ALASKA (KGO) -- Scientists say an unprecedented heat wave this summer in Alaska is killing large numbers of salmon.
A recent die-off they say coincided with the heat and they believe "heat stress" is the cause of the fish deaths.
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Heat decreases the amount of oxygen in the water in turn causing the salmon to suffocate.
During a recent expedition one scientist estimated she saw 850 dead salmon but believes the number could be much higher.
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Many of the fish are dying before they even have a chance to spawn.