West Coast shellfish farms impacted by ocean acidification
West Coast shellfish growers have learned to work around upwellings of corrosive waters and save the lives of their bivalve stocks.
Increased levels of carbon dioxide, or CO2, in the atmosphere are changing the chemistry of the oceans, making it more acidic. The CO2 surge stems mostly from coal and, to a lesser degree, oil-fired power plants. The resulting off kilter acidity reduces carbonate, the mineral building block of shells, skeletons and corals.
In 2005, oystermen first noticed failures in natural sets in Willipa Bay in southern Puget Sound, followed by failures at two of four of the region’s major shellfish hatcheries.
“In 2008 our oyster larvae production was off 60 percent, and 80 percent in 2009,” said Bill Dewey, director of public policy and communications for Taylor Shellfish Farms in Shelton, Wash., the nation’s largest producer of farmed oysters, clams, mussels and geoducks.
At first, the growers believed the killer was a lethal, naturally occurring bacterium, but expensive filtration did nothing to stop the larval die offs. Then ocean acidification blipped onto the radar screen, Dewey said, and new testing equipment proved it was the culprit.
“It became very telling very quickly that when the oyster larvae were dying en masse, it was because we were bringing in very corrosive water. The oyster is still growing a shell; it’s just that it is dissolving from the outside faster than they can grow it. So eventually they lose that race and they die,” he said.
Growers credit Washington Sen. Maria Cantwell for acting fast to get funding for monitoring equipment last year to help the $110 million industry adapt to the corrosive seawater.
“Now we can see what’s going on with the sea water chemistry and deal with it in real time,” Dewey said. “We have learned how to essentially dodge it and produce our larvae around those corrosive events.”
Wind direction provides the biggest warning when to plug intake pipes to the shellfish holding tanks. At the Whiskey Creek Hatchery, for example, growers have learned when the wind shifts from the south to the north, they have a 24 hour window before corrosive water shows up at their intake pipe. Other growers also have learned to fill shellfish tanks late in the day instead of mornings, and to use water intakes at different depths.
Research has also shown that bivalves use three different types of calcium carbonate to build their shells in stages, and not all shellfish are equally prone to corrosion. Unfortunately, Pacific oysters turn out to be one of the most vulnerable, Dewey said.
Meanwhile, early detection and gentle south winds have allowed Taylor Shellfish to rebound to record production for oyster larvae this year. Dewey said he is confident that the farmed shellfish industry, at least, will be able to thrive.
“I think we will survive and figure out a way through this,” Dewey said. “But I don’t think it bodes well for other species in the ocean and fishing interests that rely totally on natural production.”
Understanding the impacts of ocean acidification on food webs and ecosystems is a focus of Robert Foy, director of the NOAA Fisheries Science Center in Kodiak. He points to tiny snail-like pteropods, which comprise nearly half of the diet for pink salmon.
“Their physiology will be affected, they’re not going to be able to grow,” Foy repeats in his awareness efforts. “A 10 percent drop in pteropod production would lead to about a 20 percent drop in pink salmon body weight. The loss of that diet source would be extremely detrimental to pink salmon populations.”
A new article in the journal Nature Climate Change says, “the fish are OK,” belief ignores an important knowledge gap – the possible effects of CO2 during the early development of fish eggs and larvae.
Catch stats shuffle
Alaska’s 2012 groundfish quotas show some unexpected increases. The quotas were decided last week by the North Pacific Fishery Management Council, which oversees fishing in federal waters three to 200 miles offshore. Groundfish catches make up more than 80 percent of Alaska’s total fish landings each year.
Notably, Gulf of Alaska fishermen were bracing for a decrease in sablefish, or black cod, but instead got a nearly 15 percent increase to 13,000 tons, or 28.5 million pounds.
Likewise, for Gulf Pacific cod, the catch was expected to tumble a bit, but instead was increased by one percent to 65,700 tons, or 145 million pounds.
Also in the Gulf, pollock catches next year were bumped up 21 percent to 116,444 tons, or 256 million pounds.
The fish story isn’t quite so rosy for the Bering Sea, where some stocks are cycling downwards. For sablefish, the 2012 catch was trimmed nearly 10 percent to 4,280 tons, or 9.5 million pounds. The Bering Sea pollock harvest was decreased by 4.2 percent to 1.2 million tons, or 2.6 billion pounds. Better news came for Pacific cod: Bering Sea fishermen got a 14.5 percent increase to more than 500 million pounds.
Back in state waters, managers have announced a preliminary harvest of 29,008 short tons for the 2012 Sitka Sound sac roe herring fishery, an increase of nearly 10,000 tons. A final decision will be made in February.
Pollock pay back
Students at the Northwestern Alaska Career and Technical Center, or NACTEC, in Nome are putting the finishing touches on a shiny 16 foot aluminum boat they’ve built, made possible by a $100,000 donation by the Pollock Conservation Cooperative, an industry trade group made up of companies that harvest pollock in the Bering Sea.
The boat and fabricated trailer provide more than just an opportunity to travel rivers – it has enabled hands-on welding, construction, engineering and other skills to prepare for workforce entry into fisheries-related careers, said NACTEC Director Doug Walrath.
The vocational training center serves students and adults in 16 communities in the Norton Sound and Bering Strait regions. The seafood industry presents a wealth of opportunity for jobs at all levels, said Stephanie Madsen, Executive Director of the PCC and At-Sea Processors Association, when she presented the $100,000 check to the NACTEC board last week.