Diverse journeys of released turtles
THE most fulfilling part of rescuing and rehabilitating sea turtles at Cape Town’s Two Oceans Aquarium was their release back into the ocean when they were fully recovered, said the aquarium team.
The most exciting and quite often most stressful part was tracking their oceanic movements.
Fortunately, thanks to modern satellite tracking technology and the collaboration of the government, aquariums and generous donors, researchers were able to follow the journeys of some of the released turtles closely, the aquarium said.
Yoshi is the famous loggerhead turtle of the aquarium and was released on December 16, 2017. It was the size of a dinner plate when it first arrived in Cape Town, via a fishing boat, in 1997.
Yoshi has been back in the ocean for 447 days and has covered more than 18 500km.
The loggerhead has averaged 39.4km per day since being released and has crossed various borders, swam in various directions, and continues to swim against the currents, visiting areas offering a lot of food such as the new Marine Protected Area around the Protea Seamounts.
Right now it appears as though Yoshi is swimming towards Australia – where loggerhead turtles do nest. It may also choose to head north to Madagascar or Mozambique.
Another turtle, Pemba, an olive ridley, was found floating in Table Bay Harbour in December 2014, and was released within the iSimangaliso Wetland Park on March 8 last year.
It has been travelling the oceans for 365 days. Since January, it has been exploring what seems to be the middle of the ocean, and the aquarium believes it is enjoying spending time in areas with a good food supply.
Yoshi is currently 1917km west of Africa and about 251km south of St Helena Island.
In just another 3500km it will be off the coast of Brazil, where many olive ridley turtles breed. Yoshi is in a very gentle north-easterly current at the moment and in warm sea temperatures of about 25°C.
Thanks to the Department of Environmental Affairs and generous donations by some funders, the team has also been able to tag both Sandy and Noci recently and follow their journeys since their release on December 20.
Sandy is a female green turtle that was rescued by the Lower Breede River Conservancy Trust in September 2016 after having its carapace badly damaged by an apparent boat propeller strike.
Noci was rescued near Witsand, on April 29 last year, and survived a severe systemic infection.
Noci and Sandy have both been back in the ocean for 78 days.
Noci has racked up the fastest average speed of all the tagged turtles, covering a very impressive 4 122km since being released in December, with an average distance of 53km/day. Noci headed up the West Coast straight after release and went to check out the mineral-rich areas off the Salt River estuary before turning around and heading back south.
It then crossed paths with Yoshi around the Protea and Simpson Seamounts before heading into the south Atlantic currents and eddies, pretty much where Pemba did its roundabouts.
Noci is being pushed by a rather strong southerly wind at the moment and is in very acceptable 20°C water.
Since release, Sandy has spent most of its time moving between Elands Bay and Lambert’s Bay.
It has covered 1 223km, at an average pace of about 16km/day. The water temperature has ranged between a chilly 9°C and 18°C.
The crew at the Lambert’s Bay NSRI and the fisheries officers from the department in Elands Bay will all be on standby should Sandy decide to warm up on the beach.
The green turtle is still swimming strongly and sending frequent transmissions, which shows it is doing well, even in the cold.