Long-term monitoring of coho salmon and steelhead during freshwater life stages in coastal Marin County: 2014 annual report

Carlisle, Sarah; Reichmuth, Michael; McNeill, Brentley

The San Francisco Bay Area Network (SFAN) monitors populations of coho salmon (Oncorhynchus kisutch) and steelhead (O. mykiss) in watersheds at Point Reyes National Seashore, Golden Gate National Recreation Area, and Muir Woods National Monument. The watersheds, including Olema Creek, Redwood Creek, and Pine Gulch Creek, represent the majority of streams supporting salmonids in Marin County, California, and support the a population of coho salmon near the southern extent of their range on the Pacific Coast. The National Park Service SFAN Inventory and Monitoring Program and California Department of Fish and Wildlife have supported monitoring of multiple coho salmon life stages in coastal Marin County watersheds since 1998. Monitoring includes: • adult escapement surveys, which document the number of adult salmonids that successfully “escape” ocean fisheries and return to their natal streams to spawn, as well as the number of redds (gravel nests where salmonids lay their eggs) created; and • outmigrant smolt trapping, where the number of smolts (at least year-old juvenile salmonids that have undergone changes to cope with a marine environment) are captured, measured and counted as they make their way towards the ocean; and • basinwide juvenile coho surveys and summer index reach monitoring which seek to quantify the number of juvenile salmonids present in the watersheds during the summer months. Monitoring of multiple life stages presents a more accurate picture of the coho population than monitoring only a single stage, especially given the complex life history of the coho salmon. Coho salmon have a three-year life cycle in which they spend the first year of life in their natal stream followed by nearly two years in the ocean before returning to their natal stream to spawn. Since generations of related fish reproduce every third year, the coho population is divided into three distinct year classes, or cohorts. Cohorts may be labeled 1, 2, and 3. Cohort 1 was the first that was monitored by NPS in 1997-1998 as one generation returned to spawn in the winter and the next hatched and emerged in spring and were surveyed as juveniles during the summer. These fish were surveyed again when they left the creeks as smolts in 1999 and for a third time as spawning adults in the winter of 2000-2001. Succeeding generations of cohort 1 hatched in 2001, 2004, 2007, 2010, and 2013. Cohort 2 are those fish that hatched in 1999, 2002, 2005, 2008, 2011, and 2014, and cohort 3 fish hatched in 2000, 2003, 2006, 2009, 2012. This report presents a summary of monitoring results for the 2013-2014 spawner season, 2014 smolt trapping season, and 2014 summer juvenile surveys.

Long-term monitoring of coho salmon and steelhead during freshwater life stages in coastal Marin County: 2014 annual report

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