Loggerhead Sea Turtle Density in the Mediterranean Sea
[Technical Report, Formal Report]
Naval Undersea Warfare Center Division
Pagination or Media Count:
Loggerhead turtles are a globally vulnerable species of marine turtle. The Mediterranean Sea subpopulation, which ranges throughout the entire Mediterranean basin, is listed as least concern but experiences significant threats in the region including bycatch in fisheries, climate change, coastal development, and marine pollution. Broad-scale patterns of distribution and abundance can provide regional managers a tool to effectively conserve and manage this species at basin and sub-basin scales. Here NUWC uses aerial and shipboard line transect survey data collected between 2003 and 2018 to estimate density and abundance throughout the Mediterranean Sea using distance sampling methodology. A spatial density model estimating loggerhead density, abundance, and distribution across the Mediterranean Sea was generated as a long-term annual average. The model was adjusted for availability bias using dive data from loggerhead turtles tagged with time depth recorders from multiple regions within the Mediterranean Sea. Geographic extrapolation in areas near surveys was undertaken with caution. Mean abundance for the long-term average model was estimated as 994,000 CV 0.20. This estimate represents the first basin-wide estimate of abundance for this species in the Mediterranean not based on demographic models.
- Physical and Dynamic Oceanography