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Ocean acidification makes it harder for species such as oysters to survive, as high acid levels prevent shells from hardening.John Lehmann/The Globe and Mail

B.C. shellfish producers and restaurant owners are bracing themselves for another price hike for the Pacific delicacies as ocean acidification makes it more difficult for oysters, mussels and scallops to survive.

Shawn Chesney, owner of Oyster Express Restaurant, noted that the prices of shellfish have gone up 20 per cent to 30 per cent in the past three years. It's expected to jump again this year, although by how much is not yet clear.

"It's definitely not what we want to see. … Another increase in price will drive some of our customers away," Mr. Chesney said.

The acidity of global oceans has increased rapidly in the past decades and a dramatic rise of carbon dioxide (C02) is thought to be the main contributor to it.

"C02 has more than doubled in the past century, which dissolves into the water, breaks down into acid and reduces the PH level of ocean water," said Colin Brauner, a professor of zoology at the University of British Columbia.

Prof. Brauner explained that some animals adapt to the change quite effectively, but some don't.

Shellfish are among the most sensitive animals to this alteration because they often have calcium and carbonate shells. The more acidic the water is, the harder it is for shells to grow.

The acidity of water along the West Coast is especially high because deeper water, which tends to be more acidic, often wells up to the surface, Prof. Brauner said.

The expected price hike comes after a challenging couple of years for the industry.

In 2014, a massive die-off of oysters and scallops off the B.C. coast took place and millions of shellfish were found dead. Acidic water was blamed.

Last summer, Vancouver health authorities banned raw oysters in B.C. after naturally occurring bacteria were spurred on by the heat in local waters, making the shellfish potentially toxic.

Roberta Stevenson, executive director of the B.C. Shellfish Grower's Association, said oyster seeds are getting hard to come by.

"Shellfish will become more expensive if this problem continues and we fail to produce enough shellfish for the market," Ms. Stevenson said. "It comes with a lot of challenges because things are different from how it used to be. We don't know what the long-term situation will be."

B.C. shellfish growers are looking for ways to address the acidification problem. For example, they are trying to adjust PH level of waters in the hatcheries and grow shellfish with more acid-resilient shells.

"The best thing to do is to control the carbon dioxide that was created by human activity, to prevent water from being more acidic and create a healthier marine system," Prof. Brauner said.

Fisheries and Oceans Canada has been monitoring the ocean acidity of the Strait of Georgia over the past three years, but Sophia Johannessen, researcher of Fisheries and Oceans Canada, said the problem has probably been brewing for the past 30 years.

Ms. Johannessen said other factors such as climate change, which has led to an increase in seawater temperature and decrease in oxygen level in the water, may also contribute to the shellfish problem.

"A lot of things are going on here. Acidification is one problem, but it also could be a combination of all the factors," Ms. Johannessen said.

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