Indicators for an invasive species: Water hyacinths in Lake Victoria

The purpose of this paper is to create and discuss a measure of water hyacinth abundance in Lake Victoria. Water hyacinths have dramatic effects on other activities such as fisheries. However, understanding their spread and effects is hampered by the lack of reliable information. Available data on mat coverage was collected from a number of scattered reports and used to fit hyacinth growth curves for the three sections of Lake Victoria. Estimates of the annual rates of infestation are derived from this analysis and were found to be significantly correlated with effect estimates based on hyacinth-attributed generation outages in hydroelectric production. Hyacinths started to grow massively in 1992–1993, reached their maximum in 1997–1998 and were basically gone after 2001. Outages follow a similar pattern but decline faster.