Isotopic, Elemental & Bioenergetics Studies: Application of isotopic and elemental techniques to identify provenance of fishes and to facilitate bioenergetics projections of food-web impacts of piscivores in rivers and reservoirs.

Principal Investigator: Brett Johnson
Undergraduate Students: Mario Sullivan, Randy Oplinger, Justin Butteris and Michael Dodrill
Project Start Date: 7/01/02
Expected Completion Date: Ongoing project
Funding Agency: Colorado Division of Wildlife

Analyses of the isotopic and elemental composition of fish tissues and otoliths provide relatively new and powerful techniques for determining 1) origins and movement patterns (provenance) of fishes, and 2) composition of the diet over seasonal time scales. Together, these analyses provide invaluable information for determining the origins of invasive non-native fishes and for predicting their ecological impact on the ecosystems they have invaded. Identification of recruitment sources and the relative predatory impact of non-native species are crucial if control or other management efforts are to proceed in an ecologically and economically efficient manner. Objectives:
Conduct research applying isotopic and elemental techniques to: 1) track provenance of smallmouth bass in the Colorado River within critical habitat for endangered fishes, and 2) track origins of illicitly stocked fishes in Blue Mesa Reservoir. Also, research will be conducted using bioenergetics to 3) estimate food web impacts of smallmouth bass in the Yampa River and of smallmouth bass and channel catfish in the Colorado River and 4) estimate food web impacts of illicitly stocked fishes and piscivores in coldwater reservoirs.

Progress on the project since July 2004 is as follows. We completed microchemical analysis of otoliths taken from smallmouth bass from Lake Powell (8), the Yampa River (15), and 10 from the CO River near Grand Junction, but only one fish was available from Rifle Gap Reservoir last year. The Sr signatures of fish from Lake Powell have a distinct signature and that none of the 10 fish from the CO River showed any evidence of coming from L. Powell (although admittedly 10 is an insufficient sample size). More sampling at Rifle Gap is required to complete our assessment of the provenance of smallmouth bass in the Colorado River within critical habitat for endangered fishes. Otoliths from yellow perch and northern pike are being analyzed at this time by laser ablation inductively coupled mass spectrometry. In the previous year we established standardized procedures for analysis of fish stomach contents and prepared necessary reference materials to aid in the identification of prey items found in the Upper Colorado basin. Analysis of channel catfish stomachs is complete. We analyzed 67diet diet samples from the Yampa River (primarily smallmouth bass) and 117 diet samples from the Colorado River (primarily from centrarchids). Data from the diet analyses are being incorporated into bioenergetics models to estimate food web impacts of invasive fishes in rivers and coldwater reservoirs. We analyzed 25 smallmouth bass tissue samples each from both the Yampa and Colorado rivers for stable isotope signatures. Twenty four invertebrate samples (Corbicula and Physa) from the Colorado River were also analyzed for isotopic signatures. We updated CDOW/CSU research websites and we are preparing peer-reviewed manuscripts pertaining to the project.

Three detailed annual progress reports have been completed so far for work in 2002, 2003 and 2004 (39, 48 and 52 pages, respectively). Each year’s report provided recommendations and guidance that was used to design field sampling and analyses in subsequent years. Results from these reports have been used by CDOW and CSU in presentations at scientific conferences and for inclusion in CDOW Federal Aid reports; these reports have also provided the basis for peer-reviewed manuscripts that are currently in preparation.