Monitoring of the entomofauna of the treated watercourses in Côte d'Ivoire and Sierra Leone

ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA PROGRAMME DE LUTTE CONTRE UONCHOCERCOSE EN AFRIQUE DE L'OUEST ECOLOGICAL GROUP Twelfth session Bamako. 25 February-l March 1991 ocP/vcu lHYBro/e1.4 ORIGINAL: FRENCH MONITORING OF THE ENTOMOFAUNA OF THE TREATED WATERCOURSES IN COTE D'IVOIRE AND SIERRA LEONE (Summary) OCP Environmental Monitoring Unit L. Yamdogo Routine monitoring of the entomofauna of the watercourses selected by the Ecological Group, studies on the impact of candidate antiblackfly larvicides on the non- target fauna, centralization, entry and partial exploitation of the data on the aquatic monitoring in the Programme area, and, finally, coordination of monitoring activities were the main activities carried out by the Unit in 1989/L990. A. Monitoring of treated watercourses T\e 198911990 season (period covered by our report) was marked by a poor rainfall situation which led to the early stoppage of flow on some "big" watercourses in the initial Programme area. The physico-chemical factors (ph, conductivity, temperature) presented values very close to those of the previous years. The monitoring covered eight sites including three in Sierra lrone and five in Cdte d'Ivoire, scattered over six watercourses. The most striking result seems to be the absence of a marked impact of the seasonal and selective treatments made in 1989 in Sierra lrone. The variations in abundance noted in December were related to the hydrological conditions. The structure and composition of the communities are stable except at Makpankaw on th Pampana where the use of ichthyotoxins by the local populations before our visit for the colllection of pre-treatment data led to a situation that was not as good as the post-treatment one. On the White Bandama, the use of pyraclofos did not result in detectable changes as regards the densities and richness of the sa:ricolous fauna, even though the sampling made only three weeks after the cessation of the treatments showed a great decrease in the faunistic density and a rarefication of certain ta:ra. At Danangoro on the Marahoue, the situation as presented last year has not changed much; the difference between the data on chlorphoxim-permethrin and those of the other larvicides is quite marked (Fig.20). On the Comoe, the abnormally high drift of the Mockokidae (mainly Synodontis) reported in 1988 was not observed in 1989, but certain day drift values are still greater than the mean values recorded on the other watercourses of the same size. With regard to the watercourses in Sierra Irone, the seasonal and selective treatments made with Abate and B.t. H-14 from April to July 1989 did not lead to changes in the communities studied. The Tricorythidae are still present on all the sites and the global densities are as high as before the start of the control. It should however be noted that changes occurred in 1990 in the larvicide coverage of the watercourses, the control seinon and the nature of the products. The monitoring has therefore been reinforced in order to keep a more precise track of the impact of the less selective larvicides on the benthic fauna. 2B. Selection of new larvicides Tests were conducted on phoxim (40Vo EC and 50VoEC formulations) both in gutter and in river (spot trial). OMS 3050 (a 20%o EC pyrethroid) *as also the subject of gutter tests in parallel with heavy doses of chlorphoxim, phoxim and B.t. H 14. At the doses tested in river, phoxim had no visible impact on the fish. The effects on the invertebrates seem to be comparable to those of chlorphoxim. At doses of 0.025 and 0.03 ppm of active ingredient/lO min., OMS 3050 causes a benthic invertebrate detachment that is quite close to that of permethrin. With regard to B.t. H-14, an overdosage of 10 times does not, practically, change the intensity of detachment of insects in gutter. C. Data entry and exploitation The data received before the end of October 1990 have been exploited partially; the graphs and tables are in the 1989/1990 year book. An effort has to be made by C6te d'Ivoire's team especially since for three years now it has never been up to date in the sending of its data. D. Coordination of activities Regular consultations have been started with most of the teams as regards equipment, protocols, execution of research work, implementation of recommendations of the Ecological Group and monitoring of the terms of the Technical Service Agreements. Minor problems remain, but, on the whole, efforts are being made by everyone for the smooth running of the monitoring. ONCHOCERCIASIS CONTROL PROGRAMME IN WEST AFRICA PROGRAMME DE LUTTE CONTRE L'ONCHOCERCOSE EN AFRIQUE DE L'OUEST ECOLOGICAL GROUP Twelfth session Bamako. 25 February-L March L991 ocP lYcu /EMS/eo.s ORIGINAL: FRENCH ENVIRONMENTAL MONITORING UNIT MONITORING OF THE ENTOMOFAUNA OF THE TREATED WATERCOURSES IN COTE D'IVOIRE AND SIERRA LEONE (Progress Report - 1989-1990) 2MONITORING OF THE ENTOMOFAUNA OF THE TREATED WATERCOURSES IN COTE D'IVOIRE AND SIERRA LEONE (Progress Report - 1989/L990) OCP Environmental Monitoring Unit General In accordance with the recommendations made by the Ecological Group in 1987, the monitoring of the benthic fauna of the watercourses selected by this OCP statutory body (with the exception of the Sassambaya/Niandan in Guinea) was carried out by the OCP hydrobiology unit. Eight sites (Table I) were concerned with this monitoring. Among them, three in Sierra Leone were the subject of larvicide applications for the second consecutive year. Country/Sitc/Rivcr Code (Station) Start of monitoring Start of larviciding Cote d'Ivoirc Danangoro/Maraouc Entomokro/Marahoc Niaka/Whitc Bandama Bema - Upstream/White Bandama Gansc/Comoc Sierra l.eonc Musaia/Mongo Makpanka{Pampana Outamba-park/Kaba 8 t6 3 ,' 73 72 77 July 1975 Dcccmbcrl97 July 1975 Junc 1985 July 1975 Fcbruary 1939 March 1989 Fcbruary 1989 March 1979 March 1979 Dcccmbcr1975 Dccembcr 1975 April 1981 April 1989 April 1989 Table I : Stations monitorcd by thc OCP hydrobiology unit. The watercourses and monitoring stations are presented in Figure l which gives also the sites prospected on the Jong. Annex 1 gives the names of the staff members who took part in the field and laboratory work. Temporary staff was used for the sorting of the benthic fauna samples and for juvenile fish catches for the trial of new products. JHydrolory and larvicide use The discharges of the watercourses at the monitoring stations and the larvicides used from August 1989 to JuIy 1.990 are illustrated by Figures 2 to 7. The 1989 rainfall was poor, concentrated mainly on the months of August and September with an early stoppage in almost the whole of the study zote. This led to a staggering fall in water levels right from the month of October and a flow that was so low in March that it was impossible to take samples on the Maraoue and the White Bandama. During the period covered by this report, the White Bandama was used for the evaluation of the efficacy and side-effects of pyraclofos at high water. BJ. H-14 was then used at low water on the section concerned with our study. Carbosulfan and permethrin were the larvicides used at high water on the Comoe and Marahoue. I. NIAKA ON THE WHITE BANIDAIvTA (Site 3) The watercourse was used for the trial of three antiblackfly products. After carbosulfan in 1985, cyphenothrin was tested for only four weeks in 1988 and then replaced by carbosulfan. The operational trial of pyraclofos was then conducted there for eight weeks in September/October 1989. 1. Drift (a) Davtime drift The mean index of the daytime drift collected using 200 p, nets at 14h00 was between 0 and 16, the highest value having been recorded in May 1988. In 1989 and L990, the drift was less abundant with an index not exceeding 7 individuals/m3 of filtrated water (Fig. 8). After the use of pyraclofos, the values of the daytime drift index were, on average, less than those of the same period (November to April) in previous years. But the lower the daytime drift index, the less the environment could be considered as disturbed. In most cases, the Diptera (mainly Chironomidae) constituted the greater part of this day drift (Fig. 9). The day drift collected with 500 p nets was less, between 0 and 3 (Fig. 10); the maximal values were recorded in March/April with a good participation of the Ephemera. 4(b) Night-time drift At night, drift is normally higher and richer than at daytime because it is a biological activity drift. At Niaka, the value of the ratio of the night drift index /day drift index reached 193 in December 1988. The lowest values of this ratio, 4.6 and7.3, were obtained in November, i.e., a short time after the cessation of the use of the least selective larvicides. The Ephemeroptera are preponderant in the night drift, except in November 1987 and 1988 when the Trichoptera were dominant. In the day drift as well as in the night drift, Centroptilum + Baetis was the best represented group of ta:ra among the Ephemeroptera. For the Trichoptera, the Hydropsychidae and mainly the genus Cheumatopsyche were the most abundant, while among the Diptera, the Chironomidae dominated, particularlywith the Tanypodinae at night and the Orthocladiinae in the daytime. The Caenidae, Philopotamidae, Chironomini, Orthocladiinae, Tanytarsini, $ralidae, hydracarians, Centroptilum + Baetis and Cheumatoosvche disitata were resularlv oresent in the dav drift. In the nisht drift. the Elmidae, Libellulidae, Hydroptilidae and Ecnomidae were found in addition to the day-drift organisms. 2. Study of saxicolous fauna This study was quite delicate at Niaka where the sampling was made on somewhat alveolate lateritic blocks. However, the faunal density was ma,ximal in February 1989, before the use of pyraclofos on the White Bandama. The Ephemeroptera and Trichoptera constituted more thar 68%o of the fauna but in March and April, it was the Diptera (mainly Chironomidae) that were predominant. Following the operational trial, the first Surber samples were taken in December 1989, almost eight weeks after the cessation of larviciding. The density was even greater than that of February 1989 (Fig. 11) and the Trichoptera made up almost half of the fauna, the rest being mainly of the Chironomidae (35Vo) and Ephemeroptera (l3Vo). It appears therefore from these data that pyraclofos has not led to particular changes in the composition or intensity of the drift after the cessation of the trial. The saxicolous fauna densities have not been affected by it even though the qualitative composition has slightly changed with a low if not rare presence of the Coleoptera. 5II. BEMA ON THE WHITE BANDAMA (Site 4) This station, which was established in 1985 just before the operational carbosulfan trial, has been regularly monitored since then and the "Surber" data are more interesting because the sampling is made under good conditions. Unfortunately there are no pre- control data for this station, which would have made effective comparisons possible. 1. Drift study (a) Daytime drift The intensity of the day drift collected at 14h00 with 200 pr nets was between2 and 17 individuals/m3 of filtered water (Fig. 12). In most cases, the Chironomidae made up the greater part of this day drift. The Ephemeroptera were also well represented (Fig. 13). The trend of intensity of the day drift collected using 500 p nets is different from that of the 200 tt drift. Furthermore, the Chironomidae were well represented only in February, March and April, almost equally with the Trichoptera. The Ephemeroptera were also well represented (Fig. 1a). Just as at Niaka, the day drift index (500 p) was low, between 0 and 3 individuals/m3 of filtered water. (b) Night drift It was between 24 and L90, the highest value having been recorded in March 1990 (Fig. 15), dominated mainly by the Ephemeroptera as in most cases. Among the Ephemera, it is the Caenidae that were preponderant, followed by the Baetidae (mainly Centroptilum + Baetis). The ratio of the night drift index /day drift index was between 6 and 38 while it reached 193 at Niaka. In addition to the Caenidae, Chironomini, Orthocladiinae, Tanytarsini, Tanypodiinae, Elmidae, $rralidae, Hydracarians, Centroptilum + Baetis and Pseudopannota which were regularly met in the day drift, the night drift comprised not only the I-eptophlebiidae, Hydroptilidae, Irptoceridae, Ceratopogonidae, Sisyridae, Ophelmatostoma Kiminsi, Cheumatopsyche falcifera, and C. digitata but also the $ralidae, Hemiptera, Ecnomidae, Heptageniidae and Odonata. 2. Study of saxicolous fauna. The densities were high at Bema where the ma:rima were found in February 1988 and 1989 and in March 1990 (Fig. 16). 6Despite the use of pyraclofos for eight weeks, the fauna remained diversified and abundant at Bema where the situation was not very different from that of the previous years. The Trichoptera formed the greater part of the organisms, dominated mainly by Cheumatopsyche digitata. The Caenidae which were well represented in the night drift constituted less than L|Vo of. the organisms here except in November 1988 when they formed 277o. A reciprocal averaging analysis was made on the Bema data. Factorial plane FL x F2 (Fig. 1.7), constructed from the principal axes, presents a global inertia of 6lVo. The Fl a:ris contrasts the Hydropsychidae with the Baetidae, Caenidae, Tanypodinae and Orthocladiinae. From the viewpoint of the data, it is reflected in a contrast between the most selective larvicides (&!. H-14) and the others (permethrin). It seems to be a toxicity aris. Carbosulfan occupies an intermediate position while pyraclofos overlaps B.t. H-14 and carbosulfan. As regards the F2 axis, it contrasts the Hydropsychidae, Baetidae and Orthocladiinae with the Tanytarsini and Chironomini. We have no ecological interpretation for this axis. However, it should be noted that the November 1989 sample is completely eccentric compared to the rest. It corresponds to an industrial pollution caused by a sugar factory. $rraclofos does not seem, therefore, to have had a marked impact on the saxicolous fauna at Bema even though the qualitative sampling made three weeks after the cessation of the larviciding indicated a Ereat decrease in the faunistic density and a rarefication of certain taxa. M. DANANGORO AND ENTOMOKRO ON THE MARAHOUE In addition to the usual larviciding sequence: B.t. at low water, chlorphoxim during the period of rise in water level and carbosulfan/permethrin at high water, the Marahoue has been under pyraclofos treatment since the beginning of the flood-subsidence period (November 1990). These larvicide applications will enable us evaluate the impact of pyraclofos on the structure of the dry-season communities. The sampling is in progress and will be continued up to March/April 1991. 1. Danangoro on the Maraoue (Site 8) (a) Studv of dav drift Collected around 13h00 with 500 p nets, the day drift was less in 198911990 than in 1988/1989 (Fig. 18) and dominated by the Trichoptera while it was the Ephemeroptera that made up the greater part of it in 1988/1989 (Fig. 19). 7The 14h00 drift (200 p, nets) was between 0 and 19 from 1987 to 1990, and the Ephemeroptera and Trichoptera contributed largely to it (Fig. 20). The Baetidae (mainly Pseudopannota bertrandi) and the Hydropsychidae (Cheumatopsyche digitata) made up the greater part of the organisms collected in the drift. (b) Study of night drift The night drift was about ten times higher than that of the day (Fig. 2t). lt was rich and diversified, dominated by the Hydropsychidae in many cases, as in L988 /1989 (Fig.22). The Ephemeroptera (mainly Caenidae) were abundant also just as the Macronematinae (Trichoptera). While the night drift was high, it was less than that of the previous year though equally rich and diversified. (c) Study of saxicolous fauna The faunal densities were relatively high in 1990 (Fig. 21) but it was in January 1988 that the highest density was noted, while the lowest densities were recorded after the use of permethrin in 1986. The Trichoptera (mainly Hydropsychidae) constituted a good part of the saxicolous fauna at Danangoro in 1990 while the Ephemeroptera (Caenidae, Baetidae of the genus Pseudopannota) played a leading part in January 1989. On the whole, since 1984, there have been variable interannual fluctuations in the saxicolous fauna which do not seem to have been affected by the use of carbosulfan. The reciprocal averaging analysis of the data collected during the treated period, from 1979 to 1990 (Fig.2q is not very different from that for the period 1979-1989. The collections made during the months of treatment with &1. H-14, Abate(R) or B.t. preceded by carbosulfan treatments contrast with the samples taken during periods of treatment with chlorphoxim or B.t. preceded by permethrin sprayings. The particular position of the data of the first treatment with Abate(R) and of the carbosulfan data will be noted. When carbosulfan is used in the dry season, it leads to changes such that the data are found in the same area as the permethrin and chlorphoxim data. 2. Entomokro on the Marahoue (site 16) (a) Studv of dav drift The collections made with 500 p nets show a higher drift intensity here than at Danangoro, as reported in previous years. On the other hand, in both cases, a gradual fall in the ma:rimal drift intensity from one year to the other has been noted since 1987 (Fig. 2s). 8The 500 p drift was dominated by Ephemeroptera (mainly Baetidae) in 1990, while the Chironomidae were the best represented group in 1989. The same is true of the 200 p, day drift whose trend since 1987 (Fig. 26) presents characteristics similar to those of the 500 p drift. However, the highest day drift (200 p) value was recorded in December 1989 while it was in January 1990 that the 500 p drift was mzurimal. However, the Ephemeroptera (Baetidae) remained well represented in the 200 tr drift in January 1990. (b) Studv of nisht drift The night drift was high, almost 20 times more abundant than that of the day with a good contribution of the Ephemeroptera (mainly Caenidae). The Trichoptera were also represented quite well. The night drift was ma.ximal in December 1989 (Fig.27), as in the case of the 200 p day drift, but the contribution of the Chironomidae was low. (c) Study of saxicolous fauna The sa:ricolous faunawas also more abundant at Entomokro than at Danangoro. The density seems to be maximal in January as in 1988/1989 (Fig. 28) but the values were higher this year even though they did not reach those of 1987/1988. The Trichoptera (Hydropsychidae) made up a large part of the rock fauna (Fig.29) but the hydrological situation did not enable us take samples in March and April, months during which in 1989 we observed an unexplained fall in the densiry of the organisms with an almost complete elimination of the Ephemeroptera. rv. GANSE ON THE COMOE (Site 2) Not only because of the high discharge of the watercourse during the rainy season, but also the resistance developed by the vector to temephos and chlorphoxim, the treatments are made with less selective larvicides (permethrin and carbosulfan) during the high water period. For some years now, important changes have been taking place in the hydrological regime of the watercourse, leading to early cessations of flow at Ganse (December instead of March/April). (a) Study of day drift The drift collected with 200 p nets was particularly high in September 1989 (Fig. 30) even though treatment of the watercourse had been stopped three weeks before then (six individuals/m3 of filtered water as against a maximu- of nuo in 1988). The contribution of the principal ta;<onomic groups to this drift was not the same in September and October (see Yearbook), the only months for which we have data. The Ephemera and Diptera 9constituted almost 80Vo of the organisms in the drift in September while in October it is the Trichoptera that were preponderant. (b) Study of night drift (Fig. 31) It was almost equal to the day drift in September 1989 and then presented values three to four times higher in October and November. The Ephemeroptera (Baetidae, Caenidae and L,eptophlebiidae) were abundant in it. The Trichopterawere well represented only in November while the Chironomidae participated in it in a decreasing order from September to November. Among the Chironomidae, the Chironomini were the most abundant while for the Trichoptera, no taxon presented a marked domination every month. The Ecnomidae and Cheumatopsyche digitata which were well represented in 1988 were almost absent in 1989 while the Lrptoceridae and Cheumatopsvche copiosa were sampled regularly. At Ganse, among the organisms encountered only in the night drift were the Ecnomidae and Heptageniidae of which we had already talked in last year's report. V. MUSAIA ON THE MONGO (Site 73) 1. Drift studv The pre-treatment 14h00 day drift (200 p,) was high compared to the pre-treatment values in the initial Programme area. The Ephemeroptera and Chironomidae were almost equitably represented and constituted the greater part of the drift. The Caenidae were the most abundant Ephemeropterawhile the Chironomini and Orthocladiinae made up the bulk of the Chironomidae. After some L5 weeks of larviciding (April to Juty 1989), the daytime drift intensity did not change fundamentally but the Trichoptera occupied an important place in the drift. The pre-treatment night drift was high (more than 40 times that of the daytime) but became hardly six times the day drift intensity five months after the cessation of the first treatments with, just as mentioned above, a greater participation of the Trichoptera in the drift although the Ephemeroptera were dominant. 2. Study of sa:<icolous fauna The pre-treatment density of the sa,ricolous fauna was not particularly high (106 individuals/"Surber"). The Diptera were the most abundant and the Tricorythidae represented only 0.78%o of the rock fauna. 10 The situation was not influenced by the B.t. and temephos treatments made during the period of rise in water level. The Chironomidae remained the dominant fauna after the larviciding stoppage and the densities of the principal ta,xonomic groups increased (with the exception of the Simuliidae and Coleoptera). 3. Conclusion Though the quantity of data available is low for statistical analyses, the results recorded after the first larviciding campaign on the Mongo do not indicate major changes attributable to the effects of the larvicides. However, the decrease in the value of the mean post-treatment night-time/daytime ratio is the sign of a disturbance of the aquatic environment. VI. OUTAMBA-PARK ON THE KABA (Site 71) 1. Drift studv Before treatment, the day drift of 14h00 (200 tt) was diversified and the index was within the range of the pre-treatment values obtained in the initial Programme area (cf. VCU Report No. 28-1990). This index was lower four months after the cessation of larviciding but reached its initial value again in March and April 1990. The richness did not change and the Ephemeroptera made up a good part of the fauna. Among them, the Baetidae and Tricorythidae were the most abundant. The night drift almost followed the same trend as that of the daytime: high before treatment, it decreased in December and then increased in March and April. The ND/DD ratio, which was 20.4 before treatment, was only 4.7 it December, then 17.6 in March and 9 in April. The Ephemeroptera dominated in this drift, foltowed by the Trichoptera. The Chironomidae were poorly represented. 2. Study of the saxicolous fauna The density of the rock fauna was relatively high at Outamba-park before the treatments. It was slightly less in December 1989 (a few months after the larviciding was stopped). The richness was also lower but in March and April 1990 it was comparable to the pre-treatment one and the densities were markedly higher. The Ephemeroptera (Tricorythidae and Baetidae) were the best represented ta,ra on this site. 3. Conclusion The seasonal larvicide applications made with temephos and &I. H-14 do not seem to have had an impact on the fauna of the Kaba at Outamba-park. The slight decrease observed in the richness and in the density was mainly a season-related situation. 11 It is interesting to note the maintenance of the structure of the communities and of the Tricorythidae on the site after slightly more than three months of treatment with the least selective larvicides. In 1990, the treatments were intensified and less selective larvicides like permethrin and carbosulfan were used. The processing of the samples, which is in progress, will enable us evaluate the extent of the changes expected. V[. MAKPANKAW ON THE PAMPANA (Site 72) 1. Drift studv The intensity of the day drift collected at 14h00 with 200 pr nets was low (pre- treatment) at Musaia but comparable to that recorded in general in the initial Programme area. It was higher in December 1989 (post-treatment) but remained within the range of the pre-treatment values. The Chironomidae (particularly the Orthocladiinae) constituted a good part of the drift but the Ephemeroptera were also, in most cases, represented quite well in the day drift. The Hydrocarians and the Corixidae participated considerably and unusually in the day drift which was richer in December 1989. The night drift was more than 50 times that of the daytime before treatment, and low in December 1990 (while that of the daytime increased) before increasing in March and April 1990. It was richer than the day drift with a particular participation of Neoperla sp, fishes (fry) Sisyridae, Ophelmatostoma kiminsi (Baetidae), and Dicercomyzon (Tricorythidae). The Ephemeroptera (Caenidae, Baetidae and Irptophlebiidae) were predominant. 2. Study of saxicolous fauna It was quite rich but not very abundant in March 1989 (pre-treatment) because of the use of ichthyotoxins on the watercourse by local fishermen (cf. VCU Report No. 28-1990). The Chironomidae (Orthocladiinae) were dominant and the Macronematinae which made up the greater part of the Trichoptera in March L989 were joined by the Hydroptilidae, Ecnomidae and Hydropsychidae from December 1989 onwards. 3. Conclusion At Makpankaw, the trend of the daytime drift seems to follow that of the sa,ricolous fauna densities. The day drift was also influenced by the Chironomidae which constituted more than half the rock-slab organisms. After the first antiblackfly larviciding campaign, the structure of the communities remained stable despite a temporary decrease in the mean ND/DD ratio. 12 Annex 1 Staff members who took part in the Unit's activities - L. Bakone (mainly data entry and exploitation) - S. Bakayoko (part-time) - M. Bihoum - B. Coulibaly - B. Dolbezalga - J.-M. Tapsoba - L. Yameogo N.B.: For the sorting of the organisms and fishing, this year again, we used the services of the following temporary workers for a total period of 26 months: Sekou Kone, Nazaire Simpore and Abdoulaye Yago. f,l c+' t\ 9.i ma o z -loI m(f @ -{I m T n o o7 rq mz 5 oz rrl z -.1 t- o z =of, z c) C z = -:O o - z F\ _-l x o l I( ) J- (! o oc a-g o. I 6o o o 't ) l_ ) J oI o = r I I x .t I l- x @- J 6.r 1 I zr L C- a 1 x o ( a ( ,q ,)' oC 6, o oC 6)E3 CN ul -nc >:Daxo= t b$ I( \( r ) I 6 E C z m m 9. o o a (D o v o o E o o \ O q o c \ I I I ){l , I I I I \ I d lloo - l a \ I ,a\ o' ul ,rfr nY_Zo/ o- o- u xo oC o 6 I a a oIo 3 o o {N o __) o a ,6 LJ Ir--*.- @o o u Or, o u.o -l m N a I I , t moz t ao. (D o EO I( I\ N(D 3 o L 't f q) m n o z I =ozI o s c) o{ oz c r o n . O OE] 9. a,6o oc p ao o 3 3 o 4gbo a)f, @@u,qca.g Et d d^o 6 3l o9 :66a g, ooooc!o a 6. odc+;g : G o o) 1- + @ oC z ,Io-l9t--- IIra I (t o) a ic l6 1 o l ,o a o' o oL ={, o f o o f o 3 6 o l o =1- o t zt6 -.1 0 m o oa ,+ r I ( I \ LEGEND TO FIGURE 1 CODE STATION RIVER COUNTRY 2 J 8 t2 16 28 48 71. 72 73 75 76 Gans6 Niaka Danangoro Bamboi Entomokro Amou-Oblo B6ma Outamba-park Makpankaw Musaia Wulai Gbanba Como6 White Bandama Maraou6 Black Volta Maraou6 Amou White Bandama Kaba Seli Mongo J,ong C6te d'Ivoire Ghana Cdte d'Ivoire Togo C6te d'Ivoire Sierra lrone I I il tl I il l; ,{ '' !,1;t 1l .J ,q, '' 00 NJ f---)> +\\ > -l- o r_l f\ c.- rrl . o > € C l_ -) D Ar tu Q ) o Debit (mS,zsec) oo Nro N I\)o N)oOc0o I O)o l o-o I Noo)oso Noo q) o L _-._ lo z o (- Tltr (o q) @ oo{ o(o I o o -{ (o o zH9. att + (o(o o F (- (- oF 1H a o { Debit (mS,zsec) { { $l i ,l ,( '1 Nso NNo N@Ooo II Olo t! zH roNo __l ooo,o 5oNoo @o Io z 00 (, D . D > - D \ o . > ^ (f (- Tltr (o @(o oo -t @(o I oo -{ (o o E! o 6'. (- -1- (o(o O L zd d 0 a o i I a r'i:l +,1 'ai ll uNI(o I 9 @ I P ! I I o)IUlIr I Iu I o i.) I o o z rJ EEYltr @ G'(o De bit (rn3,/ sec)(ffrousonds) |! o o EJ 0q +. o o =o r-l \ J-> ^ o^ .\ Ir ^o z Cf c- oo -l @ @ I oo -l(o o z rJ9. u (- + (o(o o o 0, o c, 9) a o t :i -rl ,! :l t, Deblt (mS,/sec) rNusuror!@to"9]n ooooooooooooo *rl 0q (, frl =o z o o >\ CN (o(o o 'o n L (-(- (- Cr oC a rfl .t oo -{ o u V,I E! d t't d zH FO o u dDebit (mS,/sec) s'. ; NNo Noo COoo)o$oNoooo,o Noo 5o @ot t7 r 0o o rl ^D c(- >.\D \ \ E! it (- -C (-(- r ()(o o 9. o FU o d oC z Fl t]------.--- \- d F€ o rt a rq1' oo -l t ,;l 'tllr ,', Deblt (mS,/sec) (,{ oo N @o N olo N5o NNo Noo@oOtC)$oNooo@oOloNoo 5o -t a 00 ! @ @o (- Cz (- C oC a rq! o a oo -l//''l -Ll..-- 11 - -\l N I E! d F€ o d FU o zH d t 'l Fig. 8 Evdution der indicer de derive de iur il) {) v q, v .ll{) ;g l6 r5 14 l3 t2 lt IO I I 7 5 5 4 3 2 I 0 I l-Aug-87 27-Fcb-88 lilct de 200u o Nioko dc l9B7 o t 990 Dotcs d'cchontillonnoqe + TrichoptcrusA Chimnomidoc Evdution der indicee de derive de iurr lilet dc 200u o Nioko dc 1987 o t 990 I 4-Sep-EB 02-Apr-89 0otcs d'cchontillonnoge + Diptcrrs totoux I 1 -Aug-87 27-Feb-BE I +-Scp-BB 02-Apr-89 I 9-Oct-89 07-Moy-90 tr Ephcmeres o Foune totole Fig. 9 lU o v o v" an t o vg t5 l5 14 IJ 12 lt r0 I B 7 5 5 + J 2 I 0 tr Foune totole I 9-Oct-89 07-Moy-90 Fig. t2 Evdution deu indicer de derive de irur filct de 200u o Bcmo dc l9B7 o 1990 ll, lU v t, v (n{,g vc t7 t6 t5 l+ t3 12 il t0 9 E 7 5 5 + 3 2 I 0 I 9-Nov-87 06-Jun-88 tr Ephcmcrcs o Founc totolc 23-Dcc -88 I I -Jul-89 0otcs d'cchonUllonmgc + TrichoptrcrcsA Chircnomidoc 27-Jon-90 Frequences relatives {ooo(,lo5oo)oNooo I mt, J o oa oo II -l Cr) o o)JT' o o -lr+ 6' - J -o otf o CL o o E oCp. oEJJ o J ++o 0 o - o CL o oc - Nootr o @ o o @q, =CL o,) o 0 oo I @{ ffi+K--r c)o@ J ='9oool 3(D ='o sEi goo- i o@5(oo = = o JRo -Hqt\oN@ { =.o5 ot, .nrs. -ttOlo@ o Frequences relatives I!I J5 o o IJJE o o I'i+ 6' = -o -ot o CL o o E' oCp. o 3 o =t+o I o =. o CL o oc - oroog o @ o J o @ o CL A' A) ooOto5oo)oNooo T mt, J o =q8 ooOl @{ C.o =IXB tdx\ c-C)E J - I :@Ys @OO3t'n ='o oE-oo- Yoo'do 9(ooiF --Or =@d(o @ N) r,N\-t\r .@ =@6'JOootr6a'&o@o C.o =I(o o Fig. 15 Evohtiqr der hdicea de derive de nuit filct dc 200u o Ecmo dc l9E7 o 1990 0otcs d'echontillonnoge + TrichoptclcsA Chircnomidoe Evdulim de la farne uxicole a Bema sur le Eondomo blonc dc l9B7 o 1990 06-Jun-EE 23-0ec -BB I I -Jul-89 0otcs d'echontlllonno ge + TrichoptercsA Chironomidoc {) {) v {) .n{)() vc t90 r80 t70 150 r50 140 150 120 r r0 100 90 80 70 50 50 40 30 20 l0 0 I I -Auq-87 27-Fcb-88 l,t-Scp-EE 02-Apr-89 I 9-Oct-89 07-Moy-90 5 4.5 + J 2 {)A f(t OE\c a'Od'nxJo'oc< -b riz Fig. 16 3,5 2.5 1.5 0.5 0 I 9-Nov-87 tr Ephemercs o Foune totole tr Ephemercs o Foune totole 27-Jon-90 cHt tr TAT TAP CAE A ,TR I 0 i i ocL PSY n o tr I BI Bl opres corbosulfon I I Bl opres pyroclolos I It op..t permeln.ne A Pott'ution industrielle Anolyse foctorielle des correspondonces oppliqude oux donndes de lo piriode troitie (ddcembre 1985 d mors 199O) d A6mo omont sur le bondomo blonc. Frg 17 ! 3Fig. 18 Evdution der indicer de derive de ior filet dc 500u o Dononqoro dc l9E7-1990 3,5 2.5 1,5 0.5 I I -Aug-87 27-Feb-BB I +-Sep-EE 02-Apr-89 I 9-Oct-89 07-Moy-90 o !D v o v ao l)(, 17 tr 2 tr Ephcmcrcs a Foune totole 0otcs d'echontillonno gc + TrichoplrrcsA Chircnomidoe 0 Frequences relatives 11 -aGI -(o o o - )JE o(2. * o J -o ot o CL o o T' ocp. o 3 o =t+o o o =. o CL o oc - (,l ooE o) Io o =(o o -o {oo)oOlo5oG)oNoJoo I ]TE JO- --30Et o oo I @{ Xc-ffi+ {@ =.@oilo = E' o -s{. iq8 6 Ee @tlZoo Alr =0o =@qo =odq, NTBN'n oOcr =rro(o =oZ3qdTB3 .Tt o CT I(o o Fig. 20 Evdution der indicer de dedue de iur filct dc 200u o 0ononqoro dc 1987-1990 {) o v {) v an{)(, v L t9 IE 17 I5 l5 l+ l3 12 lt t0 9 I 7 5 5 4 3 2 I 0 I I -Aug-87 27-Fcb-BB I 4-Scp-88 02-Apr-89 1 9-Oct-89 07-Moy-90 tr EphemercsO Founc totole 0otes d'echontillonnoqe + TrichoptlrcsA Chironomidoc Evohlisr des hdicee de derive de nuit o Donongoro dc I 987 o I 990 g) o q) v (o lI) ; L Fig- 130 120 ll0 r00 90 80 70 50 50 40 l0 20 t0 0 2t t5-Oct-85 03-Moy-87 l9-Nov-8705-Jun-88 23-Dec-BB I l-Jul-89 27-Jon-90 0otcc d'cchontillonnoqc tr Ephcmcrcs + Trichoptcres o Founc totole A Chironomidoc Frequences relatives TI -tGI i'.,N o o =JI, o 9.j.+ -ao IJ -o o * o CL o o t, o Cp. o =Jo =t+ @ tr, o =. o CL o =c. o 0o =o (o o -I (o @{ o J(o @o @o{oo)o(,lo5oG)oNooo I ml, Joc- =o,)o-l a6ioo{ .Tt o ET I @{ mtk!5 o@ ={e- z3V 2 -;JO : d@ =ocLoo- G-oo5fo! =,@ =@9= =o NTBNc, .o =?g@d@9=oo --Olo@ (o .Tt o ET ! @o {) A =@d!\b{}-}EqE Az 5 5 + 3 2 Fig. 23 Evohlion de la faune uar.icole Dononqoro sur lo Morouc (1984 - 1990) Apr-84 Nov-84 Jun-85 Occ-85 Jul-85 Jon-87 Alg-87 Fcb-88 Scp-BB Apr-89 Oct-89 Moy-90 7 0 o Foune totolc 0otcs d'cchontillonnoCc + Chlronomidoc (D D m oa o o {. !trD a n ND oo .f]. tr C) tr o I o T o {I -{ -{ tr ) oo o>o > (D € o.a oJ DJ o l(D >.)>9=sgo-o Oa+DO oJ o, I@d o =oi E f o 5 o !ra (D@@ ooPE 3'd. OoQoJu9o i'o .a : N) z g>o f crf oo - ;"o =-.;.iirIO, .Db o 3 o3+ oE Ot o E8iaoO -.6+c o- Jo of: ooo rD flI Ni EA 6KioJ(D (D +O(,,'o (,OC1 a;' o; fio- =oO9o6.q -o,o cn()E oo =:,oo.fo of oo a(Do( o^ ^!39g5' rl'L (D. @o -.1 @o o. I 3ooo 6) f,(D.(o(D oql Oi JD. r) o o. o6 oE1 or6 (D- o.o.q c o. o ti n tr D tr T B7 6 5 4 J 2 {, ,u v {) v <n o ; L Fig. 25 Evdution dea indices de derive de iurr filet dc 500u o Entomokoro de 1987-1990 0 I I -Aug-87 27-Feb-88 I 4-Sep-88 02-Apr-89 I 9-Oct-89 07-Moy-90 FIg. 26 Evdution dea indicer de dedve de jrur filet de 200u o Entomokoro de 1987-1990 o Ephemercs o Foune totole O Ephemercs o Foune totole Dotes d'echontillonnoqc + TrichoptercsA Chircnomidoc 0otcs d'echontillonnoge + TrichoptcrcsA Chironomidoe lD ID v !u v .h q) I vc J4 32 30 2B 26 2+ 22 20 t8 l6 l4 12 l0 E 5 4 2 0 I I -Aug-87 27-Feb-88 I 4-Sep-88 02-Apr-89 I 9-Oct-89 07-Moy-90 'l) E o v lt) @ a(, vc Fig. 27 Evohtiqr deu hdicer de dedve de nuit o Entomoloro/Morohouc dc l9E7 o 1990 600 s00 400 J00 200 t00 0 23-Jon-87 I I -Aug-87 27-Feb-Bd I 4-Sep-EB 02-Apr-89 I 9-Oct-89 07-Moy-90 tr Ephcmercs Dotcs d'echontillonno ge + Founc totole Fig. 28 Ewlution de la laune aaxicde Entomokoro sur lo Moruoue (1987 - 1990) l) .6. 10?(Il\E bE bEqE Az 6 5 4 J 2 0 23-Jon-87 I I -Auq-87 27-Feb-88 t,t-Sep-BE 02-Apr-89 I 9-Oct-89 07-Moy-90 O Ephemcrcs o Foune totolc 0otes d'echontillonnogc + Trichoptercs a Chimnomidoe Frequences relatives TIN @ o o 3t, o 9. * o - J -o 0)t o o. o o E ocp. o - JJ o =+o 'Tt q, c =o CL o o -oo o -o o rT J o ox -I J(o G'{ I @(o o @o{oC')oOlo5oq)oNoJoo I mt)O. -JOO=rrl o@o{ g oo IMOPi{ La! o ='l9o 8'3* i -alD r" ocLoo- O-il6 -tl =@o = =o(o x-r O C-N\ A)\\=[]!t JGl -'(96' o qP oio0o @) rt t. l, T FiE a 30 5 0 Sep-88 Fig.31 Evdution deu indicea de derive de iur filct de 200u o Gonse/Comoe (1988-1989) Occ -88 Apr-89 Jul-89 0otcs d'echontillonnoqc tr Founc totole Evohtiqr deu hdiceo de dedve de nuit Ar Eoc de Gonse dc I 9EB o I 989 Dec -EB Apr-89 Jul-89 0otcs d'echontillonnoqe * EPhemercs 5 + 3 {) o v l) v ah o o 9c 1l) E{) v lD v ah e)(, v c 2 ) l5 r5 l4 r3 t2 ll l0 I I 7 6 5 + J 2 I 0 Oct-89 t, t !*.r I Sep-BE o Foune totolc Oct-89