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2006 GR Report Summary
ADULT AND JUVENILE STEELHEAD POPULATION SURVEYS,
GUALALA RIVER, CALIFORNIA, 2006
Richard W. DeHaven
December 31, 2006
SUMMARY: Seasonal steelhead spawning surveys (counts of adults and redds) conducted in 2002-2005 along an 18.3-mile reach (index reach) of the Wheatfield Fork, from House Creek downstream to the South Fork, were continued in 2006. This index reach was surveyed four times (64 miles) between December 12, 2005 and April 29, 2006 from small, aluminum drift-boats. A total of 96 adult steelhead and 2 redds were recorded; adult numbers peaked (57 fish=59%) during a late-February survey. Unusually high rainfall (60-84 inches) and stream flows during the spawning season limited numbers of adults seen and facilitated their spawning upstream of the index reach. Large numbers of juvenile steelhead (JSH), previously unseen during spawning surveys, were recorded during the first survey on December 12-13, 2005. This anomaly was preceded by relatively good rearing conditions JSH experienced in summertime 2005, due to well-above-average April-May 2005 precipitation. The 2006 adult spawning survey data will be coalesced with long-term results for later analysis and publication. Snorkeling surveys of JSH were also continued in 2006 at nine study sites established in 2005 and six new sites. The 2006 snorkeling indicated that: (1) as in 2005, Wolf Creek continued as an important producer of JSH; (2) as in 2005, both the extent and severity of impairment of JSH production in the watershed, due to excessive water temperatures, were reduced compared to 2004; (3) as in 2005, extensive stream reaches that went dry (or lacked continuous surface flow) in summer 2004 flowed continuously through the summer; (4) as in 2005, Gualala roach and threespine stickleback were less numerous than in 2004; (5) as in 2005 (and in contrast to typical years), the Wheatfield Fork became a more important producer of JSH; (6) as in 2005, and owing to much more summertime rearing in upstream reaches compared to 2004, the importance of the estuary to JSH summertime rearing (and overall annual production) diminished; and (7) in contrast to 2005 (and despite good summertime rearing conditions), overall numbers and densities of JSH declined as a result of very high rainfall and flows, especially during March and April, which may have reduced adult steelhead spawning success. Nevertheless, back-to-back years with moderate-to-high annual rainfall, coupled with high springtime rainfall, may bode well for steelhead spawning escapement in 1-2 years.
Senior Fish and Wildlife Biologist (Retired 2004); U.S. Fish and Wildlife Service (Service), Sacramento, California. Recommended Report Citation: DeHaven, R. W. 2006. Adult and juvenile steelhead population surveys, Gualala River, California, 2006. Prepared by the author (drdehave et hotmail.com), December 31, 2006, for use by agencies, groups and individuals involved in steelhead recovery efforts. 47 pp. (After March 1, 2007, report may be downloaded from the author’s website at: http://www.gualalariversteelhead.info.)
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