2002 GR Report Summary at Gualala River Steelhead Studies web site

2002 GR Report Summary

STEELHEAD SPAWNING SURVEYS, WHEATFIELD FORK AND OTHER SELECTED REACHES, GUALALA RIVER, CALIFORNIA, 2002

Richard W. DeHaven
September 2002
(Edited and Repaginated 01/2006)

SUMMARY: Because of a dearth of current information on population status of steelhead in the Gualala River, steelhead spawning surveys (counts of adults and redds) initiated in 2001 were continued in 2002, focusing on an 18.3-mile reach of the Wheatfield Fork, from House Creek downstream to the South Fork. This navigable reach, which is proposed as a population indexing reach, was surveyed a total of eight times (146.4 miles total) from small, river-dory style boats during February 2-April 19, 2002. Totals of 377 live adult steelhead and 145 steelhead redds were recorded, suggesting a total spawning escapement for this portion of the watershed of at least several hundred fish. A substantial, but unknown, amount of spawning likely also occurred upstream of the index reach, due to high-flow conditions which prevailed early in the spawning season. Spawning was well-distributed both temporally and spatially within the index reach. Tracking of 74 of the index-reach redds over multiple surveys showed that discernability was often as short as 1 week and that even in the absence of high stream flows, most redds became non-discernable within 3-4 weeks. The relatively low discernability periods are likely due to the high degree of coarse bedload mobilization which occurs along the index reach, a relatively large, fourth-order mainstem section of the river. Discernability results indicated that to avoid missing significant numbers of redds, redd surveys of the index reach should be conducted at least weekly (with extensions to a maximum of bi-weekly). Also, preliminary findings with regard to observer variation in redd detection and identification, suggested the need for surveys to be conducted in two-person teams composed of well-trained and experienced observers. Preliminary findings also suggested that confusion and misidentification of steelhead and lamprey redds may be an important confounding factor in surveys along the index reach. However, if index-reach survey results are appropriately evaluated in light of precipitation and river hydrograph, they may provide a useful means of monitoring gross changes and trends in the steelhead population of the survey-area, if not the watershed. Miscellaneous, one-time surveys of several other Gualala River reaches are also reported. All of the index-reach surveys and miscellaneous surveys are detailed in individual survey reports which are appended.

Senior Fish and Wildlife Biologist (Retired); U.S. Fish and Wildlife Service (Service), Sacramento, California. Recommended Report (available on CD from the author) Citation: DeHaven, R. W. 2002. Steelhead spawning surveys, Wheatfield Fork and other selected reaches, Gualala River, California, 2002. Prepared by the author (drdehave et hotmail.com), September 2002, for use by agencies, groups and individuals involved in steelhead recovery efforts. 47 pp. (After March 1, 2007, report may be requested on CD at the author's website at: http://www.gualalariversteelhead.info.) Disclaimer:These surveys and this report were self-funded and conducted during non-work hours, and not while in any official capacity as a biologist for the U. S. Fish and Wildlife Service.