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Journal of Applied Sciences and Environmental Management, Vol. 11, No. 4, 2007, pp. 11-14 Assessment of Gerio Lake Fishery for Enhanced Management and Improved Fish Production 1ABIODUN, J A; 2MILLER, J W 1National Institute for Freshwater Fisheries Research (NIFFR), P. M. B. 6006,
New Bussa, Niger State. *Corresponding author: Abiodun, J A Code Number: ja07085 ABSTRACT: The highlights of the Fisheries Assessment Survey conducted on Gerio Lake, Yola in Adamawa State, North-eastern Nigeria in February, 2005 is presented in this paper. There were 22 fish species found in fishermen’s landings during the survey period. About 30 fishermen were found using undersized nets to catch the juveniles of these species. Fishing pressure was found to be very high. For an optimum catch, about 10 fishermen ought to have engaged in full time fishing activities if, the fisheries of the lake is to be managed on a sustainable basis. However, a surplus of over 80 fishermen was recorded actively fishing during the period of the assessment. All these have a depleting effect on the abundance and sizes of fish harvested from the lake. A community based fisheries management system, which establishes a participatory involvement of fishermen in the conservation and rational exploitation of fisheries resources for the well being of the stakeholders is recommended for the Lake. @ JASEM Inland Fisheries in Nigeria is said to contribute about 200,000 metric tons to the total annual National fish production that stagnates at about 500,000 metric tones. Nigerians consume some 1.3 million metric tones of fish a year including up to 700,000 metric tones of imported frozen fish (Miller, 2004). According to Aquaculture and Inland Fisheries Project Newsletter, April 2004, Nigeria has over 14 million hectares of inland waters, much of which lack proper management. Nigeria could be self-sufficient in fish production and be a major exporter of fish if the, over 14 million hectares of Nigeria inland water bodies are developed and properly managed (Abiodun, et al, 2005). Catch species composition, frequency of size and increase or decrease in total catch are not available for most inland water bodies for more than two decades. Development and improved management of the country’s inland water bodies must, therefore start with increased knowledge of the water bodies, information on the current status of the fisheries and the socio-economic characteristics in fishing communities so that, people can be effectively integrated into co- management programme. The objectives of this work are to determine the size and distribution of fishing localities, fishermen, fishing craft and fishing gears around the lake and also to assess the catch composition, abundance, estimating catch per unit of effort (cpue) and the current fish yields of the lake. These are aimed at formulating a management plan, which will increase fish production and enhance sustainable fish yield of the Lake, thus improving the living standard of the fishermen and the protein intake of the fish consumers in Nigeria. MATERIALS AND METHODS Study Site: The study site is Lake Gerio. Lake Gerio is a natural lake situated between latitude 9° 4° 1 - 10° 551 north and longitude 12° 201 - 14° West. According to the local fishermen, the lake was formed naturally from a creek of River Benue that was cut off as a result of heavy siltation about 60 years ago, thereby forming a small gully. The gully was later filled with water from the rains and River Benue. The lake is about 250 hectares in size with an intensive irrigation farming being carried out around it. It is a shallow water body with mean depth of about 2 meters. Aquatic vegetation on the lake consists of mass of floating weeds, such as water hyacinths, typha grass, water lily and wild guinea corn, which move around the lake’s surface area according to the prevailing winds. Fishery information on Gerio Lake was collected using frame and catch assessment surveys. The frame survey which was conducted for five consecutive days starting from 9th to 13th February, 2005, involved going round the entire lake to identify and count every fishing localities around the lake with the total number of fishermen (both full time and shoreline), the fishing crafts and gears employed. A full-time fisherman is one that has fishing canoe(s) and fishes at least 15 days per month whereas, a shoreline fisherman is one who does not have canoe or gourd but wades in the water to fish. A catch assessment survey (CAS), which involved a detailed examination and recording of the content of a canoe that had just landed on return from fishing trip was carried out for five days in February, 2005, using properly trained ADP enumerators. As a fisherman landed his canoe on the beach, the enumerators examined the content, sorted them according to species and the gear type used, record the weights, number and beach prices of all the species of fish landed. Fishing time and the number of canoes were also recorded to establish the catch per unit effort (CPUE) expressed as kg fish caught/canoe/day. All active fishing canoes were counted to provide estimate of total fishing effort for each sampled day. Canoes catches were pooled to give an estimate of catch per unit effort (kg per canoe) for the landing for that day, which was taken as being representative of entire Gerio Lake. The number of canoes landing fish was multiplied by catch per unit effort to give an estimate of the catch at that landing on that day. The Catch per unit effort (CPUE) of gear is expressed as average weight of fish caught per day per unit of fishing effort of gear type. The estimation procedure is different from gear to gear, particularly for active as opposed to passive gears. The landings of passive gears are divided by the number of fishing units (i.e. bundles for gillnets, number of traps and number of long lines). For an active gear such as cast nets, the calculation is, total catch sampled multiplied by total number of hours fished per day divided by total number of hour(s) for fish sampled. Also informal interview and discussion were conducted to obtain information on the fishermen’s knowledge of the fish species available in Gerio Lake and the number of days fishing activities takes place in a year. RESULTS AND DISCUSSION Frame Survey - A total of 5 fishing localities were identified. These localities include 4 permanent fishing camps (a place inhabited all year round for the sole purpose of fishing,) and 1 Temporary fishing camp (a temporary fishing camp has make- shift structures that are readily dismantled and relocated elsewhere throughout the year). Table 1 shows the distribution of fishermen, their fishing crafts and gears in relation to the villages around the lake. Altogether, 85 crafts were counted 70 were canoes and 15 were gourds (large calabashes with holes in the top and little water in the bottom, majorly used in place of canoes). A total of 103 fishermen were also counted of which 93 were full-time fishermen and the remaining 10 shoreline fishermen. The fishermen used mostly gill nets, cast nets, longlines (hooks) lift nets and fish traps for fishing. During the 5 days survey, a total of gill nets (212), cast nets (32), longlines (669), lift nets (27) and fish traps (3,206) were recorded (Table 1). Catch Assessment – Table 2 gives the species composition of the catch by number and weight. Twenty-two fish species were found in the fishermen’s landings. The species composition remained relatively stable through out the period of assessment. The species represented in the catches were, Oreochromis niloticus, Sarotherondon galilaeus, Tilapia zilli, Claria spp., Schilbe spp, Alestes spp., Synodontis, Auchenoglanis spp., Heterotis niloticus, Labeo spp, Distichodus spp, Citharinus citharus and other spp,. (Polypterus, Parachanna obscura, Protopterus annecten and Marcusenius psittatus). The cichlids dominated the catches by number contributing 62.5% to the overall number but ranked third with 34.7% of the weight of the total fish caught. Sarotherodon galileaus tops the other two species of cichlids both in terms of number and weight contributing 32% to the number and 17.6% respectively. This was followed by Oreochromis niloticus, which contributed 29.4% and 16.4% respectively while Tilapia zilli contributed 1.1% and 0.7 % to both the number weight of all the Cichlids caught during the survey respectively. The Clarias spp., top the list by percentage weight followed by Heterotis niloticus, Sarotherondon galilaeus, Oreochromis niloticus, Distichodus spp., Citharinus citharus, Labeo spp., Others spp., Tilapia zilli, Alestes spp., Auchenoglanis and Synodontis spp. The order in terms of numerical abundance is Tilapia spp. Clarias spp., Distichodus, Heterotis niloticus, Labeo spp., Others spp., Citharinus citharu, Alestes spp., synodontis spp., and Auchenoglanis Fishing Gear: A number of fishermen were found using small mesh nylon monofilament gill nets and Malian fish traps of less than 1 inch mesh sizes to catch fish. Many of the fishermen know that it is a bad method to fish with such type of nets but they believed small mesh nets have higher catch rate than bigger mesh sizes. This has a negative impact on Clarias, Tilapia and almost all the fish species in the lake as many juveniles were found in the catches. Only very few fishermen used gillnets of 4 inches mesh size and cast nets of 3 inches. Catch per Unit Effort: The catch per unit of effort of the gill nets was 2.3 kg while that of longline 2.1 kg and traps 0.1 kg. Gill nets contributed 76.4 % to the total fish yields, longlines 12.3% and traps 11.3%. During the assessment, the gill nets activity level was very high while that of traps was very low and cast net was not active through out. The daily catch per unit of effort per canoe is a measure of fishing success for the average canoe and is influenced primarily by the catchability of gears and abundance of fish. The fishing success or cpue during the catch assessment survey was 4.6 kg per canoe per day. This shows the lake is very productive and good for the fisheries development if it is properly managed. Approximate Estimate of Current Fish Yields: An approximate estimate of the current fish yields is obtained from the rapid appraisal of the 5 days catch assessment. From the frame survey carried out within the same period, 85 fishing crafts were recorded (70 canoes and 15 gourds). During these days, catches from several gillnets, longlines and fish traps were examined. Most of the catches were between 2 and 6 kg per fishing day. No catch data was available for cast net and lift net fisheries through out the assessment period although 32 cast nets and 27 lift nets were recorded in the frame, so it will be assumed that catches are about the same. Based on the informal interview with the fishermen, the activity level can be put at 150-200 fishing days in a year, 175 days on average. An approximate yield could therefore be calculated as shown below: 70 fishing craft x 175 (150-200) fishing days x 4 kg/day (2-6) = 63t (Range: 21-126) Thus, the total yield can be estimated at about 63 tonnes per annum, with minimum and maximum values of 21 and 126 tonnes respectively. The total yield estimate is likely to be more because, the yields from shoreline and gourd fishermen were not included in the calculation. The estimated potential fish production of this lake based on catch assessment, field evaluation, enhancement and good management of the lake can be put at 500 kg/ha or 130 tonnes per annum. Conclusion and Recommendations: It is important here to emphasize key considerations relative to development of a management system for the Gerio Lake fishery in Adamawa State. A number of fishermen were found using small mesh size gillnets and Malian traps to crop the juveniles of highly valued fish species. Therefore fishing pressure, both in terms of the number of fishermen and the kinds of fishing gear in use, has a depleting effect on the abundance and sizes of commercially exploited species. Based on survey data, a CPUE of 4.6 kg of fish per canoe per day was estimated. However, a long time series of catch data is required for better estimate of CPUE for the fisheries of the lake. It is recommended that, the ADP Fisheries Staff should focus on carrying out a general enlightenment campaign to educate the fishermen and the fishing community on the need for responsible fisheries. In effect, the fishing community must be aware that the lake and its fish belong to them for use, exploitation and conservation. It is also expected that an effective community based management system would be established. This must:
The protection of small sized fish cannot be achieved without placing limitations on the kinds of gears used for harvesting and possibly also on when and where those gears can be used. Cast nets can be overly effective during low water when fish are concentrated and vulnerable. This gear should be totally prohibited during low flow periods. However, it could be acceptable during normal flow periods when effectiveness is reduced. Furthermore, the minimum mesh size for this gear should not be less than 2 inches in line with Federal Inland fisheries decree (ANON 1992). Gill nets should not be less than 3 inches size to protect the spawning stock of commercially valued species. In an effort to maintain the availability of fish to the households, it would be reasonable to allow children to use ‘‘noncommercial’’ gears such as traps, clap nets and hook and lines in shoreline areas. It is assumed that this kind of fishing pressure would not be detrimental to the stocks of commercially valuable species, though immature individuals of these species will surely be captured. It is certainly feasible that household members engaging in this kind of fishing can be taught to recognize small individuals of valuable species, which could be put back to the water when caught. Typically, management has been approached in a top-bottom fashion with an emphasis on strong government authority. But, it has been shown repeatedly that top – down management of the fisheries cannot work in Nigeria and thus should be abandoned (Ita 1982). We therefore suggest bottom-up community based management of fisheries in Gerio Lake and other inland water bodies in Nigeria. Acknowledgement: This work was carried out within the framework of Aquaculture and Inland Fisheries Project (AIFP)- Annex II of the National Special Programme for Food Security (NSPFS). We are deeply indebted to the project for allowing the work to be published. We also wish to acknowledge all the fisheries extension workers who participated in data collection.REFERENCES
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