Using a high-resolution acoustic camera (DIDSON) to estimate fish abundance and movement in a Lake Erie coastal wetland

Research projects in the Crane Creek coastal wetland complex (Ottawa National Wildlife Refuge) are exploring wetland habitat rehabilitation strategies and their impact on Lake Erie fishes.  Established methods of assessing fish assemblages (e.g., fyke nets) can be used to characterize fish (community composition and abundance) in a specific location, but provide little information on fish behavior and short-term rates of movement.  From a habitat rehabilitation perspective, data on fish movement and behavior are critical to both evaluate the biological response to completed projects and guide the design of future projects (e.g., maintaining an appropriate level of hydrologic connectivity).  DIDSON (Dual-frequency IDentification SONar) is a developing technology able to collect high-resolution fisheries data day or night in very shallow turbid water.  A DIDSON was deployed for 11 days in Crane Creek at its connection to Lake Erie to explore how Great Lakes fishes used coastal wetland habitats.  In addition to continuous DIDSON data, we collected real-time data on water quality, depth, velocity, and direction.  Statistical sampling and manual analysis of the DIDSON data revealed a large abundance and flux of longnose gar and shoals of small preyfish fish accessing the wetland on a daily basis.