Annual report on activities-1985, western extension: entomological monitoring (summary)

#> wP/YCU/HYBIa/86.9 ORIGINAI 3 IBEI{CH aNNUAT REPffiT 0N ACTTTrIrIUS _ 1g85 WESIINN EXI'I.;NSTON (xa, urouaRD) T.;I\]I|OUOIffi ICAL },IOI{ITCR IIG(Sumary) (*A t\t ^.i tL- I. [he entomological monitorj.rg in the Western Extensj.on area of the Onchocercia-sis Control ltograuune covers four rivers which are not yet und.er anti-black11ylarvieldirg. tluo ot' them are in l{a1i 3 - the Baoule (at }trssira), in the Senegal basin; - the Bakoye (at Kokol ata), in the Senegal basinl and the other two in Guinea l - the l'Iilo (at Boussoule), in the NlEer basin; - the i{iandan (at Sassambaya), in the Niger basin, 2. These rivers are theoretically sanpled monthly. Ilowever, because of a long annual period of drought, the I'Ialian rivers are sampled. only from June or July toNovember or Deeember. }: Guinea, ofl the other hand, accessibility or transport ail-ficulties limit d.ata collection to the period. from October or November to June. 1. In ad'd.ition to the three samplirg methods (daytime and. night-time drift with ?.00 t, nets, surber sanpler) used. in the whole kogpamme area for the nonitoring ot'the non-target irwertebrate fauna, other roethod.s were emp-Loyed.. They were the col1ec-tion of daybime and night-time driJ'ts r,vith )Oo p rnesh neisr- the use of ',lrrirogas" and.f'cold light" types of trap, ttba,sket-type" artjl'icial substrates and intercep{ion trapsfor the catching of the i-rnagos. MONII'ORT}N 4. It is difficult, al'ter only ecology and the structures of the remarks can, hor+ever, be mad.e. Guineaq rivers a yearr s obserrration, to draw conclusions on thepopulations of the rivers sampled. A few general lop-uater Friod as '*e1l- as an seems to be general for all the 5. [he evolution of the d.ensities of the inseets colIected, whatever be the method, is quite sinilar on the tmo stations sampled.. 6. The densities of the benthic fauna were rrni.ch greater durirg, the flood.-subsi-dence period. Similar observations had. alread.y been made in the Ivory Coa,st. Italso appears that the abund.ance ot' pla.nt cover (tbistichia) plays an important rolein the density of the saxieolous fauna. 7. The night-time drift, on the two stations, presented tnro peaks for the totalfauna. lhese tnro peaks were na"inly due to th.e !.ipheme=optera. The fiptera shoved, on the other hand, a d.ifferent evoluti.on on the two stations ; the abundance of thethichoptera was too lolr to be able to interlret it. B. The dayti-ne drift shored a ma:rimrn dr:rirg the increase in the fauna in May-June, This phenomenon g?oups \d on the two stations" 2. 9. 0n the who1e, the monitoring of the tuo Guinea,n stations proviiled quite ]:omo- geneous ancl similar results, compara.ble to those obtained on the stations situatedin similar geographie zones. Mal-ian rivers 10. fhe results on these two stations are sti1l too Bartial to be able to interpret them eorrectly. fhe follorirg were, hcRrever, observed : (a) - an increase in the d.ensities of the benthic saxi.colous fa"una in August and Septenber ; (b) - an increase in the night-tine drift index duri:g the spme period ; (o) - a similar increase in the d.aybime d.rift on the Baoule, which has not yet been confirmed. for the Bakoye. Monitorirg of the Fered.ouAouba 11. Experinental teraephos larviciding was camj.ed. out on t}:.e Feredougouba., a Guinean- Ivorian river, in ord.er to trrevent reinvasion by S.4amnosJrrn s.1. females of the area,s currentJ.y being treated and thereby eontrol onchocerej.asis. The srraying wa-s stertedin lvlarch after a mission had collected da.ta in February. 12. Complete sampling nas effected in February, I{arch and Apil 1985. Surber and d.aytine anci night-tinre drift samples uere ta.ken. The resnlts obtained for the Fere- d.ougouba were compared r,rith those obtained d.uring the sanre period, on tuo Guinean rivers not treaterl with anti-blackf1y insecticities a"nd monitored^ monthly : the Nian- d"an and. the Milo. 13. The results are djfficult to intertrret ecologica.lly and do not nake it possibl-eto shor* any impact of temephos. l'iLV MONITORTNG PIEII{ODS 14. New monitoring or sampling method.s ttere tested in the 1,'trestern :-lxtensi.on area.jhis involved either sampling environments not very mrch or baclly srmpled hitherto(intereeption 13sps, nel, substrates) on improving the rapid.ity and. reliability of ob- tention of samples or results (!00 p drifts, measurement of cur::ent speed., l:vel ofidentification and sortir:6s). t Measurenent of intensities of n tirm and ine drifts with 00 -rnesh nets 15. One of the trrroblerrs encountered" in the interpretation of d.ata provided by driftis the presence of ma.rry drifting young sta6es. In order to elirainate this significant cause of variation, a study has been undertaken to compare the results obtained. with nets of d.ifferent mesh sizes, 200 p ancl. 500,p respeotively ; the 500 p nets retEin only the oId sta6es. If the tria,l's lrove sitisfactory, 100 )r-mesh ndts could be in-trod.uced. at one or several stations as a replacement for the usua.l 200 p nets. A simple comparison shows a marked. di-fference in the annual evolution of tthe drift in- dices, be it on the Niandan or on tlie Milo. The d.rjjt cbtained;with the J00 p nets was relativeLy constant, but Lower tha.n that obtained r.rith the 2OO p nets. Chese two methotls are therefone not comparable and d.o not collect the seme fauna. Uithout a more in-d.epth anal;,'sis of the data a,nrl a comparison of thern with the results of the sortirgs at the 1erva1 stage of the saxicolous founa, it cannot be affirrcd. that the 500 F drift wouLd. trrovid.e a satisfactory estim=te of the fsuna nresent. New substrates 16. Substrates of thetrmod.ifj.ed.-basket'f type were placed at Missira on the Ba,oule, Kokofa.ta because ? aJ' on the Sakoye and. fienfala on the Niger. The results ohtained were unequal those placed on the Bakoye were stolen I those placed on the Baoule were colonized very well in October 1985 butgave medi@re results in December 1!B{ i Gl fina11y, those placed for three months on the Niger ivere colonized. ve=y well by a great variety of benthic invertebrates. 17. ft appears, on the rrrhole, that these substrates should remain for a long timein the r,rater before being colonized by the fauna. Thei-r use is ilrerefore ,osiible only on rivers and. d.uring seasons when the water level is relatively stable. These cond'itions a.re found. at Tienfala on the }triger d.uring the low-water season. The vrria-tions in the ir'a.ter leve1 of the Ba,oule are, on the other hand, *oo 3."pi.d and uncertain most of' the time to enable the use of these substrates a.s a semi-gua.ntitative sernnling method. fnterceptj.on traps 18. These are panels nad,e of a sticky transparent llastic nlaced ac?oss ond pbovethe river. 'Irials were carried. out s.t Tienfala on the Ni41er, T(okofata on the Brko;re and on the i"alerae. They mad.e it possible to collect severa.l hund.recls end even thou- sand.s of ad.ult aqua,tic insects. It is intended^ to briqg them into 3enerr1 use in tg}6. Sortins level L9. fhe ]00 p drjft a.nd Surber sa,m"rles are sorted to the speeies as r6.Trrds the Uphenera, the tbic]:optera and the Simr:liittae. For certain spicies, the lrrvel strgeis identified in add.ition. This work is a.irned. partl;' at obtaj"ning information onthe ecology of the species and eomrn:nities (c:,ncles, ,3powth rete, a.ssocietions and species competition, lreferend.a, etc.) anct partly et ena,bting a better understanding of the possible inpact of the ant&h1ackfly insecticides on the lotic fpuna. 2A. This work iras been going on for 3 Jrear nolr on the four stations under stucly as lart of the monitorirlg of the tivers. TAXONOIfiC AND FAI}NISTIC STUD]NS 21. The state of nrogress of the taxonomic studies is veriable deoending on thegroliIJs. Trichontera 22. It is the poup whose taxonomy is known best. At Fesent, the inventorl, of theI{ydropsychid.ae of the upper ba.sin of the Niger, the Baoule and the Bakoye ha"s been completed, A similar worl< i.s currently being camied out on the Ph.ilonotamida.e, theHydroptilidae and the "l;lcnomidae. S*o strnthesi.s studies have been rr:blished on the Philopota"midae and the Stactobiini of the Ivor;1 CoasL $*o papers are beiaq written to extend. these results to the upper brsins of the Niger and the Senegal. 23. It is planned. to have by the end of 1985 a ,genera.l inventory of the TrichorterB of the fvory Coast, r,restern }Ia.li and. northern Guinea. Ephemera 24. The taxonomic stndy of this {fou-p hes pro,gressed rmch less then that of theTrichoptera. That applies both to the hogramme area a-nd. to the whole of Africn. (a) (rl 4. 25. A very i:nportant reference eolLection has aLread;r been assenbled in Sanako from material (larvae, ima6os, sub-ima8os) collecteil in the- Tvor;;r Coast, I'f*,Li and. Guinea. However, while a grea.t part of the ilphemara species seemto have been inventoried, it appears that 90 96 of them are new species. At present, five articles are being ;rrepa- red., includ.ing a complete study of the Trichorythiilae of the fvory Coast a,nii four papers d.escribing new srecies in the Uestern lxtension area. PLeeoptera nr. P. T,wicks a speeialist of this group ha"s been oontacted. [e has been sent r first collection which is currently being' stud.ied. ft is eertain that not one species of {eoperla but more than a dozen exist in the Programme &re&. 0donata 27. fn para1leX. with the lxo6ra.mme for the strrdy of entomic lred.a.tors of S.damngsum of r^rhich they eonstitute an important element, the Odona.ta will be invent':ried. on the upper basins of the Niger and the Senegal. This taxononio studlr shouLd be faci.litatecl by the collaboration with nn Legrand., a s?ecialist of this group in the National }&rseum of Natural History in Paris, $anioennia 28. A revision of this gtroup is Ivtr:seum. 0thers cirrently being made by Dr. Sarnarcl of the British 29. For lack of time and" specialists, the data. collected on the other grlrlrs rernain at the 1eve1 C.efined. by the monitoririg protocol. ECOIOGICAL RESEARCIT 3O. Add.itional research has been ca"rried. out in order to better interpret the moni- toring results. This involved stud.ies on the drjJt and on the di.siribution of the saxj.colous fa,una. These results will be reported on sep*lratolir b1, ti:e representatives of the national tea.ms. 11. fhe stud"y of the pred.ators of the pre-adult sta;es of [.da.g3gg s.1. is the main occupation of one of the researchers of the Bamako hydrobiolqy la"boratory. Prelininary missions have alread;r 6s., undertaken to establish the distribution and the densities of the S.d.amnosum s.1. predators and thei-r rete of ::red.a.tion.