PARENT SESSION
Poster Session #22: Fish, Lakes, Streams and Wetlands.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

The influence of urban gradients on the invertebrate composition of brown trout diet in Rapid Creek, South Dakota.

Foreman, Cory^*,1, Vierling, Kerri², ¹ South Dakota School of Mines and Technology, Rapid City, SD² South Dakota School of Mines and Technology, Rapid City, SD

ABSTRACT- Many studies examining urban influences on stream communities focus on invertebrate communities, but few studies address how urban gradients might affect animals that rely on invertebrates as major prey items. The objective of this study was to examine the influence of urban gradients on brown trout (Salmo trutta) diet. In October 2000, we collected a total of 180 adult brown trout in three 100-m sites along Rapid Creek as it traverses through Rapid City, South Dakota. Trout stomachs were pumped and contents were preserved in ethanol. Stomach contents were identified to the family level if possible, dried, and weighed. The same procedure was followed in June 2001. Both urban gradient and season affected the invertebrate composition of trout diet. Biomass and the caloric value of stomach contents were higher in June compared to October. The urban gradient influenced diet composition, biomass consumed, and ultimately the caloric intake of the fish, but in a fashion that was inconsistent with predicted influences of urban pollution. For example, fish in midtown sites had lower caloric intakes than fish in the downstream sites in the June sample. Although based on a single urban creek, the results of this study suggest that the invertebrate composition in fish diet along an urbanized stream does not always follow predictable patterns.

KEY WORDS: brown trout, urban, diet