(CNN) — Scientists are blaming rising temperatures for reduced salmon populations in parts of Alaska.
Researchers on a river expedition last month found more than 800 dead salmon.
When they inspected the fish, they couldn’t find any signs of parasites or infection.
Many of the salmon were also carrying healthy eggs.
Researchers concluded record high temperatures in the water was responsible.
Stream temperatures near Anchorage surpassed 76 degrees this year for the first time since record keeping began in 2002.
Warmer water makes it difficult for salmon to absorb the oxygen they need to breathe.
Ecologists worry reduced salmon populations will work their way up the food chain and impact animals that eat them, like Orca whales.
A fishery in Bristol Bay, Alaska is reporting the opposite.
The largest sock-eye salmon fishery in the world is reporting a boom in the number of fish it is seeing return.