Fish kills from golden alga have been confirmed at Roosevelt Lake and biologists are continuing to monitor the situation, advised Arizona Game and Fish Department officials.

“Golden alga can produce a toxin that affects gill breathing organisms,” said Marc Dahlberg, acting Fisheries Branch chief. “This toxin is not known to be a health threat to humans.”

This most recent fish kill follows on the heels of a golden alga caused fish kill on approximately 20 miles of the Salt River just upstream from Roosevelt Lake during July.

The current fish die off at Roosevelt appears to be lake wide, affecting primarily gizzard shad, a species that is sensitive to the golden alga toxin. Approximately 30 to 40 large (13- to 15-inch) dead gizzard shad in various stages of decay can be found throughout the lake on a regular basis.

“We suspect that threadfin shad, a fish that is also very sensitive to golden alga toxin, are also being impacted,” Dahlberg said. “However, because threadfin are so much smaller they are probably being rapidly consumed by birds and are not as readily observed as the larger bodied gizzard shad.”

Although golden alga fish kills have occurred in a number of states, scientists are still not sure what environmental conditions actually result in golden alga producing toxins.

Game and Fish biologists said that if environmental conditions do not improve there is a possibility that the golden alga kills could extend to other fish species on Roosevelt and possibly downstream to other lakes as well.

Logo courtesy Arizona Game and Fish Department

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