Evaluating the Effects of Habitat Patchiness on Small Fish Assemblages in a Great Lakes Coastal Marsh

Wetlands are naturally heterogeneous ecosystems with resident species adapted to patchy environments. We measured how assemblages of small fish varied among four natural patches of coastal marsh in Mismer Bay, Lake Huron, USA. We sampled patches continuously for extensive time periods to describe both spatial and temporal fish distribution patterns. Fish richness and distribution varied spatially with some species restricted to one or two patches, such as Phoxinus eos and Margariscus margarita, and others widely distributed, such as Pimephales notatus and Culaea inconstans. For ubiquitous species, patch utilization varied temporally, which was explained by variation in habitat characteristics, such as macrophyte richness and growth form diversity, emergent macrophyte stem density, water temperature and depth. Northern Great Lakes coastal marshes are not static environments, and intensive sampling illustrates the dynamic interactions between fishes and this successional marsh environment. We conclude that extended sampling protocols in patchy, temperate wetlands are preferable to short surveys for making accurate evaluations about the spatio-temporal habitat utilization of fishes.