Movie-going Americans learned to fear sharks in 1975 after watching Jaws. Today another great white shark drama is playing out near the film’s setting off Cape Cod, Mass., but this time the fear is for science as well as swimmers, as two groups of researchers go head to head.

Great whites used to be hard to find along to the U.S. North Atlantic coast, but in recent years the big fish are returning, following a resurgence of seals, one of their favorite foods. A research team led by the Massachusetts Division of Marine Fisheries is in the third year of a five-year study to gauge the abundance, migration and behavior of great whites along the state’s beaches. Scientists say it is one of their best opportunities to understand what is happening to these newly-returned top predators, which play a crucial role in the ocean food web. State officials also say the study is key to making decisions about beach safety.

Two weeks ago, company arrived: The nonprofit shark conservation and research group Ocearch anchored at the edge of the state study area, with a vat of shark bait (chum) to lure the fish close enough to capture and tag. This Sunday the ship was in a similar location. The state research team worries that creating a chum slick so close to their study could alter natural movements of the sharks and ruin much of their data. “It is extremely egregious,” says biologist Greg Skomal, who is leading the state study. “All we’ve done is respectfully ask them to wait. I don’t know why they can’t.” His team also thought Ocearch could inadvertently catch one of the animals they have identified for observation. On Thursday, September 22, they say, this occurred.

Concern about artificial influences is the main reason Massachusetts denied Ocearch a permit to operate in state waters, according to letters sent to the group from David Pierce, the fisheries division director. Ocearch does have a federal permit to work in U.S. waters beyond three miles offshore, outside the state study area, which is where their ship stationed itself. Ocearch representatives repeatedly declined to be interviewed by Scientific American, but an e-mail from a spokesperson said in part, “our scientists have asked for but have not been provided any details or evidence that the claim that Ocearch activities in federal waters in Massachusetts would disrupt any studies in state waters.” The organization also notes it was asked to remain outside of state waters, which it has done.

Credit: AMANDA MONTANEZ; Sources: Massachusetts Division of Marine Fisheries; Marine Traffic Live Map

Ocearch is known for its dramatic approach: hooking great whites, lifting them onboard ship for tagging and measuring shark biology while the animal is on deck. After naming, each shark is assigned its own Twitter handle, and fans can follow its migration through the world’s seas. One 16-footer, Mary Lee, boasts more than 100,000 followers. The group has worked with many institutions, such as Woods Hole Oceanographic Institution and the University of California, Davis, and currently has scientists on its ship from Mote Marine Laboratory in Florida. Ocearch expeditions began almost a decade ago on reality television, and have garnered much laudatory media coverage. Founder Christopher Fischer’s biography notes Ocearch has been a part of 5,000 news stories.

It was Skomal and Fischer who tagged Mary Lee together, when they partnered in 2012 and 2013 to study great whites off the coast. Today, however, Skomal says that experience made him and his collaborators from the University of Massachusetts School of Marine Science wary of the possible problems Ocearch posed for their current study. Of the four sharks tagged on the previous Cape Cod expeditions—two in state waters, two in federal—two did not return to the area for about a year, and a third, Mary Lee herself, has never come back, according to tracking data on the Ocearch Web site.

Chris Lowe, director of the Shark Lab at California State University, Long Beach, who is not involved in either study, says “catching and handling can increase the likelihood that animals will leave the area in response to the disturbance. Much less invasive procedures like external tagging that do not require capture should have less effect on subsequent behavior.” The state does not use chum nor pull sharks from the water; rather it follows animals via sound-emitting tags attached by harpoon while the shark is swimming, visual identifications from underwater cameras, and aerial surveys.

It is impossible to know why the ocean-wandering animals left after being caught by Ocearch, but for comparison, Skomal says, his unpublished data suggest more than 80 percent of the sharks he has pinned with sound tags remained around Massachusetts waters shortly after getting their new devices.

Despite the state permit rejection, in July Ocearch secured permission from the U.S. National Oceanic and Atmospheric Administration (NOAA) to work in federal waters. Since Monday, September 19, the Ocearch vessel has periodically placed itself near the state study boundary, according to online marine vessel tracking data. So far its crew has tagged several sharks. One is a female caught off Nantucket Island. State researchers say that based on examination of her photo on the Ocearch Web site they already had this shark under observation for their work and named her Island Girl. Ocearch named her Miss Costa, after Costa Sunglasses, one of their sponsors. Her newly installed satellite tracker showed her making a beeline toward open ocean. Last week Skomal estimated she  retreated more than 200 nautical miles from the study zone. (When asked by Scientific American about steps Ocearch had taken to make sure Miss Costa was not Island Girl, a spokesperson responded, “we have no information regarding that.”)

The tracking and biological data from sharks like Miss Costa and Mary Lee have been valuable contributions to science and public education, Lowe says, but some in the shark research community have grown uncomfortable with some of Fischer’s superlative claims. For example, he says, shark biologists chafed to see headlines in August about Fischer announcing that an Ocearch expedition had discovered the first great white shark nursery off the Atlantic coast. In fact, the site has been discussed for decades in the literature. Published proceedings from a 1985 research symposium say “the occurrence of small- and intermediate-size white sharks in continental shelf waters of the Mid-Atlantic Bight suggests this area serves as a nursery area for juveniles.” And last week CNN reported that Ocearch had tagged a great white pup, claiming it was only the second time that such a feat had been done. The news caught Lowe by surprise. “That is entirely incorrect,” he says, noting he and his colleagues have tagged such young sharks over the past decade, as have scientists in Australia.

Media-based hype aside, George Burgess, director of the Florida Program for Shark Research at the Florida Museum of Natural History, says the state scientists are justified to be concerned about their research, whose $650,000 cost is being paid by the Atlantic White Shark Conservancy. Estimating shark populations is a delicate undertaking; only some animals can be counted, and based on those numbers researchers have to make extrapolations. For the data to be valid, he says, the study team must have an equal probability of spotting any particular shark every time it goes out. “If Greg Skomal and his crew have been fishing one way all this time … and now somebody comes in and starts chumming and putting food in the water to attract sharks, that can change the dynamics of what he is sampling,” Burgess says. “It might attract more white sharks into the area because the food is there or it might take sharks out of his research area in the shallower waters and pull them offshore. Either way, the result is a modification of his regime, which was to be sampling a natural population.”

The effect of chumming is hard to calculate. Despite common lore that a shark can smell a drop of blood in an Olympic-size swimming pool, the actual range that the sharks can smell chum depends on how the soup of blood, oil and meat is dispersed by wind, currents and tides, says Aleksandra Maljkovic of Simon Fraser University in Vancouver, who recently completed her PhD studying how ecotourism that involves chumming affects shark behavior. Once it catches a whiff, a shark can quickly find the source, swimming back and forth, gauging the strength of the odor in each nostril. Although it is impossible to pinpoint a distance, she says, if conditions were right even four miles away would not be an unreasonable possibility for a shark’s keen sense of smell, much less a half mile from the study boundary. “If the source of the chum is that close, I can’t see how they wouldn’t detect it,” she says. “If it was my study, I think the only word I can use to describe how I would feel would be ‘livid.’”

For these scientific concerns, says Cal State’s Lowe, and out of a desire not to stress the animals, it is not unusual for researchers to be denied permits to work in areas already occupied by other teams. “I’ve requested permits to do something that I didn’t know other people were doing, and gotten the same kind of response on the west coast,” Lowe says.

Shark population scientists say they are worried this shark, dubbed Island Girl and identified by side markings, was also picked up and tagged by Ocearch, which calls the shark Miss Costa. Credit: Atlantic White Shark Conservancy

The state population research is not only important for shark conservation but also can affect the safety of swimmers. Noting that about four million tourists each year visit Cape Cod beaches, the superintendent of the Cape Cod National Seashore appealed in writing to NOAA on September 19, asking the agency to reconsider the Ocearch permit. The letter said, “the data from the population study has a direct impact on the public safety decisions that are made at the seashore.”

“The bottom line,” Skomal says, “is Chris Fischer wants to do this expedition, and he’s going to do it come hell or high water.” That has left Skomal and his research team scrambling to account for potential interference, and the possible loss of one of their study sharks, in their results.