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Project Summary Sheet

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

Fiscal Year 2003 Project Summary Report

Project Title: Predicting Effects of Hydrologic Restoration on Manatees along the Southwest Coast of Florida

Project Start Date: 2000 Project End Date: 2005

Web Sites: www.fcsc.usgs.gov/manatees (see http://cars.er.usgs.gov/Manatees/manatees.html)

Location (Subregions, Counties, Park or Refuge): Southern Golden Gate Estates/Ten Thousand Islands NWR, Collier County; Everglades National Park, Monroe County.

Funding Source: USGS's Greater Everglades Science Initiative (PBS) USGS Center for Aquatic Resource Studies

Principal Investigator(s): James Reid

Project Personnel: James Reid, Brad Stith, and Susan Butler

Supporting Organizations: U.S. Fish and Wildlife Service - Ten Thousand Islands National Wildlife Refuge, the National Park Service - Everglades National Park, Big Cypress National Preserve, Florida Fish and Wildlife Conservation Commission - Florida Marine Research Institute, Rookery Bay National Estuarine Research Reserve, Mote Marine Laboratory, Marine Mammal Commission, and Cincinnati Zoo.

Associated / Linked Projects: Impacts of hydrological restoration on three estuarine communities of the Southwest Florida coast and on associated animal inhabitants

Overview & Objective(s): Determine relative abundance, distribution, movements, and habitat use of manatees associated with coastal waters and rivers from Marco Island through Whitewater Bay. Identify resources critical to manatees in the region, including distribution and abundance of submerged aquatic vegetation and freshwater drinking sites. Develop an individual-based ATLSS model to predict manatee response to changes in hydrology achieved by the Southern Golden Gate Estates (SGGE) project specifically and more broadly by the Comprehensive Everglades Restoration Plan. Additional information on population trend, distribution, and habitat use, coupled with models of hydrology, bathymetry, aquatic vegetation, and salinity, will allow development of a population-level model capable of predicting their response to future changes. This SGGE modeling effort will provide invaluable information as a small-scale test case for understanding and predicting how restoration efforts in the Everglades will affect manatees.


Strip-transect aerial surveys - To determine manatee density and distribution in the nearshore waters of the Ten Thousand Islands (TTI) and the Everglades National Park (ENP), eight surveys were conducted in summer 2001 and eight conducted in summer 2002. No additional surveys are planned for summer 2003 due to lack of funds. Survey-specific population estimates in this study were 1.09 to 4.57 per km2 in 2000, 1.62 to 6.64 per km2 in 2001, and 2.65 to 6.58 per km2 in 2002.

Radio Tracking of Manatees - Satellite-based Argos transmitters and Global Positioning System (GPS) tags were used to remotely track movements of 26 manatees (46 tag deployments resulting in 6,157 manatee-tracking days) between June 2000 and February 2003; radio tracking efforts are ongoing. Satellite-determined data are supplemented with field-based tracking which has enabled documentation of manatee activity patterns and correlations with environmental data.

Predictive model development for ATLSS - Telemetry data are being used to develop a spatially explicit, individual-based model to simulate manatee movement patterns and the response of manatees to environmental alterations. Detailed information on travel rates, travel corridors, time budgets, home range, and resource use obtained from tracking data are being used to parameterize the model. Simulated manatees travel along a network between freshwater resources and offshore seagrass bed, and alter their movement pattern and home range in response to changes in freshwater availability.

Recent & Planned Products: Project findings presented at the 2003 Conference on the Science and Restoration of the Greater Everglades. Presentations submitted to the 15th Biennial Conference on the Biology of Marine Mammalogy.

Relevance to Greater Everglades Restoration Information Needs: Distribution and movement data on manatees and the predictive model, combined with water quality data obtained from monitoring stations, will provide a basis for comparative studies in other areas within the region. Sharing of tracking and model data, such as manatee high use areas and travel patterns, are planned with TTI, ENP, and other agencies to address resource management needs. The model will integrate with the TIME model to simulate the response of manatees to different restoration scenarios.

Key Findings:

  • Reliable assess to freshwater for drinking is a critical requirement for manatees, as demonstrated by their frequent, long-distance movements alternating between offshore seagrass beds and inshore rivers, tidal creeks, and canals.
  • Manatees spend significantly more time in inshore areas such as rivers, tidal creeks, or canals during the dry season than during the wet season, a pattern that likely will be altered by increased freshwater inflow associated with restoration.
  • Manatees in southwest Florida exhibit complex behavioral responses to cold weather, including: 1) migrating south into White Water Bay, 2) bottom resting in warm water layers trapped in deeper sections of basins, canals, and rivers, and 3) sheltering in shallow bays that heat up rapidly following the passage of cold fronts and return of warmer temperatures.

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