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to be captured in trammel nets at lakeshore spawning areas and in tributaries during spawning migrations. Each captured sucker was physically handled in order to scan for the presence of a passive integrated transponder (PIT) tag. A difficulty in capture- recapture studies is that parameter estimate precision and effective modeling depend not only on the number of animals captured and released, but also on the number surviving and subsequently captured again. Although sampling effort and sample sizes increased substantially beginning in 1999, recapture probability estimates continued to remain below ten percent. Low recapture probabilities have resulted in consistently poor parameter estimate precision. In addition to trammel net capture methods, efforts were made in 2005 to increase recapture probability using remote PIT tag detection stations and a resistance board weir on the main spawning tributary to Upper Klamath Lake. In the first year of operation, the weir and remote PIT tag antennas dramatically increased detection probabilities of previously tagged fish. In 2005,5799 individual PIT tags were detected with remote antennas at the weir, compared to approximately 1000 tags detected in 2004 using past capture, handle and release methods. 3. Analysis of a preliminary microsatellite dataset for wild and captive populations of humpback chub, Gila cypha. Authors: ALLAN STRAND, College of Charleston, Grice Marine Laboratory, 205 Ft. Johnson Rd Charleston, SC 29412, stranda@cofc.edu; CONNIE KEELER-FOSTER, USFWS, Dexter National Fish Hatchery and Technology Center, Dexter, NM 88230, Connie _ KeelerFoster@fws.gov Abstract: In this study, we compared a captive stock and three wild-sampled populations of humpback chub using microsatellites, a neutral genetic marker. Our primary objective was to examine the captive population as a potential broodstock. Secondarily, we intend to develop a comprehensive strategy to develop the captive stock as a refugial population genetically synonymous with the Little Colorado River (LCR) population. First we estimated the power of the wild samples to capture the genetic diversity present in nature. We used a binomial approximation and assumed panmixia for this simple analysis. The results suggest that two of the three wild-caught samples are large enough to ensure a 95% chance of detecting an allele segregating at a frequency greater than 0.1 O. We then used a suite of six primers developed initially for Bonytail (Gila elegans) to genotype the captive and wild-caught samples. Wild caught populations did not have significantly greater levels of genetic diversity than the captive population as measured by Nei's index of gene diversity. Furthermore, the captive population appears to possess the same alleles at similar frequencies: there is no evidence for genotypic differentiation among any of the populations assayed, wild-caught or otherwise. Based upon this preliminary dataset, it appears that the captive population housed at Willow Beach represents a valuable genetic resource for recovery efforts. 7