Decline of the African lungfish (Protopterus aethiopicus) in LakeVictoria (East Africa)

Abstract

Catch and effort data for the period 1973^1990 demonstrate a dramatic decline of lung¢sh in the Tanzanian waters of Lake Victoria. Bottom trawl catches in the Mwanza Gulf showed a decline in catch rates from 67.5 kg h1in1973 to 5.5 kg h in1986. Trawling of commercial vessels in the Speke Gulf revealed a decline in lung¢sh catches from 1.3 kg h1 in 1986 to 0.07 kg h1 in 1990. The development of anoxia in the deeper waters of Lake Victoria,the algal blooms,and the decline of water transparency,all associated with eutrophication,are not likely to have contributed to the decreased catch rate. However,the lungfish decline may reflect the interaction of overexploitation by the fishery and a low level of Nile perch predation that restricts lungfish to wetland refugia. We suggest that this may have been reinforced over the past few decades by large-scale conversion of wetlands to agricultural land and harvesting of nest-guarding male lung¢sh leading to decreased recruitment of young.