Climate change killing off Pacific shellfish

Ocean acidification is killing off oysters and mussels in the Pacific Northwest. Shellfish farmers and fisherman are hard hit by the loss of business. Their one hope lies in genomic research. John Dyer reports from Boston.


Billions of scallops and oysters are dying off in the Pacific as the oceans grow more acidic. “It’s like the canary in the coal mine,” said Guy Dean, vice president of Albion Fisheries, a major seafood processor in British Columbia. “That is the early indicator of climate change and how it is going to affect the availability of various products.”

Acidification kills

In the past two years, shellfish farmers and fishermen have seen as much as 90 per cent of their harvest die. The normal attrition rate is around 50 per cent, they said. Island Scallops, a producer in Qualicum Beach, recently lost 10 million scallops as they grew on vertical cages suspended around 10 meters below the water. That’s around three years’ worth of seeded shellfish, or 10 million dollars. Company CEO Rob Saunders had to lay off 10 people, a third of his employees. “I’m not sure we are going to stay alive and I’m not sure the oyster industry is going to stay alive,” said Saunders. “It’s that dramatic.”

Saunders and others believe ocean acidification is to blame. The Vancouver Aquarium has recorded a steady decrease in water pH in surrounding waters, from an average of around 8.1 until 1974 to levels as low as 7.2 in recent years. The lower the pH, the more acidic the water. Acidic waters make it harder for oyster and scallop larvae to form their hard shells. Thinner, more fragile shells make them vulnerable to predators and diseases.

“When the pH goes down, it’s a lot harder to build that shell and we’ve seen that in a lot of other species in the lab,” said University of British Columbia Zoology Professor Chris Harley. “It interferes with everything they do, their basic physiology is affected.”

CO2 causes acidic oceans

According to the U.S. National Oceanic and Atmospheric Administration (NOAA), higher levels of carbon in the atmosphere are likely making the oceans more acidic. The NOAA recently released a report showing that carbon dioxide levels in the Earth’s atmosphere are now around 400 parts per million, a 43 per cent increase from the pre-industrial era.

Mass die-offs of scallops occurred in China in 1996 as that country’s pollution levels went off the charts. Around 2004, oysters started dying in Washington State and Oregon. Acidification was reportedly to blame. Oyster larvae near deepwater oil drilling have also died as carbon levels have increased acid levels in surrounding water.

Industry eying resistant stocks

In the meantime, the Canadian shellfish industry is under threat. It generates around $33 million in total sales per year, three-quarters of which occurs in British Columbia. The industry employs around 1,000 people on isolated seacoasts, where jobs are often few and far between.

Shellfish farmers and fisherman are hoping the Canadian government will take action. They are asking for funding for genomic research that might identify strains of oysters and scallops that can handle more acidic water. “We’ve been aware of these problems for quite a while and we just have to learn to operate our farms under new parameters,” said British Columbia Shellfish Grower’s Association Executive Director Roberta Stevenson. “Genomics offers us an opportunity to develop an animal that is more capable of adapting to this new pH level.”

It is unfortunate that growers have to adapt rather than change the conditions leading to more acidic water, added Stevenson. But they had little choice. “We are hoping to identify brood stock that are more resilient, much like how some families are less likely to get diabetes or heart disease than another family,” said Stevenson. “We need to find the sturdiest parents for our hatcheries that can work in these new conditions.”


Photo credit: artescienza / Creative Commons

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