posslble 

to develoD tectmoloQv -. packages for f~shery manaaemenl of beels due to many reasons Ihe 

formalwe gundelmes presenlW In thls commun#catlon are adequate lo aclr,eve sdbstantfdt 

Increase In ytead an0 product~on from beets Tne team of CtFR, sclentlsts under tne leadel Sntp 

of Dr V V Sugunan has done a commendable job In collecttng data from the beels of Assam 

under vanous wnstralnts and analyzlog them to develop some very useful guldeltnes I trust lhls 

builet~n apart from bang a very useful reference materlal for the beet managers, wlll go a long 

way In lncreastng the lnland fish productton In the Slate of Assam 

M. Sinha 

Director

Project participants 

V-V, Sugunan 8;Z 

B.K. Bhattachama

INTRODUCTION 

Importance of beels 

BASIC CONCEPTSIDEFINITIONS 

Floodpla~ns 

Wetlands 

DESCRIPTION OF BEEL RESOURCES OF INDIA 

Geornorphology 

Or~gln of floodplain wetlands 

Class~ficatlon of floodplain wetlandslbeels 

FISHERY RESOURCES OF ASSAM 

ECOLOGY OF BEELS 

Morphometry and hydrodynam~cs 

Physico-chemical properties 

B~ologlcal characterlsttcs 

SALIENT ECOLOGICAL FEATURES OF BEELS IN ASSAM 

So11 qual~ty 

Water quallly 

BIO~IC cornrnunlttes 

PRIMARY PRODUCTIVITY AND FlSH YIELD POTENTIAL 

Prrmary productlvlty 

Frsh yteld potentla1 

FlSH & FISHERIES 

F~sh fauna 

Flshery status of the floodplain wetlands of Assarn 

FIS~ yteld 

Flsh~ng act~vlttes In dfferent types of beels 

Flsh speces cornposltlon 

PEN CULTURE 

GUIDELINES FOR FISHERY MANAGEMENT OF BEELS 

Culture-based Rsherles and enhancement 

Community rnetabollsrn 

Culture-based fishertes of the closed beels 

Capture hsherles of the open beels 

Culture and capture systems 

F tshery 0p:ions

INTRODUCTION 

lndia has extensive floodplain wetlands, defined as low-lying areas bordcnng 

large nvers, which are seasonally inundated by the overspill from the main rlvcr 

channel. These wetlands are an integral component of the Ganga and the Hrahmaputra 

river basins, covering an area of 0.2 million hectares. They also ex~st in Manipur and 

Tripura as well as in the foothills of Arunachal Pradesh and Meghalaya They can he 

typical ox-bow lakes (I. e cut off portions of river meander bends), slouylis. mcandcr 

scroll depressions, back swamps, residual channels or tectonic dcprcsslons, thougll it IS 

often difiicult to establish their ldentity due to natural and man-made n~od~fications to 

the environment. These water bodies are locally known as heels (Assani. Wcst Rcngal. 

Arunachal Pradesh. Meghalaya and Tr~pura) mrrun, chrrtrrs and (lhrrr.~ (Rihar). /,or\ 

(Manipur), chorhu~ and boars (northern and south-eastern West Rengal respect~vcly) 

Floodplain wetlands form an Important fishery resource in these statcs and thousands of 

poor fishermen are dependent on these water bodies for their livelihood. The niagn~tudc 

of their distribution and potentlal as a fishery resource in different states can he sccn 

from Table 1 

Table 1. Distribution of floodplain wetlands in lndia 

I State / Dlrtrlbutlon I Rlvcr Barln 

I 

! Arunachirl 

i Pradcsh 

I Assan? 

I 

R~har 

I Manlpur 

I Mcghdulaya 

Trlplra 

West Eagd 

1 

I 

1 Total 

(disrrM-wlu) 

tar1 kameng. Loucr Subanr~ri. 

tur Snng, Dtbang \alley. I.oh(l. 

Chdnglanp & Tvap 

Brahmvpulra & Barsk valley 

dtslr!Cts 

Saran. Champaran. Saharra. 

Uu,rffarpur. Dsrbhmga, 

Monghyr & Porncn 

Irnphal, Thoubal & B~rhnuplr 

Wnl Khw htlls and Wca Ciaro 

hlllr 

Nonh. South & Wcn Trtpura 

diar~crs 

24-Parganu North k South. 

Hooghly, hadla. Murrhdabad, 

Maldnh, C wh Bchu. Uurdwm. 

\onh & South Dmsjporc and 

W~dnapre 

- - 

Kammg. Submrtr~. Dobang, 

I.oh>i. L>nhtng & I'lrap 

Rrahmnputra & Rarak 

(~rndak & Kuv 

Iral. Imphal & lhaubal 

Someshuarl & Jln,~rrm 

Cum11 

Hmghly. Ichhamat~. 

Bhay~rath~. ('hurni. Ksl!ndl. 

Dharub, Dhiuala. Pagla. 

Islany, Rchula. Torrr and 

llecl 

Reel 

- 

Mdun (.hau, 

& l lhar 

Pal 

Uccl 

Reel 

Bccl Charha 

& f3aor 

Ih8) 

2.500 

I Ill) OlUl 

- 4lnllul 

-- 

Ib.5lHI 

211 

5iH) 

42,SlX)

In Irld~a. the State of Assam has the maximum number and water area under 

Ilot~tlpla~~i uctlands, malnly assoc~ated wlth the nvers Brahmaputra and Barak. Locally 

~IIOWII 'IS heels, they arc n~ostly oxbow lakes, backswamps or tectonlc depressions The 

prudonliruancc of lloodplaln wetlands In Brahmaputra basin 1s attributed to the oftcll,lng~ng 

course of rivers and thelr tr~butar~es In the upper stretches. The Fiver 

14r.1l~1nirp~1lra passes through 'ones of acute seismic actlvlly. Frequent earthquakes due 

to crustal lnstahility Induce local and sudden shifts in basement levels Th~s coupled 

u~th Iicavy dlschargc of water trlggers the process of meander cutoffs leading to 

formitt~on of oxhow lakes Tecton~c depress~ons are also formed due to eanhquakes. 

S~clrilarly, thc Brahmaputra is prone to frequent and heavy floods, which break the 

Ic\ccs Ic;ldlt~g to fbrmation of back swamps and sloughs. Assam has 1.392 beels spread 

ovcr niorc than 100.000 ha. Th~s lncludes 322 on the river Barak In the d~str~cts of 

Ila~ldkand~. Kar~mganj and Cachar with a uater spread of 8,000 ha. Total area of beels 

;~~sociatcd wlth tlic river Brahmaputra and its tributaries in Assani is estimated at 0Z.OOO 

ha 

Assall1 occup~cs an area of 78.338 km', the two important physlcal reglons of 

the S~i~tc Jrc tlic Oarilk \alley (6.062 kn" dr~d tile Brahmaputra \alley \50.349 krn') 7'hc 

:.orlo kni 1011g rI\cr Wralilnaputra entcrs tllc statc through the riorthcas!cnl distric! of 

l~~ilii~k~;~ 

;it iiti cIe\at~on of' Inore than hOO ni ahovc MSI- and passes Iongltud~nall) 

tl~~oi~gli IIIC \allc? ( 150 In ahovc MSl.) hcfore enrerlng Banglsdcsh through Dhuhr~ 

tl~str~st lllc \bllolc northcrn pan of the State is bordered by t11rnala)an h~lls. ranging III 

hc~ght hct\\ccn 150 and 600 m above MSL. (aid sometlmcs between 600 and 1350 m 

MSI ) 'l'ticsc li~lls give nse to nuny fast flowing rivulets flowing downwards and 

~ilt~tiii~icly lncctlng Brahmaputra. Mik~r and Rengma hills. located centrally at the 

clcviition of 150 to 1350 m are the ongln of many streams. North Cachar hills and Boral 

rallgc (at .I relatively low elevat~on of 150 to 600 m above MSL) IS the source of Barak 

Ilvcr system l'hcsc two river systems form a network of as 111any as 33 major 

trlhut.lrlcs. Altogether, there arc 121 streams including distributaries (Fig. 1 ) 

'fhc State rccetves one of the h~yhest rainfall in the world ranging between 178 

.rnJ 705 ern. In some places exceeding 400 cm. Soil character~st~cs of the regton IS 

clo~n~r~atctl h! old alluvial types, however, areas along the bank of nver Brahn~aputra 

p;~rt~r~~l;~rly 111 the lower reaches the soil is recent alluvial. Areas adjacent to Mik~r h~lls. 

Kariglnd Iillls illid North Cachar are character~zed by either red loam or laterite soil. 

Forcst co\cr of the State esttmated to be approximately 26%. most of which are 

e\crgrccn fcircs1s. wet grass lands and dry grass lands.

Importance of beels 

If managed along sc~ent~fic lrnes. fish product~on rn heels can he Increased 

s~jin~licantl) 13es1des. man) of the closed beels (which are cut-off froni the rller 

cc~ursc) arc III a translent phase of thc~r evolution Into marshlands. Such water bodies. 

aparl Srorn iittract~ng n~~yratory and resident watcrfowls. support a r~ch faunist~c 

d~vcrsity In rhc ti~rnl of plankton. macrophytes, henth~c organisms. Insects and other 

macrophytc assoelated buna as well as a rich varlety ofa~r-hreath~ng and small s~/ed 

fishcs. sor11c of uhich arc thrcatcrlctl ones. Thus, conservat~on of these dynamic and 

pruJiict~\c hdhllata has hccomc nec:csriary for rn rrru consematton of threatened aquatlc 

spcctcs~rt~cluil~i~p fishes and uatcrfowls In add~tlon. the beds also regulate thc uater 

rcglrnc arid rliltrlcrlt c~charigc and act as natural filters liowever, a comh~nat~on of tlic 

prow"c\ 01' river hctl crolut~on irnd the cfl'ects of. cxtensi\e flood control drrd 

irri~;i~tor~ works Iiabe rctlucei1 thr fish prcldtrct~on of many heels through silt;111on. 

11a011~11 destru~t~ot~. illacrophytc ~nfestat~on and ~solat~orl from the seasonal 1lot)ds 

rcatrrctlng cntr? of rlvcrlnc fish stocks. .fhc floodplains with lhe~r assoc~atetl IC~IIL, 

iv,ltcr hotl~es ,ire cssent~ally ;I contlnuurn of the rlkers, ind~scr~ni~nate kill~ng Oi hr-ood 

;ind ~tt\i'n~lc ti\llcs of comnitrctal species durmg the hrcedlng and recrultmcnt se;isons 

II,I~~! I~dnlpcr\ 111~. prolluct~on 111 the lake as \+ell ;IS In t h ri\ers ~ Thus. there I\ a11 

II~~CIII IICC~ lo Iorir~~ili~~c sour111 17iariagcnient norms for strstairlahlc de\el~lpnlcirr ar~d 

O~NIIII.~~ ~t111i/.tt1011 111 ~hc heels Lccprng In \ic\r the conscr\atron of the produc~~> c alld 

~!.II.III~IC CCO~~\ICIII H h~lc incrcasii~g their fish productton to opttmal le\cls 

Floodplains 

1'11~. lI(~t)dj)l;iit~s iire c~tllcr pcnnancnt or terilporary uater bodies assoc~atcd H it11 

rl\crs ttlirt constantly shill thc~r hds especially in thc po~arnon rcplmes. The frequency 

uitll \\IIIc~ a rI\.cr changes ~ts course depends on a number of var~ables l~kc flow 

\elocrty, ~cd~nlc~lt transporratlon rate. slope, channel pattern, water and sedrment y~cld. 

amour11 and durat~on of prec~p~tation ovcr the catchment area, texture and lithology of 

so11. IC~IOIIIC SIQ~LIS. and so on.

Accordlng to Leopold er a1 (1964). a typical floodplain will include thc following: 

1) The nver channel 

rr) Or-bows or ox-bow lakes ~hci, rrprc.sc.nr rhc, cur-qffporrrorr ri/ rrrc*irtit/t~r 

rr1,r.r T11z.v~. urz, ustctrlh. .rt~rpc~ttrrtrc or horse-shr~c. shrlpc~tl 

hctli/\ t// (1 

:rr/ Point hars 7h~t.7~2 urc locr of tle/~osrrrntt on /he corn,t>~ .rrtlc of ccrr?,c*.\ 111 rlrc. e~lrtrr~rrt.l 

11, Mca~ider scrolls I)rprt~s.~iorr.t trnd rrses 011 rlcc c-orrrrcp.i srrlc~s I!/ Ac.~rel.r fi~vt?~~.tl II.\ rhc~ 

c.htrirrrc~/ mrgrirfcs lorcrctll~. tlontl \~rlllc:\, 151, rhc rrosron o/ fhc, c.iiri ~/~e,/lociilplurt~ .sur/trt~c, ctrlltrc~r~r~t ro rlrt, 

I hirrrttcl. ir.srr~rlI1~ t.ot~/trrrr~tig c.otrrso. mtr/c~rrul.\ cicposc~rcl 

o/ tire, [,hLrrrrre/ htrriks Tlrc>se trrc rnosrJrcqrcc~rr~l~~/u~~~~~I 

cr/ //I

6) The standing water (Ientic component): Receding floods leave permanent or semi- 

permanent standing waters in the form of sloughs, meander scroll depression. back 

swamps or the residual channel (ox-bow lakes). These water bodies expand or 

contract in area according to annual flood cycle and tend to merge into a continuous 

sheet or water covering the whole plain during the highest floods. 

Wetlands 

Thc Ramsar convention ( 197 I) defined wetlands as Areus of rntr~sh, jejr, pc~t 

Iund or et~rro, whi,lhcr tro~urc~l or crrriljciul, pcrmunenl or rcmporury, wrrh wurer whrch 

is srurrc. or flowrng. frcsh, hruckrsh or sulr ~r~clrrdrng urcus of morrne wurer.7, the clcprh 

q/' wl~rclt LII low ildt docs nor acecd nitte merres. Thus, wetland embraccs a board 

category of water bod~cs. wh~ch lncludes riverine floodplains, swamps. marshcs. 

estuaries. backwaters. lagoons. and so on. 

The heels, or floodpla~n wetlands usually represent the lent~c component of 

floodpla~ns vr; . ox-bow lakes, sloughs, meander scroll depressions, residual channels 

and the back swamps and excludes the lotic component (the maln river channels. the 

levee reglon and the flats). In addition, tectonic depress~ons located In river hastns arc 

also included under heels. Thus, all the wetland formations located at the floodplains 

can he tcrn~cd as bcels. l'hcy are either shallou depressions or dead riverbeds generally 

connected tir the pr~nc~pal rlvers andor receive backflow water from the rivers dur~ns 

floods or fronr the huge catchnicnt area followir~g monsoon ram. 

DESCRIPTION OF BEEI, RESOCIRCES OF INDIA 

Ceomorphology 

The floodplain wctlands are an integral component of the Ganga and the 

Brahmaputra basins. The Indo-Gangetic Plains are situated between the southern 

peninsula (oldest land mass in the Indian sub-continent) and the extra peninsular 

Himalayas in the north. The Himalayan mountains are comparatively of recent (tertiary) 

origin and are disturbed by earth movement, as evident from the rocks being folded. 

faulted. ova thrust and even carried over some distance as thrust sheets. The plains 

occupy the depression in the earth's crust between these two elevated regions. Here, the

sediments are of recent origin and largely consist of silt which can he easily emded. 

The Indo-Gangetic alluvial tracts, especially in the northeast, are also geologically 

unstable and experience ehquakes of varying intensities from time to time. 'Two 

devastating earthquakes occumed in the northeast during 1897 and 1950. 

Origin of floodplain wetlands 

The lithololgy, yeological structure. tectonic status. seasonal variation In rlvcr 

discharge and flow characteristics, largely deterniinc thc formation of the Iluodpla~n 

wetlands. The heels of the country owe their orig~n eithcr to the ofic~~ changing course 

of rivers in the potamonic stretches or lo tectonic adjustment. 

In the northern pan of Bihar and Wcst Bengal its also In Assam. tlic rl\crs 

cmcrglng from the central and easten) Htmalayas suddcrtly debouch into tlic plains .~ntl 

ultimately flou down as the river Ganga, Brahmaputra and Barak. Tliesc rl\ crs c;~r.l-\ 

heavy loads of silt and dctritus from the Himalayas and ovcrflo~ dur~ng the sotrtt~ucsl 

monsoon season submerging huge tracts of lands every ycar. Ihesc rl\crs changc 111~1r 

course vcry oncn creatlng numerous floodpla~n lakes ;ind bralded channels. nia~til! 111 

the forni ol'ox-ho\*. lakes. In delta~c Wcst Bengal. due to low gradielit and h~gli rl\crltlc 

d~scharge dur~ng Ihc monsoon season. rccha~incl~sat~on of rivers occurs at tlic sl~glltcsi 

ob~t~ctlon to flow. resulting in creation of heels of varicd typcs. In thc n~rthc~~sl 

(Assam. f~iotli~lls of Arunaclial Pradesh arid Meghalaya), frequent cartltquahcs cuuplcd 

w~th heavy ramfall and cuttlng actlon of rlver meanders havc rcsultcd 111 thc Ibnlii~t~O~l 

of typical ox-bow lakes, lake-like becis or true tccto~tlc deprcsslons. 'Shc Ilnrs 01 

Van~pur owe thetr orlgin mainly to the cutting actlon of the stream nlcandcrs. 

Classification of floodplain wetlands/beels 

S~nce the floodpla~n wetlands ~n~lude low lying udter bodlcs ul d~versc orlglrt 

SIL~, shape. depth, ~nundat~on pattern, ecologtcal charilc~enst~cs, err many dttcmpts 

havc been made to classify them according to these cr~terld Somc of thew 

class~ficat~ons are glren below

I) Ox-bow lakes : These are cut of portion of river meanders. The basins are 

relatively narrow, long, deep and have either bmt or straight shapes. They 

derive the name from their shape, which is usually horse-shoe shaped, cmcent 

shaped or serpentine. They receive wata from the parent river through the old 

channel or neighbouring catchment areas . 

11) Lake-like wetland: These are wide and shallow with irregular contours. They 

may be connected to the river through channels or receive wata from it during 

floods. During the mown season, the entire neighboring area gets flooded. 

turning the beel into a vast sheet of water whenas during non-monsoon seasons 

the water spread area shrinks to the basin proper. 

rlr) True tectonic dcpress~ons : 'These are created by tectonic act~vit~es l~ke 

canhquakes and usually resemble natural lakes with regular contours. Normally. 

they are not connected to riven through connecting channels but may recelve 

water from the latter during floods. Such tectonic wetlands are common in thc 

northeastern region (e. g. Chanddubi beel in Assarn) 

119 Meteorite lake: These are created by the impact of fall of a meteorite on earth. 

Such heels have regular, nearly oval shape and abnormally high banks on all 

sides, which, according to geologists, can be created when the left over portion 

of a large meteorite h~ts the earth. The morphometric features of the brcls are 

similar to those of volcanic lakes. except for the fact that they are located in the 

plains and are very shallow. 

Clussiljcurton based on woler rerenrrvm 

I) Seasonal beels: These are shallow floodplain wetlands, which periodically pet 

inundated by monsoon rains and floods but completely dry up during summer 

months. 

ir) Perennial beels: Deeper and permanent beels, which retain water round the year.

Clossrjicafion based on depth 

i) Shallow beels: Beels having maximum depth up to 5 metres. 

il) Medium deep beels : Bcels. which have maximum water in the range of 5 to 10 

metres. 

I~I) Deep beels : Beels having maximum depth of over 10 metres 

I) Small beels : Efl'ect~ve area less than 100 hectares 

i ~ ) Medium beels : Effective area I00 to 500 hectares 

11i) Largc heel . Effective area more than 500 hectares 

Ox-bou shaped. crescenr shaped. serpentine, oval, irregular braided channels. ctc 

In\estlyat~ons on floodplain wetlands of West Rengal carrted out hq ClFKl for 

the Idst decade and A half tndlcate that water res~dence and renewal ttme as well as the 

extent of nlacrophvtc lntestation are the two most Imponant factors affecting thew 

ecology and fisheries In beels that retarn rlvenne connecttons, the continuous water 

exchange affects the nutnent ~npur-output ratlo While this adversely affects the 

btologteal productlv~ty of the ecosystem, rt helps rn delaytng eutrophtcatlon process 

Raptd water rtmewal also helps In breaktng the thermal stratrficalton. rf any, In deep 

heel. whtch IS benelicral for nutrlent recycling and gaseous exchange At the same tlme. 

continuous Hater flow does not allow the plankton speclcs to stahtltze. resulting in 

lower plankton dens~ty and pnmary productton rates tn such heels S~m~larly, aquattc 

macrophytes use up large chunks of plant nutrients, thus maklng them unava~lahle for 

the growth of phytoplankton (Phytoplankton IS a better prlmary producer than 

macrophytes tn heels for efficient conversion of energy) The aquallc weeds also render

operatton of fishing gear difficult. Thus, the following hvo ecological class~fications 

using these two characteristics are much more relevant from the ecological and fisheries 

point of view than the previously discussed ones and will be largely followed in this 

treatise. 

Clclrsrjiration based on rrvertne connection 

i) Opcn bcels : These bcels retain continuity with the parent riven either for the whole 

year or at least dunng the rainy season. Such btels have continuous exchange of water 

as well as fish fauna with the parent river. 

ii) Closed btels : These bcels are completely cut-off from the nearby rivers and receive 

water mostly from their catchment areas following monsoon rains or dwing high flood. 

In recent years, nverine embankments constructed to prevent floods have converted 

many open beels into closed ones by blocking the rivcrine connections. 

C'lusstfificufion bused on fhe exienr of rnacroph,vte infestiuiron. 

I) 

ii) 

Weed choked bcels: A beel can be considered as weed choked when more than 

50% of the total water spread area is covered by aquatic macrophytes. 

Moderately weed infested beels: A bcel can be considered as moderately weed 

infested when less than 50% of the total water spread area is covered by aquatic 

macrophytes. 

FISHERY RESOURCES OF ASSAM 

The State has extensive freshwater resource wilh huge potential for fisheries 

devcloprnmt (Table 2). The floodplain lakes arc a conspicuous feature of both the 

Brahmaputra and the Barak valleys in Assam. Thm are about 1392 enlisted beels in 

Assam (Table 3) of which 423 are registered and the remaining 969 are un-registered 

and under the control of both government (505) and private ownership (464). Together. 

these beels occupy M area of 1,00,000 ha constituting approximately 61% of the total 

lentic water bodies of the State. if properly managed in scientific lines, these water 

bodies can play a pivotal role in boosting nual economy in addition to ground water 

recharge and flood control.

Tabk 2 Fishery resources of Assam 

1 Resource Area ] 

Rivcrine (km) 

I 

5500 

Ponds (ha) I 51000 

Reservotr (ha) I 1500 

Swarn~s and low lvtnn , areas (ha) I .d . , , 

Total (ha) 1 

10000 

368500 

Table 3. Beel fisheries resource under different categories in Assam 

' Catwow I Number I Area (ha) I Condition 

- 

1 Good I .Semi-derelirr I D(~rt1ic.r 

Ree~stered 1 423 1 40.000 110.000 1 15.000 1 35,000 

, Unreg~stered 1 969 1 60,000 1 Ntl I 10.000 1 30.000 

' Total ] 1,392 [ 100,000 1 10,000 1 25.000 1 65.000 

Three types of beels are found in Assam I~I;., 0.r-bow lake gpr, ltrkc !,pee and 

(rue rcctonrc dcprcss~ons. Ox-bow beels are cut-off portions of river nleanders or dcad 

rivulet courses. Many of them are connected with the main rivers through channels. 

Ox-bo~ becis are relatively narrow, long and either bent or serpentine in shape. Lakclike 

beels arc wtde. shallow and Irregular in contour. Thcy are also cannectcd to rivcrs 

through channels and receive water from them. 

The beels In Brahrnaputra basin are situated along the floodplains of rlvcrs 

D~bru. Bundih~ng, Dtshang, Dikhow. Jhanji, Kakodonga, Dhansiri, Sonat. Kapili. 

Kallong and Kulsi on the South bank and Dlhang. Mora, Jiadhal, Subansiri. Kantcny. 

Dhansiri. Ponternari, Pagladia. Manas. Aai, Champabatt and Saralbhanga on the North 

bank. In Barak valley, the beels are s~tuated along the rivers Barak, Sonai. Sushma, 

Dhaleswan and Longai. In Brhaputra valley. 342 beels are located tn Central Assam 

covering an area of 31,080 ha (approx.) followed by lower Assarn (352) and upper 

Assam (376) with water spread of approximately 29.0(m ha and 23,000 ha (approx.) 

respectively. On the other hand there are about 322 heels with water cover of 8000 ha in 

three districts of Barak valley (Table 4).

Tabk 4. DhMbuUon of bcclr la tbe river valleys of h m 

lheuDbMLt( I Rlvu B.dlll I No. d &cb I Am.(br) 

Uppr An8m 

T1nrukt4c) I Lohtl, Dtbru, Dbla, Dtngnn, Bundrhoag. DumduM 1 17 

mbrusuh(a) ] Bundthong. Dtbru, Snur 1 21 

Stbwgar(~) I Dtmow, Dahng, Dkhow. Jhanjl, Dsnlu. T& TIU. 1 54 

JohNr) 

(;olrgh.r(r) 

Nundaq 

I~MJI. Ted. Dlshot. Kakodonga 

Kakodonga, Dbnshtn. Dtflu. 

1 

1 

63 

68 

(iollpar.(S) 

Nolburc(N) 

Barpch(N) 

Shibang 

Knshna~ Balbsla. Ihdhna~ 

Pugladla. Tthu, DPmha 

Monmmru~. Ksmkhowa, Kaladlya. Bhelengt. 

23.000 

ClFRl has conducted a swey of beels in Assam during 1994 to 1998. During 

this period, 58 beels representing Upper Assam ( 25 ). Central Assam ( 12 ), Lower 

Assarn (1 1) and Barak valley (I0 ) were c ovd under the study (Table 5, Fig. 2). 

45 

48 

75 

29000

Tabk 5. Beeb Surveyed by ClFRl

Table S ronfd. ... . .... 

/an& M~trirls Rlvtr Barlns Name of &Is I Arcr(hr.) 

I I I 

Lowt,r 4 rmm I 

- 

(,oripara(S) 

\alhurl( N) 

- 

Ruq'ctalh') 

lhtr(~A .S~~~/vtr~ 

Kr~shna~, Balhaln. Dudhnr~ 

Psgladu.l~hu. Haral~n. Cihograond 

Murmuna~ Karokhoud Kaiad~ya Llheleng~ 

('haulkhoun 

Sclrclo 

Tamranga 

Ghognjan 

Sorhajan 

Morswulkhowa 

Kapla 

Chutkapla 

Tahha 

Alpajan 

Cucbar Ildrak. S~II~I. Hukni~ Kaptanpur 

Bawkand~ 

Kar~rnyanj 

Dholcswar~ 

I ongal 

ECOLOGY OF BEELS 

Botka 

Sonc 

Sakr~ty 

Howdcr 

30 

?50 

Bcel is a highly productive ecosystem which can effectively convert the solar 

ericrgy into or~anic carbon in the presence of rich nutrients available from natural 

sources. Investigations carried out by CIFRl have brought to light exceptionally high 

rate of primary productivity through macrophyte and plankton phases from floodplain 

wetlands which arc many time higher than those reported from other inland open water 

ecosystems. By manipulating the biotic communities present in the system. the high rate 

of organic productivity a! the primary producer level can be channeled to higher trophic 

levels to achieve protein harvest in the form of fish flesh. Thus, growing fish in beck is 

130 

1 

'300 I 

IS 

10 I 

I7 

3458 

I5 

9

an effective way of using natural resources for the beamnmt of man. However, the 

ecosystem processes in open wata bodies me usually vay complex due to the 

interaction of an array of physical, chanical and biological processes. Since the 

synergistic effect of these factors influence the dynamics of biotic communities living in 

these water bodies and govern the rate of output of harvestable biological material, it is 

oRen dlficult to link their fish production potential with any particular ecological 

parameters. The beel ecosystem is extraordinarily complex with wide temporal and 

spat~al variations of many key pmeters. Among the various factors that influence the 

wetland ecosystem arc depth, nature of catchment area or river basin, precipitation and 

duration of connection to river etc. 

Ecosystem processes in a beel is determined by a number of factors which can be 

brought under three broad heads 

Morphometry and hydrodynamics 

8 Physico-chemical properties, and 

b~ological characteristics 

Morphometry and hydrodynamics 

The main morphometric features that influence the productivity of beel 

ecosystem are shoreline. area, dcpth and slope. These, in turn, are closely linked with 

the hydrodynamics of wetlands. Water renewal pattern is often modified by a number of 

natural and man-made processes. The important morphometric and hydrodynamic 

characteristics of different beels scattered over Brahmaputra and Barak valley, studied 

by CIFRI over the last few years, are described below: 

Therc are thm main sources of water input into the beel ecosystem vr:. owrsp~ll 

from [he river channel, sut$ace/low and regeneration. Since the state of Assam receives 

one of the highest rainfalls in the world, the former two arc responsible for water 

renewal in the beels in this State. Rainfall directly fills the lake or rain on the riverine 

catchment feeds the parent river. Surface w-off and incnsse in river height due to 

inflow of rain water from the upper stretch, cause inundation of the floodplains. often 

causing resumption of connection between beels and parent rivers. The water gain or 

exchange of wata in Assam takes plnce during southwest monsoon when the

floodplains an flooded. Lakelike beels, through their connecting channels, exchange 

water throughout the year. Water flow into the lake md draining of excess water from 

the lake take place through the same channel. Permanently closed bctls receive ufater 

through rainfall and surface run-off. Thus, flood is the main source of these water for 

the beels. 

After recession of flood, water level in the river decreases snapping the beel's 

connection with the river. The beel gets dried up through evapo-transpiration and 

seepage. In some places, people practise robi crop on the banks by extracting water 

from the beel. The wata loss by various means causes shrinkage of the effective water 

area and lowering of depth in the lake. Consequently, the fluviatile nature of the system 

is transformed into a lentic and stagnant water body till next flood~ng. Th~s seasonal 

change from a lotic condition to lentic and vice versa bestows the beels ~ts unlque 

character. 

Pbysico-cbemical properties 

Water flow plays a vital role in nutrient dynamics and aquatlc product~v~ty 

through transport of nutrients to the organisms and removal of waste Sim~larly. 

temperature. wh~ch effects all life processes, includ~ng growth rates. Ilk cyclcs and 

overall productivity of the entire system 1s a key physical variable. The flood water and 

surface run-off carry huge load of silt and allochthonous organic matter which render 

water turbid, preventing light penetration. After the monsoons, when the system 

becomes lent~c and stagnant, the silt starts settling making the water more transparent to 

facilitate light penetration. This Increases effective photosynthetic zone mak~ng the 

system more productive. Man-made changes in the lake morphometry in the form of 

water abstract~on. embankments and nver train~ng have created rad~cal changes ~n 

hydrodynamics with far reaching implications on organic productivity. 

The crystdization process which influences the chemical composition of beel 

water depends on a variety of complex factors. However, three basic mechanisms that 

control water chemistry of beels can be discerned viz.. prec~pitation, evaporation and 

nature ofrhe bacin. The ionic composition of wafer is chiefly determined by the rain 

and the substrata ova which the parent river flows. Secondary influences on the ionic 

composition are exertad by rnacrophytes and phytoplankton. In rccent years, human 

factors related industrial, agricultural and urban activitiee started playing an increasingly

Important rolc in determining the chemical quality of water. The chemical and physical 

load brought tn by rain water or surface runsff gets concentrated by evaporation and 

altcred by chemical and biological interaction within the system. causing seasonal 

variat~ons of various parameters. 

Biological characteristics 

The ltvtng parl of the ecosystem or the biotic communities in water is governed 

by thc vanations of physical and chemical features of the wata body and trophic 

interactions associated with it. Biottc communities of the ecosystem can be categorized 

broadly as ( I) aurorrophs and (2) hererorrophs. The autotrophs include photosynthetic 

ptgmenl bring microscopic plants, plankton and macrophytes. Heterotrophs categov 

tncludcs consumers and decomposers The pr~mary organic productivity and the fish 

ylcld polcntlal of a water body thus dcpnds largely on the relat~ve abundance of 

various communit~cs and the~r associations. Beels are generally cons~dered as h~ghly 

cutroph~catcd system with h~gh rate of primary product~vity. The energy produced at the 

prlnlary stagc r e.. phytoplankton and macrophytes are transformcd into h~ghcr troph~c 

levels through food chams. It IS the eficiency at which this energy 1s transfomrrtd Into 

fish lcvcl that detcrmtnes the effccttveness of management In beels. tao maln 

path\vays.~,r:. the grci:tng choir1 and the cit7rrrrw clrrrin are found. In the grarlng chaln. 

prlmaq productlv~ty IS done by phytoplankton whlch IS grazed by zooplankton. 111 case 

of dctr~tus cham, the macrophytes produce the pnrnary energy. In the absence ot' fish 

feeding on tnacrophytes, these plants die and settle at the bottom adding to detrltus In 

such cases, detritivorous fish flourish and contribute to fishery. 

SAI.IENT ECOL.OGICA1, FEATURES OF BEELS IN ASSAM 

Soil quality 

Soil is vital in maintaining the productivity of any water body. It is one of the 

main interfaces through which nummt is released to the water medium. Apart from 

helping mineralization of the organic deposits at the bonom, soil provides shelter and 

food to the benthic fauna and flora, which play a significant role in maintaining the 

nutnent status of overlying water. Dishibution of soil types in Assam is illustrated in 

Fig. 3. Soils of the floodplain wetlands receive additional input in terms of organic 

matter. inorganic minerals. silt and clay. Since most of the floodplain wetlands are

heavily infested with aquatic vegetation, thm is a heavy accumulation of dead plant 

materials at the bottom that undcrgots decomposition. Consequently, the nature and 

propaties of bottom soils of floodplain wetlands changes h m year to year. Therefore. 

it is essential to study the soil of such water at fkquent intervals in order to assess their 

role in actual productivity. Important physico-chemical parameters of soil of beels of 

Assam arc presented in Table 6 . 

Table 6 Soil characteristics of beets in Assam 

pH 0rg.C Av. P Av.-N CaCO, Texture I%) 

gkg mg/kg mgkg g/kg Sand Silt Clay 

CIchar 

Kaptanpur 6.1 7.0 9.6 172 

Banskandi 5.6 4.8 7.4 155 

Algapur 5.2 6.4 10.5 167 

Rarnnagar 5.0 10.2 8.2 197 

~allak'ndl 

Barchurnati 4.7 11.4 6.6 205 

Boiya 4.9 6.9 8.4 171 

t

Table 6. contd. . . . . . pH 0rg.C Av. P Av.-N CPCO, Tuttun(%) 

g/kg mg/lrg fig Sand Silt Clay 

UJQml! 

Hollodunga 

Somrajan(S) 

Somrajan(N) 

Phutukabari 

Keshukhana 

Puwasaikia 

Tlnrukla 

Motapang 

Motabeel 

Udaipur 

Rampur 

Dlbruciarh 

Lomghor~ 

Mer 

Dih~ngerasuti 

gibraear 

Boka 

Borboka 

Dikhowmornai 

&c!l@ 

Gorormaj 

Borchala 

Golnanrt 

Sankar 

Nabeel 4.8 12.0 6.8 208 5.5 81 16 3 

Goruchara 5.2 13.2 9.2 220 10.5 75 21 4 

Galabeel 5.8 5.5 12.4 162 10.5 86 10 4 

Moridisoi 7.4 6.0 5.0 174 5.5 90 6 4 

DInncl 

Bodhisicha 5.0 29.1 16.5 340 13.5 73 20 7 

Mailhata 5.0 12.7 21.4 234 18.0 91 5 4 

Gathaia 5.3 11.4 15.7 210 15.3 90 5 5 -

Table 6. contd. . . ... 

pH &g.C Av. P Av. N CaCO, Texture 

fig mgkg mgkg gkg Sand Silt Clay 

Sonitaur 

Dighali 5.3 36.6 9.2 397 20,5 87 11 2 

Kharoi 6.0 5.7 17.6 165 27.0 87 12 1 

Kaloi 

Naaaon 

Samaguri 

Bameta 

Kapla 

Chotokapla 

Tabha 

Alpajan 

Nalbari 

Ghograjan 

Morasulkhowa 

6.0 7.6 17.6 180 31.3 90 7 3 

Soil of all the beels except that of Moridisoi (Colaghat) and Motapang 

(T~nsukla) were acidic in nature which 1s considered unfavourablc fbr good lish 

product~on as well as for microbial activity. Brahmaputra valley showed s11ghtIy h~ghcr 

mean so11 pH (5.3) than heels of three Barak valley districts (5.0). Reels of llpper 

Assam districts had the lowest mean soil pH followed by Central Assam and I.oucr 

Assam . It was observed that beels in the north bank of the Brahmaputra had hlgticr so11 

reactton in comparison to beels in the South bank. 

\h ~de 

range of banatlon (3 4 39 0 gkg) was observed In the organlc crrhorl 

content ol 5011 This varlatlon IS marnly depemded on thc qurntlty of macrophytes 

present in the beels and their magn~tude of decomposit~on The mean vdlucs of sot1 

organlc carbon lndlcated that beeis of the Brahmaputra valley were more product~vc 

than hose of the Bar& valley In respect of so11 organlc matter Beels In thc south bdnk 

of the Brahmaputra valley showed comparat~vcly h~gh mcrn value of so11 orgdnlc 

carbon than the lakes In the north bank Central Assam had h~yher averagc values 

followed by Upper Assam and Lower Assam

Available soil nitrogen squs represents the easily oxidisahle form of total 

nitrogen in the soil and its level is influend largely by the organic matter content of 

the soil. Available nitrogen followed the trend of organic carbon and its values ranged 

from 145 to 410 mg/l. It was ratha low in the bxls of both the Brahmaputra valley and 

the Barak valley from a fisheries point of view The low available nibogen of soils is 

mainly due to reduced microbial activities rn d slow rate of decomposition of soil 

organic matter on account of the prevailing atidic reaction of the soil. Beels of the 

Brahmaputra valley had higher mean value of a\ ailable nitrogen compared to the Barak 

valley. Beels of Central Assarn showed high. st mean value of available nitrogen. 

followed by Lower and Upper Assam. 

Ava~lable soil phosphorus, important in nfluencing the aquatlc product~\,ity. 

\*.as rather poor in most of the heels and the valu: -an@ between 0.8 and 27.0 mg kg:l 

Such lo& level of available so11 phosphoru is attributable to the prcscnrc of 

macrophytes, especially the rooted ones wh~ch ,pidly use up most of the ava~lahle 

phosphorus. Becls of the Brahmaputra valley ha h~gher level of available phosphorus 

(14.5 mg ;kg) compared to the Barak valley (8.: rng/kg). Beels of Central Assam had 

the highest mean value of ava~lable-P followed I y Lower and Upper Assam Calc~um 

carbonate content ranged from 4.5 to 67.0 gkg u !h the mean value of 23.0 gkg. Hcels 

of Barak \alley had sl~ghtly h~gher mean value I f CaCO, than beels of Rrahnlaputra 

valley uhilc same mean value was recorded in 111. beck of Lower. Central and llppcr 

Assani. 

Loamy soil contain~ng all the three fracl,.lns almost in equal proponions IS 

cons~dered to be conduccve to product~vity. Houever, most of the beels studled by 

CIFRl had poor soil texture. Beels of Karimgwj t,~strict of Barak valley and Sihsagar 

d~str~ct of Upper Assarn had better soil texture coml ared to other districts. It 1s ohserved 

that thc soil of the heels of Brahmaputra valley arc more productive than that of Barak 

valley beels. Among the distncts of Brahmaputra isalley, beels of Central Assani arc 

more conduc~ve to biological productiv~ty In resp .ct of organlc carbon and nutnent 

status of the so~l. Soil qual~ty in beels of d~ffere~: regions of Assam is depicted In 

Table 7.

Watcr Quality 

In floodplain wetlands. Hater quality is ~nfluenccd. to a great extent, by Inflow 

of water from the connecting rivers, local catchment area and by the metabolic 

processes of plants and animals livlng within the water body (particularly the aquatic 

vegetation). Water quality profile of the beels of Assam is given in Table 8.Water 

temperature of the beels ranged fronl4 to 26 "C. Udaipur bwl of Tinsukia d~strict of 

Upper Assam recorded thc lowest water temperature (14 "C) whilc Alpapur heel of 

Cachar district recorded the maximum (26'C). Sccchi disc visibility \ar~cd hctaccn I I 

and 103 cm and In eighteen beels light penetrated up to the bottom. Watcr of all the 

beels of Dibrugarh district of upper Assam uas turbid whilc most of tlic hecls of loucr 

Assam had favourable range of transparency. It was ohservcd that uccd-choked heels 

had the lowest turbidity. In general, turbidity in heel water was ~naiiily duc to silt and 

organic debris carried by the run-off waters. 

The pH of water which ranged from 6.0 to 8.2 (mean valuc of' 7.1) \$;IS 

~nfucnced rnalnl) hy basin so11 and by aquatic vegetatlon. It folloucd niorc 01. lcss 

s~mllar trend of vanatlon of soil pH. Most of the bcels of Ihc Barah v;illcy h;ld .icldlc 

uater. In thc Brahniaputra \.alley. heels of l.'pper Assam recorded the low atcragc v;lluc 

of water pll (7 0) compared lo Lower and (.'entral Assanl recorded equal mcari v;iluc ol 

7 (1 The J~ssolved oxygen lcvcls of water of most of the heels were fa~rlv h~gh ;inti 

\r~thin the optimal mnge for the growth of fishes. The values ranged bctwcen 4 0 and 

0.5 nig'l in the bcels of thc Barak valley and between 4.0 and 13.0 mg!l In the hccls 01' 

the Brahmaputra valley, the mean values being 7.8 and 7.9 mgll rcspcct~cclq firce 

carbon dioxide levels were low In most ofthc beels which ranged hetu~ccii I .(I arid 10 (I 

mgll w~th a rnean value of 4.0 nlg:l. The variations In the conccntratlons of d~ssol\cd 

oxygen and free carbon d~ox~de wcre mainly due to the rate of photosynthetic acllvlty 

by aquatic vegetatlon and variat~on In the organlc mattcr content In the hasin soil. 

The levels of total alkalinity, hardness and spcc~fic conductiv~ty of water caricd 

widely and the values ranged from 16.0 to 227.0 mgi'l. 10.0 to 109.0 ~ngil. and 18.0 to 

354.0 pmhoucm respectively. It was observed that the mean values of' total alkalinity. 

hardness and specific conductivity in the beels situated at the Brahmaputra vallcy were 

twice that of Rarak valley. In the Brahmaputra valley, beels of the North bank districts 

worded higher mean values of total alkalinity, hardness and specific conductivity than 

those of the South bank districts.

D~ssolved organic carbon content of all the baels wen relatively high, the values 

ranging between 0.8 and 5.0 mg/l. The concentration of calcium and magnesium 

exhib~ted wide variations; it was relatively more in the bcels of the Brahmaputra valley 

The values of Ca and Mg ranged from 2.0 to 34.5 and 1.2 to 20.6 mgil respectively 

Concentrations of iron, silicate and chloride in water varied within 0.02 to 2.1, 0 8 to 9 4 

and IS to 44 mdl respectively. Variations in the concentrations of these nutrients are 

mainly due to thc variations in their uptake or release by macrophytes as also due to 

allochthonous inputs during monsoon months. 

Table 8 Phyrico-cbemical charwteri~tics of water 

Temp Transp PH IX) C0: TA Hardness Sp Cond 

"C' (cm) mp'l mgtl mg!l mp:l prnhos crn 

m!w 

Ka~tanpur 20 B.V. 7.2 5.2 3.8 73 86 174 

Banska'ndi 

Algapur 

Ramnagar 

Hailakandi 

Barchumati 

Boiya 

Karlmaanj 

Sone 

Sakaity 

Howder 

Anganai 

Lllkhlmaur 

Bilmukh 

Morichamwra 

B.V. 

28 

B.V. 

B.V. 

DhemRii 

Holladunga 18 54 6.5 6.2 1.9 16 10 18 

Somrajan(S) 19 63 7.0 7.5 2.8 16 10 18 

Somraian(N) 17 B.V. 7.0 5.0 3.8 42 59 93 

~utukabah ' 18 B.V. 7.4 9.8 1.9 66 89 133 

Keshukhana 19 35 7.6 6.4 4.7 120 25 218 

Puasaikia 18 B.V. 6.7 7.0 5.7 18 30 139

Temp. Trmrp. PH DO CQ, TA Hudnear Sp.Cond. 

(ant W W W mpn ~mhoslcm 

Tinsukia 

Motapang 17 64 7.3 8.4 3.8 64 54 120 

Motabeel 18 B.V. 7.0 10.4 4.7 44 50 92 

Udaipur 14 B.V. 6.5 6.4 9.5 36 45 84 

Rampur 21 B.V. 7.4 11 2.8 135 124 248 

Dibruaerh 

Langhari 18 18 6.6 5.4 3.8 36 43 6 1 

Mer 17 18 6.0 0.7 12.3 46 43 72 

Dihingerasuti 17.5 17 7.4 6.6 3.8 89 62 229 

a!B.aQw 

Boka 19 46 7.1 6.4 2,8 20 22 24 

Borboka 20 19 6.6 7.5 3.8 15 19 15 

Dikhowmomai 21 24 6.2 1.6 19.6 55 48 89 

J m 

Gorormaj 

Barchala 

Goiaahat 

Sankar 

Nabeel 

Garuchara 

Gelabeel 

Moridesoi 

20 B.V. 7.4 8.8 2.9 58 69 131 

19 B.V. 7.6 12.6 3.0 49 69 123 

20 B.V. 7.6 13.6 3.0 37 50 103 

17 42 7.6 8.8 3.8 84 69 191 

16 46 8.0 7.8 1.9 164 149 335 

Darana 

Bodhisicha 19 39 7.0 6.8 1.9 53 78 100 

Mailhata 20 42 6.9 7.2 2.4 64 58 128 

Gathia 22 B.V. 7.2 6.9 2.4 58 79 128 

Sonitpur 

Dighali 20 B.V 6.5 5.6 11.4 38 35 47 

Kharoi 21 28 7.5 7.6 2.7 80 100 159 

Kaloi 22.5 11 7.5 8.2 3.8 86 67 169 

Naaaon 

Samaguri 18.5 B.V 8.1 8.7 1.6 59 43 112 

Mer 20 B.V. 7.8 8.4 1.9 44 29 8 1 

Sibasthan 22 103 7.2 5.6 5.1 71 58 141

Table 8. contd. 

Charan 

Moribeel 

w.Ra 

Kapla 

Chotokapla 

Tabha 

Alpajan 

Nllkrl 

Ghograjan 

Sothajan 

Temp Tnrnp. PH W CO, TA HPdneu Sp Coad 

(cm) -4 lBgn u@ mp'l pmhodcm 

Klmntp 

Mandira 25 70 6.8 5.5 2.4 18 23 31 

Dora 19 30 8.2 11.7 1.0 70 57 123 

Selsella 20 36 7.4 6.6 7.4 25 29 41 

GoalPara 

Tamranga 21 98 8.2 10.5 1.0 16 19 30 

'mS Chlortdc SIO, Ca Mg Fc PO, NO, DlsOrg C 

I mgll mgll mgll mu mgll mgll mgll mp.4 

iuliK 

Kaptanpur 85 25 7.0 7.0 15 0.08 0.01 0.08 1.3 

Banskandi 28 30 5.5 7.5 7.0 0.02 0.01 0.07 0.8 

Algapur 44 25 6.3 6.8 8.6 0.35 0.01 0.05 2.2 

Ramnagar 20 27 3.5 4.8 6.3 0.50 Tr. 0.04 2.3 

~allakandi 

Barchumati 38 29 1.6 5.8 5.8 0.16 Tr. 0.04 1.6 

Boiva 28 23 4.0 3.8 5.8 1.2 Tr. 0.04 2.9

TDS ahride SiO, CI Mg Fc PO, NO, Dlt.0rg.C 

m%i m%l W'l n%l rnd m%l m%l 

Karfmarni 

Sone 34 30 4.8 7.2 5.5 11 Tr. 0.03 2.0 

Sakalty 45 32 3.0 4.0 4.7 1.2 Tr 0.03 2.2 

Howder 22 32 2.8 5.8 6.5 1.4 Tr. 0.03 2.7 

Anganai 22 29 2.0 5.8 5.8 0.16 Tr. 0.02 2.0 

Lakhimpur 

Bilmukh 125 

Morichampora 178 

Dhemaii 

Holladunga 3.8 

Somrajan(S) 4.7 

Somrajan(N) 47.0 

Putukabari 67.5 

Keshukhana 110 

Puasaikia 70 

28 4.4 16 13 0.15 Tr. 0.03 2.5 

34 1.8 34 1.2 0.18 Tr. 0.04 1.6 

Tinsukia 

Motapang 61 20 7.0 8.0 8.5 0.4 0.01 Tr. 2.2 

Motabeel 46 25 6.0 4.0 9.6 0.4 0.01 Tr. 4.9 

Udaipur 43 29 1.2 6.0 7.2 0.2 0.01 Tr. 2.2 

Rampur 124 29 1.0 26 14.5 0.2 0.01 Tr. 2.2 

Dibruaarh 

Langhari 31 25 3.4 3.8 8.2. 0.8 0.01 0.02 2.2 

Mer 30 34 4.4 3.8 8.2 1.0 Tr. 0.02 1.4 

Dihingerasuti 115 44 4.4 5.8 10.5 0.31 0.01 0.02 2.2 

Sibsaaar 

Boka 12 32 1.5 5.8 1.8 0.23 0.01 0.02 1.6 

Borboka 7.4 25 2.0 3.8 2.3 0.80 Tr. 0.02 1.8 

Dikhowmomai 31 2.1 5.1 8.6 0.90 Tr. 0.02 1.8 -


&cba 

m j 

Barchala 

QQku 

Sankar 

Nabeel 

Garuchara 

Gelabeel 

Moridesoi 

smml 

Bddhisicha 

Mailhata 

Gathia 

s!mlmr 

Dighali 

Kharoi 

KBloi 

Nwlon 

Samaguri 

Mer 

Sibasthan 

r$ilmm 

Charan 

Moribeel 

BBrR4IQ 

Kapla 

Chotokapla 

Tabha 

Alpajan 

TDS Chbridc SiO, C. Mg Fe PO, NO, Dir.0rg.C 

mollmJImoomsnmoomsnmonmsn 

0.2 Tr. 

0.2 0.01 

0.16 0.01 

0.18 0.01 

0.16 0.01 

1.2 0.01 

0.2 0.01 

2.1 0.04 

0.24 Tr 

1.0 0.01 

0.7 0.02 

1.5 0.01 

0.18 0.01 

0.15 Tr 

0.10 Tr 

0.08. Tr 

0.03 Tr 

0.03 Tr 

0.48 Tr 

0.7 Tr 

0.2 0.03 

0.3 0.01 

0.02 1.1 

0.03 1.8 

0.02 1.7 

0.03 1.6 

0.01 1.8 

0.01 1.6 

Tr. 2.0 

0.03 3.3 

0.03 2.2 

0.05 3.4 

0.02 2.0 

0.02 2.1 

0.02 2.1 

0.01 2.1 

0.02 1.1 

0.03 1.8 

0.05 1.5 

0.08 2.9 

0.01 3.5 

0.01 1.6 

0.02 1.9 

0.02 2.7


TDS Chloride SiO, Ca Ma Fe PO, NO, Dis.Org C 

men mBn rngn mBn msn lrisn men w1 -me/l..- 

b!w! 

Ghograjan 102 34 2.0 21 6 1.2 Tr 0.03 2.2 

Sothajan 129 34 2.0 23 12 1.0 Tr 0.02 2.2 

Morawlkhowa 136 25 6.0 19 19 1.2 0.01 0.02 2.4 

Kllmnrr, 

Mandira 15 27 4.0 5 3 0.2 0.01 0.08 1.9 

Dora 62 39 4.8 15 5 0.04 Tr 0.03 5.0 

Selsella 20 20 6.0 15 2 0.4 Tr 0.05 2.9 

Goalrren 

Tamranga 15 25 5.6 3.8 2.3 0.18 Tr 0.01 2.1 

All the beels under scrutiny were poor in both the major nutrients viz., nitrogen 

and phosphorus. The concentrations of NO,-N ranged from traces to 0.08 mgll and that 

of P,O, from traces to 0.08 mgll. Such low values of nitrogen and phosphate is common 

in water bodies where these nutrients are rapidly absorbed by the rich plant 

communities. In beels, the quick turnover of these nutrients takes place due to heavy 

~nfestatron of macrophytes 

An evaluation of physiw-chemical properties of water and soil indicates that In 

spite of some adverse conditions such as acidic nature of soil and water, beels in 

general are conducive for developing culture-based and capture fisheries. The water 

quality of the beels of the Brahrnaputra valley was found to be more conducive to 

biological production than that of k ls of the Bar& valley. Among the various districts 

of the Brahmaputra valley, beels of north bank districts w m relatively more productive. 

Variations in water quality of &Is in different regions of Assam are given in Table 9.

Table 9 Water quality parameters of beeh of h am

Biotic communities 

The abundance and succession of biotic communities occupying the beels arc 

influenced mainly by the unique water renewal pattan of the ecosystem. The high 

fluctuations in water level and the alternating seasonal riverine copections arc the 

inherent characters of the beel ecosystem. Thus, the organisms inhabiting this system 

comprise a complex mix of lotic and lmtic communities. The dynamic ecological 

character brought in by the cyclic changes in the Ile morphometry, wata chemisby 

and sediment characteristics leads to some unique faunal and floral associations. Biot~c 

communities of beels, thus adapt themselves to spatial and temporal fluctuation leading 

to a high degree of floral and faunal diversity. The major biotic communities in beels 

that have a bearing on fish productivity are plankton, benthos, macrophytes and fishes. 

Plankton comprises microscopic organisms (both plants and animals) with very 

l~mited or no power of locomotion. They move about and drift in water purely at the 

mercy of water movements. Phytoplankton bearing photosynthetic pigments make use 

or the r~ch inorganic nutrients available in the beel ecosystem and synthesize organic 

matter (autotrophs). Thus, they form the base of ecological pyramid. Zooplankton, on 

the other hand live on the huge reserve of organic matter of plants or animal origin, both 

in live and dead form (detritus). Thus, zoolplankton is the secondary producer linking 

the phytoplankton with the communities occupying higher trophic levels. Zooplankton 

in beels play a vital role in making efficient use of dead and living organic matter. Both 

zoo and phytoplankton form direct food and thenby sustain a substantial portion of 

planktiphagus fishery of beel resources. 

Most of the beels studied wm found to be infested with weed at varying levels, 

some of them being wmplaely choked. Floating weeds have deleterious impact on the 

abundance of the plankton. As a result, avaage numerical abundance of the 

phytoplankton is found to be low except in Bagheavari beel in Mandira complex of 

Kamny, dismct. Out of three zones viz. upper, central and lower Assam in Brahmeputra 

valley, beels in the later two mms exhibited better abundance of plankton as compared

to upper zone. Density of plankton in the beel of uppa zone varied bctwem nil to 84 

dl. PhytoplPnkton pup WM genaally nprescnted by Chlorophyeae, 

Baclllariophyceae and Myxophyceae. 

Zooplanliters were rcpwmtad by Osrracoda, Copepoda, Cladocera and 

Rorrjcra. Generic repmentation under various gmq~ also found to be very poor. The 

Omracode were found only in Mota beel under Tinsukia district as a unique occurrence. 

Domination of one group over the other cannot be generalised, however, in many cases 

phytoplankton dominated over zooplankton. In some stray cases, poor representation of 

phytoplankton community was observed indicating low productivity. The possible 

reasons are low temperature causing poor nutrient load as indicated by poor 

conductivity and nitrate nitrogen and phosphate in water phase. 

Beels in the central Assam zone showed higher plankton count. Phytoplankton 

density in this zone varied between nil to 948 dl. Phytoplankton groups were well 

represented by good number of genera under Chloroph.vceae. Bacillarioph~~ceue, 

M!:rophvceoe, Dlnoph,vceae and Euglenophyceae. The striking feature of this zone IS 

the appearance of Euglenophyceae which was not found in the beels of upper Assam 

7me. Zoo plankters were represented by Rotifera. Copepoda. Cladocera and Prorozocr. 

In the central zone phytoplankters dominated over zooplankters as general trend. 

Plankton density was relatively richer in the beds of lower Assam zone too, the density 

ranging between nil to 8180 dl. Generic representation was found to be similar to that 

of central Assam beels. Beels in the Barak valley, with low productive water and soil 

quallty, had plankton in moderate numben, ranging between 9 and 406 uil. 

In general, productivity in terns of phytoplankton density was poor in all the beels 

of Assam. Although low pH, transparency and conductivity are attributable to th~s, low 

plankton concentration. the predominant factor is the competition with macrophytes In 

garnering sunlight and nutrients. Moderate to high level of infestation of various 

categories (emergent, submerged, floating, ere.) of macrovegetation were always 

associated with low plankton count. The relatively high plankton count in Central and 

lower Assam bcels is attributable to the low altitude with sloppy gradient of the 

Brahmaputra. In these regions, riverine flow slows down leading to the settling of 

nutrients. Relatively high temperature also favoured production of plankton. 

Distribution of plankton in diffmt beds of Assam is presented in Table 10.

Dbhlct 

Tabk 10 Planktom In different beela of Asam 

I Plankton I Wytophnkton I Zooplankton group I 

Beel 

density 

(0 

DmPP 

Crcbar 

Ramnagar 

233 

Chlorapby~crc: 

Anhtrodesmur, Mougeotra, 

Closter~um 

Brcillrriopbyceae: Nltzschra, 

Plnnulana Meloslra. Navrcula 

Copepoda; Nauplii 

' 

' 

Kaptanpur 

20 NII 

Rotifera: F~l~nla 

Banskandl 

76 Chlorophyceae: Botryococcus Copepoda; Naupll~ 

Algapur 

Hailakandi 

Barchumati 

I 

1 

126 Bacillariophyceae: Meloslra. 

1 Surirella 

44 1 Bacillariophyccae: - - 

( Pinnulana, Surirella 

Rotifera: Brachronus 

I Conenoda: Mesoor.lons 

Nil 

1 

Boiva 

' Karimganj 

I 27 1 Mvxo~hvcere :Nosroc Nil 

Sone 

163 Myxophycene: Nosroc Copepodr: Mrsocvclops 

Chlorophyceae: Spirog~ra 

I ~aci~la~o~h~ceah: sukellu I 

83 1 Bacillariopbyccae: Dlaptoma I Copepoda: haupl~l. 

--- 

Cb1orophyceae:Micrasterium Mesocsclops 

9 Bacillariuphycere: Pinularia Nil 

406 Chlorophyceae: Microsporu, Copepoda: Naupll~. 

Pleodorrna. Cbsmnrium Neodraptomus 

Dinophsceae: Ceratl um Clndocerr: Cerrodrrphnru 

Rotiferr: Tnchorrru 

I Darrane I I I I 

Mailhata 

Ciathia 

Nil I Nil 

35 1 Chloropbyceae: Microspora 

1 Nil 

I Copepoda: Nauplii 

L 

Bodischia 

538 

Baclllariopbycere: Synedro 

Chlorophyceae: Microspora, Copepodr: Nauplii 

Eudorina, Pieodorina, Voivox, Ciadocera: Eurycerus 

Zygnema. Pandorina. 

Rotiferr: Keratella 

I 

I

Tabk 10. m d 

Dlbniprll 

Lanhori 

Mer 

Dihing era- 

suti 

Brrpcta 

Kapla 

Chotkapla 

Tabha 

Alpajan 

Nalbsri 

Sothajan 

Morasaul- 

khowa 

Ghograjan 

49 

18 

26 

10 

20 

1 18 

24 

Nil 

11 

Nil 

Badllrrbpbycue: Cydo(e1la 

Nil 

Nil 

Chlorophyerre: Spirogyra 

Cblorophyalle: Mougcotia. 

Spirogyra 

Baclllrriophycere: Nitzschia 

Myxophycerc:Anabaena 

Myxophycere:Anabaena 

Nil 

Cblorophyceae: Pandorina 

Nil 

Capepoda: 

Neodiqromur 

Cladoccrr: Moina 

Copepadr: Eucyclops 

Rotiferr: Euclinis 

Copepodr: 

Mesocyclops 

Nil 

Nil 

Copepoda:Nauplii, 

Neodiapfomus 

Nil 

Nil 

Nil 

Nil

l rabh 10, conki 

eorc.rr.os 

T ~ W 

Dhema]l 

Hollodunga 

Somrajan(s) 

SomrajanOJ) 

Phutukabari 

Keshukhana 

Puwasaikia 

Golaghrt 

Sankar 

Na bee1 

Goruchara 

Galabeel 

Moridisoi 

332 

84 

22 

12 

28 

Nil 

Nil 

42 

10 

36 

11 

22 

CbloropLyart: Mougtotia. 

TripIocer(u,Staur~~tnun, 

Eudorina,Clattm'um, 

Ankictrodesmw 

B.efUmrbpbycae: 

Fragillarin, 

Pinnulorin, Tabelaria, 

Surirella,Synedra, 

Asterionella 

Dinophyccac: 

Ceratium.Glenodinium 

BrcfUsriophycue: 

Stephanodiscus 

Cbloropbyceme: 

Pach,ycladon 

Myxopbyceae: Oscillatoria 

Myxophycere: Nodularia 

Nil 

Brcillrriophyceae: Melosira 

Nil 

Nil 

Myxophycue: Oscillatoria 

Cblorophycere: Mougeofia 

BrciUariopbyceae: 

Fragillaria 

Baclllulophynre: Melosira 

Chloropbynre: Mougeotia 

Chlorophycnc P e d 

Chlorophycere: Ulothrix 

C o w : Nauplii, 

Cyclops 

RotKen: Polyar~hra. 

Kennella 

Cladoec~r: Bosmina 

Clrdocerr: Bosmina 

Copepoda: Nauplii 

Cladocera:Moina 

Nil 

Nil 

Nil 

Nil 

Nil 

Copepod.: Nauplii 

Nil 

Clrdocera: Bosmina 

I

I 

I 

Table 10 contd 

Tiusrkia 

MotWn8 

Mota 

Uhpur 

Rampur 

Nagaon 

Mer 

Sibasthan 

I Samagun 

I 

I 

Nil 

13 

20 

I I 

35 

948 

103 

Nil 

Nil 

Chlorophyeere: Spirogyra. 

Cosmarium 

Nil 

Diaophyceae: Ceratium 

Bacillariopbyceae: 

Melosira, Navicula.Synedra 

Dinophycere: Cerariurn 

Ch~orophyceae:Staurast~rn, 

Ankistrodesmus, Pediastmm 

Myxopbycere: Anabaena, 

Microcystis. Gloeotrichia. 

Rivularia 

Chlorophycere: Spirogyra, 

Uronema, Eudorina. Volvox. 

Clostarium, Actinaslrurn 

Bacillariopbyceae: 

Melosira, Pinularra, 

Tabelarza. Navicula. 

S~jnedra, Cjiclotella 

Euglenophytr: Euglena. 

Phacus 

Dinophyceae: Ceratium 

Nil 

Ostracoda: Cvcloqpris 

Nil 

Copepoda: Mesoc~rlopslops 

Rotifera: Keratella. 

Brachionus 


Rotifera: Kerarellu 


I Protozoa: Ccnrropyrts 

Copepod~l: C),rlops, 

Naupli~ 

Rotifera: Hruchronrrs, , 

Asplunchu 

I

Tnhle 10 cod 

Morlgaoa 

Mon 

Kamrup 

Dm 

Salsala 

Bagheswan 

(Mandira 

complex) 

17 

354 

639 

8 180 

- - 

B.clllrrlophyenc: 

As~monella, Melosrra, 

Tabelam, Syncdro 

Dinopbyctae: Pendinrum. 

Eoglenophyta: Euglena, 

Trachelomonas. Phacus 

Chryrophyccae: Dlnobryon 

Chlorophyceae: Xanthrdrum. 

Pedmfnun. Krrchnerrella 

Eugkoophyta: Euglena. 

Phacus 

Chlorophyceae: 

Bolryococm, Mrcrospora, 

Pedrartrum. Coelastrum, 

Krrchnenella, Pandorrna 

Clostenum 

Myxophyceae: Mrcrocystu 

Mrcrospora. Pleodorrna. 

Anks~rodesrnllr,S~a~~astr~rn, 

Tetraedron, Krrchnerrella 

Myxophyctre: Mrcrocystrr 

Baelllariophyceae: Melosrra 

Chrysophyceae: Drnobryon 

Rotifen: Frlrnra 

Rotllerr:Polyarthra 

Copepodr: Naupll~ 

Rotifera: Polyarthro 

Kerafella 

Copepoda: 

Naup111,Cyclops 

Clrdocera:Bosmina 

Rotifera:Brachronus 

Trrchocera, Frlrnra. Lerune 

Copepoda: Naupl~~, 

Mesocyclops 

Cladocera: Bosrnrnn 

Chlorophyccac is a dominant component of phytoplankton in the beels of 

Assam. A total of 24 species of Chlorophyceae, 14 species of Bacillariophvceae. 9 

species of Myxoph>ceae. 3 species each of Dinophyceae and Euglenophyceae and I 

species of Chtysophyceae r epmt the phytoplankton community. In beels of upper 

Assam zone phytoplankters represent 4 classes in the order of Chlorophyceae > 

Bacillarioph.vceae > Myxophyceae > Dinophyceae. In the beds of the central Assam 

zone, phytoplankters werc repnsented by 5 classes including Euglenophyceae. The 

class Dinophyceae, which was present only in upper Assam zone, occupied second most 

I 

I 

I

dominant position aAa Chlmuphywe in the cc~lhrl Auram zom. The order of 

domination of various cltsaes of phytoplrnktas in central Assun ame is M follows : 

Chlorophyceae > Dinophyme > BaciIlariophycene > Myrophymre > 

Euglenophyceae. 

Phytoplankton diversity in the Iowa Aasam zone of the Brahmaputre valley was 

richer. A total of 6 classes represent the phytoplankton group including Chrysophyceae. 

AAa Chlorophyceae, Myxophyceae was tbc most dominant group in the lower Assam 

zone. Low altitude, higher tcrnpmture and gradual slop provided conducive 

conditions for richer plankton growth. Greater amount of nutrient availability favoured 

the blooming of the blue green algae (Myxophyceae). The order of domination of 

phytoplankton in lower Assam becls was as follows: Chlorophycrae > Myxophyceae > 

Dinophyceae > Euglenophyceae > Bacillanophyceae > Chrysophyceae. Another 

notable feature in the becls in lower Assam was the high rate abundance of 

Euglenophyceae. 

Phytoplanktem in the &Is of Barak valley represented by the same four classes 

as was observed in the upper Assam beels. The order of domination was Chlorophyceae 

> Bac~llanophyceae 1 Myxophyceae> Dinophyceae. 

Five groups of zooplankters were present in the beels of Assam viz. Rorifera. 

Copepoda. Cladocera, Osfracoda and Protozw. There were 8 genera of Rotifera. 4 

genera of Copepoda, 3 genera of Cladocera and 1 each of Osrracoda and Proiozou. 

Generally, Copepoda dominated the zooplankton communities in the &Is surveyed, 

followed by either Cladocera or Rotifera. Members of Ostracoda were recorded only 

from the beels of upper Assam. 

Benthos 

Benthic communities varied widely in the beels in the range of 0 to 1763 

organisms/ml (Table 11). Of the three beels of Tinsukia district, Mota and Rampur 

bals arc devoid of any benthic community. Mobpang in the same district has a thin 

population of 32 units/m2. Most of the beels of Barak valley districts were poor in 

bmthic community while beels of Marigaon and Kamrup districts were rich in bottom 

macrofauna. Beels of Golaghat, Nagaon, Darrang and Sonitpur had moderate population 

of benthos. The becle of Tinsukia, Dibrugrih and Sibaagnr hod scanty or nq population 

of benthos. (hbqods dominated the benUu$ orgnnim followad by bivalves,

oligochactea and insccto. Thc bee18 of Golaghat district arc uniformly rich in bottom 

macrofauna (128-864 oqmimndml). La DhaMJi. except kshukhana with pn 

exceptionally high density (960 orgsnirmdm2), all others have scanty or nil population 

of benthos. Gastropob dominated the benthic organisms followed by bivalves, 

oligochaacs and insects.

A unique feature of the floodplain wetlands of Brahmaputra basin is the rich 

growth of marginal and submerged vegetation due to the allochthonous and 

autochthonous nutrient loading. These macrophytes often tend to replace the plankton 

community. Progicssive replacement of plankton community with macwphytes as the 

main primary producer hastens the pace of eutrophication. This also leads to higher rate 

of evapo-~ranspiration and swampification of the lake. However this process can be 

reversed through effective management. 

Opm beele, which generally harboured less rnacrophytes, wen favourably 

disposed for energy transformation through phytoplankton. Closed beels were mostly 

choked with floating (water hyacinth), submerged (Najas, Vallisneria, Hydn'lla and 

c'knra) and marginal (Typhn) vegetation affecting productivity. This was confirmed by 

!he low rate of net primary productivity ( 0 to 281 mgC/m'/day) recorded in beds like 

Dikhowmomai and Rmnagar in Districts of Sibsagar and Cachar respectively. Dense 

mat formation by rndnal and floating mmphytes was observed in a fm beels like 

Motabeel (TinsSia). Udaipur beel in the same district is choked with water hyacinth. 

Open beels like Gdkbeel (Golaghat district) wen almost fne from weed' infestation.

However, Samrajan north in the district of Dhcmaji has a good standing crop of 

rnacrophytes despite being an open beel. Weed infes&on rateby districts ii given in 

Table 12. 

Tabk 12. Infestation rate and dominant macropbytea h b&b bydlrtrict 

District 

Golaghat 

Infestation of mcrophyter (?A) 

20-70 H. Cp, Wh 

Jorhat 70-80 H, If3 

I Sibsagar 60-90 Wh, V 

T~nsuk~a 

D~hrugarh 

70-90 1 Wh 

50-80 N, V 

Dhemaj~ Cl-90 Wh, H, Nj 

CI- clear, Wh- Eicchornia crassipes, V- Vallisneria, T- Typha. H- Hvdrilla, N- 

,yvmphaeu, C- Chara Nj- Najas 

By virtue of their high nutrient status, wanner water regime and the nch 

sunshine, beels of Assam are considered to be highly productive ecosystem. In fact. 

many of them are passing through transient phases of europhication leading to weed 

choking. These water bodies are extremely rich in nutrients as reflected by rich organic 

carbon and high levels of available nitrogen and phosphorus in the soil. But, generally, 

the nutrients are locked up in the form of large aquatic plants, especially water hyacinth. 

which are not readily available as food for fishes. Decaying weeds are the main source 

of organic detritus at the bottom which normally support a good bottom macrofauna. 

comprising mainly molluscs. However, sometimes, excessive deposition of organic 

matter leads to anaerobic conditions. Similarly, due to the acidic nature of the so~l-water 

Interface, release of nutrients from the soil to water is hampered. 

PRIMARY PRODUCTIVITY AND FISH YIELD POTENTIAL 

Primary productivity 

Solar energy is fixed by both plankton and macrophyte community in beels. In case of 

Assarn beels, carbon fixation takes place predominantly through the macrphytic chain. 

In the Upper Assam, net primary productivity through rnacrophytes rang@ from 742 

mg C/m'/day (in Gala beel) to 4,618 mg C/m2/day as against 250 mg C/m2/day to 

1

1,750 mg Clmzlday through the plrytpopltnkton route. Rate of act cabon w o n in 

Central Assam wan higher in the range of 667 mg Clmzlday to 3377 mg C/rnl/day 

through macrophytes and 110 mg Clm'lday to 2,062 mg Clm'lday through 

phytoplankton. In Lower Asaam, macrophytes fixed carbon at the rate of 1,824 mg 

C/m2/day to 4.61 3 rng C/m2/day through macrophyter and 2 12 mg Clm'lday to 1,209 

mg C/m21day through phytoplankton. Thne beds surveyed in Bad valley recorded 

net primary production through macrophytes as 1,700 mg Clm'lday to 3,011 mg 

CIrn1/day while primary production through phytoplankton in this region was 584 mg 

Clm'iday to 988 mg C/m21day (Table 13). 

'Table 13. Prlmrry production (mg Clm'ldry) ofpbyloplmkton 

and merophylcr In ~l&led bnlr of Asram 

Namr *f M a NnMu~MrcrcN 

Mu+* I HFW*Un 

ERAHAHArMIU VA1.I EY 

Ilpprr Awm Mompun( 

Rokv 

1 

I 

10804 

2521 

UIIY 

[ 

I 

250 0 

11173

A beel thicky infested with water hyacinth 

Since weeds regrow after clearance, it is necessary 

to continue with clearance operations every year 

.

Gill net is a common fishing gear in beel 

Marginal areas of beels are converted into paddy 

fields causing conflicts of interests among agriculturists

Fish yield potential 

Fish yield potential is estimated as a function of the rate of primary productlvlty. 

The phenomenal rate of energy fixation recorded from the beds clearly suggests the 

high fish yield potential. The total quantum of carbon produced by macmphyies and 

phytoplankton in the beels of Assarn is enormous. Even at a very modest rate of I"," 01' 

primary carbon, this can account for a huge fish yield of 981 to 1.31 3 kgha In Barak 

valley, 817 to 1,889 kg/ha in Lower Assam , 791 to 1,399 kglha in Central Assac11 and 

476 to 2324 kglha in Upper Assam (Table 14). 

Beels of Upper Assam had the highest average yield potcntial (1245 kg/hi~,ycar) 

followed by the Lower (1 22 1 kglhaiyear)and Central Assam (1 060 kg!hrtlycar) RaraL 

valley beels with yield potential of 1093 kgha was poor compared to uppcr and loucr 

Assam areas of Brahmaputra valley. Phytoplankton chain contrihutcd to thc y~cld 

potential to a substantial extent (35%) in the central Assam. In all tllc olhcr rcy~o~ls. 

macrophytes accounted for 71 to 86 % of the fish yield potential.

Table 14. Estfnutlon of prodocdon potrstl.1 of some beel of Auam 

Barak valley 

Ramnngcrr 

Bo~ya 

Sonc 

Avenge 

-- -- 

closed 

closed 

open 

70 

40 

55 

620 

625 

1099 

782 

361 

358 

214 

311 - 

98 1 

983 

1313 

1093

FISH AND FISHERIES 

Fish fauna 

Many of the beels were managed on capture fishery norms by exploiting the 

natural fish stock. In the absence of any species management, these beels were 

dominated by small fishes (Puntius spp., Colrsa spp.. ('handa spp.. M,atus vitrorus. 

Ambassrs sp., ,4nthIvpha1yngodon mola, Nandus nanduc, Mastacembelus panrulus. 

small prawns. Borru sp.,), carnivorous catfishes (Wullugo urr14. Ailla corla. Ompok 

hrrnurularus) and air breathers IH. fossrlis, Chanrru punrturw. A. trsrudinc~trs and h' 

notopterus) and others (Table 15 

Fishery status of the floodplain wetlands of Assam 

Most of the beels were managed on capture fishery norms by explolttng thc 

natural fish stock, lead~ng to low yield rates in the range of 66 67 to 638 kghalvear In 

the absence of any sound specles management, .these beels are dom~nated hy small 

fishes, cdrnlvorous catfishes, and atr and others (Table IS) Boiya (kialldkdndt distrtct) 

and Kapla (Barpeta dlstnct) beels were the only excepttons where culture-based 

fishery was followed

Tabk IS. Fbh and fbheria o ltk be& rmweycd L. haam 

Dirtrkt Area Depth Domhut fbb FtrLhg methods 

Cachar 

(ha) 

18-30 

(m) 

1.0-4.0 fmllw w., 

Mysw UiMhu. Ambassu 

rp., A mla. N nandw. M pancalw. 

unnll prmh &la cp.. Wallago auu. 

Arlla colla. Ompht bidanis. H 

fomlu. Chma ,numanu. A 

resiudt~~ md N nokynem. 

Gudwta chapra, IMC. 

L calh. Tenwlosu rluha 

Lbq net Sumundlng mc. 

Trap (dorr), Karal 

Hallakaadl 17 0.5-2.5 Punrru~ 'pp.. Mww vicraw, Amhsls 

rp , A molu. N nondw, M pancalus. 

small prawns, fI /ossrl~s. C puncratus. 

G chapru, Cullurcd npecles (IMO. 

Dng nn. Surround~ng net. 

Casl net 

Wullugo arru 

Karlm~anj 9-28 15 0.5-5.0 hnlrus lpp.. Mvsrus vtlrarus, Ambassrr 

np . A molu, N nandus. M punrolu~ 

small pawns. Aorra sp . M cavastur. 

(I RlurrJ, H joss~lls. ('hnnno 

puncrarus. A restudmeu and h 

norqrerus, Clup~romo gnrua IMC, (8 

rhupra 

Surround~ng nn ~(rltorurl 

~ I I rrdpi . 

Darran~( 20-80 0-4.0 Punlrus spp.. (bloa spp. Borra sp . M Dcwater~ng. Gill net Lon3 

ponrulur. ff /orr#lrs (' punrrorur f llnc ('as! net 

srrrurus. ('larrus burrurhu.~. N 

Sonltpur 18-60 0.5-4.5 

noloptrrur. Hirllugn orlu 

Punrru) spp. 1)unto spp. (.ol~so spp 

Burro sp . M punrulus. H fossrlr~. ( 

puncmrur. C srr!alw.C aarulru.~; 

Clurrus harrurhur. N noroprerur. 

Wullugo uau 

Cast nct. I)r~g nn 

Jtzr~y horl~l 

L.akhlmpur 20-450 0.5-7.0 Punltvr app. Dunru spp. ('olrsu spp. CIII net. Cast nn 

Bortu sp M panrulus. L baru. L 

gonrus.C rrbu. IMC . 0 pobdu. N 

noroprcnts. N chtrula. Hhll~o orru 

Surround~ny nrt. DIP nct. 

Drag net 1f3or ,ull 

Jorhat 30-89 0.9-4.5 Punrrur spp hnro spp . Colrsu spp Gill net. Cast net 1 

Borru sp , M poncalu. Chando spp . Surrounding nut .1

Barpeta 

Area Deptb Dominant fbb 

(ha) 

30-70 

(m) 

1.5-7.0 ~'UA~~ILI ~pp . h m spp , Colrsa spp . 

2eQ5 1.0-6.0 

Bath sp . M. pancalus. Chanda spp . 

L. 8oniur.L. dh. Wallgo arru. A 

nda mull pnvns 

haw ipp. DMIO ~PP.. Cdua spp . 

h i a rp.. M pu11m1~1. M vi~rm, 

Smll prawns. Channa puncrolus. If 

fasilrs. A teshdm~, L gonrw. 

Ccula mrla, Wallgo arru 

10-50 1.0-5.0 hn11ur spp . hmro spp . (blrsa spp 

hra rp , M pclrralur. M vrtrarus. 

small prawns, L gonrur, W orru 

7- 0.3-4.0 Punrrw 'pp., Cd'sa spp , Borra ,sp , M 

pncalur. H fossrhs, C puncrarul (' 

rtrfarw. Chrras barrachm. N 

noroptern. Walla#o arru. M 

rrenghala 

10. 0.3-5.0 Punl~us spp . Crbllsa spp . Rorru spp 

Nanduq nandur, M panralus. H 

lossr/rs. C puncraru. (' ,tnurus. 

('lurras barrarhus. N no~r>prsrur. A 

rerrudrncus. Wnllap arru, IMC, 

Common carp 

IMC - (blla calla. (~rrhrnu, nlrryulu I ahro mhrra 

Fish yield 

Fisbing methods 

1 ' 

GIII mt. sunound~np ncl. 

Dm8 net. Traps 

drag ne! y~ll ne!. 

surround~ng nct, cut net 

Long Ilnu. Surround~nl: ncl 

(&r /el). Traps (Norw and 

I)r~rynr,). .Awp 

The floodplain wetlands (beels) associated with the Brahmaputra and Barak 

river systems contribute to the major chunk of fishery resources of Assam Becls of 

Assam generally posseses high potential for in srtu fish production. A numher of' them 

also provide a "collection sink' for fish produced in the surround~ng flooded 

catchments. Estimation of fish yield from beels of Assam is very difficult task due to 

the unorganized marketing activities and dissipation of catch. On the basis of enquiries 

made at the beel sites an effort was made by ClFRl to assess the yield. But the rcsults 

are far from accurate. Fish yield of the beels surveyed are in the range of 14 - 488 

kg/ha/year. Average fish yield of 17 beels in the Brahmaputra valley was estimated at 

134 kgiha, compared to 285 kgh for 6 btcls in Bar& valley. The average yield of 

Assam on the basis of enquiries made in 23 beels in the State was 173 kgba (Table 16).

Table 16 Firb productbn from different bceh of Auam . 

Fishing activities in different types of beels 

Open heels 

In open beels, new recruits come to the fishery mainly from the adjoining rivers. 

They provide breeding grounds and /nursery pastures for commercially important fishes 

during southwest monsoon months. Migration (spawningtfeeding) of Indian major carps 

(mainly (I curla. L. rohrta, L, calbasu and L. gonius is significant from the point of

view of recmitmcnUautostocking in these beels. Fishes like E. wcha and G. chapm 

mipte in large numbas during monsoon and form a considerable post-monsoon 

fishery. In addition, occurrence of juveniles (32-80 mm) and adults (up to 534 mm) of 

Hilsa has been observed in Dhir, Dora and Sona (dl open) bccls. Most recruits enter the 

fishable stock in their I* year (6-8 months). Eventhough the stocks are continuously 

exploited, stock is replenished through fnsh recruitment the next year. However, small 

mesh size of fishing nets used and intense fishing in winter/sumrner may deplete the 

stocks below the minimum reproducibk stocks needed to renew the stocks. In addition. 

in many open beels. the connecting channel with the adjoining river is blocked with 

split bamboo screens (bana) to prevent back migration of fishes into the feeder river. 

Since the open floodplain wetlands are a continuum of the parent river, such 

hindrancelin free to-and-fro migration is likely to affect the fishery of the river and 

thereby that of the beel itself in subsequent years. 

D~verse fish populations present in the beds support a multi-species fishery, 

which is more complex to understand but is more resilient. However, though most open 

beels have multi-species fishery, only a few species predominate the landings. 

Closed heels 

A majority of beels remain cut-off from the rivers due to natural causes or 

construction of nvenne embankments. In the absence of significant recruitments from 

rivers, these are inhabited by fishes that can spawn in stagnant waters like murrels. U' 

orru, N noroprerus, barbs, rasboras, loaches, err. Indian major and medium carps, large 

riverine catfishes (Bagarirus hagarius. Pungasius pangasius), N. chitala, Ompok spp.. 

Aspidoparia morar, etc. are likely to be absent there. In general, the natural fishery of 

closed beels is overwhelmingly (50 to 90%) dominated by miscellaneous fishcs 

(Punrlus spp., Rasbora spp., Colisa spp.. Mystus spp., N. noroptem, etc.). Wecd- 

choked beels are dominated by insectivorous and air-breathers like Channu spp., 

Anahas sp., N. noroprerus, C, batrachus, H fossilis, etc. Stocking of IMC seed is done 

in some closed and seasonally open beels like Samaguri and Kapla bcel. 

Fish species composition 

About 54 species belonging to 18 families wen recorded from Dighali beel 

(Kamrup district).

The common pies contributing to commacia1 landings belong to eight 

groups a6 follows: 

i) Carps (Indian major and medium carps like L, barn, C. reba) 

ii) Catfishes (A. seenghala, W. am, A, aor) 

iii) Mumls (Channo spp.) 

iv) Featherbacks (N. chirala, N. notopterus) 

V) Air-breathing fishes (Colisa spp., C. borrachur. H. fossilis) 

vi) Hilsa (T ilisho) 

vii) Prawns (Macrobrochium spp.) 

viii) Miscellaneous fishes (Puntius spp., G. chapra, Rasboro spp., Mstm spp.) 

Percent contribution of the major fishes is reported to have declined from SOu% 

to about 25% in most beels during recent years. The share of miscellaneous mi no^) 

fishes increased by 15 to more than 50% over the years. This is an unhealthy trend 

indicating reduced autostocking from rivers, siltation, macrophyte infestation and,or 

select~ve overexploitation of stocks. Many exotic fishes such as common carp, s~l~er 

carp, grass carp and the African catfish (C. garreplnus) have been recorded from beels 

They are either washed down from culture ponds by flood or stocked deliberately. In 

either case, their presence in beels may have far-reaching negative implications on our 

indigenous ichthyofauna. 

A wide variety of fishing methods is employed in the beels of Assam. FI\.c main 

groups of fishing methods used are: 

i) Passive gear: Set barrier (banas), dip nets and traps. They capture fish as they 

migrate to or return from the beels. 

ii) Active gear: Drag nets, seine nets, gill nets, frame nets. trawls and scoop nets 

These are used mainly during the dry season (October to April). 

~ii) 

Fish aggregating devices (FADS) Koralbeng fishing. This is an indigenous method 

of erecting circular patches of weeds to attract fish. Kotals are erected during August- 

September and harvested from December onwards. While harvesting, the koral area IS 

encircled by banadnets. After gradually reducing the encircled area, fishes are caught 

by using cast and drag nets.

I1 

Fishing operations in beel

iv)Fllling geu (Polo, cast net), hook & line, wounding and grappling, catching with 

hands, etc. are of minor impoltantnnce. 

v) Dewatering, which is a destructive fishing practice, has also become an imponant 

method in many small, closed beds &g., Mailhata, Sotha jan, etc.) in recent years. 

PEN CULTURE 

A series of pen culture experiments were carried out by CIFRI at different 

locations in Assam. The experiments were conducted in Peekathi (1990-91, 1991-92). 

Bageswari (1996-97, 1997-98) and Samaguri (1998-99) beels. Split bamboo screen 

with inner lining by nylon net was used as pen material. Water area covered by pen 

enclosure under different experiments varied from 0.005 to 0.1 ha. After the erection of 

pen enclosure macrovegetation were removed manually and the area was cleared off 

undesirable fishes by repeated netting. The pH of soil and water in beels are acidic. 

Lime was applied to correct the pH within enclosed area. 

In most of the experiments, fingerlings/ advanced fingerlings of lnd~an major 

carps were used as stocking material. Stocking densities varying from 6000 to 60000iha 

were tried. In some cases like in Samaguri beel during 1998-99, only silvcr carp was 

stocked and in Peetkati, Puntius javanicus was stocked along with Indian major carp 

Duration of experiments varied between 90- 180 days. Fishes were fed, in all cases, with 

a conventional mixture of rice bran and mustard oil cake (]:I) at the rate of 2 - 5% of 

the body weight per day over the period of experiments. 

In all the experiments growth rate of catla observed to be faster compared to 

other two carp species followed by rohu and mrigal. The h~ghest growth (2325%) of 

Catla was recorded in Peetkati beel over a rearing period of 180 days. In the same 

experiment, growth rate of rohu and mrigal recorded to be 1085% and 800Uiu, 

respectively (Table 17). Improved growth performance was associated with longer 

period of rearing and low stocking density. Higher stocking density and shorter 

duration did not favour encouraging growth rate. These experiments were conducted 

during October - December months aafter the recession of flood water, when temperature 

of the region starts falling. This has affected the growth. From the pen culture 

experiments conducted so far no technologies were developed. However, the following 

conclusions could be drawn:

1. Liming in split dosea It regular intervals u needed to corm3 the low pH. Rock lime 

which dissolva slowly is very w hl for prolonging the effscts of liming. 

2. Intermittmtly, phosphate fertilizer may be wd to favour plankton growth as PO,' 

concentration in Amam wrta is vay low. 

3. Detritivomus fishes like Labeo cnlbasu L. dm. Puntius samna and exotic species 

like silver carp and Cyprinus carpio can be stocked in largr numbers to get better 

growth rate. 

4. To obtain faster growth in shorter duration one year old stunted (hatchery stunt) 

fingerling can be used for stocking. 

5. To avoid slow growth due to low temperature, fishes can be stocked in the middle of 

January and rear them till end of April. 

6. Feed should be done by using hanging bag. 

Table 17 Detrlls of the pen culture experimenb conducted by CIFRI in Assrm 

Namc of Year Area Flsk Stocking Wdght DuraHon Management 

Bccl 

esrlorcd stocked delulty gain of 

Meaturn 

(ha.) 

(ndha.) (%) tacking 

(days) Limlng 

(4Jhm.) 

Feeding 

Pcetkrt~ 1990-9 I 0.1 Cltla 2000 2325 180 

Rlce 

Rohu 2000 1085 

bran:Mustard 

Mngal 2000 800 

oil cake(1: I) 

Pcctkat~ 

Bagheswan 

Baghcswu~ 

Smguri 

1991.92 

1996-97 

1997-98 

1998-99 

0 1 

0.1 

0 1 

0.005 

Catlr 

Rohu 

Mngal 

P, jrvanlcu 

Cotla 

Rohu 

Mrigrl 

Cada 

Rohu 

Mngal 

Silver 

cy, 

7030 

6160 

3370 

500 

4550 

4550 

3900 

3300 

3850 

3850 

60000 

620 

800 

. 

430 

280 

I55 

150 

75 

55 

36 

120 

90 

130 

Linung 

done 

200 

40 100 iOOO 

Rlccbran: 

Musurd orl 

cake(] ])(I 1 

5%bw ' 

Ricebran 

Mustard 011 

cakc(1 I)@ 

2% b.w. 

Riccbnn 

Munud 011

GUIDELINES FOR FISHERY MANAGEMENT OF BEELS OF ASSAM 

Biological productivity of a water body depards primarily on the capacity of the 

system to trap solar arergy and ston thm'in the form of chemical energy. The energy 

conversion efficiency at trophic levels of consumers differs considerably from one water 

body to another, depending on the qualitative and quantitative variations in the biotic 

communities. Any conversion rate above 1% can be considend as good. The studies 

conducted in Assam has proved beyond doubt that bcels in this State can yield fish at 

substantially higher levels compared to other states and other inland aquatic ecosystems. 

In an ideal situation, the commercial species share the ecological niches in such 

a way that trophic resources are utilized to the optimum. At the same time, the fishes 

should belong to short food chain in order to allow maximum efliciency in converting 

the primary food resources into harvestable materials. Thus, the basic parameters that 

abet primary productivity (soil and water quality) and affect composition of comn~unity 

and therr efficiency to transfer energy from one trophic level to the other arc the primary 

considerations in selecting management option. These factors are again dependent on 

the water renewal cycle and the species spectrum of the parent rivers and the heels. 

Ecosystem-oriented management implies increasing productivity by utilizing the natural 

ecosystem processes to the maximum extent. This will be more cost effective and to do 

minlmum damage to ecosystem and biod~venity. 

There is an ~ncreasing trend of dichotomy between intensive aquaculture and the 

more eco-friendly option such as fishery enhancement. While the protagonists of 

intensive aquaculture advocate for high input culture systems to produce maximum 

biomass from a unit area of water, there is an equally strong view point in favour of 

settling for environment friendly sustainable system of production, even if it means a 

lower yield rate. This debate throws open the whole gamut of options available in 

managing our aquatic ecosystems. 

One of the useful criteria for demarcating the culture and capture fisheries is the 

extent of human intervention in the management process. In a typical capture fishery, 

the wild untended stock of organisms is harvested with little ~ntervention on either 

habitat variables or the biotic communities. On the other hand in a culture fishery, the

whole operation is baaed on captive stock with a high degree of effective human control 

over the pbysicochanical wata quality, and other Mitat variables. The marine 

fiMw is the example of capture fihihnies and the intensive aquaculture of fish and 

prawn in small ponds is the typical culture fishery. 

Fishq management purely on capture fishcly lines, as understood in case of 

marine fisheries seldom operates in the inland waters of India, with the possible 

exception of rivers and estuaries. Catch h m rivers are ectually falling drastically in the 

world over, due to negative impact of human activities on the aquatic environment. 

Most of the open watcrs which contribute substantially to fish production such as 

reservoirs, boels, boars, chaum, etc, are managed on the basis of culture-based fishery or 

vanous forms of enhancement, which are intermediate to culture and capture fishery 

norms. However, these norms lacks conceptual clarity due to absence of clear cut 

definitions. Since semantic confusion regarding definition of water bodies and 

management norms are very much evident in the literature, an attempt is made here to 

define and explain some of them 

Culture based fisheries and enhancement 

When the fish harvest in an open water system depend solely or ma~nly on 

artificial recruitment (stocking), it is refmed to as a culture-based fishery. Many of the 

small reservoirs, closed beels, and number community water bodies in India fall under 

this system. The main focus of management here is stocking and recapture. The size at 

stocking, grow out period, and the size at capture are the important criteria in culture- 

based fishery management. 

Fisheries enhancement is the process by which qualitative and quantitative 

improvement is achieved from water bodies through exercising specific management 

options. This can be in the form of improving stock, changing the exploitation norm. 

changing craft and gear, introducing new forms of access and so on. Apart from 

improving the productio~l of absolute biomass from water bodies, it can also be in the 

form of interventions on access to the fishery or improvement in their monetary and 

aesthetic value. The common norms of enhancement which are relevant to inland water 

bodies of India are :

Stock rnhrerrr (increasing tbc stock) : augmenting the stock of fish 

has been the most common maruganent measure followed in the becls. 

Augmentation of the stock is mcarsuy to pment unwanted fish to 

utilize available food niches and flourish at the cost of cconomicaliy 

important species. Stocking of floodplain wetlaads with fingerlings of 

economically important fast growing species to colonize all the divene 

niches of the biotope is one of the necessary pnrcquisites in 

management. The main aspects of stock enhancement are the selection of 

species for stocking, determination of stocking rate and the size at 

stocking. 

Species enhancement : is planting of economically important, fast 

growing fish from outside with a view to colonizing all the divene 

niches of the biotope for harvesting maximum sustainable crop from 

them. It can be just stocking of new species or new introduct~on. 

Environmentd enkuncement : is improvement of nutrient status ol' 

water by the selective input of fertilizers. Although this is common 

management option adopted in intensive aquaculture. a careful 

consideration of the possible impact on the environment is needed before 

this option is resorted to in the floodplain wetlands. 

7 here are other forms of enhancements such as management enhanccmcnt when 

new mdndgenicnt optlons are exercised For example a water body can be thrown ope11 

for sport fish~ng to attrdct fishers or a community management approach c.in be 

ddopted The ne\r culture systems such as cage and pen culture can be resoncc1 lo lo 

augment y~cld and Increase revenue 

The beels of Assam are heterogeneous groups of fresh water wetlands whlch arc 

d~rerse In ongin, water renewal pattern, soil and water qualities and biotic communltles. 

Since management options to be adopted for obtaining higher yields depend upon an 

number of b~otic and abiotic parameters, it is impossible to suggest a uniform set of 

guidelines for all types of beels. Thus it is imperative to give stress on ecosystem 

oriented management.

Community metabolism 

Community metabolism or the tmmfc? of a ~lgy firom one trophic level to the 

other can be the major criterion for wlecting managmeat options especially the species 

selection in culture-bastd fiherics. In an ccosystm, the biological output or the 

production of harvestable organisms can be at variotu trophic levels. Under a grazing 

chain, a phytoplankton > zooplankion > minnows > carfirhes system or a 

phytoplankton > zooplankton > firh system prevails. Since no grazing chain of 

macrophyteS>jsh exists in bcel, macrophytes an invariably channeled through detritus 

chain. There are different detritus chains such as macrophytec >detritus> derrirrvore 

system, phyroplankron > detritus > benthos > bottom feeders system and macrophyres 

> associated fauna > uir hreothingjsh system. 

Two typical systems generally found in the closed and open beels of Assam are 

depicted in Fig 4 and 5. In both the cases, the birds are at the apex of the food chain. In 

an open beel, most of the energy are transferred through phytoplankfon > zwplankro~t 

> planktophagus > predatory fish chain. This is more or less the case with most of the 

open beels. In sharp contrast, closed bee1 has a macrophytes base food chain with 

dominance of fish feeding on weed associated fauna or detritus. The management norms 

in both cases should aimed at comcting the fish species spectrum with the above food 

chain in view 

Since it is very difficult to prescribe management norms for all possible 

situations, a few management options are described below. 

Culture-based fisheries of the closed beels 

Management of completely closed beels or those with a very brief period of' 

connection with the river is more like mall reservoirs. The basic strategy here will be 

stocking and recapture. Beels are the ideal water bodies for practising culture-based 

fisheries for many reasons. Firstly, they are very rich in nutrients and fish food 

organisms which enable the stocked fishes to grow faster to support a fishery. Thus, the 

growth is achieved at a faster rate compared to reservoirs. Secondly, the beels allow 

higher stocking density by virtue of their better growth performance and the per hectare 

yield is quite high. Thirdly, there are no irrigation canals and spillways as in the case of

Fig. 4. Pathways of energy flow In (Macmphyte~Wtus chain) 

K*' 

Inucts. Worms 6

Fig. 5. Path- of enorgy flow Jn (Orrdng chrin) 

LzEzz-l 

WIU birds &

small reservoirs which caw the stock loss and the lack of effect~ve nvcr connection 

prevents enby of unwanted stock. The beets also allow stocking of dehitivores as the 

energy transfer takes place through the debitus chain. 

In a culturebased fishery, the growth is dependent on stocking density and 

survival is dependent on size of the stocked fish. The growth varies from one water 

body to another depending on the water quality and food availability. The right spec~es 

stocked in right number, in right size and their recapture at right size are the determining 

factors. These have to be decided as a part of ecosystem-oriented management. The 

basic management strategies can be summarized as : 

i) Size or stockrng 

11) Stocking densrtv 

itr) Stze ur cuprure/ Selecrion ofjshing gear 

11) Species munagemenl 

1) Selecrron species 

The following arc the major aspects of culture-based fishery In closed beels: 

Erudicarton/conrrol ojpredaron and pest $shes 

In beels. which are undrainable duc to large volume of water, eradication of 

predatory and pest fishes is not possible. In beels of considerable size (more than 10 ha). 

application of p~scicides like mahua oil cake is likely to be uneconomic. In such cases. 

the aim should be to minimize the population of unwanted fish species, hy the way of 

repeated netllng as well as selective fishing for predatory fishes like W utru. 

Stocking dertsrt, 

The State of Assam, with too many water bodies to slock, has inadequate state 

machinery to meet the stocking requirements of all its beels. This has resulted in understocking 

of the beels. Stocking densities need to be fixed for individual watcr bod~cs or 

a group of them sharing common characteristics such as size, presence of natural fish 

populations, predat~on pressure, fishing effort, minimum marketable size, amenab~l~ty to 

fertil~zing and multiplicity of wata use. The main considerations tn determining the

stocLtagmtc~egmwthrmteof~speckrsttt&d,tbcwntlllityrd~,aiorrt 

rtoJrinp aad tbc growing time. ?be following f o d an k d for c d c u ~ 

stocking density in beck 

S 

P- 

Number of fish to be stocked (in numberha) 

Annual potential yield of the water body 

q The proportion of the yield that can come from the species in question 

W Mean weight at capture 

k Age at caphue 

t, Age at stocking 

-2 Total mortality rate 

It is important to estimate the values of P. In an ideal situation it can be 

calculated through primary productivity estimations. In a culture-based fishery. the 

growth of stocked fish (W) will vary from beel to beel. Thus, the assumed growth rate 

can not be uniform. However, a growth rate of 500 g per year is easily attained in case 

of Indian major carps in the beels of Assam. A more scientific approach to stock 

enhancement of the bccls is needed since the larger share of additional fish production is 

expected to come from this management measure alone. 

The range of mortality rates can be found out from the estimated survival rate. 

Table 18 illustrates calculation of stocking rates using the formula given above, when P 

= 200 kgh, q = 1, W = 0.5 kg and t-k, is I. While putting values for [he unnuul 

potenrial yield oftho water body (P) in the formula, it must be clearly understood that it 

should cover only a part of the yield that comes through stocked fish. For example, if a 

beel is expected to give a total yield of 500 kgha in which 100 kg/ha is accountable to 

natural populations, then 400 should be the P value.

The model assumes insignificant breeding by stocked population and therefore 

applies mainly to total cropping situations i.e.. those in which fish are caught below 

their minimum size for maturity, those whose natural reproduction does not take place 

and those where water body is not permanent. It shows that stocking density, which 

depends on the natural conditions of productivity, growth and morlality, are very 

sensitive to Z. Because of the very large numbers of fry needed, this fonnula may have 

very limited utility in large reservoirs. 

Tabk 18. Calculated stockiag denrity at different h ela of mortality (adopted 

from Wdcommc, 1976) 

Annaul per ccnr Estinuted number of fish 

rurv~val to be stocked (number'ha) 

1.081 

1.792 

2.0 2.955 

Despite the lack of any policy and sound scientific advice, the stocking efforts made 

in Assam beels have been very effective in improving the yield. This is because of the 

fact that success in management of beels depends more on recapturing the stocked fish 

rather than on their building up a b ding population. The smaller water bodies have 

the advantage of easy recapture and stock monitoring. The smaller the reservoirs, the 

better are the chances of success in the stock and recapture process, Instances where 

stocking of Indian niajor carps became ineffective in bccls are very rare. The basic 

tenets of stocking policy arc: 

Selection of the right species, depending on the fish food resources available in the 

system. 

Detmination of a stocking density on the basis of production potential, pwth and 

mortality rates.

Proper stocking and harvesting sckdule including staggered stodung and 

harvesting, allowing maximum grow out periad, talung into account the critical 

water Icvels. 

In case of small irrigation reservoirs with open sluices the season of ovdo\c and 

[he possib~lities of wata level falling too low or completely drying up, are also to be 

taken into consideration. 

Stockrng srze 

Since mortality of fish is size-dependent, it is vital to stock fish at a proper size 

to ensure a good survival1 recovery of stocked fingerlings. In the undrainable beds 

hav~ng large carnivorous population like W.arru, C. marulius. N, chrtalu etc. ( more than 

10% of catch) the nlinimum size of the stocking should be at least 10 cm in length. In 

beels having moderate (less than equal to 5 % of total fish catch) carnivore populat~on . 

th~s mtntmum stocking size may be reduced to 8 cm. At present, it will be difficult. ~f 

not ~mpossible, to get a steady supply of large sized fingerlings in adequate number and 

at the nght tlrne to stock the becls. It is also diflicult lask to transport large number of 

advanced fingerlings (,I0 cm In size) to the beel sites, which have remote locat~on and 

poor road connections. Buylng the seed for stocking will be an expensive and difficult 

proposrtlon, whlch In all likelihood will not be complied with. It may be noted that 

contrary to the claims, it is the lapse in stocking (in the right size, in adequate number 

and in tlme) that is mainly responsible for low yield obtained from culture-based 

fisher~es in reservoirs and beels of India. Cons~rucrron of rearlng ponds or pen 

enclosurc~s should he prov~ded rn each beeifor in situ rearing of curpflngerlrngs. 

S~ock~ng combrnarron and ratlo 

The combination of three Indian major carps and three exotic carps is expected 

to give much higher yield than IMC alone. However, in merit yean, fish farmers are 

gradually shifting from 6 species composite carp culture to polyculture of 3 species 

IMC. because the exotic q s have less consumer preference, low shelf life and the 

nsultant lower price. Since the kls have very high detritus energy, one is tempted to 

suggest a higher proportion (30 rohu:30 catla:40 mrigal) but experience with pen culture 

experiment have shown that mrigal either does not thrive well in beel bottom due to 

anoxic condition or arc difftcult to harvest.

Size at harvest 

Size at harvest of stocked fish should be at leaat 500g (in case of staggered 

stocking and multiple harvesting) to 750 g (in case of single stocking and terminal 

harvesting). This may vary depending upon the period of water retention (8.10 months) 

in the closed beels. in case of stagged stocking, it is important to allow the stocked 

fish to grow for an adequate period so as to achieve optimum growth. Thus, the stocking 

and harvesting schedule need to be worked out for each betl, depending on its water 

nnewal pattern. In case staggered stocking is adopted, parameters like stocking interval. 

minimum size at capture are to be detmnined and spelt out. 

Macrophyte control 

Keeping the macrophytes under control is the most important measure to be 

followed in the closed beels. As explained in earlier chapters, clearance of macrophytes 

creates congenial atmosphere for rich plankton growth. Since plankton is easilyldirectly 

converted into terminal (fish) production, yield rates of beels will go up significantly 

from macrophyte control alone. Normally, stocking of exotic fish is not encouraged due 

to the possibility of these fishes entering natural waters through flooding. However, in 

totally closed beels with little chance of getting flooded, grass carp fingerlings @! 10% 

of the total stocking density may be released to beel to control submerged macrophytes 

like Hydrrlla. Nujas err. 

Since the beels are plagued by the condition of low pH of soil and water, liming 

is expected to augment release of essential plant nutrients from the soil phase and there- 

by increasing fish production. Liming during post-monsoon or winter season will also 

help prevent occwence of Epimtic Ulcerative Syndrome (EUS), a common cause of 

loss of fish stocks and associated monetary loss in many beels of the state. However, 

this measure may not be cost effective in beds larger than 20 ha.

Ferrlisarion / Borrom raking 

Since the beels raceive a lot of allochthonous inputs from their catchment areas, 

and usually have larger organic matter resern, extema) fertilisation is unwarranted. 

Further, external fertilization is not sustainable ecologically since it is likely to hasten 

the natural eutrophication process of the beel. Instead of external fertili7ation. 

macrophyte clearance and bottom raking resulted in rich plankton growth and the 

highest ever production. 

Capture fisheries of the open beels 

Some bcels retain their rivcrine connection for a reasonably long time, which are 

relatively free from weed infestations. These beels are typical continuum of nvers whcre 

the management stratcgy is essent~ally aktn to riverine fisheries. Thus. basic approach IS 

to kllow recruitment by conserving and protecting the brooders and juveniles. These 

measures have the dual advantage of conserving the natural habitat of the beels alons 

with extcnding the benefits of conservation to the lotic ecosystem of the parent stream 

In capture fishery management, the natural fish stock is managed. Therefore, a thorough 

insight of population dynamics including recruitment, growth and mortality is ver), 

much essential. In order to ensure recruitment, the following parameters are taken into 

consideration. 

I) Irk.r~rrJictrrron tmdprotection of hreecling grounds 

11) ,4110~ /rc3i, mrgrotlorl of brooders undjuvenlles from bee1 lo river and vice wrsu 

111) Prorecrron (dbrood slock arrdluvenrles h, conservarlon measures 

The growth over-fishing is prevented by taking appropriate measures for gear 

selectton. Adjustments in quality and quantity of fishing gear is an essential 

component of capture fishery management. Common strategies followed are 

sunimari7cd as: 

i) increase rhe minimum mesh size. 

ri) Increuse or decrease rhefihing effori. 

iii) Ohsenv rhe closed season lo protect the brooders

iv) Strict adherence of the restriction on the minimum size ar capture. 

9 Diversity ofthe gear. 

VI) Selective augmentation ofstock, onlv if unavoidable. 

Culture and capture systems 

There are systems which combine the norms of capturt and culture fisheries. 

The marginal areas of beels an cordoned off for culture systems either as ponds or as 

pens and the central portion is lefl for capture fisheries (Fig. 6). This has been tried in 

many places of the country with certaln degree of success. 

Fishery options 

I) 

Frshen based on Itrtitr~n mulor curps 

The becl, especially the closed ones can he developed as b~g ponds has the~r 

fishery solell dcpends on stocklng with IMC. Although not donc in a scientific way thc 

heels arc hung stocked regularly. In the absence of natural rcc~itmcnt, stocktng u~th 

economically lniportant species form thc best management optlon. 

In many of the beels indigenous fish forms a substantial share of the catch 

uhlch fetch good prlce also In the local market. It IS not necessary to develop all becls 

as carp hascd fisheries Anrh/!ph(~nngodon mokr. Pun~r~rs soplrore. (ittclrt.sl(i c,htil~~.ir 

and a number of alr breathing fishes etc. can also sustain economic fishery. I,o\r ylcld 

rates can be compensatcd with the high price those fishes fetch. 'This practlcc w~ll 

prcbcnt the compartmcntalizat~on of heels and their conversion into ponds. 

rrr) Fishcn based on pen and cage culture 

Many of the beels are no1 productive and it is not practical to fertilize the uholc 

open water area. Therefore a manageable part of the water body can be cordoned off to 

stock choice species. Pen and cage culture practices are the perfect management optlon 

for the weed choked and unproductive beels. Thls solves the problem created by gear 

restriction and catchability.

Flg. 8. Dlrgnmmatlc npnwnbSion of cuttun md upkrre fkherhs 

developmet In Au8m 

. - -- 

~ CULTURE 

FISHERY 

I 

WIRE MESH 

CAPTURE FISHERY 

I

Beels also can be pPrt of an integrated system including navigation. bird 

sanctuary, post harvest, aquaculture and open water fisheries. A scheme for an beel (Fig. 

7) has been shown as an example. This plan is a part of holistic development of the 

wetland, which can benefit the local people and help retaining the biodiversity of the 

beel and its environment. It is proposed that the deep northern part of the lake can be 

retained in its natural state to conserve aquatic communities and fish population. Th~s 

will act as i reservoir for irrigation and capture fisheries. The periphery of the swampy 

southern sector of the beel could be converted into aquaculture pondsipens leaving the 

middle portion ofthis sector as bird sanctuary.

A beel thicky infested with water hyacinth

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