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ape Cod has a great white shark problem. Greg Skomal has a math problem.


Since 2009, the program manager and senior scientist for the Massachusetts Division of Marine Fisheries has studied the great white sharks coming to the Cape in increasing numbers each July through October to feed on the burgeoning seal population. For the last five summers, he has tagged and counted Cape Cod’s great whites, and now he and a couple of grad students have to crunch all the data to come up with an accurate number.

“At least some of our preliminary estimates we hope to have out by the summer,” Skomal (GRS’06) says from his New Bedford office.

The stakes have never been higher. Last September, 26-year-old Arthur Medici of Revere was killed by a great white shark while boogie-boarding in shallow waters off Newcomb Hollow Beach in Wellfleet, the first known shark attack death off the Cape since 1936. A few weeks earlier, New York physician William Lytton, 61, was swimming off Truro’s Longnook Beach when he was bitten by a shark, requiring nearly 12 pints of blood and multiple surgeries.

As the season approaches, beachgoers, surfers, and business owners who count on summer tourism to make their year are all jittery, wondering if Cape Cod’s great white sharks have changed their summers forever.

“You can’t say that anything is a permanent issue on Cape Cod, but it is safe to say that we will be dealing with this issue for many years,” Skomal says.

Skomal has become the media’s go-to expert whenever the animals, as he calls them, make news. We asked him about the real numbers, what’s next for his team, and the new normal for Cape Cod beachgoers and businesses.

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BU Today: A couple of years ago, you told us: “When you put white sharks in the same waters where there are humans, you are going to increase the potential for an interaction.” It must be a bad feeling when you hear that it’s coming true.

Skomal: Yeah. I don’t want to say I felt it was inevitable, but I felt the potential for it was higher than in other parts of the world. It certainly has played out in other areas when you have such overlap of people with a top predator and its natural prey. I can’t say I’m particularly surprised, but that doesn’t make it any easier when it happens. Although I am fascinated by this species, I am also deeply committed to producing information that will stop the tragic loss of human life.

You’re at the end of a five-year project—I wonder how you’ll report the results?

The number one question I get is, ‘How many are out there?’ I think it’s a burning question. And it has been our major focus the last five years. The population study is to get a sense of the size of this population and the abundance of these sharks off the Outer Cape and other parts of Massachusetts. It’s very quantitative. We’ve completed the field component, five seasons of intensive survey-based sampling. We have the other aspects of it, data compilation and analysis and ultimately publication in peer-reviewed journals. We’re also going to share the results with the general public and beach managers and such—it’s not just going to be written up and filed in some journal that nobody reads. I have a student working on it, and it’s going to be the basis for her dissertation.


It’s a lot of math, but honestly, the more complicated part—the key to this kind of study—is identifying individual sharks. You’re doing a kind of census each summer based on a sampling technique. So we go up to every shark we see over the course of a summer and videotape it. And that videotape needs to be processed to determine who that shark is, which is based on individual color patterns. So we might take as many as 50 or 60 videos a day, which will boil down to 5, 10, 15, 20 sharks. But boiling that down to the individuals is a monumental task: looking at and processing every video. Over the course of a summer we’ll accumulate over 1,000 videos. And we have that for five summers. We know of at least 320 individuals. That’s the time-consuming part, and we’re backlogged now. What helps is if they already have a tag in them—then we know exactly who they are. I like numbering, but the world loves naming them, so we have names. We are trying to put together an online catalog.

How many active tags are there?

We’ve tagged a total over the last 10 years of 151 individuals. The bulk of those tags are still working. Some of them have expired, but it’s safe to say between 100 and 110 are still working. We tag an average of 15 to 25 a year. I have to thank the Atlantic White Shark Conservancy for making that possible, otherwise we just wouldn’t have the funds. In the summer, the team on the boat is about five or six people, including the spotter pilot. There’s no shortage of help collecting the data; the shortage has been in the analysis.

Greg Skomal

“I’ve probably seen more white sharks in the Atlantic Ocean than anybody on earth,” Greg Skomal says. Photo by Cydney Scott

You have a number of studies underway. What will you focus on next?

For the questions we are trying to answer now—and the need for answers is heightened by the simple fact that people are getting hurt—we really need to know a lot more about the predator-prey relationship between the sharks and the seals. That’s going to be the key to a better understanding of how to avoid negative interactions between sharks and people—to avoid shark bites and shark attacks. So that’s a major focus of our work moving forward.

We’re using a variety of technologies, including very sophisticated electronic tags that give us very, very fine-scale movement information: the position of the shark in the water column, its swimming speed, its direction, its posturing, its pitch, its roll, you name it. We’ll be able to tell how that shark is moving through the water. So we’re hoping to be able to differentiate between simply cruising and actively feeding. We should be able to see those events as the shark accelerates. And those tags will also include camera technology, so we’ll be able to confirm our observations through direct recording of the behavior.

We’re really interested in what precipitates an attack on a seal. If we can get a really good sense of that and there are some predictable patterns, I think we can provide information to the general public and to beach managers that will be helpful in reducing negative interactions.

The sharks travel seasonally, correct?

They start to trickle in here, a handful of individuals, as early as late May. Depends how fast water temperatures warm up. August, September, October have consistently been the peak months. And then the sharks are for the most part gone by mid-December, with the bulk leaving mid-December. Almost all of them at some point during their migration will venture down to the southeast United States, anywhere from North Carolina to the Gulf of Mexico. There are some sharks that just stop off in our neck of the woods, like a rest stop on I-95, and keep going north. They’ll go as far north as the Gulf of Maine and Newfoundland.

Does climate change have a role in the growth and movement of the shark population?

“—it was a split second in my life. I look down, and I’m looking down the throat of a white shark with its mouth agape coming up at me.”

Greg Skomal

We have amassed a really nice historical data set of sightings data going back to the 1800s, and we can definitively say the range of the white shark isn’t changing. The white shark has been documented as far north as Newfoundland going back many, many decades. So I don’t think there’s any climate change association here.

What I think it is, is just a function of numbers of animals. The white shark population, like the seal population, is thought to have been hit pretty hard by humans—in the case of sharks, by overfishing. Particularly in the latter part of the 20th century. In the late 1990s we started protecting the white shark, so that amounts to two decades of protection, and we’ve got a population that’s rebounding. As more and more animals are around, and are drawn to the area because the seals have also rebounded after 50 years of protection, the sharks are spreading out over a broader area to take advantage of these food resources.

If you plotted it out, you’d see that reports of sharks have increased dramatically in the last decade, and that’s also a function of more people on the water and their ability to use their phones to document the appearance of these animals.

You had a close call last summer that was seen on TV news, when a great white shark jumped up at you on the boat’s pulpit. Did that give you a new appreciation for these creatures?

Well, that woke me up a little bit, I guess. If I hadn’t seen the video like 500 times, I probably wouldn’t have thought too much about it, because it was a split second in my life. I look down, and I’m looking down the throat of a white shark with its mouth agape coming up at me. I didn’t feel threatened, because I had a lot of aluminum around me, and the shark didn’t get very high out of the water, but certainly there was some level of intent there that bothers me to this day. And yeah, it gives me more appreciation for this animal.

I’ve been quoted as having nightmares every now and then about this species, because I’ve seen a lot of them. I’ve probably seen more white sharks in the Atlantic Ocean than anybody on earth, and I’ve seen what they do and what they can do. I’ve seen what they do to seals, and I’ve seen what they do to people. So the survivalist in me says this is a dangerous animal that I need to be careful of. And then the logical side of me says the probability of an attack is really low. The statistics say it’s more dangerous to do things we do every day, like getting in our cars. But I’d be absolutely insane if I didn’t think about this issue of self-preservation and the danger. It’s people who don’t think about those things—I question their sanity.

So yeah, I’m troubled by that event. Maybe it’s a sign that I’m not completely crazy.

You really are the media’s go-to choice on this story.

At times it’s flattering. Probably when it first started I would eat it all up, because not everybody gets this level of attention. I come from a big family, and getting a lot of attention as a kid wasn’t something that happened, so I maybe was prone to want it. It’s a little fatiguing, but it’s not a bad thing. I like being able to educate the public, and I use these interviews as vectors for doing that. It’s important that the public is engaged in these discussions.

You often try to put this in context: This animal is part of the ecosystem, we are not going to make it go away, we need to find ways to be safe, but also to coexist, right?

Yeah. I’ve been saying that since the beginning. In the near term, I don’t think anyone is going to be able to modify the behavior of the seals or the sharks. They’re doing what they do naturally. This is the predator, this is the prey. They’re doing what they need to do.

What we can do is modify our behavior. We’re a terrestrial animal and we’re entering the water to do something we want to do. But we don’t need to get in the ocean. In not being able to change the behavior of these animals, I’m suggesting we change ours. We’ve got to modify our behavior to minimize risk to ourselves or be more than willing to accept that risk.

What changes do we need to make?

It really boils down to staying away from areas where there’s a potential for interaction with a white shark. And that means getting out of their hunting zones along the Outer Cape. Stay close to shore, stay in shallow water. What is too deep? Waist deep is as deep as I would go to cool off in the waters of the Outer Cape, just because anything deeper is accessible by a white shark trying to hunt a seal. It really boils down to common sense.

Greg Skomal in his office surrounded by Shark paraphernalia

Skomal says knowing more about the predator-prey relationship between sharks and seals could help reduce negative interactions between sharks and people. Photo by Cydney Scott

That doesn’t work for the surfers and the divers and the spear fishermen.

Exactly right. It’s going to be those activities that require people to be farther from the beach, in the deeper water. I talk to a lot of surfers, and they’re willing to accept the risk. They want to ride waves, and they’re not close to shore many times. And they’re in water that’s over their heads, water that’s murky, water where they can’t see potential white sharks in the area. And there’s going to be that risk.

But many of them have been doing it for decades, and they’re willing to accept that risk. They’ve seen sharks, seen sharks kill seals, and feel the risk is worth taking because the probability is extremely low. So I understand that. I feel for those small businesses that are making a living renting and selling this gear that is associated with activities people might stop doing. That’s the hardships that we might be seeing.

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Joel Brown, Staff Writer for BU Today, Bostonia and BU Today Marketing & Communications
Joel Brown

Joel Brown can be reached at jbnbpt@bu.edu.

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