Does seasonal closure have effect on fishery?: the case of common carp, cyprinus carpio L in lake Naivasha, Kenya

Abstract

Studies were done on catch trends and population parameter of common carp, Cyprinus carpio in Lake Naivasha between 2002 and 2006 following a year closure in 2001 after decline in catch of Tilapia zillii and Micropterus salmoides. The fishing ban has continued between June and September every year. Total catch and samples for length frequency analysis were obtained from commercial catch caught using gi1lnets. Population parameters were estimated using FAO-ICLARM stock assessment tool (FlSAT). After reopening of the fishery in 2002, common carp contributed to the total catch was < I%, rising 10 90% in 2005 and declined to 74% in 2006. Before every annual fishing closure, the catches of common carp show a decline. After lifting of the fishing ban, the catches show a pronounced increase. The decline in catches before closure of the fishery may be due increased fishing pressure targeting the species. Asymptotic length 0 increased from 61 cm TL in 2002 to 97 cm TL in 2005, declining to 74 cm TL in 2006.Exploitation rate has been on the increase - 65% to 75% in 2002 and 2006 respectively : continual dominance of common carp is also attributed to flexibility in its diet, reproductive potential and use of gillnets of >_ 4 inches (127mm) which capture only the bigger sized carp.If further recovery and sustainability of the fishery has to be attained attained, poaching, water abstraction which are major threat to be tacked. Management strategy will require a concerted effort of all the stakeholders.