"In contrast, the Gates Creek sockeye stock, which have a higher thermal window, experienced few problems with the same high river temperatures that year."
In further investigations, the UBC team captured and placed individual fish in holding tanks of varying temperatures to simulate traversing different river temperatures before releasing them simultaneously back to the migratory run. Fish released from a high holding temperature were half as successful as those from colder environments at reaching their spawning grounds.
In a separate study, fish were intercepted during migration and implanted with biotelemetry trackers. None of the tracked salmon survived after release at river temperatures above the thermal window (at 19.5 degrees Celsius). Fish released at a cooler river temperature one within the thermal window later in the summer had much greater survival rates.
"This study shows that an increase over the past 50 years of 1.8 degrees Celsius in the Fraser River's peak summer temperatures is too much too fast for some salmon stocks," says Farrell.
"It also shows that climate change affects even the same species differently because individual populations may have adapted to their respective environments. As a result, we must develop strategies based on population or even watershed to predict, manage and conserve stocks."
Farrell adds that the same concepts may be applied beyond salmon management as another recent study co-authored by Farrell and published in the journal Science has revealed similar findings for fish and squid from the Atlantic Ocean.
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| Contact: Brian Lin brian.lin@ubc.ca 604-822-2234 University of British Columbia Source:Eurekalert |