Field evaluation of side effects of permethrin as simulium larvicide on fish

' ; i- ocr/vcu/um rc/a5.5 Fie1d. Erraluation of sicle effects of pe::nettrrin As Sirnulium lanricid.e on fish E. K. Abban Original : Engli.sh Summa.:rr flre process of ad.opting a larvicid.e for olrmtional use w t}}e ocp incl_udes .a field. assessnent of the Ia:sricid.e against non-target fauna including fish. In this study pe::nethrin was assessed. in relation to the follor.ring para^netersi a) Ctranges in species composition of catch irrmed.iately after application and after B r+eeks of rireekly applieation. b) Ghanges in cateh per unit L.ffort of fishing (cerm) c) cteanges in ttre |tCond-itior/rof fish before and after period" of e:cperimental treatment' 6) Susceptibilifu of caged. fish to pe::rretJ:ri:r. Also local fishermen were intervierred. and their catches inspected" before and after r^leeks of t,l:e trial . fie sults gnd._ d.iscussiol . 1{o fish killed (acute effect) was obsenred; and. no fish in any state of paralysis ruas obserrred r*rich could be attributed. to the r.reek\r application of ttre new chemical. I{o:ma1 fish aetivity r.ras obsenred. along the banks of flre rirrer d.uring the evening and morning after appli.catjon. . [here uere no changes in t]re series of experimental fishing wittrin 2{hr. after application and after I wks. of r.reekly treaturent that couId. suggest movenoent of fish in any d.irection due to application of chenical. . Fluctuations in CPIE sugested localized tgrper-activity in fish due to peruetJ:rin application. Houever tllis d.iri not persist for more tiran 24h. . Comparison of mean trcond.itiontt of comparable sizes and sex of fishes before and' after experimental period. shor^red" no significant d.ifferences. rhis indicated. that ruhile some food items of fish cou1d. have been affected. by the r^reekly appli- cation, t'he fish founcl alternative sources of food. d.uring flre trial period. It is also an indication that the short lirred. lgrperactivity induced. r*as not sufficient to divert fish fronr food.. ,-, -2- ' About 20 ofi effect (acute and tempomry) was recorded r*ren {o{ fishesbelonging to 18 species were exposed. to chemical. A]estps nqlsg and TiLgpia species accounted' for more than 80 ?6 of nortalities. The same species shorved. sinilar lerrels of mortarity in control experiments. &rygic4tug ad Eugdonl€ shor'red" temporary effect (1ess than ) % of their total). Rese.ysryof the tempora-rlly affected wittrin 4gh r*as fair (about 50 ?,r). Thus the mortalities of speciesr other than ALes_tes nurse and Tilapig spp.r r.ras less than 5%and. effect on fish lras reversible since recovery r^ras observed. . These results d.iscussed. with available literature indicate that Pe:methrin appried as simul.iqg larvicide und"er trydrolog.ical condition similar to t*rat obtained' d'uring ttre trial would" have no important effect on fish andfish populations. \ mrethrin I { I l I or $e riir, I ocp/culrim n/85.5 Field Evaluation of sid.e effects As Si-urulium larui.cide on Sr:rnnary - [:e process of a field assesment of E. K. Abban aclopting a lanricide for opere,tionat4se ttre Ia:sricid.e against non-targe t /avna : English by tlre OCp includes including fj.sh. In this study pe:rrethrin r.as assessed. ion to the folloving parametersiin rela/ a) ctranges in species composition of catf imned.iately after application and. after B r.reeks of neekly application. ,//b) Ctranees in Catch per Unit liffort'of fishine (CptE) c) ctranges in the It0ond"ltionl'of. fish befor.e and. after period. of experimental trealpstl' /' 6) Susceptibility of caged, -/i"1, to permetlrrin. Also Local flshermen were interviewed. and ttreir catches inspected. before and. after weeks of the tria]. ,,,, Results and d.iscussion ..' . IiIo fish kirre/ (acute effect) was observed; and no fish in ar5r state ofpa::a\rsis ruas obsenreci llhich could. be attributed. to ttre vreekly application of the new chemical. tlonnat fish activity uas observed. along tl:e banks of t]:e river d.uring the evening'and. morning: after applicatjon. .'lltcre weIC. no cbarr6,es irr Ure ssr1., o1 e:6$:rj&sn[a.L 1.islriu6 wiuritr 2{rr. after application and after I wks. of r.reek\r treatrrent that cou1d. suggest movement of fish fui any d.irection d.ue to application of chemical. ' Fluctuations in cP@ sugested localized l54per-activity in fish due tope:methrin applicati-on. Howerrer this dict not persist for more ttran 2dh. ' comlarison of mean rrcond'itiontt of comlnrable sizes and. sex of fishes before and' after experi-rrental periotl shor"ied. no significast d.ifferences. rhis indicated. that r"rtrile some food. items of fish could have been affected W the r.reekly appli_ cationr the fish found' alternative sources of food. during tlre trial period. It is also an ind'ication that the short lived. tqrperactivit5r ind.uced. r,ras not sufficient to divert fish fron food.. . -./ .. . ->- - -2- . About 2O g6 effect (acute and tempomry) lras recorded vhen 404 fishes 3.:.::": :" ,: :T"t"" were erposed. to chemicat. Ateste_s n,rsg and. riljrpia "::\ accounted. for more tJ.an B0 ?6 of mortalities. The same *""r"ffiffiu ::,tj:"X,:'r" ot mortality in control experiments. C.l:rlrsichthys and Synod.ontshoued' temporary effect fles= tJran B 9.A a,r *r.rair +^+^1\ n- sirnilar'{errels f :r v od tis. . J--t (1ess I 96 of their total). Reco,reqirof the tempora_rily affected.vitliin 4Bh r,aas fair (about 50 ,c6). Thus the nortal-ities ofs1rci.es, other Alg:tes nurse and Tilanie spp.r was less than 5?loand. effecton fish r.iEts r€\rerlitre since recovery r,ras observed.. . These results d..€cussed. wi.tl: available Per:mettrrin applied "" -A.ii1\+gg 1arvicide und.erto wl"rat obtained during tfre \iaf would have nofish populations. literature indicate that tqrdrological condition similar inportant effect on fish and