Evaluating influence of anthropogenic structures on migratory and resident fishes using fine-scale acoustic tracking

Determining how fish behave around anthropogenic structures and the consequences of such behavior is critical for mitigating negative impacts and designing more fish-friendly structures.  From 2003-2008, we evaluated the influence of structures on fishes in Lake Washington, Washington using fine-scale acoustic tracking.  Species studied included migratory juvenile Chinook salmon Oncorhynchus tshawytscha and several resident predators, including smallmouth bass Micropterus dolomieu and northern pikeminnow Ptychocheilus oregonensis.  Structures evaluated included three bridges, a lock-and-dam, overwater buildings, and various marinas and boat docks.  Results showed that structures may have a variety of effects on fish behavior and habitat use.  Structures often inhibited and/or delayed actively migrating Chinook salmon.  Conversely, Chinook salmon that were volitionally paused in their migration were often attracted to structure edges.  Smallmouth bass were often attracted to areas beneath overwater structure and adjacent to in-water structure.  No strong relationships were observed between structures and northern pikeminnow.  Further study is needed to evaluate the ultimate consequences of these behaviors on fish survival and fitness.  We conclude that fine-scale acoustic tracking is a valuable tool for elucidating relationships between anthropogenic structures and fish, and for providing information useful for guiding further research, mitigating negative impacts, and designing more fish-friendly structures.