Warmer Rivers Impacting Health of Salmon Populations

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” Our study has shown that high temperatures push certain sockeye
salmon stocks beyond their thermal window, resulting in
cardiovascular failure and death,”

“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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Warmer Rivers Impacting Health of Salmon Populations

University of British Columbia
Public release date: 12-Nov-2008

Contact: Brian Lin
brian.lin@ubc.ca 604-822-2234

UBC study establishes formula for predicting climate change impact on
salmon stocks

University of British Columbia researchers have found a way to
accurately predict the impact of climate change on imperilled Pacific
salmon stocks that could result in better management strategies.

The findings, among the first to quantify a relationship between
river temperature and salmon mortality rate, are published in the
current issue of the journal Physiological and Biochemical Zoology.

While climate change and rising river temperatures have been linked
to dwindling salmon stocks, other factors have made it difficult to
measure the exact impact – these including diseases, fisheries and
man-made structures such as dams and fish ladders.

“Calculating the affect of climate change on animal fitness has been
particularly challenging for scientists,” says lead author Tony
Farrell, who is jointly appointed in the Dept. of Zoology and the
Faculty of Land and Food Systems.

“Animals have a thermal window, or high and low temperatures between
which they are at their best for aerobic activities. Our study has
shown that high temperatures push certain sockeye salmon stocks
beyond their thermal window, resulting in cardiovascular failure and
death,” says Farrell.

Led by Farrell and Prof. Scott Hinch in the Dept. of Forest Sciences
and the Institute for Resources, Environment and Sustainability, the
UBC team has been studying Pacific salmon using biotelemetry trackers
for a decade. They have identified the optimal thermal windows for
several species of Pacific salmon, which coincide with the historic
temperatures the fish would have encountered while migrating in the
river.

In 2004, unusually warm river temperatures and earlier entry into the
Fraser River system contributed to the “disappearance” of 70 per cent
of the Weaver Creek sockeye stock.

“We analyzed river temperature data and the sockeye’s migration dates
and found that almost half of the population likely experienced
temperatures that would cause a complete collapse of aerobic scope,”
says Farrell.

“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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