Project Title: Integrative assessment of a loggerhead foraging aggregation in Crystal River. Year 2
Project Manager: Dr. Mariana Fuentes and Dr. Natalie Wildermann
Organization: Florida State University (Research and Educational Institute)
Grant Amount: $12,254.29
Completion Date: 2021-01-28
Summary: Extended efforts have been undertaken in Florida to generate and compile biological and ecological information of sea turtles in foraging habitats. The neritic habitats along the coast of Florida are crucial for the development and persistence of both immature and adult turtles of the Northwest Atlantic Ocean loggerhead Sea Turtle Distinct Population Segment. However, an important geographic gap in in-water research remains in the southern Big Bend region in northwest Florida. While more is known about the distribution, movement and habitat use of juvenile Kemps and green turtles in this region, there are still important information gaps on the foraging ecology of the less abundant loggerhead turtles in the region. Multiple incidental records of loggerhead turtles within the intake canal of the Crystal River Energy Complex have been registered by the Florida Power Corporation since 1999. In addition, in recent years loggerhead turtles have been frequently recorded in the southern extent of Crystal River within near-shore habitats. In 2018 we initiated a project, funded by the license plate, to monitor foraging loggerhead sea turtles in Crystal river. Loggerhead turtles made up 60% of the turtles (n = 42) we sighted in the southern region, indicating that there is a larger aggregation of this species in the area than previously thought. This project will expand the current monitoring project at the Crystal River foraging ground.
Results: Four field trips totaling 11 sampling days (12-15 July 2019, 26-28 October 2019, 17-20 January 2020, and 6-9 March 2020) were conducted as part of this project. A total of 5 days (2 in January 2020 and 3 in March 2020) were lost due to unsafe weather conditions. During these trips, a total of 41 turtles were sighted (25 loggerheads, 15 green turtles, and 1 Kemp's ridley). With respect to vessels, 1479 vessels were sighted in the St. Lucie Inlet and nearby waterways - the majority being outboards (63.0%) followed by inboards (11.8%) and sailboats (11.7%).
Turtles were most often sighted along the offshore reef system, particularly off Jupiter Island. Thirty-four of these sightings occurred in non-speed restricted areas compared to 5 sightings in 'slow speed minimum wake' and 2 sightings in '25 MPH' channels - indicating that existing management zones do not cover a significant portion of turtle habitat use documented by this project. Vessel density was greatest inside the St. Lucie Inlet where the Indian River Lagoon, St. Lucie River, and Peck Lake all meet. This area represents a major intersection for vessels leaving or returning to dock, traveling to popular recreation destinations (such as a sand bar west of Sailfish Point just inside the Inlet), or heading to or returning from offshore locations. Under the existing management zones, this portion of the waterway is limited to 25 MPH. Unfortunately, this location is also the most common site of non-compliance with existing speed regulations. Despite the extensive boat traffic, sea turtles were documented in this area and are at risk for severe vessel interactions.
Despite the lack of overlap between sea turtles and vessels in the St. Lucie Inlet and surrounding waterways observed by this project, the results do suggest additional lines of investigation that may be beneficial for management. First, despite the minimal visibility within the inshore waters, turtles were observed throughout the Indian River Lagoon and St. Lucie River across all 4 survey trips - indicating potentially extensive use of this system. Satellite tagging or acoustic telemetry would give a better description of habitat use within the inland waterways including the proportion of residency within the estuarine system and frequency of travel through the Inlet between offshore and inshore sites. At a minimum, regular in-water capture surveys would give basic demographic data on the turtles using this system and may provide insights into movement patterns. Second, this project spanned all 4 seasons but only provides a snapshot of vessel spatial use within the Inlet and surrounding waterways during these times. Additional surveys or supplemental data (e.g., aerial surveys, satellite imagery) are recommended to improve our description of vessel use patterns, particularly in relation to its correlation with environmental and social variables.
Publication available online at https://www.frontiersin.org/articles/10.3389/fmars.2019.00155/full