Kaare Winther Hansen
Biologist and WWF project coordinator in Greenland
Halibut is the second-most fished species in Greenland, where fishing is vital to the economy. For several years, Greenland halibut quotas have been significantly higher than biologists’ recommendations. Scientific stock assessments show that the population of Greenland halibut has declined in the past 10 to 15 years and that the average fish is 10 centimeters (4 inches) shorter than it was a decade ago. Additional surveys are needed to examine issues such as the species total biomass—the cumulative weight of the halibut in a given area—and the possible impact of predators like whales and seals on fish stocks.
In addition, quota-free zones were introduced in 2014, adding over 4,600 tons of halibut caught in the past year alone. But there is even more at stake in Greenland. This year, Greenland's offshore halibut fishery was the first of its type in the world to achieve the coveted MSC label, a mark of sustainability for fish sold around the world. However, the label was conditional on the institution of sustainable quotas for the entire fishery within three years. Greenland halibut in Disko Bay could quite easily be fished to the point where it's no longer commercially viable. Continuing the current policy gambles not just with peoples' livelihoods, but with the international seal of approval that Greenland has worked so hard to achieve. That would result in an economic disaster, and many Greenlandic families will suffer. That kind of damage will take years to repair.
The Arctic will become less productive overall in the long term for several reasons. First of all, most of the newly ice-free waters near Greenland are too deep for some commercially important species like Arctic cod, which will probably seek shallower waters. Furthermore, ocean acidification from carbon dioxide pollution will reduce the productivity of copepods, mollusks, and other shell-making creatures, further changing the Arctic food supply. Finally, warming temperatures might increase the already intense stratification of the Arctic, where warmer water floats on a layer of colder, denser, nutrient-rich water. This may prevent nutrients from the sea floor from reaching the surface and being ingested by the plankton at the base of the food chain.
These are all reasonable concerns, but there may be mitigating factors that could increase the productivity of the Arctic in a warmer world—at least in the short run. For example, deep water will be an obstacle to some species, but not necessarily to all, including some very important commercial species that live mid-way in the water column. Acidification will most likely harm some species in the Arctic food web, but they could be replaced by other species less affected by acidification.