Environmental Stability and Fish Community Diversity

Abstract

Seasonal fluctuation of water level is the most critical environmental factor affecting the fish community of the Everglades marshes. During a 27—mo period of water—level stability, fish density decreased but biomass, average size of fish, species richness, and species diversity increased. These changes were accompanied by a functional shift from the dominance of small sized omnivorous species to the dominance of larger sized carnivorous fish. The changes resulted from immigration of large carnivorous species poorly adapted for survival in fluctuating marshes. Increased predation assumed the determining role in restructuring the community under environmentally stable conditions. The fish community of Everglades marshes oscillates between opposing tendencies of species domination, which depend on the degree of water level stability.