Early last month, WHOI Scientist Michael Moore and his team spotted the first North Atlantic right whale calf in Cape Cod Bay, the summer feeding grounds for this species. Seven known calves (so far) have been born this year—an improvement given that no right whale calves were reported in 2018—but Moore said this number is not enough for the population to grow.
North Atlantic right whales are among the most endangered species in the world. At current mortality rates, Moore estimates it would take an annual, sustained production of this year’s generation of whales to restore the species to a healthy level.
One of the main factors contributing to decline in right whale reproduction, according to Moore, is entanglement in fishing lines.
“Entanglement is the number one problem we need to solve if we are to avoid extinction of the North Atlantic right whale,” Moore said. “So far our efforts to modify how crab and lobster fisheries rig and deploy their gear have failed to reverse the downward trend of right whale abundance.”
A tangled web
In trap/pot fisheries that target lobster, crab, and fish along the U. S. and Canadian eastern seaboards, fishermen use long vertical ropes or “lines” that connect traps on the ocean bottom to floats on the surface—a system that allows fishermen to locate their traps and haul them back up. When a whale becomes entangled, fishing gear can cut into its flesh, impede its ability to dive, and create a drag that exhausts its energy supply. Whales that survive entanglement often do not have the energy reserves needed to reproduce.
A study examining all available photographs of North Atlantic right whales taken from 1980 to 2009 found that out of 626 individual whales, 83 percent showed scars caused by ropes or nets, and 59 percent had been entangled more than once.
“Many animals can get out of these entanglements after a period of time,” Moore said. “But some die.” In fact, over the past five years 85 percent of diagnosed North Atlantic right whale deaths came from entanglement in fishing gear.
As the whales return to the northeast for the warmer months, Moore and his team at WHOI, and the broader ocean science community, are working to support the recovery of this population. The development of ropeless fishing lines is one area showing promise.
WHOI engineers have developed a patent-pending ropeless technology that uses a buoyant rope spool attached to the trap. An acoustic trigger releases the spool, which allows the trap to be pulled to the surface, so it can be hauled aboard. Fishing traps that don’t require a static rope could provide a solution that is safe for the North Atlantic right whale and viable for the Atlantic fishing industry.
Another device currently used commercially in Australia replaces static lines with a coiled rope and buoy inside a weighted bag attached to the trap on the ocean bottom. Fisherman can send a signal to the trap, which triggers an acoustic release, sending the buoy and rope floating to the surface.
Although not yet adopted in North America, these and other options are being tested in both U.S. and Canadian waters.
Three ways to improve things now
Until ropeless fishing lines are widely adopted, there are some ways to mitigate the impact of entanglement on right whales.
- Reduced strength and amount of fishing lines.
Scientists believe that the use of reduced strength fishing lines that allow whales to break free more easily could reduce the number of injuries and deaths. Reduction of the amount of line in the water column will also help. Moore emphasizes, however, that developing and using systems that avoid rope altogether will be the best long-term solution.
- Emergency response.
Disentanglement efforts are also helping. As entanglements occur, highly-trained emergency responders work to locate and disentangle whales. Hundreds of large whales have been freed from fishing gear along the East Coast of the U. S. by the Atlantic Large Whale Disentanglement Network, composed of 20 public and private organizations. Disentanglement is difficult and dangerous work, Moore added, and can only help a small minority of cases.
- Understanding how entanglement happens.
Finally, advances in computer modeling may play a role in helping create new solutions to the entanglement program. A new simulator, based on a morphologically accurate representation of the North Atlantic right whale, allows users to navigate a virtual whale through a water column containing fishing gear. This model, created by collaborators from BelleQuant Engineering, Duke University, and the Anderson Cabot Center for Ocean Life at the New England Aquarium, will help scientists develop a better understanding of the dynamics of entanglement to help prevent it from happening.
Addressing the issue of entanglement is a complex one, Moore said. “It’s a mix of major impact on coastal communities that rely on trap fisheries for their livelihoods, state and federal regulatory and political environments, and substantial conservation and animal welfare concerns for the affected marine mammals. But it’s time for a more radical approach. We need a major reduction in the amount of rope in the water column from all sources.”