Two Dutch Caribbean tiger sharks follow similar migration patterns

A report from The Daily Herald

The Dutch Caribbean Nature Alliance (DCNA) organised the first-of-its-kind shark tagging expedition to the Saba Bank and St. Maarten two years ago as part of the Dutch Postcode Lottery funded “Save our Sharks” project.

Eight shark researchers with a support crew and two camera teams captured and tagged tiger sharks on St. Maarten and the Saba Bank using an expedition ship. Saba Conservation Foundation (SCF), Nature Foundation St. Maarten (NFSXM), Florida International University (FIU) and Sharks4Kids scientists and conservationists equipped five tiger sharks with satellite tags during the expedition, to track their movements and presence to determine how best to manage and protect these important apex predators.

Wildlife computer smart position or temperature transmitting (SPOT) satellite tags were attached to the first dorsal fin of large tiger sharks. These tags transmit to satellites, which allows the sharks to be tracked through the ARGOS satellite system for up to four years. The tags use radio transmissions, so the satellite unit must be exposed to air to transmit. Each time the dorsal fin breaks the surface a geo-locator provides an approximate location with an accuracy of up to 250 metres.

Two tiger sharks with satellite tags named “Sea Fairy” and “Quinty” have provided the research team with some interesting preliminary results. The sharks indicate a similar migration track following the Aves ridge, a ridge in the Eastern Caribbean Sea about 500 kilometres in length, probably of volcanic arc origin.

The preliminary data received is starting to show some interesting results in terms of the migratory patterns of tiger sharks in the Eastern Caribbean Sea. Not only is this data important, but it is also critical for the transboundary management of a marine species critical to the health of the Caribbean Sea. Sharks are apex predators and as such keep the ocean food chain healthy, a food chain which in turn supports regional fisheries, for example.

“With recent shark finning and fishing activities occurring in the wider Caribbean, including incidents in Curaçao, Dominica and Aruba, it behoves nation states in the Caribbean to establish a wider Caribbean management plan for the species,” said DCNA Save our Shark Project Manager Tadzio Bervoets.

Shark Quinty was tagged under the supervision of Mike Heithaus on the Saba Bank. This 3.43-metre female tiger shark provided regular location updates. Quinty left the Saba Bank following the Aves ridge South and subsequently swam all the way to Trinidad and Tobago, a territory known for its shark finning activities. The last received location of Quinty was close to Barbados about a year ago.

Sea Fairy was the first shark equipped with a satellite tag in this region and surfaced very frequently, providing researchers with a wealth of location and movement information. Sea Fairy was a 2.40-metre female tiger shark at the moment she was tagged in the waters of St. Maarten.

She stayed the first months around St. Maarten while making forays to Anguilla, St. Barths, Saba and the Saba Bank.

Sea Fairy migrated South in May 2017, following the Aves ridge in a similar movement pattern as Quinty. After spending two months at the Aves ridge, Sea Fairy explored the open Caribbean Sea and headed to Puerto Rico and Dominican Republic. The last location received for Sea Fairy was close to Puerto Rico, also about a year ago.

“Sea Fairy’s movement patterns can indicate a nursing area for tiger sharks around St. Maarten, spending their juvenile years in sand and seagrass habitat before migrating around the Caribbean when large enough in size and maturity. It is interesting to see that both actively-tracked sharks are showing similar migration routes following the Aves ridge, which may supply the sharks with an abundant food source,” stated Nature Foundation’s Project Officer Melanie Meijer zu Schlochtern.

“In the coming year we will expand our shark movement study and will install another satellite tag on a tiger shark on St. Maarten and two more sharks will be equipped with a satellite tag on Aruba. This research will improve our understanding of the life characteristics of sharks and will provide knowledge about the population structure, abundance and migration of sharks in the Caribbean.”

Sharks are often portrayed as being dangerous killing machines, but the facts show the opposite. Occasionally shark bites do happen, but no unprovoked attack has been ever recorded on St. Maarten.

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