Scientists unravel whale entanglement damage

ELLSWORTH — Scientists from the Woods Hole Oceanographic Institution have released a new study documenting how much damage entanglements in fishing gear does to North Atlantic right whales — one of the most endangered of all the large whale species. Their migratory routes take them through some of the busiest commercial fishing areas along the East Coast of the United States — including the Gulf of Maine — and into Canadian waters.

According to the institution scientists, entanglements with fishing gear represent the leading cause of death for endangered whales. Their findings were recently published in the journal Marine Mammal Science.

Entangled whales can tow fishing gear for hundreds of miles over months, or even years, before either being freed, shedding the gear on their own or succumbing to their injuries, the scientists said.

In a paper published online Dec. 9, a research team led by the Woods Hole Oceanographic Institution quantified for the first time the amount of drag on entangled whales created by towing gear, such as rope, buoys and lobster traps. The study provides important data for teams evaluating the risks and benefits of whale disentanglements.

“We know that entanglement can change a whale’s diving and swimming behavior and depletes their energy,” said Julie van der Hoop, lead author of the paper and a Ph.D. candidate in the MIT-Woods Hole Joint Program in Oceanography, “but the big thing we have never really known is what it must be like for animals to tow the gear. Is it like wearing an empty backpack or is that backpack overloaded with heavy books? Does removing part of the gear improve chances of survival?”

Working with colleagues from the Center for Coastal Studies and NOAA Fisheries, van der Hoop used a load cell to measure the drag forces on various types of fishing gear collected from past right whale entanglements. The team tested 16 sets of gear — five sets that included floats or buoys, one that included a two-brick lobster trap and 10 that were line only — towing them behind the Woods Hole research vessel Tioga across a range of speeds and depths.

The team found considerable variation in drag created by the different sets of gear, with the presence of floats and buoys having a significant effect on the overall drag created for the entangled animal.

“Some entanglements have very low drag, for example if a whale is towing 10 meters of rope, which is basically the length of the whale itself,” van der Hoop said. “The weighted lobster trap created the most with three times the amount of natural drag on a whale’s body. That’s a huge increase in what is normal to these animals.”

On average, the team found that entanglement increases the total body drag to 1.5 times that of a non-entangled whale. The group also calculated the additional energy costs to the animal.

“Entangled animals have to spend twice as much energy to swim at the same speed,” van der Hoop said.

“This study significantly improves our understanding of the energetic cost of large whale entanglement drag forces,” said Michael Moore, a co-author and van der Hoop’s advisor. “The study also reinforces current disentanglement efforts to minimize entangling gear if it cannot be removed entirely.”

Coincidentally, on Monday the Maine Department of Marine Resources announced that it had received a $20,000 grant from the Maine Outdoor Heritage Fund that will be used to purchase a soft-bottom inflatable boat that can maneuver more safely and effectively when Maine Marine Patrol and other DMR staff respond to reports of entangled whales.

“Often, responders have to pull alongside an entangled whale which might surface underneath the boat,” DMR scientist Erin Summers, who is coordinating the purchase, said in a statement. “A soft-bottom boat will move and form to the body of the whale, making injury to the whale less likely. A hard bottom boat is also more likely to tip when hit from below, which could endanger the responders.”

Maj. Rene Cloutier, the Marine Patrol’s commander, said, “This boat will help Marine Patrol significantly improve our ability to respond to entanglements. Our fleet of vessels is built to respond to law enforcement issues, but is not ideally suited for disentangling whales.”

According to Cloutier, the wardens need a boat that is smaller, more stable, is more maneuverable when working to disentangle large animals such as humpback and right whales.

The approximately 17-foot soft-bottom boat, purchased in consultation with partners at NMFS, will provide a much needed resource for fast and effective response by the Maine Marine Patrol

“This work is conducted very close to the whale and a soft bottom boat will allow us to maneuver into position so the responders can more easily move around in the boat and handle the specialty tools which are mounted on the end of a long pole and used to cut lines from the whales,” Summers said.

Currently, Florida, Georgia, Massachusetts, Rhode Island and Maine are the only states on the East Coast with the authority and training from NMFS to respond to large whale entanglements. One DMR staff member and nine Marine Patrol officers are trained and authorized as first responders for entanglements.

The network of responders on the East Coast, known as the Atlantic Large Whale Disentanglement Network, is coordinated by NMFS out of the Greater Atlantic Regional Fisheries Office in Gloucester, Massachusetts.

The Woods Hole institution’s research is an expansion on an individual case study in 2013 of a 2-year-old female North Atlantic right whale that was first sighted emaciated and entangled in fishing gear on Christmas Day 2010 near Jacksonville, Fla., by an aerial survey team.

Though disentanglement efforts by a rescue team eventually led to the removal of almost all of the gear after several attempts, the whale didn’t survive. An aerial survey in February 2011 observed the whale dead at sea. A necropsy showed that effects of the chronic entanglement were the cause of death.

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