Project Summary Sheet

U.S Geological Survey, South Florida Ecosystem Program: Place-Based Studies

Project: Experimental Studies of Predator and Prey Interactions

Web Sites: http://everglades.fiu.edu; http://www.fcsc.usgs.gov (see http://cars.er.usgs.gov/); http://sofia.usgs.gov/

Location: Central Everglades

Principal Investigators: 1) William F. Loftus, 305.242.7835, bill_loftus@usgs.gov; 2) Joel Trexler, 305.348.1966, trexlerj@fiu.edu

Project Personnel: 1) Xavier Pagan, 305.348.4032, xpagan01@fiu.edu

Other Supporting Organizations: Florida International University and NPS

Associated Projects: ATLSS model program (USGS-BRD funded); RESTORE

Overview & Status: This is a multi-year program embodying facility construction, maintenance, and experiments. An experimental mesocosm 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 the 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 collected field data on nest predation of spotted sunfish by small fishes, especially mosquitofish to examine population regulation in novel ways. A complimentary study of predation on sunfish eggs and larvae by small fishes at two water depths has been completed in the mesocosm. The mesocosm will be used in addressing the role of nutrient inputs into the Everglades in causing shifts in marsh food webs. We also plan to examine introduced/native fish interactions, and to test potential control methods. Products are directly applicable to ATLSS models, and will be critical in interpreting the results of field monitoring studies and performance measures used in CERP.

Needs & Products: Products: 1) Taylor, R.C., J. C. Trexler, and W. F. Loftus. 2000. Experimental evidence for the roles of intraguild competition and predation as structuring agents of Everglades fish communities. In press, Oecologia; 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) The effects of competition and age structured predation in an Everglades fish community. (Poster) R. C. Taylor and J. C. Trexler. American Society of Limnologists and Oceanographers/Ecological Society of America 1998 joint meeting, St. Louis, MO.

Application to Everglades Restoration: 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.