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Fishes of the Green River Bioreserve, Kentucky: an examination of stability and persistence over the past century
Matthew R. Thomas
Department of Zoology Southern Illinois University at Carbondale Carbondale, IL 62901-6501  The Green River in Kentucky is among the most significant aquatic systems in the United States in terms of aquatic species diversity and endemism. The river system drains a diverse physiographic region in south-central Kentucky that includes a combination of lowland, karst, and upland habitats. With over 150 species, the Green River supports one of the most diverse and unusual fish faunas in the lower Ohio-Upper Mississippi basin. For example, five darter species (Etheostoma barbouri, E. barrenense, E. bellum, E. rafinesquei, and E. tecumsehi) and one sucker species (Thoburnia attripinnis) are endemic to the upper Green River drainage, and one darter species (Percina stictogaster) is shared exclusively with the Kentucky River. At least twenty of the 61 species listed as special concern, rare, or endangered by the Kentucky State Nature Preserves Commission are found in the Green River drainage.
 Most of the aquatic biodiversity is concentrated in a 100-mile reach of the upper Green River from below Mammoth Cave National Park to its headwaters in Casey County. Within this area, The Nature Conservancy (TNC) has established the Green River Bioreserve, located from Green River Dam, downstream to the Nolan River in Mammoth Cave National Park. This portion of the river harbors a large percentage of Kentucky?s native mussel species and about half of the fish species occurring in the upper Green River drainage, including rare species such as Etheostoma maculatum and Phenacobius uranops.
In 2002, TNC and U.S. Army Corps of Engineers formed a partnership, entitled the Sustainable Rivers Project, to begin re-operation of Green River Dam. Their objective is to modify releases from the Dam to approximate natural variations in flow and temperature that will benefit aquatic organisms, without sacrificing recreational and flood control purposes. The Green River Project will serve as a benchmark that will be used to anticipate successful operations planned for other rivers across the nation in the future. My research involves seasonal sampling of the fish communities at four sites in the Bioreserve below Green River Dam, following temperature and flow regime changes resulting from Dam re-operation procedures. The objectives are to compare these data with those taken prior to Dam re-operation, and over the long term, assess changes in species richness and composition, and growth trends for selected species.  I began fieldwork for this study in 2002, but was only able to obtain a summer sample in 2003 due to inclement weather and high water conditions. Baseline data (prior to Dam re-operation) were obtained in 2000 by Rivers Environmental Assessments, Inc. and SIUC ichthyologists. Fishes were sampled at each of the four sites once during spring, summer, and fall in a standardized fashion using a 15? minnow seine, 30? bag seine, backpack electrofisher, and dip nets. All microhabitats within a 200-meter reach were worked thoroughly for a representative sample. Fishes captured were held in a live well, where they were identified, enumerated, and released. Total lengths for eleven selected species were measured to monitor growth trends.
Three trips to each of the four sites in 2002 yielded a total of 53 species. Core species present at all sites included six minnows (Pimephales notatus, Cyprinella spiloptera, Campostoma oligolepis, Notropis volucellus, Erimystax dissimilis, and Luxilus chrysocephalus), one topminnow (Fundulus catenatus), one silverside (Labidesthes sicculus), three sunfishes (Ambloplites rupetris, Lepomis megalotis, and Micropterus punctulatus), and five darters (Etheostoma bellum, E. blennioides, E. stigmaeum, E. zonale, and Percina evides). As expected, two of the four sites (Tebb?s Bend and Roachville ford) closest to the dam and each other showed high proportional similarity index values (97%). Proportional similarity values among sites progressively decreased with distance from each other. Species richness gradually increased with distance downstream of the dam, with Munfordville having the highest number of species. Although species diversity and relative abundance data were similar between the baseline samples (2000) and 2002, I anticipate several years of sampling before any noticeable trends in diversity, relative abundance, and growth become apparent. The Green River has been of interest and received attention from naturalists and ichthyologists for over a century. Collection data are available from early surveys by Woolman in 1892, Bailey and Gilbert in the early 1950s, Turner and Clay in the 1960s, and then by the Kentucky State Nature Preserves Commission and SIUC throughout the 1980s and 1990s. These data provide a unique opportunity to examine changes to the fish communities of the Bioreserve section of the Green River over more than a century of alterations, such as impoundment and increased agricultural development. For example, based on these collections, we know that certain species (e.g., Crystallaria asprella, Noturus flavus, Noturus stigmosus, and Percina stictogaster) were at one time present in the Bioreserve section, but have not been collected anywhere in the entire drainage for more than 50 years. The Native Fish Conservancy Becker grant will provide me with much needed support to travel and conduct fieldwork in the Green River Bioreserve in 2004.  |
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