Only 'supersalmones' resist climate change

The team of scientists from the University of British Columbia (UBC) studied eight populations of adult sockeye salmon in the Fraser River. The results show that populations with difficult migrations are more athletic, and show a superior swimming ability and specialized cardiac adaptations.

The Fraser River in Canada is known for the great comebacks of red salmon. Photo : Robert Polo.

"This is the first large-scale study of wild fish which tries to show how different populations of the same species have adapted to specific conditions of migration. What worries us is that, as climate change alters the conditions of the Fraser River basin, some people will not be able to adapt quickly enough to survive, "says Erika Eliason, senior study author and researcher in the Department of Zoology, UBC.

The study, published in the journal Science , is "important" for conservation efforts of Fraser River sockeye and may inform efforts to conserve fish biodiversity in the basins around the world.

The temperature of the river, a key factor

The sockeye salmon has been declining since the early 90s. This has contributed to the massive die-offs of migration: between 40 and 95% of some populations of salmon have died en route to spawning.

The Fraser River has warmed about 2 ° C since the late '50s, and the last 20 years have been some of the hottest on record. The high river temperatures have been linked to high mortality.

According to the researchers some sockeye populations are more susceptible to the warming of river temperatures than others. Chilka sockeye salmon, which takes its name from the lake and the river near where spawning may be more resistant to warmer temperatures, while other populations, such as Weaver sockeye, which is named after the creek which spawns seems to be "particularly susceptible".

"The Chilka, which I call 'superfishes' could swim at a higher temperature range and wider in comparison with other populations studied. We think it has to do with the way they have adapted to cope with the difficult migration, "said Eliason.

The population Chilka traveling over 650 miles upstream, with an increase in elevation of one mile, go through the Hell's Gate (an area where the Fraser River plunges into a passage of only 35 meters wide) and travels with the most high summer temperatures to reach a glacial lake to spawn.

To measure the swimming ability of salmon populations, Eliason and his colleagues observed metabolic and heart rates in adult salmon from each of the eight populations. The experiment also found that the optimal water temperature for fish is consistent with the historical river temperatures encountered by each population in their migration routes.

In water temperatures above their optimum temperature, the salmon swimming ability decreased. "Our proposal is that this is due to a collapse of the cardiovascular system," argues researcher.

"Currently, the highest temperatures of the Fraser River during the summer months than the optimum temperature for each population examined, and the temperatures are close to lethal for some stocks", ditch the expert.

The Fraser River, with more than 2,000 kilometers, runs through the province of British Columbia in Canada, and is known for the great comebacks of salmon, in which millions of red salmon typically return to spawn each year. There are over a hundred different populations of sockeye salmon in the basin. To spawn, each population completes a single migration path that varies depending on distance, elevation gain, the temperature of the river and the river flow.

Source: SINC