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Determining the frequency of opercular deformities in age-0 native Catostomids from the San Juan River (NM, CO, UT)

Authors: Judith M. Barkstedt, Jennifer L. Hester, Michael A. Farrington

Year: 2013 (xlv)

Abstract

The San Juan River is a major tributary of the Colorado River and supports native populations of Catostomus latipinnis, Flannelmouth Sucker, Catostomus discobolus, Bluehead Sucker, and federally endangered Xyrauchen texanus, Razorback Sucker. From 1998 to present, monthly surveys (April—September) of the larval fish community were conducted in a 200 km+ reach of the San Juan River between Shiprock, NM and Lake Powell, UT. Of the approximately 170,000 age-0 native catostomids collected during the tenure of this study, C. latipinnis was the numerically dominant species (66%), followed by C. discobolus (30%), and X. texanus (4%). The high prevalence of opercular deformities noted in 2011 San Juan River samples of age-0 catostomids resulted in re-examination of the study material in an attempt to determine annual species-specific frequencies of opercular deformities. Opercular deformities (i.e., opercular shortening) expose gills and may increase susceptibility to gill diseases and other mortality risks, particularly as a result of environmental stressors. The frequency of opercular deformities in the combined 2011—2012 samples of age-0 catostomids (n = 12,933) was 8.9%, occurring in 6.1% of C. discobolus, 9.4% of C. latipinnis, and 32.1% of X. texanus. We analyzed the frequency of opercular deformities in age-0 catostomids from 1998—2012 for temporal patterns and found that the incidence of deformities varies across years, but can be as high as 100% in X. texanus and 13% in C. latipinnis. Preliminary analysis of river flow suggests higher incidences of deformities occur with both low summer flows and years with fewer low flow days in summer. Understanding patterns of occurrence of this potentially lethal deformity in native catostomids in the San Juan River is necessary for conservation, management, and recovery of these species.