Use of a Fixed-Array Acoustic Telemetry System for Fine-Scale Tracking of Smallmouth Bass, Northern Pikeminnow, and Prickly Sculpin in Lake Washington and the Ship Canal

As part of a large study to evaluate movement patterns of Chinook salmon smolts in Lake Washington and the Lake Washington Ship Canal (LWSC), Seattle, Washington, we also documented the diel habitat use and movement patterns of three predatory fishes: smallmouth bass, northern pikeminnow, and prickly sculpin.  The relationship between juvenile Chinook salmon habitat use and predator habitat use is important to understand for management and recovery of Chinook salmon.  We used a fine-scale acoustic tracking system developed by Hydroacoustic Technology, Inc. (HTI), Seattle, Washington to track tagged predators at six sites (three in Lake Washington and three in the LWSC).  Tracking was conducted from May to August in 2004-2008.  A total of 90 smallmouth bass, 42 northern pikeminnow, and 24 prickly sculpin were captured at the study sites and tagged with acoustic tags using surgical procedures.  Sculpin were implanted with M-tags that lasted 12 days while bass and pikeminnow were implanted with either an E- or G-tag that lasted 20 to 60 days.  Most smallmouth bass remained in the tracking area for at least a few days and we were able to obtain adequate movement and habitat use information.  Smallmouth bass commonly used overwater structures, areas of sparse vegetation, vegetation edges, and areas with gravel and sand substrate.  They primarily used 2-6 m deep water and were rarely in water that was more than 12 m deep.  Most northern pikeminnow left the tracking area shortly after release and provided little information. We were able to get good tracking data on approximately 14 fish. Northern pikeminnow selected moderately dense to dense vegetation in 4-6 m water depth during all times of day and night, and strongly selected small overwater structures during the day.  Northern pikeminnow remained nearshore during the day, and used both nearshore and offshore areas during dusk and night.  Our ability to track prickly sculpin varied between sites due to the bottom topography and location of the hydrophones.  Prickly sculpin were generally active at night.  At sites with complex habitats, they were often active during the day.  In comparison to other sculpin species, prickly sculpin had a relatively large home range.  For example, the mean nightly home range area of prickly sculpin at one site ranged from 61 to 191 m².  Overall, the HTI acoustic array system proved to be an effective tool in understanding the diel habitat use and movement patterns of some resident fishes.