Arctic char adapted to “life in a freezer,” Norway research finds

Arctic char have adapted to a life in the freezer, says research from the Norwegian Institute for Water Research. (PHOTO BY JENNY JENSEN/AKVAPLAN-NIVA)

The sun is now bringing more light back to the Arctic regions, with the promise of even brighter days and some spring ice-fishing not that far off from now.

But if you wonder what Arctic char were doing during the coldest, darkest days of winter, it’s simple: nothing.

And if you want to know what they’ll do during the longest days of summer, the fish will stay up, 24-7.

Norwegian researchers looked at the daily rhythms of 23 Arctic char in a lake on Bear Island, off Norway’s High Arctic coast, for their paper called, “Freezer on, lights off! Environmental effects on activity rhythms of fish in the Arctic,” which was recently published in Biology Letters.

They found that even under the ice and snow, the activity levels of Arctic char generally followed the cycle of light.

Char are visual feeders and are capable of foraging for food at “very low temperatures and light levels,” said the researchers, who determined that the fish are able to detect changes in subsurface light levels, even during the polar night and under ice.

However, during the darkest two weeks of winter solstice and throughout the midnight sun period, in June and July, the daily activity rhythms of the Arctic char in the study broke down, the researchers found.

Char became inactive in the darkness and conversely the fish showed “high rates of around-the-clock activity under the midnight sun.”

“This suggests that around-the-clock activity is advantageous in these periods. Distinct cycles of feeding, growth and reproduction are functional for a fish adapted for life in the freezer,” Kate Hawley from the Norwegian Institute of Water Research said in a release on the research.