Stream Fish Communities in the Delaware Water Gap National Recreation Area: A Multi-Species Occupancy Approach

Research staff of the Eastern Rivers and Mountains Network (ERMN), an Inventory and Monitoring network of the National Park Service, annually monitors core indicators of wadeable stream condition in the Delaware Water Gap National Recreation Area (DEWA).  However, fish communities are currently not an indicator of stream condition that is monitored in the ERMN monitoring program.  Because of their ecological importance and utility as bioindicators, we developed an occupancy-based sampling framework to assess the current condition of stream fish communities within selected streams of DEWA.  Multi-species occupancy models were used to provide a baseline inventory of species distribution for future monitoring efforts, as well as determine the relative importance of local habitat variables in structuring fish communities.  Results indicate statistically significant relationships between stream fish occupancy and habitat variables at the local level; however, the relationships varied by species and species groups.  Our results also suggest that multi-species occupancy, as a state variable, may be valuable to both long-term monitoring of stream fish communities as well as useful in predicting species’ response to changing environmental conditions.