Arctic cod spawned and hatched in captivity

13 May 2015
The new NOAA research suggests that Arctic cod may be the most vulnerable to warming ocean waters. Photo: NOAA Fisheries

The new NOAA research suggests that Arctic cod may be the most vulnerable to warming ocean waters. Photo: NOAA Fisheries

NOAA Fisheries scientists at the Alaska Fisheries Science Centre have developed a deeper understanding of cod development after successfully growing Artic cod in the laboratory.

Until now, this type of research was restricted to the short, ice-free summer period in the Arctic. But, scientists say their success means another step forward in understanding how these ‘bellwether’ fish in the Arctic marine ecosystems may cope with a warming ocean and climate change.

Arctic cod provide an important food source for seabirds, ringed seals, narwhals, belugas and other fish. Compared to other cod species, they are said to be the richest in fat content, but the new NOAA research suggests that Arctic cod may be the most vulnerable to warming ocean waters.

“We’re seeing limited temperature ranges for Arctic cod to successfully grow and survive,” said Benjamin Laurel, research fisheries biologist, Alaska Fisheries Science Centre. “Arctic cod have relatively high growth at 0°C, but are rapidly outpaced by other Bering Sea species including walleye pollock and Pacific cod above 2.5°C.”

“The temperature tolerance for Arctic cod eggs is even narrower, where 5°C is the lethal limit compared to >12°C for these other two species,” he added.

In general, scientists say Arctic marine species require colder water to survive than populations further south, but determining just “how cold” is difficult and requires specialised laboratory space to simulate the Arctic environment.

Young Arctic cod were collected during the summer months in the Beaufort Sea for three consecutive years (2012-2014). The first series of experiments focused on growth of juvenile Arctic cod in response to temperature and food availability. The second series of experiments, which is still ongoing, is focusing on the same factors during the egg and larval stage. At the same time tests were carried out on Arctic cod, scientists conducted comparative studies on walleye pollock, Pacific cod and saffron cod.

In the waters that border Northern Alaska, coastal surface temperatures can already exceed 14°C in the summer. Although offshore shore temperatures are cooler, NOAA predicts temperatures in these regions will increase by 0.5°C per decade. This research suggests that Arctic cod thermal habitat is disappearing. Expansions of temperature tolerant competitor species such as saffron cod may also put additional pressure on the species.

If these northern waters get warmer, beyond the range that Arctic cod eggs and juvenile fish can compete and survive, NOAA says it could have a major effect on the whole marine food chain – top predators may be forced to feed on other fish that are lower in fat content like saffron cod, Pacific cod or pollock and the loss of high quality prey like Arctic cod may make it especially difficult for ringed seals that are already contending with the loss of nursery habitat with shrinking sea ice coverage. 

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