June 6, 2023 report
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Tracking a tiger shark to see how it fares when moved from captivity back to the ocean
A team of marine biologists and oceanologists from The University of Western Australia and Ocean Park Aquarium, also in Australia, has tracked a juvenile tiger shark in the open ocean after its release from two years in captivity. In their study, reported in the Journal of Fish Biology, the group tagged the shark and tracked it before and after release.
Most big sharks in marine parks are temporary residents. They are typically caught in the wild and then held at the park for just one or two years. After that, they are returned to where they were captured. This is because large sharks do not survive long in captivity. In this new effort, the research team noted that few studies have explored how well the sharks fare after they are released back into the wild.
To learn more about the well-being of these sharks, the research team chose a specific subject; one 2.2-meter juvenile tiger shark living at the Ocean Park Aquarium. Tiger sharks have been known to grow to 4.5 meters long. The shark in the study was tagged while still at the aquarium to gain a baseline for its movements. The team also tagged a wild tiger shark that had never lived in captivity for comparison purpose. After giving the shark time to adjust to the tag (10 hours), the team released it into the wild off the west coast of Australia.
The researchers found that the shark's activity was higher for the first two hours while still in the tank. Such activity was attributed to the shark adjusting to the drag caused by the tag. In comparing movement of the captive shark with the wild shark, the team found some slight differences in turning rates and vertical velocity—both were attributed to living within the confines of a tank. The team found that the small differences in movements continued after the shark was released but did not hamper its ability to survive. They conclude that after some minor adjustments, the shark survived its transfer to the sea.
More information: Oliver J. D. Jewell et al, Back to the wild: movements of a juvenile tiger shark released from a public aquarium, Journal of Fish Biology (2023). DOI: 10.1111/jfb.15464
Journal information: Journal of Fish Biology
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