Pink salmon were found near our fishcamp at the mouth of a Yukon tributary (Ananuk River, near Mt. Village, AK) that had died before spawning. One (7.27.19) had been been dead for some time when observed. Another (8.9.19) was still moving, but appeared to die while being observed. Pinks often are found in this side river, but this is the first time we have seen dead fish. Water temperature in both the Yukon and Ananuk was greater than 70°F.
During the summer of 2019, LEO received observations of dead, pre-spawned, pink (Oncorhynchus gorbuscha), chum (Oncorhynchus keta), and silver (Oncorhynchus kisutch) salmon from Golovin, Alakanuk, St. Mary's, Kotlik, Koyuk, Kaltag, Shaktoolik, and Unalakleet. Fishery biologists from the Alaska Department of Fish and Game, and the Yukon River Fish Commission also received reports of unusual salmon mortalities, and conducted surveys along major rivers in the state to understand how many fish had died. In line with the observation of water temperature that George includes, biologists believe that warmer water temperatures and large salmon returns contributed to the salmon deaths.
As Jayde Ferguson, Fish Pathologist with the Alaska Department of Fish and Game, writes in response to an observation form Julie Auliye in Shaktoolik:
High numbers of fish in conjunction with warm temps and thus low dissolved oxygen create a bad situation.
Warmer water holds less dissolved oxygen that fish need to survive.
Staff from the United States Geological Survey (USGS) are writing up a summary of the salmon deaths observed during the summer of 2019, which is planned to be available in the spring.