Fish emigration from temporary wetlands during drought: the role of physiological tolerance

Fish emigration patterns from four temporary wetlands exposed to drought were studied from May to August 2004 in the Briere Marsh, France. Two wetlands became totally dry, and two experienced severe water level decline and significant changes in physico-chemical characters. Irrespective of the degree of desiccation, emigration patterns of the six most commonly trapped species, representing 98.6 % of the total abundance (Ameiurus melas, Anguilla anguilla, Scardinius erythrophthalmus, Lepomis gibbosus, Esox lucius and Gambusia holbrooki), were similar among wetlands. Emigration timing was highly correlated with published physiological tolerance levels for these species, demonstrating a tight linkage between water quality and emigration patterns. Two non-native species (A. melas and G. holbrooki) showed the latest emigration from the temporary habitats, reflecting a high level of tolerance to drought conditions that may contribute to their success as wetland invaders.