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2005 GR Report Summary
ADULT AND JUVENILE STEELHEAD POPULATION SURVEYS,
GUALALA RIVER, CALIFORNIA, 2005
Richard W. DeHaven
December 31, 2005
SUMMARY: Seasonal steelhead spawning surveys (counts of adults and redds) conducted in 2002-2004 along an 18.3-mile reach (index reach) of the Wheatfield Fork, from House Creek downstream to the South Fork, were continued in the 2005 season. The index reach was surveyed seven times (128 miles) between December 23, 2004 and April 25, 2005 from a small, aluminum drift-boat. A total of 433 adult steelhead–a new seasonal record–and 17 redds (the same as in 2004) were recorded. Adult numbers peaked (163 fish=38%) during a mid-February survey. A large proportion of the adults recorded were very large fish (>30 inches and 15 pounds), possibly owing their size (and overall high numbers) to an additional year of ocean growth acquired after adults were prevented from spawning in the river late in the 2004 season by low flows. An early rainy-season start in late October, with repeated high-flow events through April likely facilitated most of the spawning upstream of the index reach. Results continued to show the need for weekly spawning surveys when feasible, extended to bi-weekly surveys at the end of the spawning season or during extended dry periods. Spawning survey data from 2005 will be coalesced with long-term results for later analysis and publication. In addition, during early July to early October 2005, four monthly snorkeling surveys of juvenile steelhead (JSH) were conducted at nine study sites in the watershed. Results indicated that: (1) both the extent and severity of impairment of JSH production in the watershed, due to excessive water temperatures, were greatly reduced compared to 2004; (2) extensive stream reaches that went dry (or lacked continuous surface flow) in summer 2004 flowed continuously through the summer of 2005; (3) Gualala roach (GR) and threespine stickleback (TSS) were less numerous than in 2004; (4) the Wheatfield Fork, which supported very low levels of JSH in summer 2004, became an important JSH producer in summer 2005; (5) Wolf Creek, found to be an important JSH producer in 2004, continued this role in 2005; and (6) owing to much more summertime rearing in upstream reaches in 2005 versus 2004, the importance of the estuary to JSH summer rearing (and overall annual production) diminished greatly in 2005. The very good JSH rearing conditions of summer 2005 were tied to much higher summer flows (compared to recent years), the result of well-above-average late-season precipitation. In concert with the very good spawning flows and conditions also experienced in 2005, this year was clearly an exceptionally good one for the rivers’s steelhead population.
Senior Fish and Wildlife Biologist (Retired 2004); U.S. Fish and Wildlife Service (Service), Sacramento, California. Recommended Report (available on CD from the author or on the internet after March 2005) Citation: DeHaven, R. W. 2005. Adult and juvenile steelhead population surveys, Gualala River, California, 2005. Prepared by the author (drdehave et hotmail.com), December 31, 2005, for use by agencies, groups and individuals involved in steelhead recovery efforts. 64 pp. (After March 1, 2007, report may be requested on CD from the author’s website at: http://www.gualalariversteelhead.info.)
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