Influence of Surface Water Connectivity on Fish Species Richness and Assemblages on the Arctic Coastal Plain, Alaska

In the Arctic, extreme seasonal changes in hydrology influence individual fish species occupancy in lakes; however, it is unclear how these relationships scale up to influence species richness and assemblages. We examined how fish species richness and assemblages in Arctic lakes varied with surface water connectivity.  We collected fish presence/non-detection data from 102 lakes across 8,500 km² of the Arctic Coastal Plain, Alaska, and used a hierarchical multispecies occupancy framework to derive species richness and inform assemblage designations. We found strong relationships between lake and surface water connectivity characteristics and richness and assemblage patterns, where the same characteristics had greater influence in isolated lakes than in connected lakes. Isolated lakes lose species due to harsh winter conditions and have reduced potential for recolonization compared to connected lakes, which were continually replenished by the local species pool.  Species found in isolated lakes were excellent dispersers or extremely resilient to harsh environments, while species found in connected lakes were migrant rather than resident species or were rare on the landscape.  Climatic changes will profoundly influence surface hydrology, resulting in changed flow regimes and surface water connectivity, leading to fish species’ responses that will change current distribution, richness, and assemblage patterns.