Pteropods make up 45% of young pink salmon diets. Credit: UAF

Pteropods make up 45% of young pink salmon diets.
Credit: UAF


Argue all you want about climate change – even a Toys R Us chemistry set will prove that the oceans are more acidic.  Recent reports cited dissolving oyster larvae that are devastating west Coast shellfish growers. A new federal study reveals its first findings on how corrosive oceans are  affecting sea life – and it points to big trouble for pink salmon.  NOAA recently announced the first evidence that the high acid content in the Pacific Ocean is dissolving the shells of tiny free-swimming snails called pteropods.

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You might say, who cares about  pteropods?   Well, it happens to be a primary food source for juvenile pink salmon. So you take away the pteropods and you take away the pink salmon.

Mark Green is a marine scientist at St. Joseph’s College in Maine. The tiny snails comprise 45% of the diet of pink salmon; they also are a food source for herring and mackerel.

The researchers at NOAA’s Pacific Marine Environmental Lab in Seattle said the percentage of   pteropods with corroded shells has doubled in areas close to shore since the pre-industrial era.

Study co-author William Peterson said they   did not expect to see pteropods being affected to this extent for several decades.  The number of snails with dissolving shells is likely to triple by 2050, he said, when near shore waters are projected to be 70% more corrosive.

The problem stems from carbon dioxide being released into the air by human industry that is absorbed by the ocean and turned into carbolic acid.   Combine the corrosion with increasing ocean temperatures and the entire marine ecosystem is affected.

Bob Foy is director of the NOAA Fisheries Science Center at Kodiak.

In a 10% increase in water temperature, which is what most people fear in terms of climate change, there would be about a 3% drop in mature salmon body weight. On the other hand, a 10% drop in pteropod production would lead to about a 20% drop in body weight. Obviously the system is fairly dynamic, but the loss of pteropod population would be extremely detrimental to pink salmon populations.  

Pinks make up Alaska’s largest salmon fishery by volume and second only to sockeyes in value. Last   year’s pink salmon catch was  over 95 million fish valued at nearly $100 million at the docks.