Table 2. Composition <strong>and</strong> abundance <strong>of</strong> species <strong>of</strong> phytoplankton species <strong>in</strong> terms <strong>of</strong> numbers per ml <strong>in</strong> a tropical estuar<strong>in</strong>e creek (March, 2003 – February, 2004)Months 2003 → 2004 →Class March April May June July August September October November December January FebruaryBacillanophyceaeAmphora ovalis - - - - - - - - - 20 - -Cocconeis scutellum - 150 - - - - - - - - - -Cosc<strong>in</strong>odiscus centralis - - - - - - - - - - 40 -Cosc<strong>in</strong>odiscus radiatus - - - - - - - - - - 60 30Cyclotella menighniana 30 - - - - - - - - - - -Gryrosigma balticum - - 20 - - 70 - - - - - -Hantzschia amphioxys - - - - - - - - - - - 30Melosira granulata - - 2240 800 800 80 1860 310 - - - -Melosira granulata var. - - 980 5940 6810 - 780 250 - - - -angustissimaMelosira moniliformis 40 - - - - - - - - - - -Navicula cryptocephala - - - 180 - - - - - - - -Navicula cuspidata - 970 - - - - - - - 60 - -Navicula mutica - - - - - - - - - - 30 30Navicula pusilla - 520 - - - - - - - - - -Nitzschia closterium - 1120 - - - - - - 10 - - -Nitzschia longissima - 110 - - - - - - - - - -Nitzschia sigma - - - - 140 - - 40 - 20 - -Nitzschia sigmoidea - - - - - 40 - - - - - -Pleurosigma angulatum 30 - - - - 220 - - - - - -Podosira stelligera - 180 - - - - - - - - - -Skeletonema coastatum 10 - - - - - - - - - - 180Surirella ovata - - - 250 250 - - - - - - -Synedra ulna - - - - - 30 - 50 30 - 30 -Tabellaria fenestrata - - - - - - - - 10 20 - -Thalassiosira decipens 130 - - - - - - - - - - 40Triceratium favus - - - - - - - - - - 20 -CyanophyceaeMicrocystis aureg<strong>in</strong>osa - - 120 - - - 220 - - 70 - -Merismopedia gluca - - - - - - - - 30 - - -Microcystis flos-aquae - - - - - - 200 - - 70 - -108 B.E. Emmanuel <strong>and</strong> I.C. Onyema / Turk. J. Fish. Aquat. Sci. 7: 105-113 (2007)ChlorophyceaeGonatozygon sp. - - - 500 780 - - - - - - -Spirogyra sp. - - 40 - - - 30 - - - - -
B.E. Emmanuel <strong>and</strong> I.C. Onyema / Turk. J. Fish. Aquat. Sci. 7: 105-113 (2007) 109aureg<strong>in</strong>osa <strong>and</strong> M. flos-aquae were dom<strong>in</strong>ant species<strong>in</strong> November <strong>and</strong> December respectively. <strong>The</strong> greenalgae were represented by two species, namelySpirogyra sp. <strong>and</strong> Gonatozygon species.ZooplanktonTwo phyla <strong>of</strong> zooplankton (Crustacea <strong>and</strong>Rotifera) were encountered dur<strong>in</strong>g this <strong>in</strong>vestigationwith the former be<strong>in</strong>g more diverse <strong>and</strong> abundance.For the phyla Arthropoda, the sub-class Brachipoda(Cladocera) <strong>and</strong> Copepoda (Calanoid, Cyclopoid <strong>and</strong>Harpacticoid copepods) were recorded. <strong>The</strong> phylumRotifera was represented by species from the OrderPloima. A total <strong>of</strong> 18 zooplankton species, 1.e. 6calanoid, 6 cyclopoid <strong>and</strong> 1 harpacticoid copepodswere recorded. 2 cladoceran <strong>and</strong> 3 rotifers specieswere also recorded (Table 3).Whereas Acartia clausii, A. discaudata,Paracalanus parvus, P. pymaeus, Diaptomus sp. <strong>and</strong>Rh<strong>in</strong>calanus sp. were the dom<strong>in</strong>ant calanoidcopepods, Cyclop<strong>in</strong>a longicornis, Cyclop<strong>in</strong>a sp.,Cyclops strenus, Cyclops sp., Halicyclops,Mesocyclops species recorded higher outcomes forthe cyclopoid copepods <strong>and</strong> Enterp<strong>in</strong>a acutifronsrepresented the harpacticoid copepods.Diaphanosoma excisum, Diaphanosoma sp.(Cladocera) <strong>and</strong> Branchionus calyciflorus,Branchionus sp., <strong>and</strong> Lecane bulla (Rotifera) werealso recorded dur<strong>in</strong>g the study.Meroplanktonic forms encountered <strong>in</strong>cludejuvenile stages <strong>of</strong> copepod, cladoceran, barnacles,crabs, shrimp, fish eggs <strong>and</strong> larval planktonic stages.<strong>The</strong>re were two peaks for egg/juveniles abundancewith<strong>in</strong> the creek; they were March/April <strong>and</strong>September/October for the period underconsideration.F<strong>in</strong> <strong>and</strong> Shell FishF<strong>in</strong> <strong>and</strong> shell fish species, their size ranges <strong>and</strong>weight ranges are presented <strong>in</strong> Table 4. Seventeen f<strong>in</strong>fish <strong>and</strong> four shell fish were encountered <strong>in</strong> the creekdur<strong>in</strong>g the survey.Four species <strong>of</strong> cichlidae were identified. Three<strong>of</strong> them Sarotherodon melanotheron, Hemichromisfasicatus <strong>and</strong> Tilapia gu<strong>in</strong>eensis are the importantfood species. <strong>The</strong>y all atta<strong>in</strong>ed up to 16.50 cm (74.27g), 13.90 cm (42.63 g) <strong>and</strong> 15.20 cm (133.08 g) astotal length respectively <strong>in</strong> the creek. <strong>The</strong> familyGobidae was represented by Bathygobius soporator,Eleotris vitata, Batanga lebretonis <strong>and</strong> Gobioidesafricanus.<strong>The</strong> family Ophichthiidae was represented by asole species, Ophichthus rufus. Two species <strong>of</strong>Clariidae, Clarias gariep<strong>in</strong>us <strong>and</strong> Heterobranchusbidosarlis were also encountered.<strong>The</strong> Bagridae was represented by Chrysichthysnigrodigitatus. <strong>The</strong> families <strong>of</strong> Carangidae,Channidae <strong>and</strong> Citharidae were represented byCaranx hippos, Channa obscura <strong>and</strong> Citharusl<strong>in</strong>guatula, respectively. Mugilidae was representedby two species, Mugil cephalus <strong>and</strong> Liza falcip<strong>in</strong>nis.<strong>The</strong> shellfish were represented by three families,Palaemonidae, Penaeidae <strong>and</strong> Portunidae.Palaemonidae was represented by Macrobrachiumvollenhoevenii <strong>and</strong> Macrobrachium macrobrachion.<strong>The</strong>se also atta<strong>in</strong>ed adult size <strong>in</strong> the creek. Penaeidaewas represented by Penaeus notialis <strong>and</strong> Portunidaeby Call<strong>in</strong>ectes amnicola.Discussion<strong>The</strong> present <strong>in</strong>formation on the seasonality <strong>of</strong>hydrological characteristics <strong>of</strong> this tidal creekconfirms earlier observations similarly observed <strong>in</strong>the adjo<strong>in</strong><strong>in</strong>g Lagos lagoon. <strong>The</strong> regime <strong>of</strong> ecologicalfactors operat<strong>in</strong>g <strong>in</strong> the Lagos lagoon has beendocumented by several <strong>in</strong>vestigators over the years(Webb, 1958; Hill <strong>and</strong> Webb, 1958; Olaniyan, 1969;Nwankwo, 1988, 1996; Onyema et al., 2003). Furtherto this higher sal<strong>in</strong>ity <strong>in</strong> the dry season <strong>in</strong> the Lagoslagoon has been associated to <strong>in</strong>creased tidal seawater<strong>in</strong>cursion, coupled with reduced flood, water <strong>in</strong>flowfrom associated rivers, creeks <strong>and</strong> freshwater lagoons.Hence hydro-meteorological forc<strong>in</strong>g may beimplicated <strong>in</strong> the control <strong>of</strong> the hydroclimaticconditions <strong>of</strong> the study creek, namely freshwaterassociated to ra<strong>in</strong>s <strong>in</strong>flows <strong>and</strong> seawater <strong>in</strong>cursion.High air <strong>and</strong> water temperatures recorded dur<strong>in</strong>gthe study are typical for the region (Nwankwo et al.,2003). <strong>The</strong> high biological oxygen dem<strong>and</strong> value maybe a reflection <strong>of</strong> the amount <strong>of</strong> decompositionalmaterials with<strong>in</strong> the creek <strong>and</strong> aris<strong>in</strong>g from thesurround<strong>in</strong>g rich riparian mangrove vegetation.Higher plankton diversity was recorded <strong>in</strong> the dryseason as aga<strong>in</strong>st the wet periods. <strong>The</strong> algaeassemblage <strong>of</strong> Melosira granulata, M. granulata var.augustissima, Microcystis aureg<strong>in</strong>osa, Microcystisflos-aquae, Gonatozygon <strong>and</strong> Spirogyra species hasbeen implicated <strong>in</strong> studies <strong>in</strong> the Lagos lagoon overthe years especially dur<strong>in</strong>g the ra<strong>in</strong>s (Nwankwo, 1988,1996; Onyema et al., 2003).More stable conditions <strong>in</strong>clud<strong>in</strong>g flowcharacteristics, <strong>in</strong>creased light penetration <strong>and</strong> mar<strong>in</strong>esituation experienced <strong>in</strong> the dry season could haveencouraged the development <strong>of</strong> a richer planktoncommunity. Similar observations have been made byNwankwo (1988) <strong>and</strong> Onyema et al. (2003) for theLagos lagoon.In this study, it is suggested that there are likelythree broad feed<strong>in</strong>g groups <strong>of</strong> fish, namelyplanktophagus, predatory <strong>and</strong> deposit feeders with<strong>in</strong>the creek. This is <strong>in</strong> consonance with Fagade <strong>and</strong>Olaniyan (1974). Furthermore, a direct relationshipbetween <strong>in</strong>creas<strong>in</strong>g sal<strong>in</strong>ity, plankton diversity <strong>and</strong>fish species <strong>and</strong> abundance was also recorded. It ispossible that an <strong>in</strong>creased diversity <strong>of</strong> phytoplankton<strong>and</strong> hence zooplanktonic forms observed dur<strong>in</strong>g thedry season gave rise to a richer f<strong>in</strong> <strong>and</strong> shellfish
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