Bluefin Tuna Mysteriously Move to East Greenland Waters

Bluefin tuna have increasingly been spotted in East Greenland waters, and scientists are mystified as to what is driving this northward movement.

Three large bluefin tuna, each weighing in at 100 kilograms, were among several tons of mackerel caught in the area in August 2012. These fish are rare for these waters, and scientists have launched an investigation into bluefin tuna migration patterns and their distributional range.

"Bluefin tuna usually search for prey in areas where surface temperatures are warmer than 11 degrees Celsius. However, because temperatures in August 2012 in the Denmark Strait were so warm, and because one of its favorite prey species, mackerel, had already expanded its range into the region, it is likely that bluefin tuna has expanded or is presently expanding its habitat to more northerly regions," professor Brian MacKenzie, of the Technical University of Denmark (DTU), explained in a statement.

MacKenzie and his colleagues became particularly interested in the idea that climate change could be driving this unusual behavior.

"If summer temperatures continue to increase during this century, and if both bluefin tuna and its prey species are managed in sustainable ways, then it is likely that bluefin tuna could become a regular summer visitor in east Greenland waters, at least as far north as the Denmark Strait," MacKenzie said.

Scientists still aren't sure how many bluefin tuna exactly were in the Denmark Strait in 2012, but normally these waters are too cold for this warm-water species.

The DTU research team is still looking into the reasons why bluefin tuna and its summer dining menu are on the way to more northerly regions than usual.

"Regardless of whether the stock has increased or not, climate-related changes in distributions of commercial fish like these we have seen already for mackerel and herring will mean that international management authorities will need to develop new fishery and ecosystem management plans," added co-author Helle Siegstad.

The research was published in the journal Global Change Biology.