Selenium-Induced Changes in Fish Populations of a Heated Reservoir

High selenium levels and changes in abundance and size distribution of fishes were discovered after reports of fish dying in Martin Creek Reservoir, Texas. The reservoir functions as a cooling source for a coal-fueled power plant owned by Texas Utilities Generating Co. Analyses of fish muscle tissue by the Texas Department of Health showed selenium concentrations ranging from 2.0 to 9.1 mg/kg. Cove rotenone sampling by the Texas Parks and Wildlife Department indicated biomass of fishes, except common carp, Cyprinus carpio, was reduced 72%. Relative biomass of trophic groups was altered with planktivores changing from the largest to the smallest group, carnivores were initially reduced by nearly half, and omnivores more than doubled. Three years after the fish kills, planktivore biomass remained the lowest, carnivores had recovered to approximately 90% of their original biomass, and omnivores continued to dominate the community at 3 times their original abundance.

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