Gut Content and Stable Isotope Analysis of Exotic Suckermouth Catfishes (Hypostomus) in the San Marcos, TX: A Concern for Spring Endemics?




Cohen, Katrina L.

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Introduced suckermouth catfishes (Family Loricariidae) are established in a number of spring-influenced streams in North America. Impacts to native flora and fauna are predicted, but these predictions have not been tested. Purposes of this study were to quantify gut contents of suckermouth catfishes from the San Marcos River in central Texas and to assess degree of dietary overlap between the suckermouth catfish and native herbivorous fishes by comparing gut contents and by analyzing stable isotopes. Suckermouth catfishes (N = 36) primarily consumed amorphous detritus (87% in biovolume), filamentous red algae (5.4%), and picoplankton (4.1 %). Stable isotopes analysis indicated a more omnivorous trophic level. An endangered macrophyte, macroinvertebrates, and fish eggs were not found in the gut contents. Suckermouth catfish gut contents were similar (P >0.05) to those of a sympatric native herbivore, Guadalupe roundnose minnow Dionda nigrotaeniata, but differed (P <0.01) from another sympatric native herbivore, central stoneroller Campostoma anomalum. Gut content assessments of two additional Dionda species suggest high dietary overlap between the Dionda complex and suckermouth catfish. Consequently, occurrences of suckermouth catfishes in spring-influenced streams are potential direct competitors with only a few native taxa in spnng-influenced streams of central and west Texas.



catfishes, herbivores, hypostomus, San Marcos River


Cohen, K. L. (2008). Gut content and stable isotope analysis of exotic suckermouth catfishes (Hypostomus) in the San Marcos, TX: A concern for spring endemics? (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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