Is climate change driving Arctic char upriver?

Arctic char are a pretty incredible animal. They are the most northern freshwater fish on earth, can live for over 20 years, have incredible coloration, can grow to over 30 pounds and are voracious cannibals. Arctic char are the trout of the north, and they thrive in frigid, dark habitats.

In most of their range, Arctic char are classified as semi-anadromous. Many adult fish migrate out into the ocean in the spring and return to freshwater in the fall, where they spawn and overwinter in lakes. However some individuals stay put in freshwater year round, and in some cases entire populations stay permanently in freshwater.

In a study in the journal Global Change Biology, researchers from Norway and Sweden investigated how Arctic char migrations might change with a warming climate in the north. Many bird populations are showing altered migratory timing in response to climate change, but would there be similar effects on fish?

First the researchers needed to determine what factors influenced migratory behaviour in Arctic char. Why did some some populations migrate out to the ocean while others stayed put in freshwater? They found out that migration was more common in areas with low primary productivity, and in areas with shorter migration distances to the sea. So if there was lots of food around, and the sea was hard to reach, char might be convinced to stay in freshwater throughout the year.

Next, the researchers used climate models to predict the change in productivity of lakes along the coast of Norway, and how this might influence the range of Arctic char. Various climate models predicted that primary production in lakes will increase with climate change, and as a result there will be more food available for char in freshwater. This led the researchers to predict that there will be less anadromous populations, and more freshwater populations of Arctic char in the future. Ultimately, this will decrease the range of Arctic char, since less fish will migrate out to the ocean. The researchers don’t speculate on whether this will influence overall population size of Arctic char, but there might be fewer spots to fish for them in the future.

Citation: AG Finstad and CL Hein. 2012. Migrate or stay: terrestrial primary productivity and climate drive anadromy in Arctic char. Global Change Research 18, 2487-2497.

Link to the paper here

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