Behaviours of Sea Turtles in Shipwrecks in Northeast Brazil

1. Shipwrecks are one of the most common types of artificial reefs. They are home to several sea creatures, including sea turtles. Here, we aim to understand the relationship between sea turtles and shipwrecks by investigating species occurrence, behaviours and food availability in artificial reefs in Pernambuco, Northeast Brazil.
2. To map sea turtle occurrence in shipwrecks, we considered data from the literature, and we inspected 54,145 photos resulting from 867 recreational dives performed in 19 shipwrecks. We then selected four wrecks for systematic behavioural observations through 97 h and 56 min of passive video recordings. We also investigated potential food resources for turtles in these shipwrecks.
3. We identified three turtle species (i.e., Chelonia mydas, Eretmochelys imbricata and Caretta caretta), but most records were juvenile Chelonia mydas individuals using conserved wrecks. We recorded nine behaviours. ‘Resting’ was the predominant activity for all three species, representing over 60% of the records for all species. Their overall activity pattern varied. The wrecks were predominantly encrusted with ascidia, octocoral, sponge and algae—organisms that are part of sea turtles' diet. We highlight the ecological role of the shipwrecks for sea turtles since they may serve as shelter (especially for the juveniles of Chelonia mydas), potentially protecting them against predators and strong currents. The wrecks may also serve as potential feeding areas for sea turtles. We reinforce the need to establish appropriate regulations for recreational dive tourism in shipwrecks in Brazil to avoid disturbing sea turtles in this ecologically important artificial reef.