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<br />0015u6
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<br />SAMPLING VARIABILITY FOR RARE RIVERINE FISHES
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<br />1651
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<br />diel period and season did not affect variability, sampling should be conducted
<br />when logistically feasible, but sampling should be consistent with regards to
<br />season and diel period. High variability in CPUE of both gears suggest that
<br />analysis of long-term trends are more appropriate to determine trends in CPUE
<br />of native fish populations than individual CPUE point estimates, and this is
<br />probably true for other rare or endangered fishes in riverine environments.
<br />Because of the high variability in CPUE, intensive mark recapture estimates
<br />using stock assessment models may be more appropriate to determine popula-
<br />tion trends than CPUE for these rare fishes. Trammel nets in the mainstem
<br />Colorado River is recommended over electrofishing for long-term monitoring of
<br />adult native fishes relative abundance. Sampling nearshore habitats by electro-
<br />fishing or some other gear not analysed in this study (e.g. seines, hoop nets or
<br />trammel nets with smaller mesh sizes), however, may be more appropriate for
<br />detecting juvenile relative abundance or recruitment variability.
<br />
<br />I thank all the people who collected native fish in the Colorado River in 1992 and 1993,
<br />particularly R. Valdez and BIOfWEST, but also the Arizona Game and Fish Department,
<br />SWCA Environmental Consultants, Inc., Humphrey Summit Support, and the U.S.
<br />Fish and Wildlife Service. I also thank M. Allen, University of Florida, for advice on
<br />interpretation and analysis of sample size requirements and review of the manuscript.
<br />Comments from L. Coggins, USGS and C. Walters, University of British Columbia, and
<br />an anonymous reviewer greatly improved the manuscript.
<br />
<br />References
<br />
<br />Allen, M. S., Hale, M. M. & Pine, W. E. (1999). Comparison of trap nets and otter trawls
<br />for sampling black crappie in two Florida lakes. North American Journal of
<br />Fisheries Management 19,977-983.
<br />Chart, T. E. & Bergersen, E. P. (1992). Impact of mainstem impoundment on the
<br />distribution and movement of the resident flannelmouth sucker (Catostomidae:
<br />Catostomus latipinnis) population in the White River, Colorado. The Southwestern
<br />Naturalist 37, 9-15.
<br />Childs, M. R., Clarkson, R. W. & Robinson, A. T. (1998). Resource use by larval and
<br />early juvenile native fishes in the Little Colorado River, Grand Canyon, Arizona.
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<br />Converse, Y. K., Hawkins, C. P. & Valdez, R. A. (1999). Habitat relationships of
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<br />variability and implications for flow regulation. Regulated Rivers: Research and
<br />Management 14, 267-284.
<br />Counihan, T. D., Miller, A. I. & Parsley, M. J. (1999). Indexing the relative abundance of
<br />age-O white sturgeons in an impoundment of the Lower Columbia River from highly
<br />skewed trawling data. North American Journal of Fisheries Management 19, 520-529.
<br />Douglas, M. R. & Douglas, M. E. (2000). Late season reproduction by big-river
<br />catostomidae in Grand Canyon (Arizona). Copeia 2000, 238-244.
<br />Guy, C. S., Willis, D. W. & Schultz, R. D. (1996). Comparison of catch per unit effort and
<br />size structure of white crappies collected with trap nets and gill nets. North
<br />American Journal of Fisheries Management 16, 947-951.
<br />Hanchin, P. A., Willis, D. W. & St. Sauver, T. R. (2002). Comparison of concurrent trap-net
<br />and gill-net samples for black bullheads. Journal of Freshwater Ecology 17, 233-237.
<br />Harley, S. J., Meyers, R. A. & Dunn, A. (2001). Is catch-per-unit-effort proportional
<br />to abundance? Canadian Journal of Fisheries and Aquatic Sciences 58, 1760-1772.
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<br />(!;) 2004 The Fisheries Society of the British Isles, Journal of Fish Biology 2004, 65, 1643-1652
<br />(No claim to original US government works)
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