Aquatic monitoring programme: annual report 1977

a^t- \ WORtrI HEAITI{ ORGANIZATION O}TCHOCERCTASIS CONTROI PROGRAIO,IE IN TIIX VOITA RITER SASIN AREA Aquatlc Monitoring Programme Annual Report 1977 Preparetl by : Mrs B. Y[a].eh ,ili;,^-!IC ;-a:::l :: I:.G Pilccttit: f C:','ii.'-):I-G:r; - U?.)--l YCl,?-:, .'.':-:t-l.t. tt:ct: 1g77 "i:3-rt:.:i.L--.-r-"1-i:T t:'i-:s t;ele::a.Ce tc tae XeC Yc-Ltz rt i6 --:::cte at e.nrrc:::r:^.te).;- 4-lzeel-1;' i::tc:Vals Culrini; tl:e senscr: cf f1 o',1'. 1l.ive:' r'.'id.ti:, d.e1t]:, nil, l:leccl:i }ise a.nd. e',.,.r:'o::t speec1 ilere i:?a.sr-:i.sal aild 613.-r ancl ni-Si1t tine rater te:.)!err.ir:rcs reccrrleC cn eacir,rr-"r*. la.:- a:-C -.lgiti li:lii sa:rples tvere tal:en each iire, alci Srrrbcr anri- ..-riificic.l Sitbstraie (Coi:er-ete l1ocl.:sr a.i:tl. l.letal 3c.sl:ets) s3;rlnfss r','ere tal:en vhen conctitions per::itted.. Sa:rp1es t'rere tl.l;en c.n.,l- cbserveiions naoe aceor.ding tc ti:e netj:oc1s appro.red. b7 the Aquatic ..cnitorrng ?:oiocoI. ris in t976, the satlling c-c.i;es ',yere cl.r.osen to occi-lr just before ti:.e regu*Lir dosing vith,^-bate j-nsectj-cide, so as to a.'roid the ltCata.stropiric lrift'r ejiect of a sanple tallen j-ra-:edi-ate1y after d-osj-n3. Ihe delsit;' of anj-r=.] lopule.tlons present at an;r ore ti_ne i_n t}e lri:flt Ilarnoles is ex'.ressed. as Inde:: o-t]jrift (I}). Thls gives an esti.nate of ihe nu.nbe:: of a:rj.::.e.ls rer cubie ::etre of r,,'ater f:.iterecl b; tire ctrj_ft nets u-sed. lor the Sr.rrber and -'-riificiai substz.i.te (Concrete Bloc-:) sa"rcples, ti:e r:i:nber of aninaLs present i-s e::irz'essec. as ,;e-:sit;,- per sqirare r:et:e Q:rt:z) a:lc f o: iiie -^:rti.ficial- Substrate (i:etat 3asl:et) sanples t1:e dersit;, of a-ninaL lo:-r:1c-iicns i.e e>lrressed. as i.lsgn i:.-.n,:e: oi ani:le.ls per basket sanrle s. {L t/ fr, lel;in,:rn:] Jrine lnd Jr-lne Jr_rL;, legin::ins -:-u6ust -_i11fl -'luSust Septei:ber 0etober llovenber Iab] e -1, nll t(, /^ rct trl:cn i:oi ta.:en 6.C 5,5 va) 6.5 )i76_ 6.5 hr. a1 5.5 6.5 6.5 .ti l.v 1i.a-7! ll 6.5 .,o) t olJ .7n As ca:r be seen fron Table f the niI value of the river ve"ried. ]-ittle ti:roughoirt tI:.e season of f]ov ii 19?7. l- siight increase in all;a.linit;'tc;arc't-s the enC of tl:e season in 1977, s.i1d throi6hor-lt tlte thz.ee seasons of nonitorr-r6 iS noticed, bnt vrhether thLs 1:/-oul d- have at:;' nar'l:ecl effect on tite fa:rna over the lerio,i stuclied is not 1c.orzn, t;ror-ig.: ii see:s u-i:1i.i:e1;i. 2,/',,'aier lennera'b}:e i'ig. 1- gives t'-e.r-ra-- te::.;eratu:'e i.r:d fig. 2 ti,e lli;ht te::peri:ture for t977, conla:ed tritir tl:e h.'o :revio:ls seasons. lire f1u-c-buatic.-s in ienpe:atuire fcrlor,' a si::i1ar pa.ttcrn i:^, i;].:.o ti:ree Jros.:.: under consi_deration. Thrrs, _lcr boih Ie;, and -.i5ht tenileratu*'es ii:ere lt/as arl re.iti:r11y':igh readi-i;, fol1o1ie6'. |:r l-orzer terleratir_res in r:ir1se:son. :i seconde::;. pea': i-n Sep;er:cer,,bctaber i:,,as fc-.,i-_,,-or.,,ect. ;'-:'r-eeli-ne to';;i::ri3 N,-"g gri(r. o:;,:.e se-so:1. _.,a.;, -uen;::atu:cc v::r:ecl beti,,een -o - ^- -c ..)- .'-- ::exir-,-'rr i:r cic.:::' l i-7r . ':.,j ? ..i- j r:i::ri:-.r;: i-:r '-'.t-:-.tst i!?l . r. ..ove:-ber l.T', :'".'. !?77. --:;.'--i ;::.",::-.-.1.-::-r-,s ',-l:-Lrr bcf...'cr:: 3{..1.o 't .-::::...: ... .-:::re .i77 -l\ ^^.--. ?: . -" U :'i:-i"','.:' 1..- - -'.,'C lter l-!77. 't ? / tl-- --,..16)r^r- .''-c si..o',',':. in li;. 1,s i: !n^ta.^^rats^.- --'^o 'l a"' n* r'..r -lel: ic:"her. t i--1i-,u ) lJr-. 7.';1r\ : t i;llc c:C o: i ei:be:: :.::7. sir..il:r rejine bc;:-niln5 cf t1 / a,1rnr. -nrrn. rnr"l -i n6'--,1r--6 -'-:- ./ -... . _ _. _. .:.j,: .J-ijU. :.-' .. -.;,,.eJ: li]s 41 5:,nr.i 6 sl:cr; tr::]rver"cvel-s fc:. l-975r 1975 anri 1977:es:eeiivelJ-, :.nr li:ls 7, 8, rr:d I s-ro',;';--c.-li;ci::.r1;c z'3tes for il7-t, 1175:::r't- 1177. rt is in:led.iate1J, noilce:.bl-e tl::-:t tl:c v3.r'i,'r.tio::s in Lts-11. '.::i ],ir:cl::.::e r..ies for -1-o7l a::d l-!7? s-ror-: e si" i 1rr' l::-'b'bei:1, i'tl.:icl: is l:.nl.i.:e 'ui:r=.i fc:' L976. In -!-975 a.i:ct -"t-!77 tl:e n-r::i;.-'.r:: d.e:>ths anil- Ci-seh::."Ce z':.tes scecrcreC. a.t il:e be3innJ-::; of i-ls.r';6;'";e: gre:ii1;' c:ceedec iLrose reccrdc(1. i:r 1976. iror.iere::, in 1i76, ti:e cleptl: ;-:r:. crsch:-::;e raies fh-:ci:r.e.ted :rore freiu-e::t'l; tirr.ou;iro'lrt il:e a) Clirocreia in bcth !s:r l;iff (:i;:-c) r.na l-igirt frift (rie ff) ti:e resu-i-is fcr 1.976 eni \977 rese:bie e:.e,: othc: ia botl: r:imbers ani. laticln of .r!-ui:,.t:ct:. Tj:e I.). f-.r 'lo7E t.ro^ .-j^ -r-' -Li r2 \/i-.r.s --,;;.el t-rL4 ffu1i Cf tr-c f;O latel Jre:.1'S, ::::l tl:e Ia;, 9=i-a= Cf l-9?5 si:riied a ccnsideral;lo increase r:: --ii.-'.',st ancl iiepie:bel:, ',..'l:icli l.;c.s t:ot re-,:e:.iei. i-:- 1!76 and 1977. ,-'-i o ' rll ,- &^.-7-r, ^UJ,,.,,!!-r, ncti-eer.bl e i-- orl + --r^^!.-g: i--l;r'l;'-.cl'.,ci-l n -.- lligiri -'rift rcs'-tlts (:r-:,. i;i) a5arr: s.-o'.',' ::.".iirr v:::j-"tic:: pnii;en-.s, r-nrl lrcrr: a"1sc, tl:e n'.rr.:e:s icr !i77 vere inte:':'e'i.i:';e bcf,,-,'ce.-;-:cc::lecria.r jc:' 1.75 e.:.cl. \976. \ -,.n I . ---1r, r.trtqO " / :i-.::_-li-i--i- l.o li:'.rl-i..J-_g:i:lii.rjl,',rc:o iocol'j e;. l: f ,- . \iI:CSti;' - a.C'-C:S-:/ 'ireSCnI l-I ;::3 --'L;' -.:'1:t i975 or 1975t end the 1l-ttc::n of vari:'.ilor cf e-'t:e:' of. the 1-,revicrls .,e:.rs. In the ili;ht lrift, i:.oi'icver, (::-;. 15), t::e 1!77 th:.n i:r -,'-!7j :rr:c'. 19761 t)rorr;h ti:e pat'tern cf sinilar i:r a1-1- th:ee -1ree.r:s st'.rr:-ied . f .1. \t:.s coitsiste:t1;' 'l e,g- in vari:r.tio:i'.-.'As t-erp.'l'lrab'l -' .\ --,!.,, ".n:tOl]crt-.iela. In tbe lc.Jr -i:ift a'f 1977 (:iC. le) the I.l. lras ge:rcla.l-1;'-'i11',srreiia.ie bef;;een thei fo:: i975 l.r.d !176. Ilc'.'le.rc:r tjre:e i?as a. r-j:i-rrr'.:n reco:cj.ed- i-:r,Iul;' !977 1',rhereas 1::1975 r.nr1 l-9751 'r:::e .'.ii;- lo;'-,.li.ti-r:ns 1'.re:e lo:';e: +i:.: t::ose of .rLr.ne and,1u6it-st. I:: ti:e -,i-;irt l,rift (:i.:. 17) tltele';as a s:-::il.:: pa.ttern of va:ri.o.iior: in all three se3.soils ;tur'.leri. Ilo',','ever, t-re I.J. jc:1977';a.s 1o'.'re: i:: Ji'-ner JulJ' r.::rl -'-u-5ust ti:a:,: fortlle preeeecli:1';c::s, iho'-61: in ti:e l-a.'cer ironil:s :.i; est:bfis:te:. :-iscif l.t levc-l-s ir:l;err:ed.ia.te be'i;,','eer il:.ose of 1975 :.::c't ]-!76. '-tr': e':o:;e:a ;:':,.1i; '.:i.';. f :) tlic i:-:'-i:'.,- l l o"' :'r:.i:::'; .-'c::' c:.:l;- Ju::e 1:: --.i-T "o'.';c'"L i:;' i-'.;. jL:c3C[,';C il: ].1. - - re-j 1,i 'i : :-':l:'ril,',. !.:r; t';l: D.,- ,: l.c'.'c1 :f -:-.p';i,^tir':: tj-r.i ,,','ts el:,:-_:.:c..i;i;- .'..;i:c: tl:-:, -;:::.i -2- o:1976r thou;l: it::e're: reaeh.er- tl:e l-eve]s rccc::ded- fo:. --rrJust r.nc le-te::ber 19?!. In;et:eral , tite ee1'.ret:ce of iariation seer: j.n i977::.esei:;:-l eci tl:et cj 1.976 ncre tl:an i.rat of 1975. i-: t::e -li:-:t ].r.;-i':; (:lig. .r9) titc:;r.tterl-, oi.rr:::-.tlc::.::ese::b1crt- i'r:t oi -tlil,; t,l''l .l'1; a. ca:-srs;e:-.-i;l;- ..:;,',e: 1evel o: :.-]., :::i l-or','ez' (c::cept fo1 jpl;') t]-:.n t::rt of 1976. ^\ ^.: / ( con:.ta fha T)orr l]r'i -i:ro -cJ,r,-ft fol ti:.is CTolr.:D (fig. ZC) in 1977, sl:orved, til;e fl:e f,,:o preceeciiry )'ec.:sr 1:i;hesi; :iii:r.')ei's reeo:d-ed at the be5inning of ti:e season, o.ncl a. late resu.rSenee a'b the el:d-. Tne leve] of f.!. ir 1-977 rias for most of tite season interrled.iate betr;eel 'bi::.i o: \975 and l-976, In the lligi:i lrlft (iig. Zf), tl:e rrariaiioi: of I.). thror_rghout 197T resenbl-ed tire pattei'n sl:ot'.'li in 19761 bu-t tite leve.l yre.s a}r'ra;'s ioverr olcept in 1lsv6:ilbs:, uhen it ivas actu_ail;. iri*nur tiran il:.at reecu,dec for both previou.s .rears. J) Ti:r-.'.1ociii:re rn the )a"- irifi (tis. zZ) tue i.t_-.. for 1977 r,;as _:ig:er.i;har fl:at fc: eitlier of ihe 'lrrevious Jrea.lts, ni:cl- shoi'red- a :igir 'l evel fcr laie June, fo11ol.:ec1 by a steady decl-lne to 3e'",f,s'rfsr, a-nd a res::rgence:rt tj:e encl of the season. The ratte:':r of varj-aiio:t i-n I.). fc:1977 reserabled in este::iial-s fl:at of l-976 r^*!^cr l-?.nn 'lC?tr vleLt J: I ). I:r tt:e ,.ighi ],:ift (fiS. 2j) U.,e v:=iatlon peiiert tl:'.t ci L:74, i';itlr '-t'.'.r:be..:s i-r:ier.r:ec1i.rte' betveer- tirt ci of I.D, for L977 r.ese:rbIei '-. ; ] 3]](: -l-:' ii r; r '-\ +^ -6- -,-; 4+ | nl .. c, ) . - -* u \--ru. -.,., in I o77 i'ips in'be:;.ci.:-:'.tc l.'et'.'ecli t::i.t tl:e '.::itellir of vr.tiatio: bore nc::e s.::i-]-:-rii;' to ti-.:.'l; I':ift / ^. ^- \ .1i:;. ?5) o: 1.177 also sl ,o',-I:r a seq'-r.c:rc" o: v::iltioi" sl''j.-l-1":' l:e.re-r-s.ce:re:al-1;-belov thai of L?75t:1i-i aitove tj:it of \176, .\ --i/ -ren]-ntre.-14 Ir ti:e ia,;r I)r-ff, (trg. 26,\ 197, irad, an f.i). fron .inne to.'-r,r;,,i:t i-,,hich -,;as 3r'ea.t1;' in exccss of that recc:d.ed fc: ti:e ilo nreviou"s lreais. lror the resi of ti:.e seascn, the pattel.:: cf vr.r.ia.tion it 1977 :'esenbled flrat sho',vn il 1976, :;i:en there was a steacl.J. c'.cclilc j-n I.I., though'uiiere 1'ras a sligirt resuxcenee in coth lioverber 1-975r and -,ovenbe,r 1977. fn t;:e l]i3i:t tl:ift (tiC. Z7), ti:e I.D. of lgTT rzas ;reaier at the start of the see"son tL",an ihat of 1976 e:ri. less thar: ti:at of 1975. A Io,,yer reaciinS in July fo11o;ed., ti:o:i5i,:. less pronounced tha.n in the tr;ro nretlctis;-e:l:s, r.l:ct in L975 an ' 1977 i;he na;:j.niui :eacii-::; of ihe season ',i'a.s lreeori.ed. ir: iugusi/iepte::be:. T-rj.s i-s j-n coi:t:ast to L976, r.lheii -Ie:;-:\tere.';iere absei:t fro;: fl1e :-iJl:i iz,ifi i:-.:in3 these :rontl:s. Ilead.iq;s jor the enct of ihe se3-son in 1977:.ese:rblei- tjrat of 1976, nore tl:ai: il::.t of )-975. oi o: rn t.:e -.!;::t .-,r:ft (:i:. 29) t:lc ve:iation il r.). jc:: -r--77 s):-,':s ,l:e- 1!r: ai-'i'ratj+"'^ +'t:.t of .l-:76 t:ra:: t:'?"t o! 1.i7->, i.'-ol;;-'::,r:-:''i; flc:: t--c l:itl.-se.sonr4 liqr ,- uu vu u- l :.:ii:inii:: rn -"-u'--:.st, i--c ]-cvcl- ',-lcs co::si:i;e:rtr;' ,::er.trr ;':.:: t-::.i ci c::i:rci of ii:c' ?.i6^6a,.ri I rr.' a6^ 1--F ::)'lc,i-".1. :.r:'::r. !1:e I'a,-- -)rift (li:. lc) s-oJs a -;ai;er:: of v:.:j:.tio;::'o:c or -'l-cs; si: i-1:.:. in all tl::ee ::cars l:::cl.c:: co:rsidcrl.iicr. I-o,;'everr i-'e ::rr:bc:.s in-rc-l.vcr. :-:: 1177 :re 1or,'er t,:an ihose oj 1975 e:-:.]- 1976 in e11 ncntl:s e:cept,fr-i.3-;'. i:: tl:c -.i;hi ..riit (ij-,:'. lf ) ti:e ',ra-r'ia;ion of f.n. i: \977 s.:o',is a ;rec.te: F.i *'i'i -,hi +r, +.1 +t.!ar-:r(,!au! er, ',:a.-b cf 1!76 il:a:1j75, c.::cl ,;.'itl: the e::cepiion oj the start of the season, is nore or less ir:tei.neciic.ie befi'leen tnat of L975 ai:c1 1976. is in a975, no::e of ;i:e tiu,:a r.or-r-tinelJ' recori.ed in 197I have been elininated fron the fanna, ilesrite occaslcn:.r abserecc dlu'1nc the se:so:: of ilo;. The o'rei.arl- inr:ressi-o:: is'il-:t i: i9?7 the fauna follor;ed a regi-ne of fluctr,:_ :rti-:rs of ntr-:.i:e:s rrrore'ti-;q f,lr:i ob:ervec ir: iiTS i-:-:r fl::.'; iT: i!75, cics-_+te ti:e :';:"-ier l-ever a.::r'. iiscl::.:3e =a.ie s of 7!7j a:cl. i!77 bci::,: :.:c:e l-il:e c:.clr othcr ttian ;::r.i cf L976. ]i:-z'ir:3 tlj-s ij;;1e il:c I.r--'. fc: r-rr.::;- liroujs','.'as at a 1eve.L irter- :nc. tl:.e fi"rst ;rer.r c: '1:.rylci.;ita; ;iilt --ibitie, L975" l-i:'.': -. ::.r-rs i', .c t-':c :r---;c: l-:-.-el ',i:,r '5cc lla.bl-e 2 i'-,ri,cl la::'rl.cs. . -en'-" lg::ritjl:..'i l-]Ji 24th -"o.rc::ber r:(,vu a-:9 u , i ):l-ie::croltc:a Cl-i:'onoi-.ic',ae 1l i -:,r-rl- icj_ae --e:iptcre" /.ri ana rn Ian;'poCinae Ce'l eoptera ..c3.filla. ?riehoptera Total- (a11 ari.::r.-'-s ) .)rt.Jo., +.-: t.t2 -', -' t -'. -:- 1i4 o t'r* ai!. Co a^^ ^^occ.al 0 -da -a!-i [.lO -, vt-.-. vJ ^,- a. - - ''-'r o'- i "ri Ia.blc 7 }-,rb er" lqItl:..-.e s .- Iga. -r -r e n s j .-..-/n2 I 9 76 June '1 0a ', *- !- a T - l,"r9.' , , - - / . -t2 .a aa .-Lo'-.- =a)D o'r'r -a ^^j)O r L3 LrCt;1..25 c2 224\-a 4c I o* \a4.425 7 ()ocl rAt ,2 - J' .iir !, L, ./.+ r-). ) acU.U ^aa *e . a n + L'O. C nrD .) 'l'l !: r ,-' ? ..7 .7 .O.D Qotl I, a\ Ir ! ( aln'rrr,r- c.UO. U ?ra c. C :/.- o - ','i .', otrc c 'l Oa). a:t/uL.v +ri77.= JC)+ . - 6-,a,.(, 7i^', ( ca^ <.': ^ t -.- -. '-) ,o I 1.r71:.i -, i -J.- -9- i.re.ble 4 l,-rr.be: T:i.rnles, llea:r lensitl'/':'l 1!77 Stai't Ju.ne -:ni .Iune 0ctober o-relrber I I a anA.r-,6+.1v4!br --chercrc;ter.a Ci:i-:'or:o:.id a.e SinL:,liiae :ieniptera ldonata lan;'pociinae Coleoptera -ealina !richoptera ?otaI faff anina,fs) 1n .7 c7\ i)oi, a(}UrU o -^L'O 1n .-,J-l.l L(. t ,c5.6 ^r\^ ^L' !7U. U -L, )V,',_ . -: ijoO 1tD .4'.'L . .- o ^6CroC) ,4?O O 2r=71.1 0 :"!o a o 44.4 ??o o t in ^!t!.-.i 1 't'lc c *, L-- . r rAl-,,t;i'-'.- 0 ^-C.o(1 0 ''l'I tr [LL). - ".t55,5 l-, 119 . g C 0 .CL'o U r.j oa oo o 0 0 o.o a a.JA ta-, -VLi. Li q,? ? =t1617.7 {r)02.7 !1re57.e As noted fo:'ihe lrift Sar.'p.lss, no taxon iras been efimi-nateci that r,vas ror,.tine1.r' recorclecl in previ-or-rs years. If one eoi:'rares ,,heA/* of the total fauna for tire ti:ree J'ears und.er corisid.era.iion, it eer: be seen thai the fiSu:re foy 1977 is il:-gher tira.n iira.t for 1975, vririetr rs 1n t'-:-rrr higher tl; th:.t fcr l9li. Tab_'l-e 5 i1 of lotal la.una lnhenc:.:onte:a, Frie':ontez.: _ Ci:1:cno:ridae i.'l,o 1977 t976 ..r-:' / / .rl11.o o.77 a '7'7 1c)7.< ' 'r C)7? -_ Lv . L_'i I ,'- ^-- ' -- -:L:. !._' . ):: . :: . /oo -;r r'l -. 1a aa) ' .1 :-^ --(-a - - '.-.a- - 't - ^.1 o? "qOAA'-rr-.ro+- 'v{J "'v u l:tr? 7a 'iJ-a/- ^ctobc: a!':l.':,Cr . l/r-.--. i r 7," .-. ) -10- .'io-,','e'rer, tabl-e 5 iil-u;l:c.tes ic','r ii:e r:opo:'tiori of -'.ue;.ez'o--be:a, T:1c--orie:i: end Ulliro:ro:'r,r]"ae i_:r tlrc tcti.r fa.li'::r-, i:.ave ch:.r:5ed f:'o:.t 1i75 to \:77. ,lcjor-u: r.:-d !ro'-t--,e.'i; (flZO) sta.te tlrei i:-r tiie :.ive:s ':.rc;- str;diect il:e.- four-rd tirat C,'i-:o:^,oni-i].ae ,-ier': lecs se::si1;ive 'bo il:e e:lfeci;s of --irzte il.a.n i:i- cr-,opte:'i., a:d 1:'iei:opie:a ,.rerc 1e $n ::e::sitive l-;re.:" rl.r-:ele:.o1-.ie:::.. :-,abl e 5 irAiac{-n^ rl'"'- ihe orono:i--olt o-3 C^-_ilonc: i-r-rr_,e i:: i,:c lc,;i,_l_ 1:"n.:,. ';ra.s -.rrlci: ;::e:ie.: it a?77 tl-'.li: in -1-975. T,re rorce'ria;;c cf .}l.e::e:opte-r-a l-.ccreasc:]., r','l-:i-'te the perce::tage of }'icito;tera j-nc:.ec.secL siighi1;; in 1977. '-hes: ii;i:::es inc:-ie:.ie tirat l-rl:il-e ihe-re hn.s]:een no -#ilclesate d.estruetive effect ot". rltc far:.n:,r rl a result of ,',ba.te treatrneitt, ii,re:'e h:,:.s bee:: a cl-istinct 'r':ol"lutionrrefieet, as ii-ie ehe.n3in3 :ropor-bic:s of ti:e vr::io'-r.s col:;one:jis of the f:.1:::. il--l.r:ist:a.ie. S.!-:?IERX lesu-Lts a.nci ehFe::r';tj,gns This netl:ocl ','ra"s noi ver';r- su:ceessfully r:tilisefl iir l9TT. rn -r:u5,-1st Septerber tl:e vaier l.evel vas too i:i5h for the bl-ocl:s to be ::eaei.ec]- in ai-'d in cctobe:' tne aliar:.tue; rve.s ]ou-ld to hzve bee;: vance.-, i:ecr- a.rd h.a.c re-set. labl-e 5 3i.'res -hl:e ::esn.'-;s obt:inerl b.,, firis refl:od. Ir.bi-e C Cone.lpte llce :: ij::':rie::s Tcial ?e.u::-. 5rln2 1 a7A :_ li u:ine C aa\ . 'l'a\.lr,i,\.) rt i ^-,^ -J-_r O -,-L a!: ?i "). I . - ^ .71 ^, -a ', t-' . " . -ethod. a::ri safet;.-, io be l',;cl'i- a rn, _. . lt .-1 -'I o-'- ' a <41 ^"c''-t'u-r - g fn eontrast to tj:e Surber sa;rples, thi.s method shovs a d.ecreas e ::nT./nZ for 1977 corpa::ed. I'rith t-':at of 1975r though botl: ye:rs shoved greater ;ropulation d.ensities rn iiovenber ti:an e::rli-er in the season. ,.\X I.IF iC Uri SI.RS I-1r!-TE- - -I ts[.Ai, 3-{S,'OT SA] PIil? S Resul-ts arcl observations_ Ihe results obtained by tiris rneti:od are given in Iable 7. table Z IGtal Baskei Sa:o1es. nunbers of ani.rrals oslret 0ligoehaeta August:Start: End a976 :Sept.76: Sept.76 : --- : -------O:O:0 .iove:rb. 7976 z o,J t Ephemeroptera Chirononid.ae Dl-mu].ld.ae Heniptera Od.onata Tan;rpodlr:ae " Coleoptera Hyd.racarina Trlehoptera totar(au a,.i.a1i '.trt47.5 ; F si-rnuliclae of total i" ; rez : 71 z-29.5 i ztt I tis :0:0 : o , o', :72.525 :o3o :: :1:O : 455.5 . 916 : FS"5 : 14.8 IIov. ]-975 7) B6 366 o o 2.5 0 7tr 57 o.5 7.5 \1,5 0 o 1 17.5 1 1 42.5 544.5 58,5 B1 _t1 33,5 t gg.l U o B o o 58.5 2]-3 46.2- October: 1976 | --.--- : A'/. g8.5 , A, .74 : o: o 23.5 : 0 : 5.5 z -.- - 2)+r.> i :: :117. ' 897.5 : .0: , o''; :1: ; 5.o; :o: a. ;25; '. 579, ro+ 823 g.g . 66.7 o : June I tg77 -12- Table 7 continued. July !977 Septenber l-977 : Cctober z L977 : -------- '4a ,rc o 0 o 76 0 5 471 656 0.9 llovsiber' __!?::__ 1 35 t38 3 o U o 0 69 6l.2 eB7 z 4.33 : Ar4;ust z \977 0ligochaeta Epheneroptera Chirononidae Simulid.ae ileniptera Od.onata Tanypod.inae Coleoptera HJdracarina lrichoptera total (afl- aninrals )t dl)a Sl-mulLdae of total z2 'qL ,rcA i ,.zlo ,r :r .20 a :0 'l-1].23, :Lr42B. . 7O ' )aL ' 323 2r028, 0 4 47 1 0 o t4 (., 1 652 o 25 39 o 0 ,7 / 0 o 241 o 't a'l 55i 569 U o 54 0 6 904 722 o.Ij : : 2.47 28.A The samplir:g effort available by thls qethott !-i?,s halved Ln 1977 by the -) theft of one of the netal baskets, soon after their installation at the begin4ing of the season. Despite the inaceuracies lnherent ln thls method, sueh as the impossibilityof relatirr& .'. nunbers of animals collected to a }::onn unit area, and its recognized. underesti-uatlon in sarnpllng, the results fron this nethod. illustrate certain interesting features. ' (ne;oux a.nd venard (tgll) state that t5.6 /" of animnls fot-:.nd. in these sa^up1ez's renain in the interstices of the lateri-te bloelrs vriren -breated, i'rith the acid ,/ fo:matin . m:ixture, ratirer than einerge to be solleciecl.). ff one cc''rllr.res the total- lrumbe::s per sa-n1:l-er fo: t-:re nonti:.s of llovenber for 19751 1976 and. 1977t ti:e fauna is seen to have increased. ratl:er than dinlnished. The tota-] nu:bers per saripler are, rzith tire exceptlon of JuISr s1d Cetoberr h:;her in l-977 ti:an in 1975,',v}icir i-nd.icates a5ain tl:at the ToiaL fairna 1ia.s r:itc]-er8one ito drastic c]:anges during tj-re tvo J,ears of treatnent. _L3 _ Ilovreverl the percentage ofsinnllldaeof the Iotal nunber of ani:nals per basket sar,rpler, was notieeably less in 1977 tban in 1976. The only dlscrepaney in this sequence oeeured. in Septenber l9TTr vrhen the pereentaCe of Slsulidae in the Total fa.una rose to zB lt after being on)-y 2,4'l i in .trg;ustrand c.9 l, in cctober. The Y.c.u. Ii6nthly Report for the ouagadougou seetor, septenb er L977, states that d.ue to a na.L-estjs-r"t'ion of the ar:cunt of inseeticidc i:ced.ed to treat the Red Volta with its rapidl;' falling lvater 1eve1 in tirat nonti:., ceriaj.n breeclirrg sites escaped f,reatrrent. Consecluently, 575 ad,ult Simulir:re d.a:nosr:ra I'rere collected fron the sub-seetors of Ouagadoqgou, leo, and Tenlodogo (tvithout including the region East of Fad.a I'ItGourma) ln Septenber. In contrast to this, 71 adult S.. d.annosr..m trere collected 1n alL the sub-sectors in the previous nonth, August 1977, and. only 12 adult flies caught in al-l the sub-sectors in Septenber L976. '-'rlsor the high percentage of parous flies 1n the septenber 197T captures :indicate- il:a.t theywerethe result of .1oeal breedlng, e consequence of recent I-larvicitiirlg control failure._ __ _.. __. :crc:,irsrotB Table 8 gives seasons of flon for ihe Annual llean of Sa.nples for the ied Yolta, d.',:ring the 1975, 1976 and. L977. table g Anlual lle:.ns Total I) Day ll lt :Ti_t-r -.rLrr U D,/::t suber(a11 sa::ples for ti:.e ;,e:.r) n/.2 turber --o'1. "u.rao1"u or] " .rrz'n' Co:-erete llocl:s arJ-1 sarples for t-:e ;,ear D,/n': Ccne:eie 31ocl:s -.'or. . salpr es _ o::Iy 1 C)?tr1)t) 3.667 25.436 L8rBAe.24i '7 C]00 ! €.t rJ)J.aw o 0 l-979 o o1 04. L:9 'l ? ac\oL). - vL 2r 4'63.66 Br7i6.g 779.i71 a 1'ta na *, I r-*. l4 : 1a.7.7 =i-i-L2 : l.Bo5 . 15.844 A oaz ^'cd.1raL).J)U : ljra57.61 576.202 :l-, 551.gJt lable 3 continuecl 1 07q 58.5 '^'7e 587.25 t?77 1 r\n? ?:!-r\Jvl.))Aninal-s1/b::l:et ,'.11 sa::31es for the ;'e:r -/.1!:11-nal-s,/ oa3-:cf ITov, sa-lples on1;r It ean be seen that while the oean IoD. for Day Drift ls slightly lower each successive yearr the mean I.D. for the llight Drift for 1976 is markedly Lower thaa that for 1975. Howeverl the figure for 1977 is higher than that of the preceding $€&?r The same sort of difference between 1976 antl Lg77 can be seen in tU,e i/nz of animals found by Surber samplingl whether all the samples taken throughout the year or oal-y those taken in November are eonslderedr and lt ts also observable ln the results from the Basket samplers. This wouldt tniileate tiiat in 1975 the rlver system at ?6 Brirlgel when compared w'iti L975t was subject to some adverse infLuence, presr:mabIy larvtclding o? Sr cle.n4sElla with Abate. Iloweverr'the flgbres "for L977 show that the far:na at this site has recovered sonewhatl whtch would suggest that_ the effeets of thls ad.verse -influence are not necessariLy cumulative. Incleedr the resuLts from the lfleta1 Basket samplers wou]-d. inclicate that the Abate treatment was having lnore or Less ths clesired. effect, in that the populatlon of Slmulildae was being greatl-y reduced, without causLng tlrastic alteratlons tn the compositlon of the non-target fauna. [hts phenomenon has a]-so been noted. la the ORSTO},[ annual report 1977 on monitoring. the rivers studied by them in fvory Coast, As rzas cbcerved in previous Annual -lelorts or:. ti:.e Red. Vo] ia, anC is il-l-ustrater in fiSrues {', 51 6t 7r B and !, t,:e Reci Volta at P6 3rid.3e is su-bject to rapicl ehanges j-t:'',;ater leve-]- aud Disci:erge rates tlrrougltout the see.son of f1or.,,. The fiStrres 4 - 9 shor clearl;- tiret tire vrater 1cvels and Discharge raies of :igTS and 1977',','eie sore 11!:e eaeh otirer than those of 1976. These changes are bound to exert ar irfluenee on tire fauna, lrrespective of tl:e larvicidirg treatlent. ' qLP' q ' oon . J-9.) . uU, t-te ff one c::lresces the st:-te of the fa'.rna cf iire :i','or at c:.ci: soason b7 fornula : ilea:: the results are as foL-:-ors '1 .,7tr :;u- I - ffi L975 5 =ffi 7977 I'6 =ffi )aJ, Index of Dfift ctr A7A .#J! ,.oO 1 li.9a3 2.314 r_6..qI.4 1.805 6.936 4.962 9.316 . As the 0.:1,.S.T.0,I.1. lgnirobiologists state, llight Drift ls considered to be the resuLt of natl-rra1 bloLogical aetivlty i.n the fauna, whereas Da;'Drift is consid,ered to consist of anar:als i-njured or displaced ln some fasi:i-on (lhaunatic Xritt). The higher the rati.o gLven by the -formu1a, the nore the :.rlver systen under conslderatlon ls eonsld.ered in a stable sittration. Ilnat the figrrre for 1976 is l-ower than that for 19?5 is to be expected. as a resultrof gre Abate treatreent. t'lr" hlgher figure for 1977 would suggest that d.espite the general reduction ln the trb,una, the river systen, at least at the polnt under study, is re-establlsirlr:g an equilibrium, rather than being successi.vely reduced. Ilowever, lf one conslders the Day and l{ight Drift for each year separately, tal:ing the results for 1975 as the t'norinaltr or untreated state of the river (i.". rcA i), one obtains flre folJ-oring figr.lres : Df t976 is 76,84 :0, iil tgr6 is j4.97, i m L97T is 66.22 f, Tirese fi.gures a5ain indic:rte that rvhile tl:e Abate trenb:ent certeinly had. a severe effect on ti:e faui:a, this effeet does not appear to be c'*rmlative, and the fauna is .lrobabI,v ir tire process of estabLisirinc a new, albeit 1or:rer, equilibrir.r,n, in whlch all tire nain eomponents of the faui:a have surviyed. It is interesting to note that in 1977 both Chi-rononid.ae and lbichoptera formed a bi3ger percentage of the total fauna than in L976, rzith Spheneroptera slightly redueed and. Si:n:I.iidac greatly recluced. Oring to the rapld life c;rcle . of Chironom:i.d.ae, this group tends to be a ready colonizer. Its presence as a large pereentage of the total fauna can therefore be talcen as evid.enee of pollution, ir: thls case b;, Abate, In contrast, Trichoptera are generally consid.ered t?.b: rather sensitive - !o lnsecticidal- {mpactl and the inereased numbers in the surber sa;rpIes of t977t con;rared with Jliose of l-976 -sr4gest that the pollution effect tras not too extrene. The pereentage of fuhe:reroptera 1n tlre tp_laL fauna in 1:977 was slightly --'Lower than that of 19761 but in the latter Dart of the season 'the number lncreased. ln the Slgirt lrift to le.rels higher than ln tgl6. [he proportion and ntlabers of Si.nulilclae eontinued to clecline in 1922. '. Only di:ring Septeraber did they occur in large numbers in the Sasket Samples. ...At that tiae they comprlsed, 28 fi of the total sanpled fauna (see Sable T). [hls eruption coincideC rzitir tire suspersion of treatnent in the area rvj:ich resulted in the re-establisluent of breeding S. aders-i..and S. da:ru:osun In t}:,e couroe of stud,;"ir:g the Drift sanples of 1977t in aCdition to gre invertebrate fauna, the sanples for Iarly June, Late June and. JuJ;'rere observed to eontain nary: alevins (fis:r i:atciJi.ngs). fn the Drift sanples for Oetoberr many sma1I adult fisi: vrere found. These observatlons wouId. sl4gest that 11re effect of Ab.:.t: tree.tneni on the fish fauna of the Red Volta at p6 Bridge nas not of a grossf ,l deleterious nature.J lt+ )ejoer:r--1.or-rbet (:.:Ze) fou:rd. iron the-'",'or': o:1 tire litXr t',at t-:e i.:r-nedirte effect of ^-bate ap21-icaiion l'/as a red.uction oi ti:e fa'-rrra by 2O-iC ,',. It iras boen statei earrier (olino::1976) ti:at tire I.D. of tire pre-tre:tne:rt fc.;na of the i?ed Volta i'ras nuclt Io',-rerbhan ih:.t fo'-tnd. for rivers::r the lvor;' Coast. iior'rever, the Red. Volta is nct a lepxanent stleprn, and indeeC at ?6 3rldge is eon;J_etly d.r; fro:c about the enC of i[ovenber to the beginr:in5 of June ever;, j'ear. Suci: a natural rrcatastrophie[ effect of vrater regine, plus the ptqrs;caI effects of ' the rapicl and. violeni flttctuati.ons of water leve] anC d.isctrarge woulC tend to produce a farma less rj.eh and. varj-ed than the lor-Iand. rivers wj-th tireir less variable water regimes, such as those str^die{ in Ghana and the Ivor;r Coast. fhis rrTenporary. Strgamrr effect, wouldn it is s,.ggested, tenda to obscr.re sone.,yhat the --- --d,etails of tire effects of Abate on the inrertebrate fauna. l{everti:e1ess, it wou'l d appear froa the results obtained fron P6 Brifue o'rer the three years eonsidered, ti:at while the Abate treatment has had-1ts d.esired. effect in greatly red.ucirg Si-utilir:n breedlng, it t r" had., as io"""""r, a detrjaental effeet on the non-target fa',rna, Holrutu=, tl,is tietrinentat effect appears not to be cu:aulative, and on the evid.enee so far avaiLable, the river fauna appears to be establishi::g a new, if lorver, equilibrlun. -18- SUTIi]AXY 1) After tvro years of treatment of the Red Volta at Pd 3ridge lvith Abate insecticj-de, aI"l ti:e i-nportant conponents of the fauna vdrich lyere recorded in the pre-treatnent period. (tgll) a.re sti11 pz.esent. 2) There is an indication that population levels of inverteb::aies rvere higher in tlre second year of treatrcent (tgll) than in Lg76, r-ihlch su56ests that a new equilibrir.rm is being attained.. 1) Abate treatments appeer to irave reduced the invertebrate fauna by as mueb as one third. Ilovrever, there are narked natural fructuations in populati.on densitles, by month and by year. These probably arrive na-inIy as a result of differing flow regimes (weIl illustrated by Figs 4-9) so that categorlcal statements eoneernlng a sole cause of the diminution of the faunal density t/ -teter-enees cuptea Iejoux ar:.d Tror.rbat (WleY Connarq.tive Ioxicit3- of ttro 0r6ano-phosphorus fnseetlciCes for ti:e non-target aquatic fauna in a tropical environnent. O.n.S.T;O.i,i. itsport lio 1 (in :n6fish) 15tfr June 1926. )ejorur and Venard. (fgZO) Effieacitd conparde d.e deux types d.e substituts artificiels Rapport 0.R.S.[.0.1.I. lio J Y.C.U. i,ionthly leportl Cuagaclougou seetor - Septenber tgTT O.R.S.T.O.I[. Convention ORSICI.|-0IJS. Sr.rveillance du rlilieu aquatique Rapport An::ue1 d.rActivitis 1977 O.R.S-T.O.I',I. Conventj.on ORSTOI.i/OIS. Sunreillance d.u mil-leu aquati-que Aquatic l,lonitoring Programne, Ouagadougour Upper Volta. 7/ Aquatic f,ionitorlng Programre, Ouagailougou, Upper Volta. Retl. Volta, Annua1 Report 1976. .' 2/ 3/ 4/ 5/ 6/ Frg. I DAY TEMPERAIURE ? TqliiJ,i 6 ,75 ,76 '7? trr't I I I It/t/r/t/t/tfrl\ll '.J I \ t * El""'.'..... Seplembcr Oclobcr NovembcrJul yJunc Fig. 2 NIGHI IEMPERAIURE ? TFlii6*tr .75 '76 '7? \l\\ \ \ A I Iitil il il \ \ \ tr August 5eptcmbcf Ogtobcr Novcmbcr DccemberJrr ly - CrnS.2 u .9 ! s, U o Ul o A rrl Fi9. 3 TRANSPARENCY OF WATER SECCHI ?ilr6* t75 '76 DISC REAOINGS l-J : i rII:J ,77 21 23 2t 20 ..x ".ttrt I I I I I I I I I I I I I I I I ,rl x r8 t7 r3 l2 x\\ ..\ ..\ ..\ i.\ Er..""\X- July Aug us I Seprember October Novembcr Deccmber UI o tE 3.0 .= E oq ?t ct Fig. 4 RED VOLTA I975 RIVER LEVEL t saMPLTNG DA IES 5 Seprember November December Fig. 5 REO VOLTA I976 River Lcvel A'l Sompling dolos x t I\ I \ I 1{\ v x l t lr. ll f 'r I II \ I lrI k ,x ,\t .l \ ;>, \i ,' \r x \lX f \r ,'\ i xi *-/ I I I x x x.ixixx x)( DecemberNovemberO cl oberSeplemberAugusiJuly Fig. 6 vo LTA 1977 LEVE L SAMPLIN G DATES RED RIVER t l, r, t, E .5 3.0 3 o. oa Et e tg I :tb e Et J uly Augusl O c lober November December 0l,l E o or o .c U t4o t00 .900 800 700 500 400 ln.0 7. 6. 5. 4.0 t.0 0.9 0.8 0.7 0.6 0.5 0. Fig.7 RED VOLTA I975 DISCHAR6E READINGS J unc Augusi September October Novcmber December Fig. t RED VOLTA I976 DISC HAFGE REAOINGS x ix tf I I T I l I I l I I I I I I t I I I I I I xt t I I I I t I I t I )< I I x I I I I IIt }{ \ t Il/rltlt, \! \i x T l1It ,tt\lr ,\ I I I T-T r3. 12 lt.0 I 8.0 t-o 6.0 5.0 1.0 .s 2.0 l.o 0.9 0.8 0.? * t I I I I I t NovembcrScptember' O ctoberA ugustJutyJune u{,l/l E (, E'i o ! Uu o d o ra E t o ol o E t, la 6 00 90 80 70 50 Fig. 9 RE D VOLTA DI S C HARGE 1977 READINGS q q h tr .tr "tr ri t.o OE o.? '0- 0.5 0. 0.3 ? : tr September Dec e mber F;9. I o OLIGOCHAETA Doy Drift 9xtrlltd *6 '75 '.76 ',77 t.0 u-9 OE 0-7 0.6 0.5 0.4 0.3 0.08 0.07 0.06 005 0.04 =ct E 0o2 x a,I't I 0'01 0 F.. rIt NovemberSeptcmberX August Fig. I I OLIGOCHAEIA Night Drifl ? T?5 *tr ,75 ,76 ,77 0.09 0.08 0.0 7 -0.0 6 August - ScPtcmber ,- 0ctober -Novembertro Fig. l2 CHIRONOMIDAE so 6.0 7.0 6.0 5.0 Doy Drif I ? TqlliJ itr '75 '76 ',77 0.8 0.7 0.6 0. tr 0.3 0.2 cl \ "..\\\\z \. ., x \:\..\:\\\\\ v4,/\a\ \\\ \\ \ \\ \ x NovemberSeplcmber OcloberAug6l =ct o xtt! c 70 50 50 10 90 60 70 5 5 10 t,0 0,9 0.E . 0,7 0,6 - 0.5 0'1 x" ,75 F,9. 13 CHIRONOMIDAE Nighl Drill xtrt:l: t: *,tr ,76 '77 AugrrSt Septembcr O ct ober Norcmber Ftg 11 SIMULIDAE Doy Driltxtrt. tr '77 x ,76 o I '75 t.0 0.t 0.8 0.7 ti3 0.5 tr s: \ ix:\ ?\r ,\ I I '0.3 :'c TC 'i,.i 0.1 I 0.06 o.07 0.0 6 0.0 5 0.0 r 0.009 0.00E 0.007 o.006 o.00 o.00 s 0.04 o x 0.03|l, 1' I I I I I I I I I I I I I Ix: O ctober tr -----x N ovember o 0ecemberSeplemLerAuQu s tJu ty ,1" \ Itl/t/t/ l/rl x F : :tr ,7? r5F,g. SIMULIDAE Night Dr ?rltli ,7 5 '?6 \ \\\\\\ ,\\ & :\i\ :\ Octobcr Nov€mbertrSeptemberAugusi ' 0.9 0.8 ra 0.6 G d:8 e' Q; UI a'c fr' ct b 0.02 x ru ! 0.0 0. 0.06 0. o.ot 0.0t 0.009 0 0.00 0.006 0.005 0.0 0 Fig. l6 EPHEMEROPTERA Doy Drif t ? Tqll:lriJ *6 '75 '.76 ,77 \ \\ '.0 0.8 0.7 0.6 0'5 0'1 0.1 0.09 0.0 8 0.07 0-0 6 0-0 5 0'0 4 \ \ \ \ \ \..\j T!x tr 0'3 =tl o o'2 x a,I' s November x \ September October Fi9, EPHEMEROPTERA Nighi Drif I ?TPll:6 *6 '75 '.76 '?7 70 60 50 40 8.0 7.0 6. 5.0 o x € 2'o c r.0 0'9 0.8 0.7 0.6 0.5 0.1 \\\ -x \ \i.1.0 =o 3.0 \ \ lt. \u I t \\\l \\ \\ \\ \\ \\ NovcmbcrSeptembr OctoberAugrrslJuty t8F,9. IRIC HOPTERA Doy Drilt e rFliilr:t,ttr)75 ,76 ,77 .tr.. '02 0 007 005 005 001 o 009 0 008 0 007 0 006 o 005 0 004 ?T I I t \\\\\\ It I I I I I I I I \x- _\ o * o02 o x o1' c x I { I I I I I x NovemberSepiember OctobcrAuguslJulyJ unc Fig. 19 T RICHOPIEFA Nighl Drilt T I?litr ,75 '76 '?7 q I I I ot 0 lttii/l,t,t,t,t, \i u o ;02 009 00 oo7 005 004 003 x o! c irovem berSepiember ' OctobcrAugustJ ulyJ un€ Fig. zo ODONATA Doy Drif I*----- f iPI itr ,75 '.76 '77 '07 '06 \1 l't\ \ \ '01 E'oa6 '0t '009 '0 08 '007 'boe "'005 ,004 '0 03 t/ttl 0 *'0It! c Itrl:tj l:I fi :l ;l :liljr :l;r:l I IIII IIII -* Seplember Oclobertrtr Novemtrr 9.0 8.0 7.0 6'0 5.0 1.0 3.0 .; ct - 0,2 o x a,E c I.0 0.- 0,7 0.5 0,s 0.1 0.3 0.1 .09 '08 '07 '06 .05 '04 .03 F,9. z l ODONATA Night Drif I I rtrlli6 *tr '75 ,76 ,77 .E x Y JulY Auguil Seplember Octobar November Fig. 22 IANYPO D I NAE Doy Drift 70. 0. 0. T T?Jitr ,75 46 ,7? .tr ,}i 'qii il \ x t I \ t t \ 1 \ \ I I t \\ \\ \\ I I I I I t I I o o.oz o x o! s oroo Augusl 'Seplcmberr Oclobcr, ! November 7. Fig. 23 IANYPODINAE Night Drift?TFlti6 t6 ,?5 ,76 ,17 6 5. I I , I I I I I I I I 0. 0.i o.l ct Eo x o! s ---x tr \. "q 0. o0 0. Septcmbcr' O clober Novembcr ' December 21Fig. COLEOPTERA Doy Drif t TT?Ii tr ,75 t?6 ,77 \:\:\:\:\:\ ;\:\ E o,o2o o x oT' \ x I t I I I I t I I I I I I I I I I I I I I I 0.009 0.008 0.o07 x IrIrit ,l ,t l1 I x'.. /\ '. .ji\ ii /\i\i\/r/r/\ ,\/\ ,llt! Septcmber' Octobcr I NovemberAugustJuty r0. -9. 8.0 ?.0 Fig. 25 C O LEOPTERA t DriftTtr *ti '7 6 ,77 6. 5. Nigh I ,?5 1 3. ,2. I l'..;t\BI \I Itl 0. 0,6 0.09 0.08 0.0 7 c.06 .o.ot 0.04 0.03 ct 0.2 o \rI I I I I I I I I I I I I I I I I :tr x I I I I I x ""-El' \ I \ I I t 1 t \ I 1 \ \ \ \ t \ NovcmberSeDlcmbcr' OctobcrAug ustJuty x ov s Doy9rliA,l t? 5 ,76 Dri ft B tr ,?? t.0 I 0. 0.7 Ip.{ 0.t ('0- 0.1 a'o -l €'0;3 J'C- 8.f- a 0.2 I i I p 0.( 0,07 0.06 0.05 ' ooo2 xoE c rl t t t I I I I t t I I I I I I Ix. \".1". \1 \ \ I \ I O c iober tr o Fig. 26 HEMIPIERA July A ug usl September November r0.0 . r8. 8. 7.0 d.i F'(,.27 H EMIPTERA5.0 f{,. tr tr '77 Night Drirt PTltl,l '75 ,7 6 1, 0.08 0.o7 ,tr l(------x I I I ! t o.z x o! s r0.0 -o.o o,01 0.03 Sep?ember' October I November x Fig. 2E HYDRACARINA Doy Drilt 0.9 0.E 0.7 0.07 0.06 0.0 0. 0J) 0.008 0.007 0.006 0.oo a 0.004 TI?J *trt75 t76 ,77 ti t't"./r. ,li\/\/\ ,\/\x\ \\\\\\\\tI x- = 0.03 c! o x 0.02o! s Scptcmber' October' NovembcrAugrrst Fig. 29 H YORA CARI NA tti9ht Drilt ? iElliItid*rI ,75 t?6 t?? t. _.8 0.7 0-6 o 0.2 o x ot _c 0.09 0.08 o.o1 .0.05 to.o5 J 0.0 4 0.0 3 NovemberSeplember t oc lobcrAug us I \ I \ \ \ t \ \ \ \ t tr"' Fig. 30 IOIAL ALL ANIMALS Doy Drift 9 80. ?0, 'o I T?t itr '75 ,76 t77 ..0 7.0 6.0 5.0 c! z. o x t,T' C r.0 0.9 0.t 0.': ? , 0.5{ 0.1 NovembcrScptcmber OctoberAugustJuly Fig. I OTAL ALL AN IMALS 50 lro Niglrl Drilt?T?lit5*6 .7 5 ,76 '?7I 2 : f ,8 70 60 50 LC 2 ct o x a,! s 9 I 7 5 5 1 N ovcm b crAvgust September