- ID: 16812
- State: Finalized
- Owner: Matt Polacek
- Spatial Design Category: Simple Random Sample, Non-Stratified
- Sites in Design: 32
- Has Location Privacy: No
- Data Repository: WDFW - Statewide Integrated Fish Distribution (SWIFD)
Predatory fishes will be collected by boat electrofishing along the shoreline in a downstream direction. The electrofishing boat is a custom-built 2016, 20-foot Smith-Root Electrofishing Boat powered by a 115-horsepower outboard (propeller) engine. Electrofisher settings will be pulsed direct current (DC) at 60 pulses per second, 40% power, and low voltage range (50-500 V). Electrofisher output will be generally 2-4 amperes and adjusted to achieve fish galvanotaxis (narcosis). The crew will consist of a certified boat operator and two netters. Sampling will occur one hour after sunset to one hour before sunrise. A similar level of effort (e.g., electrofishing seconds, distance (m)) will be used at each site within each stratum.
Temporal stratification of sites during sampling will provide data representative of the period of greatest overlap between non-native predator fishes and rearing/migrating juvenile salmonids. Two sampling times will occur to collect predator fish diet contents. The first will occur during the first half of May to represent age-1 chinook, sockeye, Coho, and steelhead smolt (e.g. yearlings). The second will occur in early to mid-June to represent age-0 Chinook smolt outmigration (subyearling).
Stomach contents will be collected from WAL and SMB using gastric lavage. Less common non-native fishes (e.g. Largemouth Bass, Yellow Perch, Black Crappie) will be collected and evaluated for predatory impact on salmonids. Fish will be measured, weighed, scanned for PIT tags, and stomachs/diet contents will be stored in individually labeled Whirl-Pak bags. NPM and CC will be measured, weighed, and euthanized (Close et al. 1997) and stomachs will be dissected and placed into individually labeled Whirl-Pak bags. The entire digestive tract will be removed from NPM. Samples will be preserved with 95% ethanol, stored in a cooler with dry ice, and transferred to a lab freezer until analysis. Otoliths will be removed from a sub-sample of SMB and WAL >150 mm and scales from SMB and WAL <150 mm, and opercles from NPM for aging. Aging structures will be analyzed by the WDFW aging lab.
Area of Inference