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Response to CDFG NCWAP Staff re: Electrofishing Data Interpretation

Fish Populations in KRIS Gualala

According to the California Stream Habitat Restoration Manual (CDFG, 1998): "Electrofishing used during habitat inventory methods outlined in this manual is generally used to describe species composition and distribution within a stream. The single-pass method is most commonly used for these data. All fish captured are identified to species and then counted and returned to the stream." Although some presence and absence sampling occurred in the Gualala River basin in 2001 for coho (Scott Harris, personal communication), fish sampling conducted by the North Coast Watershed Assessment Program (NCWAP) was in association with habitat typing as described above. IFR deleted Topics in KRIS Gualala from the database and Background pages that incorrectly used from coho surveys.

Nowhere in the NCWAP Methods Manual (CA Resources Agency, in review) nor in the Stream Habitat Restoration Manual (CDFG, 1998) does it state that fish samples associated with NCWAP activities or habitat typing are in any way skewed with regard to age classes as a result of the sampling technique. In fact CDFG (1998) says that sampling associated with stream surveys should consider:

• Species composition
• Juvenile rearing areas or general distribution
• Spawning areas or general distribution
• Sizes (lengths) of adults and juvenile
• Age classes of juveniles (based on lengths)
• Relative abundance in selected areas
• Biomass (weight per unit volume)
• Habitat utilization
• Timing of spawning activity
• Timing of juvenile emigration

Furthermore the CA Stream Restoration Manual (CDFG, 1998) says such samples should "provide a general assessment of fish presence, distribution and habitat utilization within a stream. It is essential to know what fish species exist within a stream and particularly the status of ‘target’ species. The upstream range of adult spawners and juveniles is important information for planning habitat enhancement work within a stream. Relative abundance of a species may suggest trends in past or future population numbers. Age classes of juveniles may indicate the quality of summer and winter nursery areas” (emphasis added by IFR). The lack of older age juvenile steelhead in CDFG electrofishing samples in numerous areas of the Gualala River basin in 2001 justify IFR’s conclusion that summer rearing habitat may be insufficient to support older age steelhead, which in turn effects adult recruitment.

The NCWAP Manual (CA Resources Agency, in review) says only that “Biological data on salmon and steelhead will be collected through spawner surveys, snorkel surveys, electrofishing, and downstream migrant trapping.” Three questions posed in the fish habitat section of the NCWAP manual suggest that CDFG should have been collecting fish data with more than a presence or absence focus:  

• “What is the linkage between current habitat conditions and the likelihood of salmon and steelhead populations to successfully reproduce and do well? 
• What is the linkage between current habitat conditions and the numbers of salmon and steelhead returning to streams as adult spawners?
• Do the channels provide the diverse habitats needed to support all life stages of salmon and steelhead?”

IFR has addressed these questions using recent and historic CDFG data in the Fish Population Background page as well as in Hypothesis #1. There are no arguments offered in any CDFG or NCWAP related publication that show that IFR use of fish data in KRIS Gualala is outside the bounds of fair use.

References

CA Department of Fish and Game. 1998. California Salmonid Stream Habitat Restoration Manual. Third Edition. Inland Fisheries Division. California Department of Fish and Game. Sacramento, CA. 495 pp. http://www.dfg.ca.gov/fishing/manual3.pdf

CA Resources Agency. 2001. DRAFT North Coast Watershed Assessment Program Manual. April 2001. Sacramento, CA. 107 pp. http://www.ncwatershed.ca.gov/.

CA Resources Agency. 2002. DRAFT Gualala Watershed Synthesis Report. April 2002. Sacramento, CA. 145 pp. http://www.ncwatershed.ca.gov/.

Harris, Scott. California Department of Fish and Game Fisheries Biologist, Region 3, Willits, CA.