Impact of the baited hook fishery on the recovering endemic fish species in Lake Victoria

Abstract

As gillnet yields of Nile perch stagnated in the middle of the 1990s, the hook and line fishery intensified in Lake Victoria. Frame surveys show that the number of hooks used in this fishery grew tenfold in the Tanzanian waters between 1992 and 2002. The increased use of endemic fish species as bait has gone largely unnoticed, but is thought to impede the recovery of these species in the lake. A survey was conducted in March 2003, covering 51 sites, to assess the impact of this fishery targeting Nile perch on the endemic species. The species used as bait were juvenile Clarias (41%), haplocromines (37%), dagaa (Rastrineobola argentea) (10%), Synodontis (3%), Mormyrus (2%), and Labeo (1%). The total annual weight of the mostly undersized and illegally caught (beach seining, gillnets below 3″ mesh) baitfish was estimated at 7,465 t. The size of the Nile perch caught is bait-dependant, with catches using Clarias bait having a modal length at 61–62 cm TL of which 20% is above the legal upper size limit. Catches with haplochromines and dagaa bait have a mode at 49–50 cm TL, with 62% below the legal lower size limit. Seasonal variations in the fishery and management implications of its legalization are discussed, while the threats to biodiversity conservation and the stability of the ecosystem are addressed.