Migration routes and foraging behaviour of olive ridley turtlesLepidochelys olivaceain northern Australia

Abstract

The foraging ecology of endangered olive ridley Lepidochelys olivacea sea turtles is poorly known in Australia, with only a limited knowledge of their foraging distribution inferred from captures in trawl net fisheries. We attached satellite transmitters to 8 olive ridley turtles in 2004 and 2005 at a nesting beach in Australia's Northern Territory to document their migratory routes and for- aging behaviour. Three turtles moved up to 40 km from the nesting beach before renesting on the same beach within 12 to 23 d. The turtles made post-nesting migrations of 165 to 1050 km to 5 differ- ent foraging areas and used coastal, continental shelf and continental slope habitats. The use of one foraging area by 3 turtles, together with previous trawl data, indicate a predictable source of food in this area. Distinct foraging areas indicate that foraging behaviour differs from the meandering oceanic movements of turtles in the Pacific. During migration and foraging periods, turtles dived to the substrate with maximum depths of 150 to 200 m and maximum dive durations of 120 to 180 min. The locations of foraging areas overlapped with existing trawl fisheries and oil and gas exploration and mining.