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2010 GR Report Summary

ADULT AND JUVENILE STEELHEAD POPULATION
SURVEYS, GUALALA RIVER, CALIFORNIA, 2010

Richard W. DeHaven *1
December 31, 2010


SUMMARY: Seasonal spawning surveys of adult steelhead conducted in 2002-2009 along an 18.7-mile reach of the Wheatfield Fork, Gualala River, California (Index Reach), were continued in 2010, along a reduced, 9.4-mile reach. The shortened Index Reach was surveyed five times (47 miles) from a small, aluminum drift-boat between late December 2009 and late April 2010. A record low count of 31 adult fish was recorded; and a record low population estimate of 296 fish was generated, using Area-Under-the-Curve (AUC) methodology. However, results were likely biased low, due to poor fish-counting conditions (high flows and turbidity) during the season. A spawning population for the Wheatfield Fork for 2010 in the range of at least 500 to 1,500 fish appears more likely. One mid-summer (July 16th) snorkeling survey at 15 sites in the watershed revealed a robust JSH (juvenile steelhead) population concentrated upstream of the estuary and excellent summertime rearing conditions, owing to high stream flows and favorable water temperatures. High flows were a function of above-average rainfall; favorable water temperatures were a function of high flows and mild summer air temperatures. Such ideal JSH rearing conditions should portend good adult spawning returns in 2-3 years.




*1 Senior Fish and Wildlife Biologist (Retired 2004); U.S. Fish and Wildlife Service, Sacramento, California. Recommended Report Citation: DeHaven, R. W. 2010. Adult and juvenile steelhead population surveys, Gualala River, California, 2010. Prepared by the author (drdehave et hotmail.com), December 31, 2010, for use by agencies, groups and individuals involved in steelhead recovery efforts. 26 pp. (This report, with Appendix, to be available on the author’s website at http://www.gualalariversteelhead.info by mid-2011.)

 

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