Entanglement Mitigation

Removing entangled gear from whales is dangerous work. It involves sharp tools, unpredictable ocean conditions, and stressed out whales that don’t always welcome the rescue boat. Anyone who does this work has gone through hours of training and has to wear safety gear. Disentanglement efforts sometimes take hours to complete and are not always successful.

disentangling a whale

The best solution is to reduce or eliminate the conditions that lead to entanglement. This requires action and changes in several areas: 

Closures
Seasonal closures for trap/pot fisheries have been set up in select areas along the New England coast to try to avoid migrating and feeding whales. Canada has done the same. Once migrating whales have moved on, the closed areas can be opened to fishing.

Sinking Lines
In Massachusetts waters the law mandates that the lines between lobster pots and similar fishing traps must sink rather than float in the water column. Other states have similar laws, but may not apply to the entire coastline.

Line strength
Years ago, the lines connecting buoys to the pots and traps set on the bottom were made from natural fibers. Starting in the 1950s, synthetic fibers like polypropylene were used in these lines. In the 1990s, copolymer began replacing polypropylene. These synthetic ropes have become increasingly stronger, lighter and very difficult to break. They are also more likely to stay tangled on a whale. Research is underway to lower the breaking strength of these thin, strong ropes without changing their diameter.

Breakaway swivels and links
The connections between lobster buoys and vertical lines can be made out of plastic with a weak spot in them. The same holds true for connections within gillnets. These links and swivels are designed to break when a certain amount of force, for example 1100 pounds (499 kg), is applied by an entangled whale pulling on the gear. This increases the possibility that whale can break free from the gear, and not stay entangled.

Ropeless Gear
Trap/pot fishermen in Australia are using gear that keeps the buoy and vertical line out of the water column. Their solution is to keep the buoy and line coiled up on the ocean bottom next to the end trap or in a container that will open when it receives a wireless signal sent from the boat that will collect the traps. The buoy will rise to the surface so the fisher can pull the pots out to remove his/her catch. Similar technology is being tested here in the U.S., on both coasts. An example of this ropeless gear is on display in the Whales Today exhibit.

Pingers
Pingers were created by scientists working with fishermen from the Gulf of Maine to help smaller cetaceans avoid fishing nets. The pingers are attached to the nets and emit a low, but audible noise every four seconds. Porpoises seem to dislike this noise and swim away from it. Pingers have been mandated by NOAA for use on gillnets, as part of cetacean Take Reduction Plans, since 1998. They have been shown to be 90% effective in reducing harbor porpoise bycatch when used properly.