Population structure of green sea turtles at a foraging ground in the southeastern Persian Gulf

Despite its extreme climate, the Persian Gulf hosts substantial sea turtle populations, which are unique due to their ability to survive in the hot, climate-challenged environment. Along the sandy and muddy shores of Qeshm Island, Iran, fishers set arrow-head fish traps, locally known as moshta . We collected green turtles ( Chelonia mydas ) from these moshta during 2016, 2017 and 2018 to determine their population structure and genetic origin. Curved carapace length was measured, and sex and age class were determined via laparoscopy. Tissue samples for genetic analysis were sequenced to identify unique mtDNA haplotypes for each turtle, and a Bayesian mixed stock analysis (MSA) was used to determine their genetic origin. We captured 338 green turtles, which were predominantly juvenile (326, or 96.4%) with only ten subadult (3.0%) and two adult turtles (0.6%). The overall sex ratio was 66% Female: 33% Male (2F: 1M). This finding suggests climate is not leading to undue feminisation and that these turtles may be acclimated to the warmer Arabian region temperatures. A subset of 211 turtles was sampled for genetics. Unfortunately, some samples were not identifiable, resulting in 118 turtles for which sex and age class were known, and 93 samples from individuals of unknown sex and age-class. There were no significant differences between male and female stock origin and these were combined for an overall genetic stock determination. The MSA estimated that the majority (96.36% ± 0.048SD) of all green turtles originated from the Oman nesting stock located just outside of the Persian Gulf, with negligible contributions from Kuwait or Saudi Arabia which lie within the Gulf – a surprising finding given the proximity of these rookeries. These data contribute to our understanding of the population structure and connectivity of sea turtles in a particularly data-sparse and yet important (climate-wise) sea turtle habitat in the NW Indian Ocean.