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.
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.
Many of the fish are dying before they even have a chance to spawn.
Scientists say heat wave is killing large numbers of salmon in Alaska