Vol. 15—1961 - NorthEastern Weed Science Society
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Vol. 15—1961 - NorthEastern Weed Science Society

Vol. 15—1961 - NorthEastern Weed Science Society Vol. 15—1961 - NorthEastern Weed Science Society

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08.06.2015 Views

486. weeds increased the food 4.3 ti.JDl!lswtJAtit woUld hove been in their absence. More than one-belf of the 61 species present were restricted to weedbeds, while only a few species were restricted to veedless bottom • .Studies in deeper wpters showed less variation between weedbed and weedless zones. :tn part this is due to the presence of fever stems in deep beds and in part, to the presence of large burrowingf6rms .'inthe open bottom which increAsed the 'Weight though not the availabU1 ty as food for most fishes. . Since tbe extreme richness and productivity of Ohautauqua Lake is not typical of averAge vaters of the Stete, these results may not be capable of extension to all waters. Quantitative studies 'Were~ also mde on 10 beys, ponds and reservoirs in tile Lake Ontario Biological Survey (1939). Seven of these contAined 'Weedbeds. There 1mS no accurate measurement of the extent of these beds so computation cannot be made on the same basis as with Ohautauqua. Individually, the~ food in weedbeds ranged from 0.7 times higher than in weedles8 areas in a bey in which no shallow water beds were present, to 22.8 times in a bey too shallow tor the developnent ot D typical deep-water fauna. The average food content in tbe weedless sections of these waters was 7,,8 g/m 2 , while the weedbeds, including both deep and shallow areas, was 21.9 g/m , or a 2.8 times increase in tood organisms over the weedl~ss zones. In the veters ~thout weeds, food ranged from 1.8 to 7.6 glm tor an average of 3.8 g/m. Except that these included two reservoirs where the establishment of weeds WASprevented by fluctuation, it could be argued that the absence of weeds indicated low fertility, hence'2low productivity could be anticipated. The reservoirs averaged onJ:y.2.65 glm • A number of species of fish require weedbeds for spawning areas and a few are quite particular as to the depth of the bed. titUe information is available on preference for certain plants. Absence of 'Weedyareas would appear to prevent satisfactory spawning of these fishes end the destruction of all weeds in waters in which they are present would lead to their eventual elimination. " :".' " The young of bo~h game aDd fore.ge species require shelter from predation. Many food organisms.1Il81' be cropped satisfactorily only by smell fishes or fish with special feeding mechanisms. High productivity requires util:1zation of much of the food supply in growth of smiU.l fisbe,s. In turn the protein produced is converted' to growth of the larger species through predation. Without the sbel ter provided b1 weedbeds against predation, opportUDity for grow:t~ would be red~ and much of the food supplY would be poorly utilized. Both forage aDdpreda.cious species vould be reduced and growth would be slow in the latter group. . ~. "prpduetion would rasu! t and ihe balance would tend to favor OJJ1coar!e, :rapl

e readily inferred. .Waterfowl are even more dependent upon rooted vegetation than are the fishes. While any removal of weeds will slightly reduce total productivity; d.. j:. is believed that some vegetation may be',removed, or species changes effe~rted, in almost any water without signific.a,nt ,damage to aquatic resources. ; Such removal improves the waters for othercrrecreational purposes and, in some instances, may result in a desirable 'sh1ft"in fish populations although this contention has not yet been supportei:Fby. 8.1Vexperimental data. The degree of removal that can be permitted and"still maintain satisfactory fish production has also not yet been established. Concei vably it will be different in different waters and will also vary with the species present. Most rich lakes are in a state of dynamic balance in which either rooted aquatics or algae predominate. Except where abruptly sloping bottom or other physical features restrict rooted vegetation to a narrow band, algae is sel- . dom a problem in the presence of rooted growth. Heavy algae production prevents the establishment of weedbeda. Inter,ference witheithel'type of growth can throw the balance in the oppoai te .direction, since the grOwth depends on the availability of nitrogen, phosphorus and in part on the abundance of calcium. Sources of the fertilizing elements may be either sanitary sewage, or runoff from rich agricultm-al lands. No control procedure in use attacks the basic problem which. is high fertility. -- Control Methods: Formerly, a cottage owner confronted with a weed problem that interfered' with bathing in the vicinity of his dock got busy with a rake. The same method was used to open a path through a weedbed to give his boat access to open water. Nowhis first thought in a similar situation is "Can't some chemical be used for a permanent solution. n In part this may be evidence that the population is becoming chemical minded. in Part it may stem from the desire to avoid physical exertion, but it is largely due to widespread advertisement of chemical methods. Chemicals used in vegetation control can be defined either as 'shotgun' or specific. In other words they can readily control nearly all vegetation, or are capable of controlling easily only a few. Frequently a chemical may be made less specific by increasing the dosage. All vegetation is not equallyobjectionable to a cottage or boat owner and with development of chemicals to cover a range of plant species it should be theoretically possible to remoye the objectionable species, leaving the others to fulfill the functions for whioh they are best suited. Such a procedure would allow the 'use of the fertility by sane form of rooted vegetation and aid in the prevention of! nuisance growth of algae that develop all too frequently when extend va weedgr9Wths are removed by one of the •shotgun' type chemicals. . Any chemical can be expected to have toxicity to fish and to the organisms on which they feed. &lfety requires that the deaage level fer weed

e readily inferred. .Waterfowl are even more dependent upon rooted vegetation<br />

than are the fishes. While any removal of weeds will slightly reduce<br />

total productivity; d.. j:. is believed that some vegetation may be',removed, or<br />

species changes effe~rted, in almost any water without signific.a,nt ,damage to<br />

aquatic resources. ; Such removal improves the waters for othercrrecreational<br />

purposes and, in some instances, may result in a desirable 'sh1ft"in fish<br />

populations although this contention has not yet been supportei:Fby. 8.1Vexperimental<br />

data. The degree of removal that can be permitted and"still maintain<br />

satisfactory fish production has also not yet been established. Concei<br />

vably it will be different in different waters and will also vary with the<br />

species present.<br />

Most rich lakes are in a state of dynamic balance in which either rooted<br />

aquatics or algae predominate. Except where abruptly sloping bottom or other<br />

physical features restrict rooted vegetation to a narrow band, algae is sel- .<br />

dom a problem in the presence of rooted growth. Heavy algae production prevents<br />

the establishment of weedbeda. Inter,ference witheithel'type of growth<br />

can throw the balance in the oppoai te .direction, since the grOwth depends on<br />

the availability of nitrogen, phosphorus and in part on the abundance of calcium.<br />

Sources of the fertilizing elements may be either sanitary sewage, or<br />

runoff from rich agricultm-al lands. No control procedure in use attacks the<br />

basic problem which. is high fertility.<br />

-- Control Methods:<br />

Formerly, a cottage owner confronted with a weed problem that interfered'<br />

with bathing in the vicinity of his dock got busy with a rake. The same<br />

method was used to open a path through a weedbed to give his boat access to<br />

open water. Nowhis first thought in a similar situation is "Can't some chemical<br />

be used for a permanent solution. n In part this may be evidence that<br />

the population is becoming chemical minded. in Part it may stem from the desire<br />

to avoid physical exertion, but it is largely due to widespread advertisement<br />

of chemical methods.<br />

Chemicals used in vegetation control can be defined either as 'shotgun'<br />

or specific. In other words they can readily control nearly all vegetation,<br />

or are capable of controlling easily only a few. Frequently a chemical may<br />

be made less specific by increasing the dosage. All vegetation is not equallyobjectionable<br />

to a cottage or boat owner and with development of chemicals<br />

to cover a range of plant species it should be theoretically possible to remoye<br />

the objectionable species, leaving the others to fulfill the functions<br />

for whioh they are best suited. Such a procedure would allow the 'use of the<br />

fertility by sane form of rooted vegetation and aid in the prevention of!<br />

nuisance growth of algae that develop all too frequently when extend va weedgr9Wths<br />

are removed by one of the •shotgun' type chemicals. .<br />

Any chemical can be expected to have toxicity to fish and to the organisms<br />

on which they feed. &lfety requires that the deaage level fer weed

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