Heavy predation on juvenile salmonids is one factor that may limit the recovery of their populations. FISHBIO recently completed the field and laboratory portions of a study to examine the diets of salmonid predators, including striped bass, largemouth and smallmouth bass, and Sacramento pikeminnow. We caught hundreds of predatory fishes using electrofishing techniques at night, and used mechanized pressure to flush out fish stomach contents. Mechanized pressure is one of the most effective non-lethal stomach content collection methods, and has been shown to be up to 100% effective for both smallmouth and largemouth bass. Objectives of the project included documenting the rate of predation on sensitive species such as juvenile Chinook salmon and steelhead, recording the wide variety of prey items consumed (ranging from small insects to a nine-inch-long alligator lizard), and observing how diet changes with the size of a fish.

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