San Joaquin River - Mossdale Kodiak Trawl Monitoring Methods

Sampling is performed with a 1.87m x 7.6m Kodiak trawl net. The Kodiak trawl uses two boats to pull a net equipped with spreader bars, wings, and a “belly” in the throat of the net (to improve capture vulnerability). Fish are collected in a live box (.36m x .36m x .49m) attached to the end of the net.

The sampling intensity is five days a week from April through first two weeks of June and three days a week for the remainder of June. The study period is April through June.

All trawling occurs during daylight hours, generally starting between 0745 and 0900 hours. Sampling days usually consist of 10 tows at 20 minutes per tow. Sampling is also conducted three days per week from July to March by the US Fish and Wildlife Service Lodi office.

All fish are identified to species, if possible, and enumerated. Unidentified fish are retained for laboratory identification. Chinook salmon are checked for dye marks, radio or acoustic tags and adipose fin clips. All non-marked Chinook salmon are considered “natural” for the purpose of this study. Fork length measurements are taken for the first 50 Chinook and first 30 of any other non-salmonid species each tow.