Begun in 1987, Mossdale Kodiak Trawl is part of a larger effort to provide information on the vulnerability of Chinook salmon and steelhead to water project operations. In particular, managed releases from reservoirs on the Merced, Tuolumne and Stanislaus Rivers often result in altered flows downstream on the San Joaquin River mainstem and the southern Sacramento-San Joaquin Delta. These flows can affect out-migrating Chinook salmon and steelhead. The Mossdale Spring Trawl is conducted two miles downstream of Mossdale Landing County Park (river mile 56), and upstream of the Old River confluence near Lathrop, CA. USFWS and CDFW have been coordinating sampling at the Mossdale Trawl site since 2000 when year-round sampling was implemented.
The long-term monitoring effort is intended to track the abundance and distribution of Chinook salmon, steelhead trout, and other resident fish species. Typically, USFWS samples July – March, and CDFW samples April – June. In 2022, a collaborative effort was initiated to incorporate protocols and equipment used by each agency. This involved an integrated sampling plan using a mix of crews and gear from each agency throughout the year to assess consistency and ensure data comparability.
Left image: USFWS and CDFW staff retrieving Kodiak trawl net and live box.
Right image: CDFW and USFWS staff measuring and recording fish caught. CDFW photos.
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