Some hope among the (sea) stars: Researcher says populations may be recovering from disease
But, despite a boom in baby sea stars, they're not out of the woods yet
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Carlos Robles has spent three decades surveying sea stars in the shallow intertidal waters off the coast of Vancouver Island, but when a mysterious wasting disease almost wiped them out in 2014, he feared their extinction.
Today, he’s a little more hopeful.
“The numbers are still down but it looks like they’re going to recover,” said Robles, a researcher from California State University in L.A.. “That’s really the question, how fast and how far the come-back will be…My guess is that they’re going to recover in the next few years.”
Every year, Robles spends time in Barclay Sound, just south of Uclulet, taking detailed notes and photographs of the area's sea star population.
Robles speaks almost four years after six local sea star species, popularly known as star fish, were hit hard by wasting disease, which causes the sea-dwelling creatures to rot and fall apart.
Robles says the disease caused a steep drop off in sea star numbers.
The secret to the stars' recovery may lie in the recent explosion of food sources, he explains.
Mussels and barnacles are both main food sources for sea stars, but in the absence of the multi-armed predators, their numbers have increased by five to eight times, Robles says. As a result, the sea stars that didn’t die from wasting disease are now “knee-deep in chow.”
“Many of them are chubby…the ones that are surviving are really packing on the weight,” he says.
After the 2014 disease hit, researchers saw a boom in baby sea stars the following year, prompting a widespread and perhaps premature belief that sea stars were successfully repopulating.
In his 15 square-kilometre research area, Robles says the surviving baby sea stars have grown and are now about 15-20 centimetres in diameter, roughly half the size of a full-grown adult.
But, they're not out of the woods yet, he cautions.
“Is that cohort of really young juveniles going to survive, or are they going to get knocked down by disease?...or really come surging back in the next year or two [because there’s so much food available]?”
Jessica Schultz a scientist for the Ocean Wise Conservation Association, says not as many of the baby sea stars in her research area in Howe Sound have survived as she had hoped.
“We haven’t seen too many babies around in recent months. There was kind of a big explosion in 2014 and 2015 with tons of babies, which could be that the sea stars that were sick reproduced quickly as a response to stress...but those super abundant babies that we were seeing in those years kind of disappeared and we don't know why.”
The young sea stars may have also contracted the wasting disease, or simply gone into deeper water, Schultz says. Overall, the sea star population is low and patchy. Predatory stars such as the sunflower stars and the sun stars are still quite rare.
“I wish I could say otherwise, but unfortunately lots of the stars that were most affected by wasting are very rare still,” she says.
I think the word ‘recovery’ should be used quite cautiously."