FISH TRANSPLANTATION AS AN ECOLOGICAL TOOL IN BOOS G FISH PRODUCTION: TIGA CASE STUDY

Transcription

1 FISH TRANSPLANTATION AS AN ECOLOGICAL TOOL IN BOOS G FISH PRODUCTION: TIGA CASE STUDY N.O. BANKOLE, E.O. 'TA, and A.N. OKAEME National Institute for Freshwater Fisheries Research (NIFFR), PMB 6006, New Bussa, Niger State, Nigeria INTRODUCTION ABS1'.RACT The paper discusses the status of the Tiga Reservoir Fishery pre-and post Clupeid transplantation. This was achieved by examining the species diversity, abundance and distribution with mitigating factors. It concludes with a verdict on the achievement of the transplantation exercise. With the recent spate of over-exploitation generally observed and reported on most of Nigeria's major inland waters artd the world over, it becontes pertinent to employ measures that will not only stem this trend but boost or improve the fish production in these inland waters. This is in view of the fact that more fisherfolks make the means of their livelihood through involvement in artisanal than commercial fishing. Between 1996 and 1998 studies conducted on twelve water bodies in Kano State revealed a paucity of fish species (average of 3 spp per reservoir) as well as poor yields (Ita and Pandogari, 1986; ita and Mohammed, 1987). Low fish density was attributed to be the major factor responsible for the poor yields. Stocking the reservoirs was thus recommended for the realization of their full potentials. Stocking of fish through transplantation can be a very useful measure in the management of small to medium-size water bodies. It could be carried out to improve the yields, reduce the raenace of rooted vegetation, eliminate or reduce th.e impact of predators through supplantation, fill vacant ecological niche, establish hardier species in a reservoir, and for sport fishing. Examples of such raeasures as listed above had been reported in Welcome and Henderson 1976; Ogutu-Ohwayo, 1990, Holcik, 1991; Welcome, BACKGROUND 1NFORMA,TION Geographical Setting Detailed information on the location, climate, vegetation and case history of the Tiga Lake has been reported in Adeniji and Ita (1976), Bankole, (1989) and Mbagwu, (1989). Physical Features The Physical Features of the reservoir according to Adeniji and Ita (1976), Galkowski and Galkowski (1980) and Abdullahi (1982) arc as follow:- Maximum length =40.42 lan Maximum width '24.42 km Maximum depth =40.0 m Mean depth =13.0 in Surface Asea =17, hectares Total storage capacity 178,49 x 10W. Other Features The Lake experiences an urinal draw-down of about 3m, (Sturm, 1984). This exerts an 204

2 Table 1: A Comparison of Species recorded in Various Reports on Tiga Lake between 1976 and *1996 Gill-net *1976 Rotenone **1986 Gill-net ***1989 Gill-net No Mean Mean Mean wt Mean wt No. wt No (gm) wt Species (gm) (gm) No (g) Hydrocynus forskali Labeo senegalensis Labe cottbie Alestes baremose Auchenoglanis occidentalis Synodontis gambiensis Barbus occidentalis Clarias anguillaris Tilapia zilli Alestes nurse Gnathonemits senegalensis Barilius senegalensis Sarotherodon galilaeus Oreochromis Mloticus Cluysichrornis niloticus Schilbe mystus Hemichromis bimaculatus Barbus sp Barbus macrops Barlius sp Alestes dentex Alestes leucescus Malapterurus electricus Bagrus bayad Mormyrops deliciousus Hyperopisus bebe Bagrus docmac Micralestes acutidens Pelmatochromis guentheri Source: Adenzji and ta (1976); Bankole and ha (1986); Bank le (1989). 205

3 Table 2. A Comparison of Ratios of Gill-net catches at the shore, surface and bottom habitats of Tiga Lake (1976*) and (1996") SHORE SURFACE BurTom * ** influence on the seasonal development of the marginal vegetation in the littoral zone of the lake. Imeybore et. al., (1986) reported the Lake to be quite rich in macrophytes, (16 Spp). Among these are Echinochloa stagnina, E. Pyramidalis, Polygonium senegalensis, Cyperus digitatus, Leesia hexandras, Vcssia cuspidata and others. Pre-Clupeid Status.:- The earliest reports on the Tiga Lake (Adeniji and Ita 1976, and 1982) had all reported that the inshore waters of the Lake were thickly populated with fish and that eighty percent of the fish caught came from the littoral margin while the hypolimnion was devoid of fish as a result of low dissolved oxygen (0.3mg/1) and thermal stratification. The pelagic zone of the open water was however found to lack fish. This they adduced to the lack of pelagic species to serve as food for carnivores. Ita (1979 and. 1982) therefore suggested that Clupeids be used to stock the open waters to reduce the concentration of carnivores along the shores as well as their predatory effects on the tilapias. This in turn is aimed at increasing the productivity of the Lake. Twenty three species from nine families were reported in Adeniji and Ita. (1976) while twenty eight were reported in Ita (1979 and 1982). However, Bankole and Ita (1986) recorded nineteen species from eight families in experimental gill-net catches and most of the fish caught were juveniles. (Table 1) In all these reports the catches were dominated by Ciehlids. Other species of prominence include Bagrids, Characids, CypriMds, Mochokids and Schilbeids. The species as reported in various reports are shown in Table 1. Table 2 also shows a comparison of the ratio/distribution of fish in the three habitats sampled in Adeniji and Ita (1976) and Bankole Table 2 (This report). CLUED) TRANSPLANTATION INTO TWA Due to the concentration of fish at the littoral margin (80% according to Ita, 1979), the recommendation was made to introduce clupeids to: (U.) Fill vacant ecological niches Effectively utilize the open waters and the abundantly available food there. Reduce the effect of carnivores on the Cichlids in the littoral margin. Create a better spatial distribution of fish. Increase fish production and Improve the returns and well-being of the fisherfollcs ou the reservoir. An effort to carry out the recommendation as well as achieve the above led to the transplantation of Clupeids from Kainji Lake between 1987 and 1989 to stock Tiga Lake. Over 150,000 clupeids were transplanted. MATERIALS AND METHODS Clupeid Collection Prior to transplantation, the effect of 0,vo capture methods (use of Atalla lift net and Dala dragnet) were ascertained alongside temperature and oxygen on the survival of live clupeids during acclimation and transportation. (Sado and Ita 1992). Dala dragnet was favoured over Atalla lift-net for the capture and collection of clupeids because it has a less stressful impact on the fish during capture. It's efficiency is also enhanced by wave action which is the contrary for the latter. 206

4 Description of fishing gear The Dala dragnet is a seine net without a codend but has a weighted foot rope. The netting material is made of 4mm mesh polyaraine materials. It is usually about m long and m deep. (Sudo and Ita 1992). Transplantation of Clupeids Clupeids consisting of Pellonula afteliusi and Sierrathrisa leonensis were placed in oxygen inflated double-lined polythene bags at an average of 400 fish/151 of water. The bags were held in packaging cartons and transported in a refrigerated-van. Transportation was undertaken at night to take advantage of low night temperature conditions. Monitoring of fish tolerance was done periodically throughout the duration of the 7001cm haulage from New-Bussa to Tiga Lake in Kano. The trip lasted for 10 lis. On arrival at Tiga Lake fish were gradually conditioned in the lake water while still in the polythene bags, before being released at the middle of the lake. Clupeid Sampling at Tiga Lake Sampling for Clupeids was done vvith Atalla liftnet. The choice of atalla was promised on its popularity with tbe traditioiaal fishermen on both the Kainji and Jebba Lakes Also, because tree sturaps in Tiga Lake were not cleared to such a state that the Dala drag net could be effectively used. Description of the Atalla-lift net The Attila lift-net consists of a rigid frame naade up of four raffia palm poles. To this frame is affixed a mosquito meshed n.etting material. Two of the four corners of the frame are usually fitted to the side of a boat. The boat is constructed to carry the net and so is named the Atalla boat. The two corners thus fitted are positioned to be able to operate as a pulley system to facilitate the lowering and lifting of the net in and out of water while sampling. Experimental Gill-net Sampling Experimental gill-net survey was done with graded fleets of gill-nets comprising 50.8, 63.5, 76.2, 88.9, 101.6, 127.0, and 177 8mm (i e 2, 21/2,3, 31/2, 4, 5 and 7 inch) stretched meshes. Each of these nets measured 35m long and 3 meters deep giving a total fleet surface area of 735sq meters. Catch per fleet was raised to catch per 1000sq meters so as to standardize the catch per unit effort. The fleets of nets were used to sample six sampling stations spread all over the Lake and as fixed in Bankole, (1989). RESULTS AND DISCUSSION Catch Composition and Species Diversity Fourteen species belonging to seven fatnilies were recorded in the experimental gill-net samplings. Table (3) These are: Mormyrops deliciosus (Mormyridae) Lobeo senegalensis Lobeo pseudocoubie (Cyprinidae); Chtysichthys auratus, Auchenglanis occidentalis Bargus boyad (Bagridae); Schilbe mystus (Schilbaidae); Glorias anguillaris, (Clariidae), Synodontis filamentosas Synodontis schall Synodontis gambiensis, Oreochromis niloticus Sarotherodon galilaeus and Ti lupia zilli (Cichliclae) The following five other species were recorded with the Atalla fishing net while sampling for Clupeids- Pellonula afzeliusi, Sierrathrisca leonensis Physailia pellucida Micralestes acutidens Barilius senegalensis. (Clupeidae); (Schilbeidae) (Characidae); and These brings the total number of species recorded during the entire sampling to 19 species and frora 9 families. 207

5 Table 3. Relative Species Composition abundance and distribueon by habitats in experimental gill-net catches at Tiga Lake between July-August, 96. SHORE SURFACE BOTTOM TOTAL MEAN SPECIES No wt No wt No wt No % wt % Mean (g) (g) (g) (g) wt(g) MORMYRIDAE Mormyrops dehciosus I CYPRINIDAE Labe pseudocoubie Lobeo senegalensis BAGRIDAE Chrysichthys auratus Auchenoglanis occidentalis Bagrus bayad SCHILBEIDAE Schilbe mystus CLARIIDAE Claras anguillarts MOCHOKIDAE Synodontis filamentosus Synodontis schall Synodontis gambiensis C1CHLIDAE Oreochromis nlloticus Sarotherodon galilaeus Tito,* zilli Catch per unit cffort/kg/100sqm Y '' '' Y.08 Overall CPUE 2.72 'i'

6 Table 4: Summary of Fish Distribution in the Various Habitats and Sampling Stations. STATION SHORE SURFACE BOTTOM A B C D E F TOTAL % Table 5: Clupeid abundance at Tiga Lake, August CLUPEIDS PHYSAILIA (STA- TOTAL SUB- PEA NO SIL NO TOTAL TOTAL SUB NO IN SAMPLES TION) WT(g) SAMPL IN IN NO IN WT. SMP SUB- E SUB SUB- SUB (8) (AVT) SAMPLE WT(g) SAMPLE SAIvIPLE SAMPLE (g) Sample 1 C Sample 2 C Sample 3 F Sample 4 F Sample 5 D Sample 6 D Sample 7 E Sample 8 E Sample 9 A Sample 10 A

7 Table S Continued TOTAL (1) 4360g SUB SAMPLE Total (2) Total # of Clupeids in Sub Sample (3) % PEA = Pellonula afzeliusi SIL = Sierrathrissa leonensis PHP = Physailia nellucida Table 6 (a) Anal sis of Variance Table for Variability Among Habitats Source of Variation Degree of Freedom Sum of ssquares Mean square F-ratio Among Habitat NS Within Habitat Total F (5.12) = 3.106; 0.01 (5.12) Table 6(b) Analysis of Vaviance table for variability Among Stations Source of Variation Degree of Freedom Sum of squares Mean square F-ratio Between stations(among) ** Within Station Total F 0.05 (2.15) =3.682 F. 001 (2.15) =

8 The Physailia was transplanted with the Clupeids, while the Barilius and. Micralestes species had always been indigenous to the Lake but were only caught as bye-catches with the Clupeids, Table (5). With this, the total number of species ever recorded in the lake becomes 34 from 10 families. 13ut the highest ntunber of species recorded with gill-nets alone was recorded in Bank le and Ita 1986 (19 Spp). Spatial Distribution of fish and abundance Table 3 shows the distribution of fish in the various habitats for th.e six stations sampled. Twelve of the species recorded with the experimental gill-net were caught in the shore set with the exception of Labeo senegalensis and Synodontis schall. Only five species were recorded in the surface set. These are Schilbe mystus, reochromis niloticus, Sarotherodon galilaeus, Labe pseudocoubie and Labeo senegalensis. Nine species were recorded in the bottom set. The spatial distribution of fish in teims of abundance is given in Table % of the fish caught came from the shore in terms of munber while 37.20% and 40.77% were recorded from surface and bottom sets respectively. Thus, more fish were caught from both the surface and bottom habitats than the shore. Also in terms of weight more fish were caught from the surface (41.37%) wid bottom (38.91) sets than the shore (19.72%). Furthermore, Synodontis garnbiensis accounts for 75.00% by weight and 65.48% by number of all the fish caught. (Table 3). Sarotherodon galilaeus (10.12%, and 6.74%) and Oreochromis niloticus (4.46% and 5.19%) ranked a distant second and third in terms of number and weight respectively. The highest fish catch was recorded at station D both by number and weight (121:29577g); followed by station B (81:15400g(; E (59:13410); A, (19:6895g): F, (25:3335g) and C, (21:3215g) respectively. Analysis of variance was carried out to test wheth.er there was any significant difference between catches in the different habitats and stations sampled. The results are presented in Tables 6 (a) and (b). It could be observed in table 6a that there was no significant difference between the catches in the different habitats sampled at both 5% and 1% level of significance. But the result presented in Table 6b shows that there was a highly significant difference between the catches in the different stations both at the 5% and 1% level of significance. Previous reports had all indicated the dominance of Cichlids in the reservoir (Adeniji and Ita 1976; Bankole and Ita 1986; Bankole, 1988; 1991). It was only in 1990 that Clarias dominated the catches from Rum Station of the Lake with the insurgence of Synodontis (Bankole 1990). This occurred about a year after the clupeids had been introduced. This promted Bankole (1991) to state that the introduction of clupeids into Tiga Lake must have started enhancing the productivity of the reservoir, because the catches seemed to be picldng-up again. The dominance exhibited by Synodontis gambiensis in this survey though unanticipated also came about post-clupeid introducdon. The absence of such prominent predators like Hydrocynus and Malapterurus could be attributed to decrease under fishing pressure. Earlier reports had hinted at over-exploitation (Bankole and Ita 1986, Bankole, 1989). This is however open to question because the period of observation was not sufficiently long enough to reflect any cyclic fluctuations in abundance. It could also be that they had moved into deeper waters with the clupeids, especially as the sampling occurred during low water. At this period most of the productive shallow inshore areas of the lake get exposed. One indeed expected to record the preying on small clupeids in the open waters. The overwhelming presence of Synodontis registered in all the habitats (particularly the surface waters and which had improved the production from the lake, could probably be linked to a new found dietary switch over. The usual diet of Synodontis from various studies had been insects (Sandon and El- Tayib, 1953; Petr, 1967; and Willoughby, 1974). It could have become converted to an opportunistic feeder on clupeids. Its survival could thus have become better enhanced by this new feeding habit. A similar observation was made in. lake Kariba where Synodontis and Eutropius had been observed to feed on Sardines (Marshall 1984). This was found to have improved the production (Junor and Langerman 1982). 211

9 Catch per unit effort (CPUE) Catch per unit effort from experimental catches gave an estimated mean of 1. 16kg/1000sqm (± 0.70); 3.37kg/1000sqm (± 2.51) and 3.17kg/1000sqm (± 2.08) for shore, surface and bottom sets respectively. Overall mean CPUE was 2.72kg/1000sqm (± 1.03). Table 3). This also suggests an improvement over previous CPUE. In 1986 and 1987 when the mean CPUE obtained for the Lake were 0.91 ± 0.27 and 0.54 ± 0.15kg/1000sqm respectively. FISH PRODUCTION Indeed the general/overall fish production from the lake seemed to have received a big boost. The total weight of fish caught.for the short duration of the survey' (2 weeks) was g (71.83kg) (Table 3). This was more than the 63,390g (63.39kg) recorded by Bankole for a period of thirteen months (Bankole, 1989).from June 1987 to June A cursory observation of a few fishermen's catches showed the resurgence of.the 'disco' Tilapias so cplied because of their tendency to reach huge sizes. The Tilapias particularly OreoChr011liS niloticus and Sarotherodon galilaeus could reach more than 2,0-4.0kg per one. These were last seen in fishermen's catches around But many of these Tilapias were observed during this survey. This could possibly imply the effect of the predators on the littoral margin liad been reduced due to the presence of the clupeids. Alter the last batch of clupeids were stocked (to make 50,000 number) in 1989 the transplantation exercise was terminated. By late 1990/early 1991 fishermen had started reporting frequent contact with the newly introduced species in their catches (Bankole, 1992). This prompted a survey to confirm the, establishment of the introduced clupeids. Light attraction and electrofishing methods ivere employed. With the two methods the presence of clupeids in all the stations sampled were established. Pelionula alitelinsi dominated the catches then. (Bankole 1992). The si/.es recorded also reflected the presence of a lot of,juveniles which led to the observation that the clupeids had established having been able spawn and with their widespread distribution all over the lake (Bankole 1992). In this study. Atalla lift net was used to sample for clupeids. This 1,vas not because it is the best or more suitable gear o.r method but for expediency. This is because neither much of the productive inshore nor the less productive pelagic/open waters had their stumps cleared enough for Me employment of trawling as recommended in Otobo (1977) or Dala seine as employed in Sado and Ita (1992). The efficiency of the Atalla was greatly hamp ered by intense wave action during the study. However, it remains the most affordable and popular gear used for catching clupeids by Urhobo and Ijaw.fishermen both on Kainji and Jebba Lakes as well as the fishermen oh' the Upper Benue River Basin Area. It was on this premise that the gear was opted for. More especially as the biomass of the clupeids had not been determined to know whether its large scale exploitation will not jeopardise the purpose for which it was sto cked. Result of Atalla fishing The result of the Atalla fishing method revealed the abundance of clupeids in all the stations sampled. Over kg of clupeids were obtained during the period of sampling. This is composed of Pellonula (*Must, Sierrathris.s'a leonensis and Physailia pe/lucida (Table 5). Physaiiia pe/lucida rnade up 72.0% of this catch while the remaining 28% comprised of 54.26% Pellonula and 45.74% of Sierrathrissa Some of the clupeids were observed to be ravid, This ensures continuity and progeny maintenance of the translocated chipeids. From the sampling, it is evident that a good stock of clupeids have become established at Tiga Lake. The two species seemed to be very abundant in all the station. This ag,rees with the trend observed in Lake Kariba. Clupeids were introduced there between 1967 and 1968 and by 1970 Limnothrissa miodon was found.to be present in good quantities all over the Lake. It could therefore be averred that erection of large surface areas provided by creation of man-made reservo irs enhances the growth and development of clupeids. Fish frying is a delicacy among fish mongers in Kan State. This wrecks a lot of havoc on the juvenile of fish in the Lake. The introduction of 212

10 clupeids, a freshwater sardine will equally ensure a relief on the juvenile of Alestes and tilapia which used to be the most affected by this. It will serve as an alternative. But the fishermen must be taught how to catch the clupeids a knowledge which they do not have at present. SUM1VIARY AND CONCLUSION The introduction of clupeids seemed to have significantly improved the abundance and spatial distribution of fish in the Tiga Lake. Thus it has achieved the purposes for which it was targeted (iraproving the general fishery of the lake) the filling an ecological niche, create a better spatial distribution of fish as well as improve the fish production (and general fishery of the Lake). With this achievement, clupeids could be transplanted to other reservoirs where need be to improved and boost their fishery. REFERENCES Abdullahi B.A. (1982) ZooplanIcton studies on Tiga Lake Nigeria.M.Sc. Thesis, Department of Biological Sciences, Bayer University, Kano, Nigeria. Adeniji ILA.; and ha, B.O. (1976) Preliminary investigation into the limnology and fisheries of Tiga Lake, Kano State, Nigeria. Unpublished report to Kainji Lake Research Institute, New Bussa 20p. Bankole, N.O. (1988) The fish and fisheries of Lake Tiga (A Man-made lake) in Kano State. Nigeria, National Institute for Freshwater Fisheries Research Annual Report P , Bankole, N.O. (1989). Biological Studies on selected fish species of Tiga Lake Kano State. M.Sc Thesis, Department of Biological Sciences, Bayern University, Rano. 142 p. Bank le, N.O. (1990) Gill-net monitoring at Tiga and Jakara reservoirs in Kano State. National Instaute for Freshwater Fisheries Research Annual Report p Bank le, N.O. (1991). Fishery Survey of Tiga and Ruwan Kanya reservoirs in Rano State. National Institute for Freshwater Fisheries Research. Annual Report. (1991) P Bank le, N.O., Awoojebi S. and Mathew I. (1992). Preliminary Report of Studies on introduced clupeids (Pellonula afzeliusi) of Tiga Lake in Rano State. National Institute For Freshwater Fisheries Research, Annual Report p Bankole, N.O., and Ita, E.O. (1986). Preliminary report on gill-net monitoring of the inshore habitats of Tiga Lake in Rano. Kainji Lake Research Institute Annual Report p Galkowski, E. and Galkowski, K. (1980). Main Projects Data of Dams and Reservoirs, Water Resources and Engineering Construction Agency. Kano State. Holcik, J. (1991). Fish introduction in Europe with particular reference to its central and Eastern part, Can. J. Aguar. Sci. Vol. 48. Supply. I Imevbore, A.M. A.,Obot E. A., and Ofezia, I.E. (1986). Report on vector Borne diseases problems of small scale water Resources Development Projects in Nigeria. World Health Organization andinstitute of Ecology. University of Ife Nigeria. Ita, E.O. (1979). Approaches to the evaluation, management of and development of Tiga Lake Fisheries Nigeria. Proceedings of the International Conference on Kainji Lake and River Basins Development in Africa. iba dan II - 17 December, p Ita E.O. (1982). Fisheries survey of Tiga Lake, Kano State, Nigeria. Kainji Lake Research Institute. Annual Report p Ita, E.O. and Pandogari A. (1986). Preliminary investigations on the fish - and fisheries of some randotnly selected reservoirs in Kano State. Kainji Lake Annua/ Report p Ita, E.O. and Mohammed S. (1987). Further investigations on the fish and fisheries of some reandomly selected reservoirs in Rano State. Kainji Lake. Annual Report p Marshall, B.E. (1984). Small pelagic fishes and fisheries in African Inland waters. CIFA Tech. PapaDec. Tech. CPCA, (14) 25p. Marshall, B.E., Junior, P.J.R and Langerman J.D. (1982). Fisheries and fish production on the Zimbabwean side of lake Kariba, Kariba stud., (10) Mbagwu, 1G. (1989). Preliminary Survey of macrozoobenthos of Tiga Lake, Rano State Nigeria. M.Sc. Thesis, Bayer University Rano (1989). Ogutu-Ohwayo, R. (1990). The decline of the nature fishes of Lakes Victoria and Kyega (East Africa) and the impact of introduced species especially the Lates niloticus and nile tilapia Oreochromis niloticus. Environ Biol. fish, 27: Otobo, F. 0. (1977). The Biology of the Clupeid fishes in Lake Kainji Ph.D thesis, University of Ife. Petr. T. (1967). Food preferences of commercial fishes in the Volta Lake. Volta Basin Research Project University of Ghana, Legon. (Tech. Rep. 22). 213

11 Sado, EK. and Ita, EO. (1992). The effect of Capture methods, temperature and oxygen on the survival of live freshwater clupeids during acclimation and transportation. J. Aqua. Trop.7 ( Sandon, H. and El-Tayib, A (1953). The food of some common Nile fish. Sudan Notes, Rec Sturm, i1/44.0, (1984). On the Biology of the catfish. Chrysichythys auratus (Geoff( ay) in the man-made Tiga Lake in Northern Nigeria. Freshwater Biology Weicomme R.C. (1988). International introduction of Inland aquatic species FAO Fish Tech Pap Welcome, RI,. and Henderson, H.F. (1976). Aspects of the management of Inland waters for Fisheries FAO. nsh. Tech. Pap. No p. 214