The black tip reef shark, known as Carcharhinus melanopterus, is common in the Indo-Pacific geographical area extending from Madagascar to Japan and Oceania. For that reason researchers were very surprised to find the species in Costa Rican waters off Cocos Island National Park.
In this way this shark became the first recorded for the island and to the Eastern Tropical Pacific, stretching from Mexico to Peru.
The finding was revealed by Lopez and Ilena Zanella-biologists Mission Shark-organization and by rangers Geiner Golfín and Maikel Perez. The four are participating as researchers in a monitoring project in Chatham Bay.
The details are part of a scientific article will be published shortly in the Journal of Tropical Biology, which is preparing a special issue dedicated to research on Cocos Island.
Since 2010, biologists and park guards, evaluate populations of white tip sharks (Triaenodon obesus) for evaluate its abundance, growth and distribution in the reef ecosystem.
To do this, researchers use a hand line with a circle hook 1.5 cm in diameter. The shark was up on deck. Then place a mark-type flexible plastic that will study them over time.
On 29 April, the rope caught a white tip, captured a black fin. The shark measured 89 cm long and was at a depth of 13.4 meters. It was a male juvenile stage.
Once removed the hook, they took photographs and measurements such as size, sex and maturity. The whole process took about five minutes and then released.
“The presence of a blacktip of reef in Cocos Island suggests that a pregnant female (pregnant) traveled at least 5,000 km and was there to give birth in Chatham Bay,” the study said. For Lopez, this migration could be due to changes in ocean currents or water temperature.
“It would be essential to continue monitoring the bays to determine if this individual is an isolated phenomenon, or is the beginning of the arrival of a new migratory species, or may even be that they live there for a while but is very rare,” Lopez said.
Moreover, according to the reproductive biology of the species, the female may give birth to about four young, which makes the researchers suspect that there are more individuals in the bay.
This species of sharks live in coral reefs in shallow water. Usually found in coastal ecosystems, but have also been observed on islands.
“These sharks show high site fidelity of coral reefs, lagoons and sandy bottoms,” the researchers in the study.
Cocos Island and had reported another species of blacktip shark Carcharhinus limbatus called, which is common in bays and inlets.