Grant: 23-005R
Project Title: Information to Protect Florida's Most Valuable and Vulnerable Sea Turtles from Vessel Strikes: Year-One Surveys and Gulf Coast Hot-Spot Identification
Project Manager: Blair Witherington
Organization: Inwater Research Group (Non-Profit Organization)
Grant Amount: $32,748.45
Completion Date: 2024-10-30
Summary: Vessel-strike mortality in Florida's sea turtles presents population-level effects and is the most frequent, identifiable cause of death in strandings. This mortality is high in adults near nesting beaches. This project is the first year of a two-year effort to survey vessel strike-vulnerable turtles off Florida's gulf coast nesting beaches. The project goal is to produce information that would change human behavior to reduce sea turtle boat strikes. Our objectives are to, 1) use transect surveys and distance sampling to develop a "heat map" of sea turtle spatial distributions for a densely occupied area within Florida's nearshore waters, and 2) leverage FWC nesting beach data to predict density of strike-vulnerable turtles for the majority (~1300 km) of Florida's coastal waters. Our study adds necessary statistical power to east coast surveys. We will use the same type of transects 21, 5-km, shore-perpendicular lines between Anna Marie Island and Sanibel Island. Surveys will take place twice in June and twice in July, using a specialized research vessel with a sighting tower. We will use Distance Sampling analyses modeling environmental covariates to make turtle density estimates from transect data, and use the density estimates to generate distribution "heat maps" using Density Surface Modeling. We will use FWC Statewide and Index Nesting Beach data, combined with our distance sampling estimates, to predict in-water turtle densities elsewhere in Florida. We will form our data output products to be most useful to the assignment of sea turtle protection zones and to illustrate the relative hazard of boat strikes for sea turtles
Results: During the data collection and analyses for this one-year project that commenced in June 2023, we measured sea turtle abundance over four days of nearshore surveys, which included 21 shore-perpendicular transects, each 5 km in length, spanning from the north end of Anna Maria Island to Sanibel. Initially, strong winds and rough seas hindered our survey efforts in June, but we successfully completed the planned transects. We attempted to continue the surveys in July 2023; however, during the first leg of the transects, our survey vessel suffered a catastrophic failure in one of the legs of our sighting tower, forcing us to halt the surveys for the year. Although we completed the June transects, we decided to pause the project until July 2024, intending to complete the remaining transects. Despite our best efforts, we were unable to repair the vessel to a satisfactory and seaworthy condition in a timely manner. After a year had passed since the original set of transects, we concluded that the project would need to be discontinued and reported as it stands.