Warner Sucker 2014 Annual RME Report. Scheerer, P., D., Peterson, J., T., & Clements, S., P. Technical Report 2014.
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Warner suckers (Catostomus warnerensis) are endemic to the lakes and tributaries of the Warner basin, southeastern Oregon. The species was listed as threatened by the U.S. Fish and Wildlife Service in 1985 because of habitat fragmentation and the threats from introduced non-native fish. Recent recovery efforts have focused on providing passage at irrigation diversion dams that limit sucker movement within the Warner basin. To provide a baseline to assess the effectiveness of passage restoration activities in lower Twenty Mile creek we: 1) obtained a population estimate for suckers in the lower Twentymile Creek drainage, 2) described their current distribution, and 3) tagged suckers with a passive integrated transponder (PIT) to assess future passage success at the Dike irrigation diversion. We captured fish using three gear combinations (backpack electrofishing, hoop nets, mobile PIT antenna). We used a Bayesian Jolly-Seber (J-S) open population estimator to estimate sucker population size, apparent survival, and immigration. We installed a fixed, flat-plate PIT-tag antenna near the upstream boundary of the survey to evaluate the timing and numbers of suckers moving upstream during our study. We estimated there were 482 suckers in lower Twentymile Creek. We estimated an apparent survival of 88% over the duration of the study and an 8% immigration rate. We found some evidence that fish length was positively related to survival, no evidence that the apparent survival of translocated fish differed from those residing in the study area, no evidence that capture probabilities differed with the number of hoop net sets, and no evidence that hoop net capture probabilities differed from the probability of detection with the mobile PIT antenna. We only detected one sucker at our fixed PIT antenna. We PIT tagged a total of 147 suckers that we can monitor in 2015 to assess passage success at the newly reconstructed Dike Diversion.

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