The effect of long term exploitation by the gill net fishery on the multispecies fish stocks in Kainji Lake, Nigeria, 1969-1997

Seisay, M.D.B. and Du-Feu, T.A. (1997) The effect of long term exploitation by the gill net fishery on the multispecies fish stocks in Kainji Lake, Nigeria, 1969-1997. New Bussa, Nigeria, Nigerian-German (GTZ) Kainji Lake Fisheries Promotion Project, (Nigerian-German Kainji Lake Fisheries Promotion Project Technical Report Series, 11) (ISBN: 978-037-010-2; ISSN:1119-1449).

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Abstract

The findings are presented of an assessment made of the gillnet fishery in Kainji Lake, Nigeria from 1969 to the present, on the basis of data sets from commercial and experimental gillnet fishing, with the purpose to detect trends in some key fishery monitoring indicators. During this period, there has been an increase in the number of small meshed nets in the fishery resulting in a shift in the mode to lower mesh sizes; consequently, the average mesh size declined gradually in the fishery. This trend is found to be directly correlated with the decline in the CPUE and mean weight of the fish species. It is argued that the observed trend in CPUE and mean weight is forcing the fishermen to switch effort to gears such as traps which have very small meshes and can indescriminately take all sizes of the fish. It is shown that the catch composition by weight of Citharinus citharus, Lates niloticus and tilapias declined in the gillnet fishery in the late 70's and early 80's. Recent data, from 1994 to 1996, however indicates that C. citharus is recovering, but with declining mean weight. This suggests that the exploitation pattern is shifting to the smaller fish through the use of small meshed nets. In general, however, there has not been drastic changes in species bio-diversity in the Lake as a result of predatory effect and ecosystem overfishing as has happened in other great African Lakes. The species composition since lake formation continued to be dominated by fewer that 20 species. The potential yield for the lake has been estimated to be 32,166 tonnes (excluding clupeids) and the required optimum fishing effort to be 1,814 fishing canoes. In view of the relative stability of the species diversity in the lake and the current fish production level, it is proposed here that this MSY be adopted for all species. This would be achieved with the current effort level in the lake assuming that the efficiency of the fishermen and their gears do not improve. It should be reviewed after 10 or more years of catch and effort data collection. (PDF contains 65 pages)

Item Type: Monograph or Serial Issue
Title: The effect of long term exploitation by the gill net fishery on the multispecies fish stocks in Kainji Lake, Nigeria, 1969-1997
Personal Creator/Author:
CreatorsEmail
Seisay, M.D.B.
Du-Feu, T.A.
Series Name: Nigerian-German Kainji Lake Fisheries Promotion Project Technical Report Series
Number: 11
Date: 1997
Publisher: Nigerian-German (GTZ) Kainji Lake Fisheries Promotion Project
Place of Publication: New Bussa, Nigeria
Projects: Nigerian-German (GTZ) Kainji Lake Fisheries Promotion Project
Issuing Agency: Deutsche Gesellschaft für Technische Zusammenarbeit (Nigeria Office)
Additional Information: Pag. 42 does not exist due to pagination error
Uncontrolled Keywords: Nigeria, Lake Kainji; catch composition; fishing effort; gillnets; lake fisheries; mesh regulations; multispecies fisheries; potential yield; stock assessment
Subjects: Fisheries
Biology
Item ID: 3846
Depositing User: Ms Maria Kalentsits
Date Deposited: 11 Aug 2010 10:08
Last Modified: 29 Sep 2011 16:44
URI: http://aquaticcommons.org/id/eprint/3846

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