MANAGEMENT OF INDIGENOUS FISH SPECIES IMPACTED BY INTRODUCED MOSQUITOFISH - AN EXPERIMENTAL APPROACH

The negative effects of introduced mosquitofish (Gambusia affinis) on native fishes of the American Southwest have been well documented. How ever, little experimental information is available to determine the le vel to which populations of Gambusia must be reduced before reintroduc ing native species. To simulate various options for managing indigenou s fishes impacted by mosquitofish, we observed population growth of th e least killifish (Heterandria formosa) with different starting densit ies of the eastern mosquitofish (Gambusia holbrooki) in replicate meso cosms. The presence of mosquitofish at all densities examined had a si gnificant negative effect on population growth of least killifish. The refore, complete removal of introduced mosquitofish appears to be the best management option for maintaining populations of native fishes.