Snorkel Seining As an Effective Method for Capturing Juvenile Chinook Salmon

Spring Chinook salmon follow a variety of juvenile life histories, and various capture methods are necessary to sample them in certain habitats. This technique was developed to sample stream-type juveniles rearing in the upper reaches of spawning tributaries. This method allows us to access areas of river that are not available to other sampling methods. Sites were located on the McKenzie river mainstem and tributary of Horse Creek. Our technique uses, two snorkelers to locate fish while two crew members set a pole seine perpendicular to the downstream flow. Snorkelers move fish downstream and guide them into the seine net. Snorkeling to scout sites enables us to increase catch efficiency, thereby only sampling if sufficient numbers of fish are present. Fish are implanted with passive integrated transponder (PIT) tags to identify individuals, then released at the same site. Snorkel seining allows us to recapture individuals multiple times throughout the season, providing us with individual growth data. PIT antennae downstream can detect these fish once they migrate, providing data on migration timing. This has shown previously undescribed life history patterns in juvenile Chinook salmon, for example some juveniles stay in freshwater for up to two years before migrating to the ocean.