Determining the Benthic Macroinvertebrate Community Composition of Freshwater Streams from Fish-Gut Analysis

The monitoring of changes in benthic macroinvertebrate communities over time facilitates the evaluation of any changes that occur in the function and structure of aquatic ecosystems. We hypothesized that it would be possible to determine, through running simulations, which trophic group of fishes' gut content can and should be used to best determine benthic macroinvertebrate community composition. Researchers could use this knowledge to estimate historic benthic macroinvertebrate communities of aquatic systems from fishes catalogued in museums. These historical data could then be compared to current data to see how macroinvertebrate communities have changed over time. In this study, we identified the fishes whose gut content most accurately reflected the benthic macroinvertebrate community of Marshalls Creek in East Stroudsburg, PA. We collected fish species and benthic macroinvertebrate samples at various sites and at different times of year to reflect seasonal variation. Enneacanthus gloriosus (Bluespotted Sunfish), Lepomis auritus (Redbreast Sunfish), and Catostomus commersonii (White Sucker) were the species that best represented the benthic macroinvertebrate community from their gut content. We determined that these species predicted 81% of all taxa that occur in summer. To estimate sampling distribution, we ran 100 simulations in R 3.0.2 on each combination of 3 fish species to determine the average quantity of taxa consumed (to the family level) along with sampling variation. Data obtained from the dissection of museum specimens could then be compared to data obtained from more recently collected specimens and a comparison made to determine changes in the macroinvertebrate community over time.