Abundance and movement of fishes among nearshore habitat types in small boreal shield lakes

The littoral zone of lakes consists of a mosaic of habitat types, which support fish communities that contribute greatly to biodiversity and food web stability. Yet, relationships between habitat and littoral fish abundance, species composition, and the extent of movement among habitats are not well understood. We carried out a habitat-specific mark-recapture study of small littoral fishes in two small boreal lakes in central Canada. We found that the abundance of littoral fishes was lowest in the habitat type with the least amount of structural complexity, while areas containing coarse woody material were associated with high fish abundance and biomass. We found little difference in species composition among habitat types, although smaller individuals tended to prefer habitats with high structural complexity. Mark-recapture data provided evidence for fidelity to the initial marking habitat type, though this was higher in the lake with more open habitat areas, which may have acted as barriers to movement. Our data also indicated that these small-bodied species can move appreciable distances (up to similar to 1 km) throughout the nearshore zone. This research suggests that maintaining structurally complex habitats is important for littoral zone fish productivity by supporting growth and survival, and by facilitating movement among habitat patches.