Discussion Paper

Lake Victoria Fish Stocks and the Effects of Water Hyacinths on the Catchability of Fish

Mar 15, 2008 | Eseza Kateregga, Thomas Sterner

This was created in partnership with Environment for Development .

Abstract

This paper analyses the effects of the invasion of water hyacinths on fishing in Lake Victoria. We built two fairly standard Schaefer-type models that have one innovation: they allow the water hyacinth abundance to affect catchability. We estimated static and dynamic CPUE (catch per unit of effort) functions for Lake Victoria fisheries. We investigated the trend in the lake’s stocks during theperiod 1983–2000 and focused particularly on the effect of the water hyacinth on fish stocks and on catchability coefficients. The results shows that while fish stocks have fallen since 1990, this decline appears to have been at least temporarily halted by the declining catchability of fish due to the growing abundance of water hyacinths. The impact of the hyacinth on the catchability of fish was greatest in the Kenyan section of Lake Victoria. Although the hyacinths had many negative effects, one important effect has been to effectively hinder fishing and, thereby—paradoxically—stop or at least postpone serious overfishing.