Project Personnel: Shawn Liston, 305-348-4032, sliston@fiu.edu

Supporting Organizations: Florida International University and NPS provide lab and logistical support

Associated / Linked Projects: ATLSS model program (USGS-BRD funded); RECOVER

Overview & Status: This multi-year program embodying facility construction, maintenance, and experiments is nearing the end of its funding cycle. The experimental mesocosm array was constructed in Everglades National Park as a cooperative effort of FIU, USGS, and NPS to address questions about predator-prey, competitive, and indirect interactions difficult to study in the field. Two experiments that examined mosquitofish predation and competition with other cohabiting small fishes in the Everglades marshes have been completed. Results showed that growth of juvenile mosquitofish could be limited by the presence of other juveniles at densities within the range found in the Everglades. This suggests that food limitation is a potential factor for juvenile fishes in Everglades marshes, as had been suggested by earlier field studies. The relative role of food versus predator limitation is central to any model of fish population dynamics, such as the ATLSS model. We have completed the study of spotted sunfish nest predation by small fishes, especially mosquitofish, which demonstrated a feedback loop in the Everglades food web. Mosquitofish prey upon eggs and larvae of spotted sunfish, which in turn eat mosquitofish as they grow. Water level was inversely related to the degree of nest predation and probably helps explain why sunfish populations grow during high water years. The mesocosm is now being used to address the role of nutrient inputs into the Everglades in causing shifts in marsh food webs.

Needs & Products: Products: 1) Taylor, R.C., J. C. Trexler, and W. F. Loftus. 2001. Experimental evidence for the roles of intraguild competition and predation as structuring agents of Everglades fish communities. Oecologia 127: 143-152; 2) Turner, A. M., J. C. Trexler, F. Jordan, S. J. Slack, P. Geddes, and W. Loftus. 1999. Conservation of an ecological feature of the Florida Everglades: pattern of standing stocks. Conservation Biology 13: 898-911; 3) Pagan, X. O., J. C. Trexler, and W. F. Loftus, in review. Effects of water level and predation on survival of spotted sunfish (Lepomis punctatus Valenciennes) larvae in the Florida Everglades. Copeia. Several posters and presentations at meetings. If funding allows, we would like to examine introduced/native fish interactions, and test potential control methods.

Application to Everglades Restoration: Products are directly applicable to ATLSS models, and will be critical in interpreting the results of field monitoring studies and performance measures in RECOVER. The results will improve the ATLSS fish model by adding credible rules on biotic interactions now missing. Data help explain patterns in the data from monitoring and field research.