Cape Cod 5

First Friday: Sharks!

Even sharks are carrying mobile devices these days.

At our May First Friday breakfast meeting, shark researcher John Chisholm told us how technology is helping them track great white sharks in the Atlantic.

Most of the work he and Greg Skokal do for Massachusetts Shark Research is on the cutting edge of technology. They know white sharks are along the coast, but can’t yet predict where you’ll find them. Elsewhere in the world there are four hotspots, in California, South African, South Australia and Mexico. These have become popular Eco tourism destinations. What these four places have in common with each other (and with us) is large seal colonies,

Shark sightings are a recent phenomenon on the Cape, largely because grey seals were exterminated through bounty programs. By the 1960s there were very few seals in the North Atlantic.

It took the awhile to repopulate, but they’re back and growing exponentially. With the seals has come evidence of predation. In the past decade they’ve been documenting evidence of white sharks. They weren’t seeing the sharks, but these were clearly white shark predations. In 2009 they confirmed a white shark off Lighthouse Beach in Chatham.

They are now tagging sharks with three different types of tags. The conventional way to track them was to number the shark, and document where it was seen next. Using technology helps to fill in the information between sightings.

Fun fact: These sharks are so close to shore, one of their concerns is not running the boat aground while tagging. That’s where the seals are, so that’s where the sharks are.

Pop up archival transmitting tags measure depth light and temperature every 30 seconds. Data is archived then transmitted to Argos satellite after detachment. Habitat preferences and movements are derived from this data, despite a lack of underwater GPS.

Acoustic tags are attached the same way, but send out a coded signal, like morse code. These tags help researchers understand shark habitat and behavior, showing local movements and patterns. Data can be downloaded when needed. They are designed to give us a sense of the behavior of sharks in the area, to help towns understand what is happening.

The third way of tracking sharks is working with underwater vehicle, using an acoustic pinger. This vehicle is loaded with cameras, following the signal and the shark in real time. It follows the shark for a day, after which the tag pops off to be collected. John had some great video from this vehicle.

Some of these sharks they’re tracking are 70 years old, so these are sharks that have been out there. We’re just seeing them now as they hone in on our seal population.

LargeMarge-sharkresearch

This photo was taken from Nauset Beach by Shelly Negrotti and published in the Cape Cod Times (among many other places). Researches didn’t think it was a white shark at first, but then used fingerprint recognition to match the dorsal fin to Large Marge, a white shark they’re tracking.

You can follow some sharks online through Ocearch, which uses yet a different kind of tag. This tag shows much more activity, with greater range. “Lydia is basically rewriting the book on white sharks,” John said of one of the sharks Ocearch is currently tracking. “At one point she was closer to Ireland than anything. No white sharks have been documented in the UK. And she obviously can’t be the only one doing this.”

They need to track more sharks, but the technology is very expensive. Massachusetts Shark Research is funded solely by grants and donations – some of which comes from Atlantic White Shark Conservancy, based in Orleans. People may get the impression that by tagging the sharks, towns can monitor where the sharks are and when it is safe to swim, but they are tagging a very small number of sharks within the population. They have no idea of a population, but there are more than they thought.

Their to do list includes:

  • Expand receiver coverage
  • Get a population estimate
  • Find new technology – with real time receivers
  • Expand outreach and education
  • Tag, tag, tag

So far, there are only 39 sharks tagged. “We may see a dozen sharks, but we can only tag one or two,” John said. “It is not an early warning detection system.”

However, sharks are not interested in attacking humans. They much prefer seals. There was a man in Truro who was bitten by a white shark, but that bite did not indicate a shark attack. “What do you do with that tomato you’re thinking of getting?” John asked. “Sharks don’t have hands, so they do it with their teeth.” When surfers are attacked, it is because sharks are convinced it is a seal.

Despite the recent sightings, shark populations are in decline because they reproduce so slowly and are in demand by fisheries, mostly for their fins. Shark populations around the globe are in decline.

Another fun fact: The US Navy has been interested in shark skin for decades because it is so hydrodynamic. There is no drag. Drag under water produces sound, but sharks are silent.

For more information on Greg Skomal and John Chisholm’s research, see the Massachusetts Shark Research page at mass.gov

 

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