Sea cucumber die-off near Vancouver Island prompts fears of wasting disease that nearly wiped out sea stars

When Kathleen Reed descended for her usual weekly dive off the coast of Nanaimo, B.C., last Saturday she was shocked by how many dead sea cucumbers she saw.

Reed has completed more than 500 dives and says she'd never seen so many of the deep red echinoderms turned pale, limp and slimy.

"There were hundreds of them. They were just white and dead in various states of decay, littered all over the sea floor. It was shocking and really disturbing to see," said Reed.

Experts and harvesters fear that sea cucumbers found off the coast of Vancouver Island are being hit by an illness similar to sea star wasting disease, which swept through the B.C. population in 2015 and 2016, killing 96 per cent of the creatures.

Sunflower sea stars were hit particularly hard. It's estimated that some 5.7 billion sunflower sea stars died, bringing the species close to extinction. 

Symptoms first appeared as pale blotchy lesions or white spots on the skin and ended with the animal dissolving. 

The symptoms are similar to those now affecting sea cucumbers along the B.C. coast. 

Sea stars and sea cucumbers are both echinoderms or spiny-skinned creatures. While sea stars hunt, sea cucumbers are bottom feeders; they act like a garbage truck, eating organic detritus — or waste — found in the sea floor sediment.

Sea cucumbers perform an important ecological role and could help clean up aquaculture sites, according to Emaline Montgomery, a research scientist at the federal Department of Fisheries and Oceans Pacific Biological Station in Nanaimo.

More study is needed to determine what's causing this mass mortality event, but climate change is likely part of the explanation. 

Montgomery said that warmer water temperatures could play a role in stressing the animals, which may make them more susceptible to pathogens or viruses.

"Usually when sea cucumbers get stressed they might start to exhibit these bizarre symptoms where their outer body wall turns white. It gets kind of mucousy. It literally looks like their skin is disintegrating or melting," she said.

Seven years ago, sea cucumber wasting was reported in Friday Harbour in Washington state and near Admiralty Island in Alaska. Since then it's been noticed near one Washington aquaculture farm as well as in Howe Sound, near Sechelt, B.C.

A study last year led by Ian Hewson, a Cornell University biological oceanographer and expert in viruses of the sea, described an Alaskan outbreak.

Those sea cucumbers were stricken with "lesions and fissures and sloughing of epidermal tissues," then rapid "liquefaction."

Global market for sea cucumbers

Canada does about $30-million in sea cucumber trade. B.C. has about a one-third share of that market.

Thom Liptrot, president of the Pacific Sea Cucumber Harvesters Association, says divers pick the prickled creatures along about half the B.C. coast. 

B.C. has approved 85 licensed fishers who are allowed to take 16,000 pounds or 7,200 kilograms each, according to Liptrot.

Dried sea cucumber is shipped to China where it is used to treat everything from arthritis to heart disease and boost virility. Fresh sea cucumber can be flash-fried in garlic and butter and tastes "somewhere between a clam and a squid," Liptrot said.

Otters and sea stars also enjoy eating sea cucumbers, which sometimes escape by rolling.

Liptrot has had reports of dead sea cucumbers near Comox and Sechelt and now fears the elongated echinoderms are being hit by a wasting disease similar the one that nearly wiped out sea stars along the B.C. coast. 

"[The wasting disease] has been around a long time and it's taken out sea cucumbers before — but never a mass extinction like the sun star," he said.

'If we lose the vacuum cleaners of the sea ... we are in trouble'

Reed, an avid naturalist and diver, recalls seeing a few sea stars stricken with wasting disease, but said last Saturday's discovery was more devastating. 

On her Aug. 28 dive Reed said that every sea cucumber she saw between the depths of 10 and 25 metres appeared dead. She checked three spots that day: Dolphin Beach, Tyee Cove and Wall Beach, near Parksville.

While Reed did see some mottled animals after the heat waves earlier this summer, she said they now appear to be "just kind of melting in place" and littering the sea from Madrona Point all the way to Blueback Community Park — spanning the entire Nanoose Bay Peninsula.

"It was really, really concerning. I don't think I've ever been so concerned while diving. If those guys go — if we lose the vacuum cleaners of the sea — we are really in trouble," she said.