EASTHAM — “There isn’t a single alternative or suite of alternatives that can 100-percent guarantee the safety of all individuals who choose to enter the water,” coastal scientist Adam Finkle told a crowd of about 100 at Nauset Regional High on Oct. 17.
Representing the Woods Hole Group (WHG), Finkle presented the results of the Outer Cape Shark Mitigation Alternatives Analysis completed by the consulting group. Its conclusion: no alternative can guarantee safety from shark attacks.
But a “guarantee,” one citizen argued, is too high a mark to aim for.
“There’s very few guarantees in life,” said Bob Wagner of Wellfleet. “Airbags are not 100-percent effective but people still get in their cars. It’s not stopping people from making cars because there may be an accident or a death that results if an airbag doesn’t deploy. People have to accept these risks.”
Wagner directed his remarks to members of the Shark Working Group that includes Outer Cape town officials, National Seashore Supt. Brian Carlstrom, and Megan Winton of the Atlantic White Shark Conservancy (AWSC). The group fielded questions from the public after the presentation.
The study, Finkle said, was not intended to produce a specific recommendation for action. The event, therefore, left many wondering what the next step is for dealing with the increasing shark and seal presence in local waters. Citizens and officials agreed that doing nothing is not an option, but without a clear-cut course many questions remain.
Finkle, as project manager, gave an overview of the 192-page report. WHG plans to publish an executive summary that highlights key findings before the 2020 summer season for town and Seashore officials to review, he said.
The analysis looked at 27 alternative strategies to mitigate encounters between sharks and humans in three categories: technology-based, barrier-based, and biological-based.
| Technology-based | Barrier-based | Biological-based |
| Tagging (acoustic, real-time alert) | Flexible Exclusion Barrier | (Smart) Drum Lines |
| Tagging (satellite, real-time alert) | Rigid Exclusion Barrier | Cull Nets |
| Visual Detection (planes, helicopters) | Semi-Rigid Exclusion Barrier | Seal Contraception |
| Visual Detection (tower-based) | Bubble Curtains | Seal Culling |
| Visual Detection (balloons) | Live Kelp Forests | Indigenous Harvest |
| Visual Detection (drones, tethered drones) | Simulated Kelp Barrier | Electric Shock |
| Acoustic Detection (sonar buoy, real-time alert) | Electrical Deterrents | Scent-Smell |
| Electromagnetic (active, wearable/mountable) | Electromagnetic Deterrents | Modify Behavior |
| Magnetic (passive, wearable/mountable) | Acoustic Barriers | |
| Adaptive Camouflage |
The study uses a detailed matrix to grade each of the 27 alternatives based on a set of six criteria: limiting factors, cost, permitting, effectiveness, potential impacts on humans, and potential environmental impacts. Each of the six categories contains a set of individual criteria.
For example, the limiting factors are weather, marine conditions, effective range, effective depth, resilience to storm impacts, and commercial availability.
Finkle went through each alternative with the audience. Some seemed promising but there were problems in every case.
“None of the technology-based alternatives physically separates sharks from humans,” Finkle said.
The study found that barrier systems have been installed in Australia and have been effective in excluding sharks from swimming areas for humans. But they come at a price.
“A barrier would likely have extremely long permitting timelines and high cost if proposed locally,” he said.
Biological-based alternatives were less promising.
“Removing a couple thousand seals from the population is not likely to have a significant effect on the great white shark population,” Finkle said. “It’s also plausible that a reduction in the gray seal population may cause other gray seals from the greater northwest Atlantic population, close to 500,000, to move into the area to occupy that habitat.”
One citizen pointed out what he called an error in the report, which suggests that a permit is required to operate a drone in the National Seashore.
“[Drones] can be flown over the National Seashore, but they cannot take off or land within it,” Carlstrom said.
Others questioned how well a drone could spot a shark beneath murky Cape waters.
The 27 alternatives were chosen after WHG reviewed strategies used around the world, feedback from local towns, and feedback from a public survey.
The survey was conducted in February and received 573 responses.
“Results of the public survey proved critical to the development of this comprehensive list of alternatives,” the report states.
The survey found that 50.1 percent of respondents said they preferred technology-based alternatives, 38.6 percent said they preferred biological-based alternatives, 16.2 percent said they preferred barrier-based alternatives, and 30.7 percent said they preferred an alternative that considered the human dimensions of the problem like engaging in “shark smart behaviors.” (Respondents could choose more than one answer.)
Cost will be a significant factor in any decision that is made about shark mitigation.
Jay Coleman, who owns a house in Eastham, questioned where the funding would come from for any proposed project. “You’re not going to get the money I don’t think from the federal government or from the taxpayers, are you?” he said.
“I think that the results in this report and the money decisions are going to be made at a lot higher level than the shark working group,” said Chief Ranger Leslie Reynolds of the Seashore.
The report is available to view online at eastham-ma.gov/home/news/outer-cape-shark-mitigation-alternatives-analysis.
