9691

• UCREFRP Catalog Number: 9691
• Author: Recovery Implementation Program.
• Title: Recovery Implementation Program For Endangered Fish Species in the Upper Colorado River Basin 25th Annual Recovery Program Researchers Meeting.
• USFW Year: 2004.
• USFW - Doc Type: Moab, UT.
• Copyright Material: NO

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Bioenergetics provides a framework to quantify the biomass of prey consumed by fishes
based on their thermal experience, growth rate, body condition and the availability of
their prey. Using data on seasonal diet composition, it becomes possible to estimate
predation by the type of prey consumed, e.g., invertebrate vs. fish. By calculating the
amount of food consumed by a tish in each size class (trophic stanza), and scaling these
per capita estimates of prey consumption up to the entire population with abundance data,
it becomes possible to estimate of overall demand for tish prey by piscivores. Population
level estimates of piscivore consumption of various prey clarifies which species or size
class ofpiscivores may be exerting the greatest predation demand in a fish community.
Because the predation impact on native fishes by nonnative piscivores is of increasing
concern within Critical Habitat for endangered fishes in the Upper Colorado River Basin,
bioenergetics analysis has the potential to identify which species or size-class of
nonnative piscivores exert the greatest predation threat to native fishes. The level of
refinement attainable by applying the bioenergetics framework is reliant upon the quality
of the data available. Examination of piscivore diet by season is necessary to detect
predation on native vs. nonnative species. Projection of predation demand by piscivores
at the population or river reach level is reliant on sound estimates of piscivore abundance.
Further, these estimates of abundance should be unbiased in their representation of size
classes in the population. By meeting these sampling standards accurate estimates of the
amount of fish prey consumed by piscivores are possible. This infonnation would allow
managers to identify the most problematic species and target the most predaceous size
classes to optimize the ecological and economic efficiency of efforts to remove or control
nonnative piscivores. Further, these estimates can be used to detennine how many
nonnative piscivores need to be removed to protect and restore native fishes and facilitate
recovery of endangered ones. An example is presented for nonnative channel cattish,
northern pike and smallmouth bass in the Yampa River using available data and
identifying data needs and model limitations that must be addressed by additional
research to optimize the utility of this technique.

Elemental and stable isotope markers of non-native fish provenance in the Upper
Colorado River basin

Whitledge, Gregory W.', Brett M. Johnson I, Patrick 1. Martinez2, and Anita M. Martinez2

I Dept. of Fishery & Wildlife Biology. Colorado State University, Ft. Collins, CO:
2Colorado Division of Wildlife, Grand Junction, Co.

Non-native centrarchids are present throughout much ofthe Upper Colorado River basin
and can adversely affect recovery of threatened and endangered native tishes through
predation or competition within critical habitats. Identitication of sources of centrarchids
to critical riverine habitats is crucial if centrarchid control etlorts are to proceed in an
efficient and effective manner. We are employing stable isotope and elemental analyses
oftish otoliths to determine origins and reconstruct movements of centrarchids in and
upstream of the Grand Valley reach of the Colorado River. Otoliths are mcrabolically
inert structures whose elemental and stable isotopic compositions reflect those of the