As part of their regular monitoring of crab populations the Puyallup Tribe of Indians is tracking the impact of a mysterious ailment that is decimating sea stars.
An outbreak of sea star wasting syndrome was first noticed early last fall in British Columbia. The syndrome starts as small lesions and eventually the infected sea stars disintegrate. Since the syndrome was first noticed, it quickly spread throughout the Salish Sea and along the Pacific coast.
While there have been documented outbreaks before of the syndrome, nothing on this scale has ever been recorded. There is no known cause.
The tribe started regular crab surveys in April 2013. “Since then, we started seeing a lot of sea star by-catch,” said George Stearns, shellfish biologist for the tribe. “One pot near the north point of Vashon Island was literally full of sea stars.”
The tribe regularly monitors eight stations between the north end of Vashon Island and the Tacoma Narrows. Each station includes nine crab pots.
George Stearns (right) and David Winfrey, shellfish biologists for the Puyallup Tribe, count and measure crab caught in a monitoring study in southern Puget Sound.
During the tribe’s early surveys, the sea star population seemed healthy. But, Puyallup tribal scientists recorded a sharp die-off in October. “We saw one monitoring site go from four sea stars per pot in April to 12 in September to zero all together in October,” Stearns said. “We went from catching over 100 sea stars to none within a month at that site.”
“Across the entire area we’re monitoring, we’re seeing a massive decrease in sea star bycatch,” Stearns said. “Some of the sea stars we are finding are literally melting in front of us.”
When a diseased sea star does catch a ride on a tribal crab pot, it deflates quickly. Within a few minutes, a normally rigid sea star will be hanging on the pot like a wet rag.
The main focus of the crab monitoring work by the tribe is to pinpoint exactly when the crab in the tribe’s harvest area molt, or shed their shells.
“Crabbing during the middle of molting, which makes them soft and vulnerable, can increase the handling mortality,” Stearns said. “Its a common practice to shut down harvest during the molt. But, we’ve only had a general idea of when that occurs down here.”
The data collected will also help the fisheries managers put together a more complete picture of crab populations in the South Sound. “We GPS the locations so we’re at the same spots and put the pots in for the same length of time,” Stearns said. “So, we know we’re comparing apples to apples each month.”
Sea star immediately after being caught. Photo by George Stearns.
Sea star five minutes after being caught. Photo by George Stearns.