Characterizing the Timing of Juvenile Alewife Outmigration Using Time Lapse Photography: I’ll Be Watching You!

Burgess, Michael*, Eric Schultz, James Knighton, Katherine King, Ryan Adams, University of Connecticut, Storrs, CT

Diadromous fish rely on connectivity between freshwater and marine habitats, and monitoring migrations between those two environments is essential for management and conservation of these stocks. However, behavior in such connectors is poorly understood for many species. Alewives are one such species, and the connections they need to move between habitats often dry up. This is of particular concern for juvenile alewives, who leave their freshwater spawning grounds in the midst of drought season. To study how habitat connectivity breaks may be affecting this species, we set out to characterize the timing of juvenile movement. We considered capture based enumeration, PIT tagging, fish counters, and videotaping. However, these techniques require substantial data processing, large amounts of manpower, and/or existing structures. As an alternative we have designed a system that eliminates many of the drawbacks of these techniques, while still providing reliable data on migration timing. This system is a time lapse photography (TLP) setup that takes a picture every minute, 24 hours a day. TLP is not limited to installation at previously established structures, and requires a fraction of the data processing and storage space that videotaping does. Our TLP setup can run for 72 hours continuously prior to requiring battery changes, and only requires a single person to maintain. This process taught us how finicky the nomenclature is regarding the term “Waterproof”. To our knowledge this is the only existing TLP setup for monitoring juvenile fish migration, and has allowed us to actively monitor 6 different sites concurrently with limited manpower.