Last July, On The Water publisher Chris Megan headed south of the Vineyard with shark expert Dr. Greg Skomal and Capt. Mike Pierdinock aboard the Perseverance for a day of shark fishing. During the trip, Dr. Skomal took a break to give some insight into the different shark tagging technology in use today off the New England coast.

On Conventional Tags:

Dr. Greg Skomal: The conventional tag is very straight forward. It’s a little marker you put on the fish.

Chris Megan: The only way you’re going to get information from this is if another angler picks it up, retrieves the tag, and then gives you the measurement, size and all of that information, right?

GS: Exactly. You get two data points. Where and when you tagged it and where and when you recaptured it. This is a tagging program run by the National Marine Fisheries Service since the early 60s. They’re almost coming up on 50 years of tagging sharks. They’ve tagged over 200,000 sharks with these conventional tags.

CM: Where’s the best place to clip it? Is one place better than another?

GS: Right at the base of the dorsal fin. It’s the lease intrusive. I’d like to think of it as running up to someone and piercing their ear.

On Satellite Tags:

GS: [This] is what we call a pop-up tag. The way these tags work is we leave them on the shark and they actually detach after a certain amount of time and float to the surface.

CM: So you’re not getting any information any transmissions back from the shark, it’s just going to be released, and it’s going to tell you where to go and pick it up? Or, once it floats to the surface, does it transmit data back to you right away?

GS: That’s it. We don’t go get it. If it’s nearby we try and go get it because you get more data if you pick up the tag. What we do is rely on the tag itself to transmit to the satellite system which then e-mails me the data. Then we do a retrospective analysis that lets us recreate the three-dimensional movements of the shark after we tagged it. So it doesn’t give us real-time information. People think, ‘It’s a satellite tag, we must know where it is at any given moment.’ That’s not the case.

On Acoustic Tags:

GS: Think of [the acoustic tag] as a pinger. It’s a tag that just emits a sound pulse. Ping, ping, ping, ping. It transmits any time that shark swims within range of one of our receivers, which we have fixed in the water off of Chatham, near Nantucket, the Vineyard, the Cape. What we’re trying to do is figure out where the sharks are spending their time, so if it swims anywhere near that receiver, that receiver is going to do a time stamp on who was there and when it was there. So if Shark A swims near Martha’s Vineyard, it’s going to pick it up and say Shark A was here at 2:30 in the afternoon on July 3rd. It’s a different technology but it gives us better information about the small-scale movements of the fish.