SITKA — Alaska fisheries officials concerned about the spread of an invasive marine species have denied federal and university researchers permission to study the organism’s effect on herring eggs near Sitka.
Biologist Tammy Davis of the Alaska Department of Fish and Game said Tuesday the state will instead focus on eradicating Didemnum vexillum, also known as D vex, which has been found so far only in Sitka’s Whiting Harbor.
“We feel really hopeful that eradication is possible,” Davis said.
The Sitka Sentinel reports D vex, also known as sea squirt or ascidian, is a carpet tunicate that grows over and smothers other organisms on the sea floor. The slimy organism reproduces quickly and sticks to objects.
It was first detected in 2010 and the department suspects it arrived on aquaculture gear, Davis said. Whiting Harbor, an inlet between the north end of the Sitka airport runway and a World War II causeway, was the site of oyster farming.
The department has requested proposals from contractors to kill the invader. Whiting Harbor covers about 34,783 square feet and patchy distribution of the invasive species covers more than one-third of the harbor.
“It’s been successfully smothered with dredge spoil,” Davis said. The state of Washington has had success smothering D vex with tarping material, which creates an anaerobic environment, she said.
The state last month denied a permit sought by National Marine Fisheries scientists to study the tunicate. Similar research of the organism’s effect on the development and survival rate of herring eggs is underway off San Francisco.
Sarah Cohen, an associate professor of biology at San Francisco State University, said herring spawn in San Francisco around January. She and fellow researchers are analyzing data collected there.
“I’m excited about what we’ve found out so far with stuff down here,” Cohen said. “We did see interactions between the herring eggs and the D vex and I hope we can get that information out really fast.”
The early indication is that it’s “something to be concerned about,” she said.
NFMS research biologist Katherine Miller said Alaska coastlines differ greatly from the ones near San Francisco and scientists were hoping to gather data from Whiting Harbor that could be used for management of the tunicate.
“We don’t know how it affects spawning species like herring,” Miller said. “We thought particularly this (the annual Sitka Sound herring spawn) was a good opportunity to see how it would affect spawning and development of the eggs.”
University of Alaska Southeast associate professors Jim Seeland and Marnie Chapman requested the permit for Whiting Harbor. The project called for boats and other gear to place herring eggs in infested areas.
D vex is spread by objects such as boat hulls and floats.
Miller said the denial surprised her.
“We’ve got a gigantic coastline in Alaska ... There’s a lot of potential vectors for moving (D vex) up here, like boat hulls,” Miller said. “It could easily get into other parts of Alaska. The potential for that is quite high and knowing impacts has a lot of value.”