IMPACT OF RING NET FISHERIES ON EXPLOITED FISH STOCKS AND HABITATS WITHIN THE INSHORE MARINE WATERS OF KILIFI, KENYA

Abstract

Ring nets are small modification of purse seines used along the Kenyan coastline for pelagic fishing. Introduction of the gears from Pemba, Zanzibar in Tanzania in 1990s has since caused resource-use conflicts associated with environmental degradations. This study investigated impacts caused on the physical and biologic environment in Kilifi fishing grounds. It was conducted in April, May and September 2014 for Southeast Monsoon and October, November 2014 and March 2015 for Northeast Monsoon (NEM). Environmental impacts were assessed through analysis on fished depths, habitat characteristics; species composition, fish sizes and gonad status of dominant pelagic in the landings. The gears fished in common sites with depths between 16.4 ± 3.5 m in NEM season and 17.2 ± 3.6 m in SEM season (ANOVA, F = 4.167; p = 0.2). During fishing, the nets were in contact with the sea floor which caused physical abrasion and damage to benthic habitats. Catch composition of ring nets comprised averagely of 84.1% pelagic and 15.9% demersal species. Fishing within sheltered and nursery grounds in SEM season captured high proportion of juveniles. The numbers for males and females caught were different across the season and deviated from the ratio 1: 1 which was attributed to reproductive roles during capture. Majority of fish harvested in SEM season were immature (stage I) which was a result of fishing on juveniles in the nursery grounds. High fish catches in NEM season was associated with ring net fishing on spawning aggregations which resulted in landings of heavily hydrated fish in stage IV (spawning). Ring net fishery can be a better source of increase fish productivity but there is need to regulate its operation and prevent further environmental degradation and enhance sustainable management. Keywords: Kilifi, ring nets, season, depths, species, juveniles, spawning.