Shark migration study yielding first results

Saba is well-known for its rich marine life and many researchers have come in the past to investigate and publish their findings, writes The Daily Herald. The latest researcher who set foot on Saba is Dion Vink, who is studying Marine Biology at Van Hall Larenstein Higher Vocational Education in Leeuwarden, the Netherlands. Vink is now in his second year of studies and came to Saba to do his internship on sharks, their behaviour and especially their migration activities. This study is financed by Institute for Marine Resources and Ecosystem Studies Imares in Wageningen, the Netherlands. Imares was established to provide scientific support deemed essential for developing policies and innovation with regard to marine environment, fishery activities, aquaculture and the maritime sector.

Vink has spent three months on Saba and recently returned to the Netherlands. He was sent to Saba with two missions. First, he was to obtain samples of DNA from several sharks and also was to apply tags on the sharks to study their migration activities. Getting their DNA was not an easy job. According to Vink, it was “pretty exciting.” He went along with some local fishermen to catch the sharks. Vink would then take out a tiny sample of the shark’s fin. After this, all sharks were released back into the water. No sharks were permanently harmed during this procedure, he asserted. All samples are taken back to Imares for further analysis.

His next assignment was tagging the sharks, which involved catching more sharks and putting sender units into them. “Shark populations are decreasing worldwide. If our findings conclude that sharks stay in the same area for longer periods of time, it might be possible to declare these areas protected marine parks,” said Vink. “If this will happen someday is to be decided by Imares, World Wildlife Fund and the local government.”

Eight receivers were planted in Saba waters and attached to buoy chains or concrete blocks at a depth of between six and 15 meters. The receivers will be in the water for one year. Target species are the nurse shark and the Caribbean reef shark. “The biggest nurse shark we’ve caught was 2.10 meters and the biggest reef shark measured 1.80 meters,” said Vink. A special technique was used to apply the sender unit. After the shark was caught, it was laid on its back, which induced the shark into a state of “tonic immobility.”
Certified Imares researcher Erwin Winter, who visited for two weeks, made a small incision in the abdominal cavity of each shark to insert the tag. After three stitches, the sharks were back into the water with minimal harm done.

Twelve sharks in total were tagged this way; eight reef sharks and four nurse sharks. “We would have liked to have six of each, but the nurse sharks proved to be a lot harder to catch,” explained Vink. Just before Vink left the island, he was able to reveal the very first findings of his work. As the receivers were pulled out of the water for their first readout, data showed that the sharks indeed stayed in the same place for a longer period. Thorough data analysis must be performed before any results may be published, but Vink was very optimistic about the possibilities of a follow-up study next year.