Sea Turtles stranding on Greek coasts: The most important causes
The growing number of sea turtles found dead or injured on the Greek shores led ARCHELON to establish the National Sea Turtle Rescue Network in 1992 and later, in 1994, the ARCHELON Sea Turtle Rescue Center, where there is the possibility of treatment of injured turtles as well as of their reintegration into their natural environment.
Sights of dead sea turtles from many spots of coastal Greece are often published in the media. Apart from cases of deliberate injury by humans that are more obvious and usually isolated, the main question of public concern is whether these deaths are related to natural causes or anthropogenic activities.
The Coast Guard are responsible for recording the events and this is very important in order to avoid double entries. Each and every year the Sea Turtle Rescue Centre of ARCHELON receives all the «Sea Turtle Stranding Sheets” from the Greek Coast Guard Units, along with photos and other relevant information. The cross-referencing and processing of the data by ARCHELON is in progress, but there are no easy answers.
Cases have been found where dead turtles have obvious signs of interaction with fishing gear. But even those that do not bear external signs, it is possible that they have drowned or suffered from other lethal damage due to their accidental entanglement in fishing gear.
"The data on the exact number of turtles caught accidentally on fishing boats in Greece are insufficient and little is known about their immediate and indirect mortality that follows," says Kostas Teneketzis, a coastal management researcher who works with the National Marine Research Centre. ”There are times where a relatively higher number of dead sea turtles are stranded in a location. Even then, it is hard to reach conclusions because it is possible that dead animals have been transported by waves from really far.
Based on the available data at Mediterranean level, the annual number of turtle catches on all fishing gear in Greece has been estimated by Paolo Casale (2011) at around 9,700, with 3,500 of them involving catches in static nets and bottom longlines while the rest 6,200 catches concern trawlers, purse seiners and surface longlines.
"Despite the incomplete data, the small coastal fisheries in Greece, which mainly use the tools that have the highest mortality rates, seems to be responsible for a large number of turtle deaths. The death rate of sea turtles from entanglement in their nets can reach up to 80% of the accidental catch cases", adds Aliki Panagopoulou, sea turtle expert with ARCHELON, who published a relevant survey in 2017.
There have also been cases where dead turtles have suffered external injuries from hits to the head and shell, indicating a deliberate injury. This information is consistent with the large percentage of such cases amongst the cases treated at the Rescue Center of ARCHELON. Deliberate injuries by humans are easier to identify as cause of death and fortunately are not a wide spread practice.
Also, the effects of plastic sea pollution become more apparent over time, as sea turtles that have consumed plastic may suffer a slow death. It has been proven that the gastrointestinal system of turtles cannot process plastic, as pieces of plastic were found in all turtle necropsies that took place in 2018 at the ARCHELON Rescue Center. Turtles have also been reported dead due to involvement in plastic waste.
There are cases where the natural causes of death cannot be ruled out, but they are not easy to identify. "Unfortunately, it is not possible to perform an autopsy on any of these animals. Also, many of the animals that are stranded are in a state of advanced rot, with the result that scientific conclusions cannot be drawn about the causes of death", adds Dimitris Fytilis, Head of the ARCHELON Rescue Center.
What to do if you come across a dead or alive stranded sea turtle? See more info on our website: https://www.archelon.gr/eng/help2.php?mid=1&mid2=25
Irini Kasimati, Rescue & Rehabiliation Officer, Tel./Fax: 210 8944 444, 6941 511 511, e-mail: email@example.com.
Dimitris Fytilis, Rescue Center Manager, Tel. 210 8982 600, 6944 929 622, e-mail: firstname.lastname@example.org.