Fishing gear is entangling whales at record rates along the West Coast of the United States, and now environmental groups are urging regulators to take action to keep the giant marine mammals safe.

The number of whale entanglements reported for gray and humpback whales nearly doubled—from 16 incidents in 2013 to 31 last year—killing seven of the animals in 2014, according to data obtained from the National Marine Fisheries Service by environmental group the Center for Biological Diversity. Twenty-five entanglements have been reported in just the first four months of 2015.

Fishing gear set near the coastline is catching whales as they migrate between Arctic feeding grounds and tropical breeding grounds, snaring the marine mammals in nets and ropes that wrap around their fins and flukes. The lines, nets, and buoys can make it difficult for whales to swim, and the gear often ends up lodged in the whales’ skin—leading to serious injury and sometimes death.

NMFS researchers have responded by examining specific fisheries to see how best to limit whale interaction with fishing lines. For instance, Dungeness crab gear appears to be disproportionately trapping whales off California’s coast.

“The pot and trap fisheries are the most commonly documented source of serious injury and mortality of humpback whales in U.S. West Coast waters,” said Catherine Kilduff, an attorney with the Center for Biological Diversity.

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Some 800 commercial fishing vessels drop more than 200,000 crab and lobster traps along the California coast during the annual fishing season—and thousands of recreational anglers drop traps as well.

While trap limits were established by the state two years ago, entanglements continue to increase.

“We are hoping to work with the state and fishermen to come up with measures to reduce entanglement risk in the next few months, before the start of the next fishing season,” Kilduff said.

Some of the changes fisheries on the East Coast have made to avoid entanglements with endangered North Atlantic right whales could possibly be implemented on the West Coast, said Dan Lawson, a NMFS biologist.

Options include installing improved fishing gear attachments designed to break away to avoid snagging whales and limiting the time a trap or net can remain in the water without being retrieved.

The rate of entanglements has steadily increased since NMFS started recording incidents in 2000. Lawson said that could be due to a number of factors: more people on the water, which means more chances of spotting ailing whales; more citizens aware of how to report such incidents; and healthier, larger populations of gray and humpback whales traversing the West Coast.

“This is certainly a priority issue for us, for both gray and humpback whales, in terms of the rising number of reports and the severity of the issue,” Lawson said.