Persistence of fish assemblages on sand and gravel bar habitat in the Alabama River, Alabama
Type of Degreethesis
Fisheries and Allied Aquacultures
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The Alabama River is a biologically diverse system containing over 180 native fishes and at least 33 endemics. Many studies have surveyed species of conservation concern, such as the federally endangered Alabama Sturgeon (Scaphirhynchus suttkusi), Alabama Shad (Alosa alabamae), and Crystal Darter (Crystallaria asprella), but few have documented entire fish assemblages. Maintaining fish assemblage data is an important process in monitoring species and assemblage composition through time. In this study, I surveyed fish assemblages of sandbar habitat in the lower Alabama River and 9 associated tributaries. Diel and seasonal surveys were conducted along 19 sandbars from Dixie Landing (river mile 22) to Claiborne Lock and Dam (river mile 72). A total of 55 species were recorded in 44 collections during summer, fall, and spring 2010 – 2011. One species of conservation concern, Crystal Darter, was detected during our survey (n = 34). Fish assemblages in tributaries contained percid and cyprinid species not detected in our sandbar collections and clupeid species detected in sandbar samples were absent from tributary collections. Similarity indices were used to compare our data with historical data. Our samples had low similarity to historical samples of R. D. Suttkus and the Geological Survey of Alabama, suggesting fish assemblage shifts. Diel comparisons indicate low similarity reflecting large numbers of catfish species detected mostly in night collections. These data also indicate seasonal faunal changes among sandbar fish assemblages. In 2010, we detected extremely high numbers of Gulf Menhaden (Brevoortia patronus) during summer and fall indicating a new distributional record. Gulf Menhaden were collected during summer and fall 2010 collections. However, no Gulf Menhaden were detected during spring 2011 samples. Finally, sandbar area varied from 0.75 - 64.7 acres. Correlation analyses indicate no significant relationship between sandbar proximity or area and species richness, however we suggest ongoing anthropogenic disturbances such as dredging may affect richness among these sites. Data presented in this study suggest temporal shifts in fish assemblage structure. Ongoing habitat alteration on the Alabama River is leading to assemblage homogenization and potential loss of biodiversity. Future monitoring of fish assemblages and their habitats in the Alabama River, downstream of RM 72, is useful and managers and biologists should consider diel and seasonal sampling to accurately document fish species and assemblages.