Assessment of long-term impacts of temephos used as simulium larvicide on riverine fish and prawns of Bioko Island, Equatorial Guinea: 4th progress report

tt ASSESSMENT OF LONG.TERM IMPACTS OF TEMEPHOS USED AS S'MUL'UM LARVIGIDE ON RIVERINE FISH AND PRAWNS OF BIOKO ISLAND, EQUATORIAL GUINEA 4t'PRocRESS REPoRT BY ABBAN, E. K. AND E. AMEDORME (cslR-wATER RESEARCH INSTITUTE, ACCRA, GHANA) CSIR-WATER RESEARCH INSTITUTE P.O.BOX M. 32 ACCRA, GHANA TEL. +233-21-779514 E-mail:wri@ghana.com August,2005 t - o t *E :i '"t i r I 8 ll0v. 2005 iI- I.L[J TABLE OF CONTENTS Pages Contents. Acknowledgements. Summary/Abstract. 1 .0 lntroduction... - 2.O Approach and Methods....... 2.1 Approach 2.2 Methods. 3.0 Results. 3.1 3.2 4.2 v I VI 1 2 2 3 5 6Status of fish environment during study.. Fish species occurrence in relation to application of temephos to rivers of Bioko lsland 2001-2005. -.. 3.4 i Catch (C.P.U.E) trends of individual mesh nets" 3.4 ii Trend of prawn catch (CPUE) in relation to river treatment with ephos I 13 21 temephos 22 3.5 Fish Co-efficient of condition (K) in relation to river treatment with temephos 25 4.0 Synthesis, Discussion and Conclusion.. 30 4.1 Preamble. 30 Re: Occurrence of fish species in relation to river treatment with temephos 30 Re: Species richness of catch in relation to river treatment with temephos'. - 31 I 3.3 Fish species richness of catch per sampling event in relation to tem application (2001-2005)'... 3.4 Trend of Fish catch (CPUE) in Bioko rivers in Relation to temephos aPPlication a { 1 { 4.3 ll TABLE OF CONTENTS Pages 4.2 Re: Trend of fish catch (oPUE) in relation to river treatment' 32 4.3 Re: Status of fiSh ,Condition' in relation to use of temephos in Bioko rivers 32 5.0 Conclusion.. 33 LIST OF TABLES AND FIGURES Table 1.i: status of Aquatic Habitat of River Matedero at lengema' 1ii status of Aquatic Habitat of river Musola at River Mouth' Table 2 Fish species occurrence in rivers of Bioko lsland. 2a River Apu..... 2b River Matedero...... 2c River MiruPururu 2d River Musola. 11 t 6 7 11 '11 11 .11 Fig 1- Drainage Map of Bioko lsland, Equatorial Guinea' Fig2- Species richness of catch per sampling event in rivers.. 2a River Apu at Malabo-Luba Bridge' 2b River Matedero at-Lengama... "' 2c River Mirupururu Airport Bridge........ 2d River Musola-at River mouth. Fig 3.0 Trend of Total CPUE in Number in Relation to River treatment with- temePhos (2001-2005)..' .. 3.i.a River Matedero 3.i b River MiruPururu .vir 12 12 12 12 12 .14 14 ...14 14 L 1 { 1 3.i.c River Musola ill 31 TABLE OF CONTENTS Pages tl Fig 3.ii. Trend of Total CPUE in weight in relation with river treatment with temephos (2001 -2005)... .. 3.ii.a River Matedero b River Mirupururu. c River Musola...... Fig 3 iii. Trend of C.P.U.E (Numbers) in relation to river treatment: 2001-2005. Fig 3 iv Trend of C. P. U. E (Weight) in relation to river treatment 2001-2005... Fig 4.iTrend of Prawn catch in River Musola at SEGESA in numbers"' Fig 4.ii Trend of Prawn catch in River Musola at SEGESA in weight.''"'"''"' Fig 5 Trend of condition 'K' of frequently occurring fish species (1999-2005)"' i. ln River Matedero. 15 15 15 15 16 18 23 24 26 26 27 2A 34 37 In River Mirupururu ln River Musola.I lt. References... Annex t { lv t LACKNOWLEDGEMENTS We are indebted to the management of the African Programme for Onchocerciasis Control (APOC) for the opportunity and resources provided us for this work. Our gratitude and appreciation go to the WHO representation in Equatorial Guinea and the country's Onchocerciasis Task Force for providing in-country administrative and technical supports. We are also grateful to management and staff of CSIR-Water Research lnstitute, Ghana, for time, resour@s and technical support provided for this work. a { 1 v Summary/Abstract Following obtaining baseline information on characteristics of freshwater fish fauna of Bioko lsland in 1999, annual monitoring of strategic characteristics of the fish and prawn fauna were done to assess long-term impacts of temephos being used to control Simulium Iarval populations in the island's rivers. Strategic characteristics of fauna monitored in relation to temephos treatment of rivers were: o Fish species occurrence o Fish species richness of catch . Catch per unit effort (CPUE) of fishing for fish and prawns and . Co-efficient of conditions of fish species. After two main treatments of rivers in 2001 and 2003 annual monitoring results from 2OO1 to 2005 indicated no long-term impact of temephos on fish fauna characteristics monitored and thus the aquatic environment. Results obtained in the study compares favorably with a large body of literature on temephos, used for over 2Oyears in controlling larval populations of Simu/ium in West Africa from 1974 till 2OO2. lt is therefore our conclusion that, properly managed, temephos use to control Simulium larval populations in rivers could be obtained without Iong-term impacts on aquatic fauna. t T f, i vl iiri, I rl 3'4 0' firtLfl$o CONCEPCION 0 8'50', ,l 3'4 0 3'30', 3'.20', 3o', tcl 8n 3'2 0 URECA 2 8'30' 8',10' Fig 1. Drainage Map of Bioko lsland, Equitoriat Guinea. t I I 8'30', 80 40' 8'50 ir G"'f MOCA Ytl l:'. I .j i ! a 1.0 INTRODUCTION The BIack fly, Simulium damnosum is the known carrier of a nematode filarial worm, which causes river blindness or Onchocerciasis in humans (Zimmerman, ef al 19921. The disease is also manifested by several bodily symptoms including skin lesions, known as 'Kraw-krow' in West Africa (Boatin et al 1997 Cheke, 1998). The disease and the fear of it, until the 1990s, greatly reduced human and socio- economic developrnental efforts in several Africa communities especially, in savanna gears of West Africa WHO, 1985). These impacts of river blindness influenced the world community to establish, in 1 974, a control programme for the disease in West Africa, named the Onchocerciasis Control Programme (OCP). (Boatin et al 1997) under the auspices of the World Health Organisation (WHO). The basic strategy of OCP was insecticidal attacks on larval populations of Simulium which lived in fast flowing segments of rivers, thus larvicides were put directly in segments of rivers. During the life-time of the OCP, a micro-filaricidal drug, ivermectin (MectizanS shown to be effective against the causative organisrn of Onchocerciasis in humans in the early 1980s, become available for use (Abban et al, 2002). Encouraged by the potential of ivermectin, the international community effectively replaced OCP with the African Programme for Onchocerciasis Control (APOC) also under the auspices of WHO, to control Onchocerciasis through administration of the drug. However, APOC considers vector elimination for disease eradication where appropriate, through the OCP approach of insecticidal attacks on the vector larvae directly in segments of rivers (Wilson et al. 1996). Vector elimination attempts have been considered by APOC only where there could be sufficient evidencethat the vector population in question was among other characteristics, geographically and genetically isolated. I ! I j a1 ,1 a Bioko lsland of Equatorial Guinea is an area receiving APOC assistance to control Onchocerciasis by administration of the mico-filaricidal drug, ivermectin. However, the population of the disease vector, S.damnosur?, was, considered isolated (Wilson et al, 1996). Thus APOC initiated vector elimination activities, involving attacking larvae of the vector at their riverine habitats with an insecticide. The insecticide chosen was temephos, which had been extensively used by OCP for more than 20 years with great success. Especially, for its high specificity against the target organism and general ecological friendliness (Hougard et al. 1993, Yameogo ef a/ 1993, Paugy ef al 1999, Calamari et al 1998, Abban et al 2OO2'). However, APOC appropriately, has undertaken impact assessment of the larvicide in Bioko rivers, irrespective of the accumulated knowledge by OCP on temephos. lt was also important to study possible impacts of temephos on the aquatic environment of Bioko because the island is an UNESCO designated world heritage conservation site. The present report constitutes an aspect of the assessment of impact of temephos on the aquatic environment of Bioko island and contributes to information on aquatic fauna of the island as well as the larvicide's behavior in water generally. 2.0 Approach and Methods 2.1 Approach: As indicated earlier, the study's purpose was to assess impacts of temephos, applied directly to rivers as Simu/ium larvicide on the environment as could be detected from indicator fauna characteristics. The main approach adopted was to estimate levels of relevant fauna parameters during annual Dry-seasons, which usually lasted from January-April. This was because larviciding of rivers had, for various technical reasons, been scheduled for dry seasons (Wilson et al. 1996). The initial years' (1999 & 2001) work consisted mainly of: 2 (a) Survey of rivers for selection of representative ones and stations on them for monitoring studies and. (b) Obtaining pre-treatment general and specific baseline information on the environment and characteristics of the fauna to be monitored. These included information on: (i) River habitat quality assessment Fish species occurrence and distribution. Using a variety of fishing gear and observations from local fishers' catches. Fish species occurrence and richness of catch using standard gear for monitoring Estimation of catch (CPUE) by monitoring gear Estimation of immediate impact of treatment on fish and prawn catches. Estimation of coefficient of condition (K) of fishes. ( ii) ( iii) (iv) (v) (vi) J I And establishment of the following as monitoring parameters o Habitat assessment o Fish species occurrence by monitoring gear o Fish species richness of catch per sampling event. o Estimation of catch per unit effort (CPUE) of fishing for fish and prawns o Estimation 'Condition' of fish species 2.2 Methods: 2.2.i Assessment of aquatic habitat quality (As fish environment) Prior to each year's sampling event, measurements of major characteristics of th e fish environment, including for example, river width, depth and related vegetation were estimated (see Table 1). lnformation obtained provided some backgroundfor interpretation of sampling data. 3 I { {2.2.ai Determination of fish species occurrence and richness of catch As a measure of continued occurrence of fish species at a study station in relation to temephos application to river, fish fauna was sampled using a baftery of gill- nets. For Bioko rivers, a battery of four nets, each measuring 6. 0m long and 1 .0rn deep but having different mesh sizes of netting material (meshes 12.5 mm, 15.O, 17.5 and 20.0 mm) were deployed. The battery of nets was deployed for two consecutive'Nights' (i.e. approximately 1800h-0700h) to constitute a sample of fish at a station. Fish caught per mesh size-nets were individually identified based mainly on keys provided by Leveque, Paugy and Teugels (1990; 1992) and Schneider (1990). 2.2.iia Estimation of catch per Unit Effort (CPUE for fin fish and Prawns) For fin-fishes, fish caught by battery of gill-nets per sampling event provided material for the estimation of CPUE by Number and weight. For prawns, nurnber of prawns captured by ten prawn-traps positioned in the same locations through- out the study and without bait was the basis for estimation of catch. (Number or weight). For fin fishes, the expression below was used to estimate CPUE CPUE = N x 100 / I xZxnx d and W =Wtx100 / lx2xn x d (Leveque, 1988) Where N = number of fish caught W = weight of fish in grams. I = length of net in meters d = depth of immersion of net n = number of nights of fishing. For prawns, CPUE in relation to river larviciding was studied on River Musola, where the ten prawn traps were deployed for five 'Night' (1800hr-0600h0 and 'Day' (0700h-1800h) catches. Catches were recorded per'Day' or'Night. 4 I 2.2.iv Estimation of Goefficient of Condition (K) of Fish: Fish 'Condition' is an expression of the 'well being' of a fish in numerical terms. For each fish species the value is a constant or about so for class size of the species, especially in the same environment. The value is estimated by the formula: K = W x 100 / L3 (Leveque, ef a/ 1988) Where W = weight of fish in grams. L = standard length of fish in cm. 3.0 RESULTS 3.1 Habitat Quality status of fish Environment during study Tables 1i and 1ii summaries status of fish habitats of rivers Metedero and Musola during sampling events on the rivers from 2001-2005. Similar recordings were made for rivers Apu and Mirupururu. However, virtually no changes occurred in characteristics of fish habitat in the later rivers. On the Matedero, habitat characteristics which altered during the study period were mainly: Stretch of river, the mean width and mean depth. The changes resulted from actions related to construction of a bridge across the river at about 500m downstream of the station. The actions included temporary pilling of soil across part of river resulting in increase in depth and width but decrease in flow. Also, a tree on one bank was caused to almost fall into the river resulting in increased percentage of river shaded. On river Musola, changes in the fish habitat during the study period which influenced catches, were primarily physical. Mainly, a bridge collapsed at the mouth of the river downstream of study station. A temporary repair of the situalion completely or partially cut off sea water intrusion into lower part of river at different times. The situation restricted marine water fish availability at station. The repair works also caused some pilling up of soil in river, greatly reducing river depth and stretch. 5 a '! { 1 i t (o o oo =E f E x o E o 1zc o -o Eo oo og oE =L .o o o o)o co L o o- otr o o o o(U =L o) o) E(U Lo o- .cooo oLooo N o, o) o, o, o) o,oN oN oc oc E E = E = E = E EE E lr)ooN o ci(o (oq s Nro o c) '= o c)o !; c)o f odI uiJoo E. 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LU tlr o Io tlJ E, U) T\ p c o c eg o o) o>o Enco= >e -oE(E.=66 -YEc-(6U'dlv sCceg g -o- c '68EEx(Ufo oERE;(,,>cD o-(E>es a.o EeEtiDt( FEg(u -foh F o (trE(Uo_o(l,o(/, rr7 (tre*oE8g6 o= -or .9 a4ll rri +Foz lololol TI orl6)l6)l -l 5l ol =lul url >til r-l <tll OI(,)lfl =ltl uJl >l EI rr-l olrl <l EI ol +l ol FI <l =ld <t u-l ol alflFI -<lol ! 1 := o -o(U t_ T { L oo(L L oo 0- o o(L lr)N o NN Loo 0-c I .o =a o I afa (u = o I -o =o (u = c I o f V) c I o Ja o LIJ uJ rLa z ulttrfo iL a 3.2 Fish species occurrence in relation to application of temephos to Bioko lsland rivers (2001-2005). Table 2 shows lists of fish species encountered in rivers of Bioko during 2001-2005 in the study of possible impacts of temephos application to the rivers on fish. Sub-units of Table 1 (ie. 1a,2b,2c and 2d) show species encountered on four representative rivers on the lsland. Table 2a - River Apu References to possible impact of river treatment with temephos on fish species occurrence, table 2a shows that the only species which occurred in a pre'treatment sample, was the only one that also occurred in a post treatment sample. River Matedero at Lengema via Malabo (Table 2b) Fish species occurrence in study samples of river Matedero in 2001-2005 shown in Table 2b indicate six species encountered. The Table also shows that four of the fishes were common to pre-and post-treatment samples. The 'extra' two fish species occurred only in post treatment samples. River Mirupururu at Malabo-Airport Bridge (Table 2c) Table 2c shows that six fin fishes and Macrobrachium were encountered at the river Mirupururu station in five samples take between 2001 and 2005. Of the six fishes, five were common to both the pre-and post-treatment experimental fishing catches. The sixth, T guineeusr's, (the only known tilapia of the Bioko lsland) was not encountered in catches after 2001. R. Musola/ at Mouth of River (Table 2 d) Table 2d, shows occurrence of fish species on various sampling events during 2OO1 - 2005 on river Musola at the mouth of river. The Table briefly indicates the following: 8 o 16 fish species were encountered in the five sampling events from 2001 - 2005. There was one sample a year during January, except in 2003 during which a second sample was taken in May. The 16 species could be divided into two 'ecosystem groups' of fishes. First, were the true or primarily, freshwater fishes (species 1-8 in Table 2d). Then the salt water fishes (9-16 in Table 2d) some of which could also be considered as temporary freshwater visiting fishes from marine water. The situation was accounted for by the station being the lower part of river, including segment of river influenced by marine tides. . One specie (A- spilaunchen) occurred in all samples o Three species, (8. Sporator, C. cameruneensis and H. bimaculatus) occurred in two of the five samples (ie 40% occurrence). . Nine species occurred in only one of the five samples (20%o occurrence each) . Of the species which occurred in only one sample, the salt water fishes, typically Liza and Lutjanus species, were predominant. o the salt water species occurred in 2001 and 2003 ii samples. . in the 2003 (i), 2004 and 2005 samples, only primary freshwater species were encountered. Reference to the possible or potential long term impact of river treatment on fish species occurrences. The results above suggest no impact of larviciding on the freshwater fishes. 3.3 Fish species richness of catch per sampling event (2001-2005) in relation to Temephos application to rivers. Figure 2 represents number of fish species caught per sampling event in study rivers on Bioko lsland in relation to temephos application to rivers. (Also see Table I of Annexes). Observations made on individual rivers are shown in fig 2a, 2b,2c and 2d. t 9 1 a { I IFigure 2a-River Apu: The figure. Shows that only one fish species was encountered in 2001, prior to the Ground larviciding treatment and also after both the Ground and comprehensive operational treatment. lncidentally, it was the same species of fish on both occasions (see Table 2a). The river was not sampled in 2004 and 2005. The situation indicated no over-all alteration in species richness of catch with treatment of river. Figure 2b-River Matedero Fig. 2b indicates that a species richness of three (3) was recorded on four out of five sampling events. Of the four occasions, two were prior to the comprehensive operational river treatment (between the 2003 (i) and 2003 (ii) sampling events) and two in 2004 and 2005. The over-all status of species richness of catch was not altered two years after comprehensive operational treatment of the river with insecticide. Figure 2c-River llirupururu Fig. 2c indicates that a species richness of four (4) was recorded on four sampling occasions out of a total of five sampling events on the river. Of the four occasions, two were prior to the comprehensive treatment of river in 2003 and two after, in 2004 and 2005. The level of species richness of catch was also maintained between 2001and 2003 after the Ground larviciding in 2001. The overall situation indicated no change in species richness of catch with treatment of river. Figure 2d-River Musola Fig. 2d indicates that species richness of catch in River Musola consistently decreased in the five samples obtained between 2001 and 2005. The situation t 1 i 1 I l0 Table 2. FISH SPECIES OCGURRENGE IN RIVERS OF BIOKO ISLAND 2OOI .2005 a. RIVER APU b. RIVER MATEDERO LENGEMA (via MALABOI c. RMER MIRUPURURU . MAIABO - AIRPORT BRIDGE (upstream) d. RIVER MUSOLA. RIVER MOUTH.LUBA BRIDGE I SAMRLING YEARS -+ 2001 2003 2004 2005 2006 NAME OF FISH I il Epiplatys sexfaciatus + + ITI SAMRLING YEARS ---+ 2001 2003 2004 2005 2006 NAME OF FISH I il Bahus campthacanthus + + + + + Bahus lineatus + Bathygobius sporator + + + Ch romidotilapia guntherii + + + Claias cameruneensis + Macrobrachium spp + + + SAMRLING YEARS ---) 2001 2003 2004 2005 2006 NAME OF FISH (i) ( ii) Barbus campthacanthus + + + Barbus tn'spi/os + + + Bathygobius sporator + + Brycinus longipinnis + + + + + Pe lvi cach romLs faenrafus + + + + ? Tilapia guineensis + Macrobrachium spp + SAMRLING YEARS ---+ 2001 2003 2004 2005 2006 NAME OF FISH i il Aploche il icth ys sp il a u c he n + + + + + Aplocheilicthys kabae + Barbus bynni occidentalis (cf) + Bastrychus aficanus + Bathygobius sporator + + Clarias cameruneensis + + Ep i pl atys sexfascaafus rath ke i + Hemichromis bimaculatus + + Hemicaranx bicolor + Liza dumeili + Liza falcipinnis + Lutjanus dentatus + Lutjanus endecacanthus + Lutjanus goreensis + lobofes spp + Protogobius schlegelii + t 1 d 11 -t IFig2. c. 2 U) E r.szIo tr o llJ6 0.5 UJLoo SPECIES RICHNESS OF CATCH PER SAMPLING EVENT lN RIVERS : 2001- 2005 RIVER APU - MALABO. LUBA BRIDGE 2001 2003(i) 2003(ii) 2oo4 SAMPLING EVENTS 2005 RIVER MATEDERO - LENGEMA ( via MALABO ) I + 2001 a U) uJzIIt .tt llJ o lrJI U) b 5 4 3 2 1 0 NOTE 2003( i ) 2003( ii ) SAMPLING EVENTS 200/ 2005 d I t I - R IVE R RU, MALABO. AIRPORT BRIDGE a U']UzIo e. U)g o ut(L o 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 2001 2003(i) 2003(iil 2oo4 SAMPLING EVENTS 2005 - V \ r\-./ - RIVER MUSOLA - MOUTH (t, o ulzIo e. o Lll o uJ o-o 9 I 7 6 5 4 3 2 ,| 0 I \= I 200s(i) 2003(ii) 2004 SAMPLING EVENTS 2001 2005 12 cr. { ta was attributed to alterations in the study area. The major changes in study area were a physical reduction of the study area (Table 1ii) and blockage of connection between the sea and lower reaches of the river, which was the study area. The blockage was in place during the 2003 (i), 2004 and 2005 sampling events and partially during the 2003 (ii) sampling. The blockage effectively eliminated sea water intrusion and thus the salt water fishes that 'visited' the lower parts of river. Evidence of this is available in Table 2d where saltwater fishes were absent frorn catch during sampling events when blockage was in place as indicated above. Thus, the reduction in species richness of catch was mainly attributed to absence of saltwater fishes from catch due to physical changes in study area. 3.3.0 Trend of Fish Catch (CPUE) in Rivers of Bioko lsland in Relation to Temephos Application to River Estimates of fish catch trend was based on fish Numbers or Weight caught by the battery of gill-nets during six sampling events from 2001-2005. As indicated in the 'Methods' section of this report, the battery of nets consisted of four equal sized gill-nets made of different mesh size netting material. (see Fig 3.iii) The mesh sizes, deployment of nets and formula for estimating Catch per Unit Effort (CPUE) of fishing have been stated earlier in this report. Figure 3.i and 3ii: Show the trends of total catches made by Number and Weight respectively, by the battery of nets per sampling event in three representative rivers of Bioko between 2001 and 2005. The figures also indicate treatments of rivers with temephos during the period. River Matederc (Figs 3i a and 3ii a) Figurcs 3.i (a) and 3ii (a) show trends of total CPUE by numbers and weight respectively in River Matedero during 2@1- 2005. By numbers, the figure indicated that the catch increased in subsequent sampling events from 2001 till2004. The 2003(i) CPUE was about 54% higher 1 i 1 i { l3 ! 6ooN o 'Joot co F G, o(Lt a o co 5 =jtftf(L f,t =E. TU E, =I.IJ(, z uJ) on UJo I.IJF =t UJ E, rotol il?lolol6rl ;l ol -lo-l lIII =lluFI -lFl BI FIzl rul =lFI <t urltlFI EI rul >lEI olFI zl ol FI 5I UJItl zl EI uJl ol =lfl2l =l ,il ?l cl ol rlFI olil ol ol zllultlFI lulFI ol =l !aooN oFz ltJ =>o llltoNZ J o- - 8ooN ooN $ ooooooooooooooooo@!NOO@!tN? (oN)E'n'd'o -rvror uJ(, o tr.dt (DfJ r 1-f, o = 5 oof =E tu t clt ott I 1 I t 1 l I I t ar.l d) =lzI E uIdl lzI to Rca 2 u.l _ul s96-Nd . ooN oooN oC' oooooGrooooooooF@roioN (o$ E'n'd'c rvror o E ul @ -fzr oooooo6oooooo@rotoN(orlln'a'c rvror g, oool ooN r,o8p z uJ uJieo=Rd =o o €tN oo t tooN oFz UI ; u.rooO-Nd = ooN oooN ooN LU oo tr t.)t dI RI E .t o -l (Lol t ..1 ool co fl<' =l iHl 5 -l tFl :f =l 3Fl tfrl = =l trFI IUpl e FI al uJl >I EI PI zl ol FIlllulfrlo -l m El 3gl s =ls3l yil u.lql dil tr EI Ebt =2l fr El a lUlFI olzl lr, -b' FII uJ 3 tr loooN iooNU) Fz u.l -l!:oi;zo-Nd =o ooN ooN NOO@*NO (6x ur ud'E'n'a'c'rvlol (o\tNOO@!}NO (6v ul ud'r'n'a'c'rvrol -o a o(t CDlt { ,, t 1 F -(9 UI =tr F -I UJ 3 B taooN oFz IrJ =il E9 G = -o ooN oo oo6N NOO@iNO (6v q ud'a'n'a'c lvlor (o Fig 3 iii. TREND OF C.P.U.E. tN RELATION TO RIVER TREATMENT : 2001 - 2005 RIVER MATEDERO . LENGEMA U)t llJ d! =fz z 14 ?q o 350 300 250 200 150 100 50 412.5 tr 15.0 tr 17.5 r20.0 2001 2003( i ) 2003( ii ) SAMPLING EVENTS 2004 2005 b. RIVER MIRUPURURU - I'IAI.ABOAIRPORT BRIDGE od UJ(D =fz z ,4 ?q o 800 700 600 500 400 300 200 100 0 412.5 tr 15.0 EJ17.5 120.0 2001 2003(i) 2003(ii) 2004 SAMPLING EVENTS 2005 I a. NOTE I i 1 t I I 16 0 t Fig 3 iii TREND OF C.P.U.E. lN REI.I\TION TO RIVER TREATMENT : 2001 - 2005 RIVER MUSOI.A. MOUTH 350 300 250 200 150 100 50 2001 2003(i) 2003(ii) 20u SAMPLING EVENTS 2005 I I c E LU cn :)z z uij d o a't2.5 tr't5.0 o17.5 r20.0 0 NOTE 1 1 d 17 Fig 3 iv. TREND OF C.P.U.E. lN RELATION TO RIVER TREATMENT : 2001 - 2005 a. 7000 6000 5000 4000 3000 2000 1 000 FII[J =z ui f{ o 0 2001 2oo3( i ) 2oo3( ii ) SAMPLING EVENTS NOTE 2004 2005 b I I RIVER MIRUPURURU - MALABO AIRPORT BRIDGE . 2OO1 - 205 FI(9 H z 14 ?(L o 7000 6000 5000 4000 3000 2000 1000 0 2001 2003(i) 2003(iil 2004 SAMPLING EVENTS 2005 412.5 tr15.0 o17.5 !20.0 I t I i q I I 18 RIVER MATEDERO - LENGEMA 112.5 tr 15.0 tr 17.5 t20.0 Fig 3 iv. TREND OF C.P.U.E. lN RELATION TO RIVER TREATMENT : 2001 - 2005 R.MUSOLA. MOUTH 6000 5000 4000 3000 2000 1000 2001 2003(i) 2003(ii) 200/. SAMPLING EVENTS 2005 i I c FII IIJ = =ti l o- o 0 NOTE l I 1 i 1 I I I III 412.5 tr15 0 El17.5 t20.0V 19 i icompared to 2001 catch. The 2003 (ii) catch was higher by about 22% compared to the 2003 (i) CPUE. And the 2004 CPUE higher by about 11% compared to the 2003 (ii) catch. However, the catch of 2005, which was about 670/o lower in value compared to the 2004 catch, was comparable to the 2001 catch. lt must be noted that the 2001 CPUE value was recorded prior to treatments of the river. Catch made in 2005 was most comparable to the relatively lowest catch made in 2001. The trend of catch over the period by Weight (Fig. 3.ii (a) was similar to CPUE trend based on Numbers with slight differences in magnitude ,which were attributed to differences in sizes of fish caught on different sampling events. River Mirupururu (Figs 3i (b) and 3ii (b) Total catch trend in River Mirupururu from 2001-2005 are represented by Figs.3.i (b) and 3ii (b) by Number and Weight respectively. The Figs indicate that catch values at 2003 (i) sampling were 87% higher by Number and 30o/o higher by Weight compared to the 2001 sample. The 2003 (ii) sample showed a higher percentage increase over the 2003 (i) sample compared to the increase in catch of 2003 (i) over the 2001 catch value. However, catches made in 2004 and 2005 were both lower compare to catch of 2003 (ii). The increases and decreases in CPUE could not be related to river treatments indicated. This was because if the increased CPUE recorded at 2003 (i) over the 2001 catch was related to tre treatment in 2001, then the CPUES recorded in both 2OO4 and 2005 should haye been higher compared to the CPUE of 2003 (ii) sample. As they were a year and two years respectively after the treatment in 2003, just as the 2003 (i) sample was two years after the 2001 sampling event. River Musola (Fig 3i c and 3ii c) The trend of Total CPUE in river Musola showed increases from 2001 to 2003(i) (93% N) and also from the 2003 (i) to the 2003 (al) sample (59 % N). lt was considered that if the increase in catch was related to treatment of river, llre increase between the 2003 (i) and 2003 (ii) should have been higher compared to what was observed between 2001 and 2003 (i) sample. Further more, effecl ofi t , i I I 20 {treatment in 2001 could not have physically lasted till 2003, two years after the event. ln the long-term, there appeared to be no trend in catch after the comprehensive larviciding and thus involving the 2003 (ii) the 2004 and 2005 catches. 3.4.i Gatch (CPUE) trends of individual mesh nets. Figures 3.iii and 3.iv show catches (CPUE) of battery of gill-nets deployed for sampling fish in three representative rivers of Bioko island for the study reported on here. The figs. afford opportunities for consideration of individual mesh size nets catch trends as well as relative catches of mesh size nets over the study period. For example, in Fig. 3iii a, catch series of net mesh 12.5mm from 2001-2005 did not indicate a pattern in relation to river treatment. CPUE of the mesh showed a decline in 2003 (i) sample compared to the 2001 sample two years after the 2001 treatment. However, the catch of the mesh in 2004, after the 2003 treatment showed an increase over the 2003 treatment. Comparing the catch trend in river Matedero (fig. 3.ii a) to observations made in river Mirupururu (fig 3. iii b) net mesh 12.5mm recorded an increase in 2003 (i) compared to its catch of 2001 after treatment in 2OO1. A situation which does not compare with what obtained in the previous river. Again catch trends of the same mesh size net (i.e. 12.5mm) in river Musola (fig. 3.ii c) was different from 'trend' in two previous rivers. Similarly, the catch trends of net mesh sizes 15.0mm, 17.5mm and 20.0mm were not comparable. lndicating that in relation to treatment of the three rivers no common pattern of catch could be established for all nets. Also important to note was that fluctuations in catch by net mesh 20.0mm was the most extreme compared to other mesh size nets. The situation was considered unlikely since the mesh should capture the biggest size fish in the range and thus be least affected if fluctuations in CPUE of all meshes were to be related to the treatments. Figures 3. iii a, b and 3.iii c considered in relative catch per mesh size net to others per sampling event also did not indicate a pattern in relation to river treatment. t I I I ! ! I 2t jI 3.4. ii Trend of prawn catch (GPUE) in relation to river treatment with Temephos (Figs.4.i and 4.ii) Figure 4.i. Shows'short' (within 7 days) and long term (between years) trends in prawn catches by Number in relation to temephos treatment of river. Fig.4.ii. shows the same trends based on weight of prawns caught per sampling event of 5 consecutive 'Nights 'or 'Days of sampling (see 'Methods' section) ln the long-term, results of 1't samples of fig. 4.i.a, b, c and d indicated that after every series of catch, for example, within 4.i.a, b, c or d, the prawn population recovered to record the highest catch at the beginning of 'next' series of catch. Thus the first sample of each set recorded the highest catch. lt was also possible to deduce that the extent of population recovery could be related to interval Iength. For example, between January 2003 and January 2004, the population recovered to record about 100 prawns in the first catch, just as it recovered between 2003 ii (May) sample and the sample of January 2004. However between January 2003 and May the same year, recovery was apparently not'complete'. The low catch recorded in the 1't sample of 2005 was attributed to an ecological situation of river bank vegetation loss and thus loss of cover at sections of river including some trap positions. Vegetation on river bank provided hiding places for prawns. The lower 'Day' catches recorded in all cases compared to 'Night' catches indicated that the prawns moved more at'Night' compared to 'Day'time. Reduction in catch within any series of catch indicated the immediate impact of sampling by removal. Thus treatment after 2001 and 2003 (i) sampling events did not apparently influence catch in 2004 and 2005. ! i 22 Fig 4 i. TREND OF PRAWN CATCH IN RIVER MUSOLA AT SEGESA IN NUMBERS .tAN 2003i 120 100 80 60 40 20 0 SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 NIGHT / DAY MAY,2003ii SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 NIGHT / DAY JAN , 2OO4 JAN ,2005 a. c. oz @u -oF !NIGHT IOAY b. 80 70 60 e50z ;40u5soF6zo 10 0 d oz oU -oF o 60 50 40 30 20 10 0 INIGHT TDAY SAMPLE 1 SAMPLE2 SAMPLE 3 SAMPLE 4 SAMPLE 5 NIGHT / DAY I I I ! I 1 ! INIGHT TDAY 120 100 80 II NIGHT IDAYfl-rI e 7,nu uJ5eoF o20 0 SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 NIGHT / DAY 23 Fio 4 ii. TREND OF PRAWN CATCH lN RIVER MUSOLA AT SEGESA lN WEIGHTS JAN,2003 i a 1 200 1000 800 600 400 200 0 SAMPLE 1 SAMPLE 2 SAMPLE 3 NIGHT / DAY SAMPLE 4 SAMPLE 5 MAY,2003ii 5 @U IoF O 700 600 500 400 300 200 100 0 SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 NIGHT / DAY TINIGHT trDAY 2004 c. 1400 1200 ^ 10003 8oooU5 6003 ooo 200 0 NIGHT DAY SAMPLE 1 SAMPLE 2 NIGHT / DAY SAMPLE 3 SAMPLE 4 JAN ,2005 t o ut -oF o 700 600 s00 400 300 200 100 0 SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4 SAMPLE 5 NIGHT/OAY trNIGHT IOAY 3 oU IOF o b d I I I{ ONIGHT ODAY 24 t l a3.5 Fish Co-Efficient of Condition (K) Trends in Relation to River Treatment with Temephos Table lll. i in the Annex shows estimated mean 'condition' (K) of fish species encountered in sampling events before and after temephos treatment of rivers Matedero, Mirupururu and Musola all on Bioko island. Table lll. ii, also in the Annex, shows mean K values of frequently occurring fishes in the rivers. Figure 5 (i) and 5 (ii) graphically show the trends of mean Ks of fish species which were encountered in the various rivers before and after operational treatments of rivers in 2001 and 2003. On river Matedero, Fig.S.i only Barbus campthacanthus had been encountered in 'appreciable' numbers both before and after treatments of river. The figure shows that the mean K of the fish before and after treatment of river were comparable. Thus river treatments with temephos did not induce a change in the 'Condition'of the species. Figure 5 ii shows status of estimated mean 'Condition' (K) of three fish species which occurred in pre-and post-treatment samples on River Mirupururu during the study (2001-2005). The fishes were Brycirus longipinnis, Pelvicachromis taenitus and Barbus fn'spr7us. Figure s.ia.(a) shows that the trend of mean 'condition' ol B. longiprnms fluctuated closely around the value of 2.7 in the five samples taken between 2001 and 2@5. Complete operational treatment of river occurred in early 2003. The Fig. therefore indicates that the 'Condition' of the fish was not altered by treatment of river with temephos. Figure 5 ii. (b) shows trend of mean K of P. taeniatus from 1999-2005 with treatment of river occurring comprehensively in early 2003. The fig. shows trat between 2001 and 2004 the K value of the fish fluctuated closely around about 3.5. i t I lI I ! l 25 t Fig 5.i a TREND OF CONDITION 'K'OF FREQUENTLY OCCURING FISH SPECIES.1999 .2005. RIVER MATEDERO, LENGEMA ( via MALABO ) 3 2.5 2 1.5 0.5 Y zo Eoz oo I a 1r 0 1999 2001 200/. 20052003 i 2003 ii SAMPLING EVENTS b NOTE I II { 1 d it 1 I LLI I r I iI I I I V 3.5 3.rl 3.3 3.2 3.1 3 2.9 2.8 I I t Y 2003 i 2003 ii SAMPLING EVENTS v z o F oz oo I U)tr 1999 2001 200,t. 2005 26 -t aFig 5 ii. TREND OF CONDITION ('K) OF FREQUENTLY OCCURING FISH SPEG|ES.1999 - 200s. RIVER MIRUPURURU, MAIABO - AIRPORT BRIDGE ( up-stream ) HIGH LOW . CLOSED 1999 2001 2003 i 2003 ii SAMPLING EVENTS 200,1. 2005 NOTE 3.5 -aYu 6 r.s tr62z 8,u IAl tr 0.5 0 I b. l I c d i I + iY I r r Le{ v zItoz oo I 9. TL 4 3.5 3 2.5 2 1.5 ,| 0.5 0 HIGH LOW . CLOSED 1999 2001 200s i 2003 ii SAMPLING EVENTS 2004 2005 v zo Fdzoo IIlr 5 4.5 1 3.5 3 2.5 2 1.5 1 0.5 0 I HIGH LOW . CLOSEO 1999 2001 2003 i 2003 ii SAMPLING EVENTS 20u 2005 27 l aFig Siii. TREND OF GONDITION fK')OF FREQUENTLY OCCURING FISH SPECIES.1999 - 2005. RIVER MUSOLA, MOUTH.LUBA BRIDGE. 4 1 999 2001 2003 i 2003 ii SAMPLING EVENTS 2004 2005 3 2.5 v o E 1.5z81 Iu, 0.5IL I I I I Ii Y 0 1999 2001 2003 i 2003 ii 2004 SAMPLING EVENTS 2005 1999 2001 2003 i 2003 ii SAMPLING EVENTS 200,4 2005 v zo Eoz oo IL LL 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 v zo F6z oo ro tr 3.5 3 2.5 2 5 1 0.5 0 b NOTE I t c. l t I , I I Ift V I I I I t 28 I It While in 1999 and 2005 the values were lower but comparable. The over- all indication from the Fig. was that the value of K has remained stable with treatrnent of river. Figure 5 ii.(c) shows condition of B. trisprTus in early 2003, prior to full operational treatment of river and in 2004 and 2005 prior to further treatment. Comparison of values of 2003 and 2004 indicated no change in fish 'condition' a year after treatment. However, the value of the K of a single specimen in 2005, indicated an increase in K value of the fish. Without another treatment between the 2OO4 estimate and that of 2005, it was considered that the 2005 value was 'unusual' but could not be associated with river treatment with temephos. This was based on the premise that, if the 2005 value was related to the treatment of river in 2003 the value in 2004 should have been higher compared to value obtained. Therefore the 'condition' of the species was considered to have remained stable since the treatment of the river in 2003. Figure 5. iii. (a, b and c) shows status and trend of mean condition (K) of three fish species which occurred in some samples taken from river Musola before and after treatments of the river. Figure 5 iii. (a) shows trend of K of A. spilauchen which had occurred during all sampling events on river Musola during the study. The mean K values per sample indicated that the value had consistently been about 3.0. A situation indicating no change of K rave with treatment of river with temephos in 2003. Figure 5 iii (b) shows values of mean K estimated for B. sporator in River Musola on three occasions that the species was encountered in a total of six sampling events., The 2001 sample was obtained prior to both Ground and comprehensive treatments of river in 2001and 2003 respectively. The range of individual K values in the 2001 sample makes it comparable to values obtained in 2003 and 20O4. Thus indicating no change in K value of the fish with treatment of river in 2003 up till 2004. t 1 II 29 -{ I I I L, Figure 5c (iii) shows the status of K of H. bimaculafus in River Musola in 1999 and early 2003, both before the operational treatment of the river and the value in 2005 after the treatment. 4.0 Synthesis, discussion and conclusion 4.1 Preamble: The major concern that necessitated the study reported on here was possible long- term impacts of temephos on the aquatic environment of Bioko island. Temephos is the insecticide being used against larvae of Simulium damnosum, the vector of Onchocerciasis in Bioko, to contribute to eradicating Onchocerciasis on the island. The larvae oI S.damnosum inhabit fast flowing segments of rivers. APOC, the implementing agency of the disease control, chose temephos based on accumulated knowledge of its specificity to Srmulium lawae and minirnum impact on fauna (Abban and Samman, 1982; Abban et al 2OO2; Calamari et al 1998; Haugard et al 1993; Paugy et al 1999; Yameogo ef a/ 1993; 2001). However, APOC did not assume the environmental appropriateness of temephos in the Bioko aquatic environment but instituted an impact assessment study to which this report contributes to. This report concerns long term impact assessment of temephos on fish and prawn fauna of Bioko rivers, with special reference to parameters of the fish fauna, including: . Occurrence of fish species . Species richness of catch o Catch per Unit Effort (CPUE) of Fishing of fin fishes and prawns o ?rd coefficient of condition of fish species, all in relation to use of the larvicide in the rivers of Bioko. 4.2 Re: Occunence of fish species in relation to Temephos use Results obtained after six sampling events per river between 1999 and 2005 on four representative rivers indicated that no change in species occurrence had occurred that could be attributed to use of larvicide in the rivers during 2001 and I { t I { 30 12005. A similar observation was made by Paugy ef a/ (1999) after 20 years of Simulium larvicides use in rivers of West Africa. However, in the present study an ecological change at the study site on river Musola effected a definite change in species occurrence. The situation contributed further to the consideration that if temephos had caused a long-term change in the water environment, species occurrence could be a reliable parameter to assess the situation. ln the long-term, the impacts of two treatments of Bioko rivers in 201 and 2003 had until 2005, caused no detectable difference in fish species occurrence in rivers. 4.3 Re: Species nbhness of catch in relation to iver treatment with Temephos Results of assessment of trends of species richness of catch in relation to treatment of rivers (Fig. 2) could be summarised as follows: o Four rivers were studied during 2001-2005. . Five samples were taken on each river during the period. . !n relation to treatment, one sample was taken on each river prior to any treatment of rivers. o One sample after 1't treatment in 2001 (May) o Three samples after 2d treatment, which took place in January-April 2003. The samples were obtained in May 2003, January 2004 and January 2005. ln three of the four rivers, species richness of catch before and after all the treatments remained constant. ln the 4h river a physical barrier which restricted movement of some fish was responsible for reduction in richness of catch. Conclusion drawn was that temephos treatment did not influence species richness of catch. A similar deduction was arrived at from analysis of 20 years of Simutium control in W. Africa by larvicides application to several rivers (Paugy ef a/ 1999). 1. I I I i J 3l It 4.4 Re: Trend of fish catch (CPUE) in Relation to River Treatment The trend of catch (CPUE) on four rivers based on Number and/or Weight of fish caught (Figs. 3i and 3ii) could not be attributed to introduction of temephos to rivers. For example, on river Matedero Fig 3i a, 3 ii a CPUE (N) recorded in January 2003 was 54% higher by Number and 63% by weight compared to estimates made in January 2001. The difference could not be attributed to treatment of the river in 2001 after the year's sample had been taken because time lapse between the 2001 sample and 2003 sample was about 24 months. Available evidence indicate that where temephos or other larvicides, eg Permethrin, had apparently influenced CPUE, the effect did not persist for beyond about 72 hrs. (Abban & Samman, 1982, Yameogo ef a/ 1993). The situation could also be supported by the current data (Fig. 3i) which shows that the trend of catch was broadly not uniform in the four rivers which received treatment at the same period. Fig.3i for example, first shows that CPUE recorded on R. Matedero in 20M after the treatment in 2003 was higher compared to the 2003 CPUE. However, on the river Mirupururu the 2004 catch was less compared to the 2003 (ii) CPUE. Data on R. Musola could not be used here due to change in environment already elaborated on. 4.5 Re; Sfafus of fish 'condition' of Fish specr'es in relation fo use of Temephos in Bioko Riyers Fish 'Condition' (K) summarily expresses the 'well being' of fish species in numerical terms. Usually, the K of a species is a constant, at least, for various size classes of a species. Thus if environmental conditions were induced to change unduly, the 'condition' of species would be expected to be affected. Results of monitoring 'condition' of fish species in three representative rivers in Bioko (Fig 5i, Sii and Siii) indicated clearly that no change had occurred in the K of species which had occurred before and after river treatments. The situation suggested that introduction and use of temephos had not caused any environmental changes including e.g.-availability of fish food to deny fish of its nourishment that could have caused a change in K. Also, the results indicated that l I 1j Z I I 32 tthe fish had not been 'disturbed' or stressed by the introduction of the larvicide in the rivers. Thus the maintenance of their 'condition'. Similar results had been indicated by Yameogo ef a/ 1993; Paugy ef a/ 1999. Gonclusion From the above it is our conclusion that temephos had not caused undue impact on the aquatic environment of Bioko. Also, the Srmu/ium larvicide did not stress fish in Bioko rivers. Therefore, as was anticipated, based on accumulated knowledge on the larvicide by OCP, properly managed use of temephos against Simulium larvae could be continued to control river blindness in Bioko lsland, Equatorial Guinea, without affecting fish and prawn fauna in the long-term. i. I 4 I i JJ i t_ I { t I a il ti ! References Abban, E. K. and J. Samman, 1982: Further observations on the effect Abate on fish catch. Environ. Pollut. Series A.27,245-254 Abban, E. K. ; B.A. Boatin, J-M. Hougard, C. Leveeque,and L. Yameogo (2002) Preserving the environment: a major OCP concern one the past twenty-five years. 50pp. OCP/EG District. General. Orig. French/English. Boatin, B; D.H. Molyneaux; J.M. Hougard; O. W. Charistensen, E.S. Alley; L. Yameogo; A. Seketell and K. Y. Dadzie. 1997: Patterns of epidemiology and control of Onchocerciasis in West Africa. Journal of Helmintholgy: 71,91-101. calamari, L. Yameogo; J .M. Hougard and c. Leveque. 1998: Environmental Assessment of Larvicide use in the Onchocerciasis Control Programme. Cheke, R.A. 1998: Getting under the skin: An inaugural lecture delivered at the University of Greenwhich: 29th April 1998, 49pp. Hougard, L-M; P. Poudiougo; P. Guillet; C. Back; L.K.B. Akpobua and D. Quillevere 1993: criteria for the selection of larvicides by the Onchocerciasis Control Programme in West Africa. Leveque C., C. P. Fairhurst; K. Abban; D. Paugy; M. S. Curtis 1988: Onchocerciasis Control Programme in West Africa te years monitoring of fish populations. Chemosphere 17 (2): 421-440. Leaveque, c., D. Paugy and G. G. Tengds (1990): The Fresh and brackish water fishes of West Africa Vol. 1 pp389. 34 1Leaveque, C., D. Paugy and G. G. Tengds (1992): The Fresh and brackish water fishes of West Africa Vol. 2 pp702. Schneider, W. (1990): Field guide to the commercial marine resources of the Gulf of Guinea; FAO species identification sheet for fishery purposes. 268pp. Prepared and published with the support of the Regional Office for Africa (RAFR) Paugy D; Y. Fermon; K. Abban M.E. Diop and K. Traore. 1999: Onchocerciasis Control Programme in West Africa: A 20 year monitoring f fish assemblages. Aquatic Living Resources, 12 (6): 363-378. wHo 1985. Wilson, M. D; R. A. Cheke; J. Mas; J. P. McCatl; R. P. Post and A. Sima. 19g6: Evaluation of potential eradication of Onchocerciasis from the island of Bioko, Republic of Equatorial Guinea (WHO/TDR Project No. 05/18113/,, id.950612). Final Report and supplement. Unpublished Report for wHo/TDR, Geneva. Yameogo, L. J-M. Taposoba and D. calamari (1991): Laboratory toxicity of potential blacHly larvicides on some Africa fish species in the Onchocerciasic control Programme area. Ecoloxicol. Environ. saf. 21: 24a-2s6 yameogo, L., E. K. Abban, J-M. Elouard, K. Traor6, and D. Calamari (1993). Effect of permerthrin as Simulium Larvicide on non-target aquatic fauna. Ecotoxicology, 2: 1 57 -17 4. Yameogo; K. Traore; c. Back-M. Hougard and D. catamari. 2001: Risk assessment of etofentox (Vectron R) on non-target aquatic fauna, compared with other pesticides used as Simulium larvicide in a tropical environment. Chemosphere 42 (2001) 965-974. t 1I { I I i 1 35 {I Zimmerman. A, K. Y. Dadzie; D. De Sole; J. Remme: E. Soumbey Alley and T. R. Unnasch 1992; Onchocerca Volvulus DNA probe classification correlates with epidemiological patterns of blindness. J. lnfec. Dis; 165: 964-968. 1 t 1 ) 36 Table 1 ANNEX SPECIES RICHNESS OF CATCH PER SAMPLING SITE AND EVENT INRIVERS OF BIOKO 2001 - 2005 *River was not sampled j { I I { RIYER /SITE 2001 2003( i ) 2003( ii ) 2004 2005 APU AT MALABO - LUBA BRIDGE I 0 1 * t MATEDERO AT LENGEMA ( via MALABO ) 3 3 4 3 3 MIRUPURURUAT MAI-ABO - AIRPORT Bridge 4 4 3 4 4 MUSOLA AT THE MOUTH I 6 4 3 2 37 { Table ii ANNEX NAME OF FISH SPECIES. NUMBER AND WEIGHT CAUGHT PER MESH SIZE NET JANUARY.2OO5. a. RIVER MATEDEROAT LENGETA via HALABO b. RIVER TIRUPURURU AT If,AI-ABO . AIRPORT BRIDGE (upstream) c. RIVER MUSOLA AT THE TOUTH - LUBA BRIDGE * d a i I 1 MESH SIZE OF NET 12.5 15.0 17.5 20.0 TOTALS NAME OF FISH SPECIES NWt NWt NWt NWt NWt Bahus campthacanthus 2 7.6 1 12.5 15 350.1 00 18 370.2 Clarias cameruneensis 00 1 119.7 00 00 1 119.7 Chromidotil apia guntheii 1 6.6 00 00 00 1 6.6 TOTALS 3 14.2 z 132.2 t5 350.1 00 20 496.5 MESH SIZE OF NET 12.5 15.0 17.5 20.0 TOTALS NAME OF FISH SPECIES NWt NWt N YVt N VYt NWt Brycinus lon,gipinnis 2 21.3 14 118.9 4 18.8 00 20 159.0 Bahus tnsp//os 00 2 18.3 00 00 2 18.3 Barbus campthacanthus 00 1 10.1 00 00 1 10.1 Pe lvi c ach ro m i s s u e nth e ri i 00 00 00 1 15.2 1 15.2 Barbus spp 1 2.7 00 00 00 1 2.7 TOTALS 3 U.O 17 147.3 4 18.8 1 15.2 25 205.3 MESH SIZE OF NET 12.5 15.0 17.5 20.0 TOTALS NAME OF FISH SPECIES NWt NWt N VVt NWt NWt I 60.1 3 33.5 00 00 H e michrom i s bim acu I atu s 00 00 3 68.5 0 0 3 68.5 TOTALS 3 33.5 3 5E.5 0 0 11 162.1 38 Ap loch e i I ichth vs so i I a u ch e n E --6011 (ooo ot E F. !(o o) a$ roooN (o (o\6l (\. o,q c\l !tooN .c. to N @q N N t- c! N (f)N $r- 6i ro c? (f) G s (o (o(o tN c\i (o r- c.j(,)ooN EL (f, 6tq ol o r aN \rt(fi r lf, c\,i oC'N oE e{ @q? tt$ CD oq N @(r)(fi c! o, ri Not(D ol o $ (a o? @ c! C! o eo o-(r, ca5 ao Or (U a a) s .s .g otrs u)5c ot c0 (r, o a_ aa 'tr at,fa G co ot UI oz J(L =a T -U) TL lt o r.u =z u, R(u oo a- Eoo (r,:a (E co cD5 (E o(E a/, E a ()I (D o- (rt t,q oo .s5 o) (E a(E E aa(o E5 ()(! a a() (E I I (oooN E F- roooN !(o @ F C\I rr) 6i (oo(.i @@ o tooN E rO (fr- C{v sq c\i C\l @ o? o E $ lo aN cf)q tt @ c!(o F N r t i- (rl,ooN E (f) rO\t N (t) (r) oq 6l (o ooN p c(\t o)r c\i r o) oq ot o, ol o 't ot 5 oJ (U a(E oB E Q o t, =sq(u() osa E(U o c/,5 €oa U) E. u.l (, z. J(L =a 1 IL Lrlr o lU =z t){ oo (r, Sa (u a o Qo o_ ct, a/,5 ao Or (E a cr) ta coos To E(u o (r,(! 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C\l t Nt!t oo) 6i (f)o c.i r o)q ol (oq C\l s(9 d F (9ooN P(o o) o) o) c.i O)(o 6i @o c.i GI rI @q(o (o\ F (f, @ ooN Ec(\t o(f, lo @ c.i (t, o)q N (o(o ^i lI)I (oq C\I o d (9 @ c.i (o c'i (9ot ot or o @ q c-,1 (f, loq(r) (a a N @ oq (o (f) F- c.i (\I r{) .q := o O)o Q a/) to5 ao o,o a o- o eo o. co ar) =aoIc oa q EG U(r, b eo (U N -t (r) .s o .E oN J s{l aD (E EoBooo _q\a (r) 5 €oa C"Ssoo Eo to =o (r, oa (l)\s e u)f, (E o C" .E xo(t, ar)\ (B .s uJa @ E, U oz J(L =a 1 -U) LL IL o UJ =z co o5o a_ u, a)\ o Eo oo a_ ooa(E\ IA\ .e o oo a. art U,q oo To\(U o t,(U (E C) (o (D 5oo .Ea aD E e o EoI o o .ao xc(E G .e oI 't o E5E (U N J (r, J (E coE at, c(E = -t cDfc q (U ooo(DBc(D eJc(EL\5 -t 6 U) o eob eJ e(E 's\ 5 -l aaC" (a o oao -t (U E E =o or5 I I I I I t l I Table lll, ii ANNEX TREND OF CONDITION 'K'OF FREQUENTLY OCCURING FISH SPECIES RIVER MATEDERO AT LENGEMA (via MALABOI RIVER MIRUPURURU AT MALABO - AIRPORT BRIDGE (up-stream) RIVER MUSOLA ( AT THE MOUTH ) 'a SAMPLING YEARS 1999 2001 2003 2004 2005 Barbus campthacanthus 2.19i0.37(3) 2.46!0.11(11) 2.47tO.25(1O) 2.5310.17(21) 2.52i0.20(18) Ch romidotil apia gu nthe ii 3.2610.17(4) 3.06(1) SAMPL]NG YEARS 1999 2001 2003 2004 2005 Brycinus longipinnis 1.93 (41) 2.77tO.35(41 2.65t0.46('10) 2.74t0.18(66) 2.74!0.13(23\ 2.7610.29(16) Pelv icachromis taen iatus 2.28 (2') 3.3810.,r2(2) 3.44(1) 3.76(1) 3.35 (1) 2.0e (1) Baftus tnspr/os 2.6210.04 (3) 2.66t0.34(2) 4.49 (1) SAMPLING YEARS 1999 2001 2003 2004 2005 Aplocheilicthys spilauchen 2.16 ( 18 ) 3.07t0.25(9) 2.99r0.26(9) 2.92t0.25(2) 3.08 (1) 2.9410.04(10) Bathygobius sporator 2,3610.49(3) 2.0310.07(4) 1.94r0.04(2) Hemichrcm is bimaculatus 3.8s (3) 3.68 (1) 3.26 (1) a I { 41 I