Researchers Report Spike in Ocean Sunfish Strandings

Ocean sunfish. Courtesy of NOAA Fisheries Northeast Fisheries Science Center.

HYANNIS – Marine researchers are reporting a spike in sunfish strandings this fall as waters continue to cool off Cape Cod.

Ocean sunfish, also known as mola mola, is one of the heaviest known bony fishes in the world. Adult sunfish typically weight between 550 and 2,200 pounds.

It is a unique shape and resembles a fish head with a tail and has a mainly flat body.

As the sunfish are migrating south to warmer waters they can get trapped and cold stunned, mainly in Cape Cod Bay, similar to what happens with sea turtles.

Marine biologist Carol “Krill” Carson, the president of the New England Coastal Wildlife Alliance, said sunfish strandings average between 20 and 40 per season, and there have been 135 carcasses documented this year.

“This year is our busiest season and we have exceeded all previous seasons already,” Carson said. “The stranding season hasn’t even ended.”

The sunfish stranding season typically runs from mid-August through the end of December.

“It’s been a really bad season for ocean sunfish,” Carson said.

Marine researchers have heard reports of increased numbers of ocean sunfish in Cape Cod Bay and surrounding waters throughout the summer from boaters.

“If there is that many more animals in the area during the summer, than of course, that means we are going to have an increase number of animals stranding in the fall,” Carson said. “And I think that is really what’s happening.”

As the fish try to head south for the winter the geography inside Cape Cod Bay can cause the fish to get stuck as the waters continue to get colder.

“They can tolerate cold waters for just so long,” Carson said. “Then they become cold-stunned, a type of hypothermia, and then they wash up.”

Cold-stunning occurs to populations of sea turtles, and sometimes torpedo rays and thresher sharks.

“We have been finding a lot of live sunfish that are getting caught in shallow water areas. Wellfleet Harbor is a huge trap for all kinds of marine animals,” Carson said.

“Once in Wellfleet Harbor, it is really hard to navigate out of Wellfleet Harbor back into Cape Cod Bay.”

The alliance, which is an all-volunteer non-profit, has been rescuing quite a number of fish throughout the fall with the help of local residents.

Alliance volunteers and other community volunteers have formed Team Mola.

“We are all connected and we all try to get to the animals as quick as possible to try to rescue them and to try to move them out of these dangerous tidal areas back into deep water,” Carson said.

Ocean sunfish are not endangered and are not protected in any way, but their numbers are decreasing across the world.

“There really is no funding for this kind of work. There is no funding for rehab,” Carson said. “If we have an ocean sunfish that is alive, all we can do is push them back into deeper water and hope for the best.”

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