Long-term coho salmon and steelhead trout monitoring in coastal Marin County 2007: annual monitoring progress report

Carlisle, Sarah; Reichmuth, Michael; Brown, Erin; Del Real, Casey

The National Park Service has conducted fisheries monitoring of watersheds in Point Reyes National Seashore (PORE), Golden Gate National Recreation Area (GOGA), and Muir Woods National Monument (MUWO) that contain coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss). These watersheds, including Olema Creek, Redwood Creek and Pine Gulch Creek represent the majority of salmonid-bearing streams in Marin County, California, and support the southernmost stable populations of coho salmon on the western Pacific Coast. These monitoring efforts, conducted with support through the NPS Inventory and Monitoring Program and California Department of Fish and Game, have supported multiple life stage monitoring of coho salmon in coastal Marin watersheds since 1998. This report presents a summary of results from adult escapement surveys, outmigrant smolt trapping, summer index reach monitoring, and basinwide coho juvenile population estimates for Olema, Redwood, and Pine Gulch Creeks. Performed in conjunction with winter spawner surveys and summer juvenile surveys, the spring outmigrant surveys on Olema, Pine Gulch, and Redwood Creeks permit an evaluation of abundance and survival associated with the freshwater portion of their life-cycle. Monitoring results for 2007 track different life stages of the three coho cohorts. During the 2006-2007 spawner surveys, reduced numbers of spawners were observed for this year class when compared to 2003-2004. Olema Creek watershed redd numbers, which takes into account John West Fork, declined by 13%. Redwood Creek mainstem had a 51% decline in total coho redd production from the previous year class. Of the four consecutively monitored years of this cohort on Redwood Creek, 2006-2007 had the lowest coho spawning activity. On Pine Gulch, no spawning activity was observed. Based on juvenile population estimates made during the summer of 2004 and smolt production estimates calculated during the spring of 2005, the reduced escapement was likely caused by poor ocean conditions. Although the 2006-2007 had reduced escapement, the 2007 calculated juvenile population estimates for both Olema Creek (31,936 ± 4,122) and Redwood Creek (7,832 ± 1,640) were the highest on record suggesting above average spring survival for both creeks. On Pine Gulch Creek no coho were detected while performing juvenile coho surveys marking the first missing year class since the recolonization of Pine Gulch was documented in 2001. Although the calculated 2007 smolt production estimates for all three watersheds were lower than average, survival rates from egg to smolt were higher than average. Smolt outmigration observed in spring 2007 were small, when compared with other years, but represented relatively high overwinter survival when compared with summer 2006 population estimates. The Olema Creek outmigration estimate of 1,098 ± 116, indicated a juvenile to smolt survival estimate of 61.2%. The Redwood Creek outmigration estimate of 520 ± 126, indicates that the juvenile to smolt survival for this year class was 49.5%. In Pine Gulch Creek, the 219 ± 33 coho smolts represented nearly 75% of the total summer 2006 juvenile estimate (295 ± 201). These outmigration totals indicate strong overwinter survival, likely due to a mild winter.

Long-term coho salmon and steelhead trout monitoring in coastal Marin County 2007: annual monitoring progress report

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