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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Science Program (Place-Based Studies Initiative)

Fiscal Year 2003 Project Summary Report

Project Title: Influence of Hydrology on Life History Parameters of Common Freshwater Fishes from Southern Florida (Cooperative Agreement No. 02ERAG0040)

Project Start Date: March 3, 2002 Project End Date: December 3, 2003

Location (Subregions, Counties, Park or Refuge): Everglades National Park and WCA-3A and 3B

Funding Source: USGS's Greater Everglades Science Program (PBS Initiative)

Principal Investigator(s): William F. Loftus (USGS), Leo G. Nico (USGS), Joel C. Trexler (FIU)

Project Personnel: Timothy Konnert, Shawna Baker, Stephen Estes

Supporting Organizations: Florida International University

Associated / Linked Projects: Aquatic Community Structure and Dynamics in Seasonally Variable Wetlands, ATLSS.

Overview & Objective(s): Assessment models like ATLSS require proper parameterization of life-histories of species they simulate. We are identifying parameters for south Florida fishes here, in the context of hydroperiod gradients that are key management challenges in CERP. Some life-history characteristics are plastic in response to the environment, so disturbance factors like hydroperiod are likely sources of spatial variation in fish life histories. We have studied hydroperiod effects on recruitment, size/age structure, growth, and fecundity of several fishes from variable-hydroperiod areas. These parameters determine population dynamics and are needed for model simulations. We have targeted small fishes in the marsh, to supplement data gathered earlier from Shark River Slough. We have also studied large fishes from canals, including exotics.

Status: The small-fish segment of the project is ongoing, but nearing completion. For Florida gar (Lepisosteus platyrhyncus), gonads from >500 specimens have been weighed and used to calculate reproductive seasonality across time and among 5 sites. Ovaries from 144 females are being used to estimate fecundity. 491 Florida gar were dissected and stomach contents analyzed. Stomach contents of most have been identified, counted, and volume estimated. Of the 456 stomachs examined, 176 contained food items. Additional work is needed to identify items to lower taxonomic level.

Recent & Planned Products: -Konnert, T. 2002. The Effects of Hydroperiod on the Life History Parameters of Poecilia latipinna and Heterandria formosa (Poeciliidae) in the Florida Everglades. M.S. Thesis, Florida International University, 91 pp. -Poster on this work presented at Greater Everglades Ecosystem Restoration Symposium, April 2003. -We are helping prepare an invited talk with D. DeAngelis for the 2003 American Fisheries Society meeting that will lead to a publication. -Murie, D. 2003. Final report on age and growth estimates from otoliths for large-fish species from South Florida canals.

-Datasets: Otolith-estimated age-length data on three species at 6 Everglades locations that vary in hydroperiod. Fish were collected in both wet and dry seasons, approximately 30 specimens aged for each collection (total approximately 360 specimens per species). Age-length data for large fishes from canals.

Planned Products: -Baker, J. S. Influence of hydroperiod on the life history parameters of Lucania goodei (Fundulidae). M.S. Thesis, Florida International University. In preparation, expected Summer, 2003. -Datasets: Otolith estimated age-length data on flagfish and spotted sunfish from 6 Everglades locations that vary in hydroperiod. -We anticipate publication of several peer-reviewed manuscripts on these data: 2 papers in Konnert's thesis, 1 in Baker's thesis, Murie's work, etc.

Relevance to Greater Everglades Restoration Information Needs: This work is influencing new developments in the ATLSS fish model, ALFISH. Don DeAngelis is using results in new model will be used to make choices of options to be incorporated into the much larger ALFISH. Current efforts are focused on the addition of canals to the simulations to assess impact of system de-compartmentalization in CERP. Also, we have used knowledge developed from this in suggesting Performance Measures in cooperation with Everglades National Park and South Florida Water Management District.

Key Findings:

  • There is no simple relationship between the shape of survivorship curves (indicating life span) and hydroperiod in sailfin mollies, least killifish, or bluefin killifish. Hydroperiod effects that we documented arose from variation in age-specific reproductive rate.
  • Population growth rates [r] were greatest in short-hydroperiod sites, possibly because of immigration to these sites in the wet season. Release from predation at short-hydroperiod sites could also yield this result.
  • Spatially explicit simulations of fish communities used for assessment must account for the effects of the physical environment on their dynamics.
  • Large fishes are multi-year species that move in and out of canals with flooding/drying regime.

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