Linking loggerhead locations: using multiple methods to determine the origin of sea turtles in feeding grounds

Area of Science:

• Marine Biology
• Conservation Genetics
• Ecology

Background:

• Marine megavertebrates like sea turtles exhibit natal homing, returning to specific locations for breeding.
• Amvrakikos Gulf is a critical foraging ground for loggerhead turtles, characterized by long-term residency and a male-biased adult sex ratio.

Purpose of the Study:

• To determine the natal origins of loggerhead turtles inhabiting Amvrakikos Gulf, Greece.
• To investigate the factors contributing to the observed male-biased sex ratio in the Gulf.

Main Methods:

• Flipper tagging and satellite telemetry were employed to track individual turtles.
• Mitochondrial DNA mixed stock analysis was conducted on 95 loggerhead turtles from Amvrakikos Gulf.

Main Results:

• Flipper tagging and satellite tracking linked 20 turtles to Greek nesting sites, predominantly Zakynthos Island.
• Genetic analysis revealed 82% of turtles in Amvrakikos Gulf originated from Greek nesting stocks, with 63% from Zakynthos Island.
• Lesser contributions were identified from Turkey, Cyprus, and Libya, suggesting a potential link between male breeding frequency and foraging ground proximity.

Conclusions:

• Amvrakikos Gulf serves as an important foraging area for loggerhead turtles from multiple nesting populations, primarily Greece.
• Conservation efforts in this foraging habitat can benefit diverse breeding stocks.
• Understanding source populations is crucial for evaluating the effectiveness of conservation measures for marine vertebrates.