CSU Fisheries Ecology Laboratory
Provenance of nonnative fishes in the Upper Colorado River basin
Funded by U.S. Fish and Wildlife Service, Upper Colorado River Endangered Fish Recovery Program
Patrick Martinez, Colorado Division of Wildlife
Anita Martinez, Colorado Division of Wildlife
Gregory Whitledge, Department of Zoology, Southern Illinois University
Floodplain corridors bordering the main stem rivers in the Upper Colorado River Basin are considered an integral and necessary element in the recovery of the four endangered big river fish species. Nonnative fish species are present throughout the Upper Basin (Martinez 2002, Trammel et al. 2002), and can adversely impact the recovery progress for endangered fishes through predation or competition at critical life stages or in critical locales (Tyus and Saunders 1996). Four species in the Family Centrarchidae (largemouth bass Micropterus salmoides, green sunfish Lepomis cyanellus, bluegill Lepomis macrochirus and black crappie Pomoxis nigromaculatus) are considered to be the most problematic.
Control of nonnative fishes has been a recovery program goal since at least 1996, but control efforts have met with limited success, partly because the predominant source of nonnative fish in the Colorado River is unknown. The large number of potential sources and the inability to determine specific habitats where nonnative fishes are reproducing and recruiting has been a vexing problem. Managers’ work would be greatly facilitated by knowledge of the origins and movement patterns (provenance) of nonnative fishes, which could provide insights into the most promising and efficient management strategies to control them. However, it has not been possible to study nonnative fish provenance by conventional means because physical sampling and mark-recapture techniques are inadequate given the scale of the problem.
The advent of stable isotopic and microchemical analyses of otoliths has provided a new avenue for the study of fish provenance by exploiting natural markers that reflect a fish’s environmental history throughout its lifetime. A variety of stable isotopes of common elements provide naturally occurring markers to track origins and movements of nonnative fishes in the upper Colorado River basin. In this study we used elemental and isotopic analysis of water and fish otoliths to identify, for the first time, the sources of nonnative fish found within riverine reaches of critical habitat in the Grand Valley, Colorado.
Identify recruitment sources of nonnative fishes in the
1. Determine whether the origins and movements (collectively termed provenance) of centrarchids in the study area can be identified using stable isotope and/or microchemical analyses.
2. Determine the proportion of centrarchids in backwaters within the study area that originated from out-of-channel ponds versus in-channel habitats.
3. If feasible, pinpoint “hotspots” where centrarchids present in connected backwaters have originated by narrowing the list of possible sources (e.g. from “off-channel ponds” to specific ponds or groups of ponds).
Publications to Date
1. Whitledge, G. W., B. M. Johnson, P. J. Martinez, and A. M. Martinez. 2007. Sources of nonnative centrarchids in the upper Colorado River revealed by stable isotope and microchemical analyses of otoliths. Transactions of the American Fisheries Society 136: 1263–1275.
2. Whitledge, G. W., B. M. Johnson and P. J. Martinez. 2006. Stable hydrogen isotopic composition of fishes reflects that of their environment. Canadian Journal of Fisheries and Aquatic Sciences 63:1746-1751.
Dr. Brett M. Johnson
Department of Fish, Wildlife and Conservation Biology
Colorado State University, Fort Collins, CO 80523-1474
voice: (970) 491-5002, (970) 491-2749 fax: (970) 491-5091
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