We continue with the decompression study in sea turtles caught incidentally by trawl
The project, which started in 2014 and with a scientific publication of the results of the first study, has secured funding for another two years from NOAA’s Bycatch Reduction Engineering Program (BREP). Once again, it will be a collaboration between SUBMON, the Oceanografic of Valencia, the Brazilian NGO NEMA, NOAA and the University of Florida.
The first study confirmed the high prevalence (100%) of gaseous embolism (blood gas bubbles) in sea turtles of different species caught by trawling at different depths, and the high percentage of mortality after release (20%) after being on deck for two hours (here you can see the results of the first study).
This second part of the project will focus on finding out how keeping turtles on board affects their post-release mortality. Until now, good practice protocols for trawlers recommended keeping captured animals on deck for recovery. However, the gas embolism begins to develop as soon as the turtle reaches the surface of the sea. While the animal remains on deck, this embolism worsens, so the recommendation after the first study was to release these turtles as soon as possible. Our theory now is that, if the animal is released quickly and still in good physical condition, it can dive and “re-compress”, gradually eliminating accumulated nitrogen in blood and tissues.
To confirm this theory, in this second phase the protocol will be as follows:
- Turtles captured in good condition will be divided into two groups at random, releasing one after 30 minutes and the other after 1 hour on deck. Animals that arrive too tired or comatose will be kept on deck until they can be released.
- Immediately after the hoisting on board, an ultrasound of the kidney, liver and heart of the animal will be performed to confirm air embolism and assess its level. Then a blood sample will be taken and a physical and neurological exam will be done. In group 2, a second ultrasound and neurological examination will be completed prior to release.
- A satellite transmitter will be placed on all the animals that are released to know their diving profile during the first 3-4 days after the release and to estimate the % mortality during the first month.
Before starting the fieldwork, a training course will be organized in Brazil, in collaboration with the NGO Tamar, aimed mainly at the Brazilian observers who will carry out this work, where they will become familiar with the protocol and the forms to be used, and they will be trained in the handling of the ultrasound machine and the biochemistry equipment.
The project will begin on October 1 and, COVID-by, SUBMON and Oceanografic personnel will travel to Brazil in early 2021 to carry out the training course and bring the necessary equipment for the study.