Role of Aquatic Habitat Connectivity in the Life Cycles of Great Lakes Fishes

Longitudinal connections within river networks and between lakes and tributary systems play important roles in the life cycles of many Great Lakes fish species. These roles include movement among distinct habitats for spawning, feeding, and over-wintering, refuge from thermal stress and disturbances such as floods and pollution events, and migration to relieve intraspecific competition or rescue small populations. Fish passage barriers, such as dams and road crossings, have fragmented aquatic ecosystems throughout the basin, thereby limiting the expression of these functions. Barrier removal is typically expected to benefit riverine fish populations, but the extent of this benefit may depend on the spatial context of the removal and is often difficult to quantify.

This presentation will first review examples of specific functions of connectivity for a variety of Great Lakes fishes. It will then describe the latest estimates of the degree of fragmentation of river networks in the basin by road crossings and dams. Examples of fish population and community response to barrier removal of the installation of fish passage structures will be discussed. This review will provide the foundation for a discussion of gaps in our understanding of the roles of connectivity, the distribution and characteristics of passage barriers, the cumulative effects of widespread barrier removal, and tradeoffs with various ecological costs of connectivity.