Grant: 22-003R
Project Title: Exclusion analysis and assessment of late season nests to identify breeding sex ratios and productivity of a large and growing nesting aggregation on the Gulf of Mexico
Project Manager: Jake Lasala
Organization: Mote Marine Laboratory (Non-Profit Organization)
Grant Amount: $30,401.48
Completion Date: 2024-05-14
Summary: Since 1982, staff of the Sea Turtle Conservation and Research Program (STCRP) at Mote Marine Laboratory have documented nesting trends on 35 miles of Sarasota, Florida beaches. Since 2007, marine turtle nesting numbers have noticeably increased in the region; likely due to conservation efforts in the region and the Gulf of Mexico. With the help of 300 annual volunteers, interns, and the Longboat Key Turtle Watch, STCRP has documented 133,000 sea turtle crawls and over 3 million hatchlings. However, little is known about late season nests and how productive they are in comparison to the rest of the nesting season. While these beaches are known to be productive for hatchlings, it is also critical to identify the number of breeding adults within this population. The STCRP tagging program has tagged nesting females since 1983 and has monitored the number of nesters on Casey Key (a high-density nesting beach), but male numbers are unknown. This is a critical data gap in recovery plans for sea turtles. By assessing known female IDs from the long-term tagging program, remigrant and repeat nesters nests can be assessed to quantify late season nest productivity and to determine if there are differences in male contributions over the course of the nesting season through exclusion analysis. Staff at STCRP began a breeding sex ratio study in 2020 on Casey Key and has since expanded to nearby beaches: Siesta Key and Venice Beach. This project includes surveying and mark/recapture data collection for Mote's long-term tagging site on Casey Key and expansion to these activities to other beaches to assess the breeding sex ratio for marine turtles nesting in the region.
Results: At the end of the 6-month report, all samples had been collected for the 2022 nesting season. Collectively between the Siesta Key and Venice beaches we collected hatchlings from 182 nests (144 loggerheads, 38 greens) and sampled 2,914 hatchlings. Hurricane Ian impacted some of our late season nests, but because of the storm track shifting south - most of our late season nests survived the storm. Analysis of paternity was delayed due to unforeseen circumstances and we were granted an extension. For the final report, all samples from 2022 have been processed. The overall breeding sex ratio of the loggerheads from this study period was 1.9 males for every 1 female, which is a little lower than it was in Sanibel. However, this is due to the increased sampling of repeat nesters here in Sarasota. Taking that into account, the breeding sex ratio is actually higher than in Sanibel. The Sea Turtle Conservation and Research Program at Mote Marine Laboratory recently published findings of nesting behavior from 1982-2021. In this paper, we found that emergence success has declined over the study period and that it differed by beach (Lasala et al. 2023).