Investigation of Trophic Transfer from Oyster Reefs to Predatory Fish in Southwest Florida

Abstract

Reefs formed by the eastern oyster Crassostrea virginica are ecologically and economically important in the estuaries along the east and gulf coasts of the United States. Reefs of C. virginica play a vital role in improving water quality in estuaries via filtration and by providing refugia for mobile benthic organisms that use the interstitial spaces of reefs for refuge, feeding, and reproductive activities. Consequentially, these organisms are essential as a food source for higher trophic-level organisms such as recreationally and commercially important fish that use oyster reefs as feeding stations. This project investigated the link between oyster reef communities and the trophic transfer of biomass to tertiary-level predator fish in Estero Bay, FL. Fish were captured in proximity to isolated reef structures and gut contents analyzed. Sampling of fish was carried out around oyster reefs using an entanglement net (also referred to as a gill net). Fish were sampled for analysis of stomach contents using importance index analysis. Prey items were identified and compared, with organisms classified as oyster-reef indicator species. A total of 294 fish belonging to seven species were sampled during spring and summer months. The results demonstrate that 53% of the total importance index were several key prey items identified as oyster-reef indicator species. These species contribute to oyster reef biomass transfer to higher trophic-level organisms, indicating the critical nature of oyster reefs.