Monster Machines: This Torpedo Keeps Social Tabs On Sharks

Monster Machines: This Torpedo Keeps Social Tabs On Sharks
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Sand Tiger sharks have been patrolling coastal waters worldwide for more than 250,000 years. But with only a pair of pups born every few years, this placid apex predator is succumbing to human pressures.

Part of the problem is that we still know virtually nothing about their habits — we can’t help them if we don’t understand them. But that’s fast changing thanks to this seawater-sipping, shark-shadowing, scientific submersible.

Sand Tiger sharks are found everywhere from Japan to Australia to South Africa and beyond. In the US, their habitat spans the Eastern seaboard. But even with such a wide range, the threat to Sand Tigers is very real. The International Union for the Conservation of Nature now lists them as Vulnerable (fewer than 10,000 individuals in the wild); that’s just one rung below Endangered and four rungs below full-on extinction.

This is why the University of Delaware is collaborating with Delaware State University, Delaware Department of Natural Resources and Environmental Control (DNREC), and the NMFS for a five-year tagging program to track and study where these sharks go, what they do in their free time, and who they hang around with. Funded by a $US350,000 grant, researchers, led by Dr Dewayne Fox, associate professor of fisheries at Delaware State, hope to craft a conservation and repopulation plan for Delaware Bay’s Sand Tigers and help mitigate potential shark habitat destruction from large projects like the Army Corps of Engineer’s ongoing dredging projects.

Now, since conventional satellite tagging technologies provide zero data on the conditions surrounding the tracked animal, they can’t provide any insight into why sharks go where they go, which is exactly the sort of information necessary to set up protected habitats. Instead, researchers rely on a trio of tracking tag technologies and a long-distance undersea glider dubbed OTIS (Oceanographic Telemetry Identification Sensor) to find them, once implanted in a host shark.

OTIS normally patrols coastal waters studying oceanographic and climatological changes as part of the Mid-Atlantic Regional Association Coastal Ocean Observing System (MARACOOS) by sampling water conditions but has been outfitted with a pair of acoustic “ears” to sense the signals emitted by the tracking tags. OTIS, supplementing a 70-unit network of stationary receivers throughout the Bay, now skulks up and down the East Coast, taking in small samples of water and alerting researchers of the encounter whenever a tagged shark comes within range. If desired, OTIS can then begin following the shark — for up to two weeks on a single battery charge — sampling the waters as it goes.

By measuring the temperature, water clarity and oxygen levels of these samples, researchers hope to find clues to not just where these sharks travel but why as well. The team has already discovered a subpopulation of Delaware Bay Sand Tigers that dutifully swim to Florida every winter and return to the bay each summer. Scientists weren’t even aware that Sand Tigers travelled that far, much less annually migrated such distances.

Since 2006, the research team has tagged more than 500 Sand Tiger Sharks with one of three types of tags — an acoustic transmitter that utilizes the Delaware Bay network, a satellite archival tag that logs the shark’s travels for a year before popping off and floating to the surface for retrieval, and a VEMCO mobile transceiver (VMT) that not only transmits location data but also pings nearby VMTs, logging the interactions of two or more tagged animals.

“In the past week our new, specially equipped glider OTIS — which stands for Oceanographic Telemetry Identification Sensor — detected multiple sand tiger sharks off the coast of Maryland that were tagged over the past several years,” said Matthew Oliver, assistant professor of oceanography in UD’s College of Earth, Ocean and Environment. “This is the first time that a glider has found tagged sharks and reported their location in real time.” [MSNBCUniversity of DelawareDelaware State UniversityWikipe]

Image: Matthew Breece