Sea Stars: wolves of the ocean floor

Roy L Hales/ Cortes Currents - Kelly Fretwell from the Hakai Institute recently described sea stars as wolves of the ocean floor.

Sea Stars prey on Oysters

The topic came up when I mentioned that they prey upon the oysters in Gorge Harbour, on Cortes Island.

Julia Rendall, President of the Bee Islets Growers Corporation,said they normally eat about a third of her crop. The bottom clusters are “all chewed, eaten.” She remembers the summer that Sea Star Wasting Disease reached the Gorge.

“That was the year I had the very best harvest, for shuck oysters,” said Rendall..”I got about $8,00 a raft instead of $5,000.”

Other oyster growers.have told Hakai researcher Alyssa Gehman that, thanks to sea star wasting disease, they no longer need to hire people to dispose of the sea stars preying on their oysters.

Why having ‘wolves’ on the sea floor is beneficial

“It is an interesting anecdote, but I think having the broader loss of this keystone predator has an even bigger impact,” said Fretwell.

Ochre Sea Stars keep mussel populations in check, so that other species can colonise local ares.

The devastating Sunflower Sea Star losses in the Pacific Northwest has had a terrible effect on kelp. The sea urchins, who are normally kept in check by sea stars, are voracious consumers that can remove entire kelp forests. They turn them into “urchin barrens.”

“Sunflower Sea Stars help keep kelp forests alive and healthy. Then those kelp forests can support a ton of other species that are important for fisheries and the integrity of the food web. ,” said Fretwell.

She added, “Research has shown that when a species is removed from any coastal system, the biodiversity really decreases.”

photo Kelly Fretwell – photo by Koby Michaels, Hakai Institute