Aquatic connectivity and fish metacommunities in wetlands of the lower Great Lakes

Although many local and regional variables structure fish assemblage composition, few studies have assessed the effects of aquatic connectivity on fish assemblages in wetlands. Fish and habitat surveys were conducted in 12 wetlands across the lower Great Lakes basin in the spring and fall of 2003 and 2004. Spatial and temporal connectivity were classified into four connectivity classes to evaluate the interaction between aquatic connectivity and fish assemblage structure. Sequential, nested analysis of covariance was used to model the effect of habitat area and connectivity at long- and short-term time scales on aggregate descriptors of assemblage structure (i.e., species richness, piscivore richness, abundance, and diversity). Although no species-area relationship was detected, increases in connectivity were shown to positively affect species richness and piscivore richness. A variation decomposition method indicated that a combination of aquatic connectivity, followed by environmental and area variables, was most influential in structuring fish assemblages at short-term time scales. Connectivity thus influences both the local species pool present, as well as the abundance of these species within a wetland. Future fundamental and applied studies (e.g., climate change predictions, impact of humans on water budget, wetland management) on wetland fish assemblages should include connectivity as an important structuring process.