Low oxygen levels likely cause of mass fish die-off in Nevada, USA

Wildlife officials are trying to figure out the cause for mass die-off of fish in manmade lake Sparks Marina along U.S. Interstate 80 east of Reno. Nevada Department of Wildlife spokesman Chris Healy said that over the past month, an estimated 100 000 trout, bass and catfish have died in the marina. The die-off is apparently the result of a dramatic, unexplained drop in dissolved oxygen levels.

Healy said for The Associated Press that 'the 100 000 dead fish figure is something that is probably a pretty conservative guess,' and estimated they've stocked close to 1 million adult fish in the lake since they started in 1998. 'We don't know if any small fish have survived, but for all intents and purposes, the fishery doesn't exist anymore.'

"Scientists say a bitter cold snap could have caused oxygen-poor waters to rise from the old rock quarry's bottom to the surface, but they don't understand what sparked the massive die-off. Fish biologists confirmed low oxygen levels caused the death of an estimated 3 000 fish in one corner of the lake in mid-December, but Healy said they thought at the time that the event was localized and of limited impact. Since then, they've been unable to detect any live fish in the 77-acre lake. Numerous dead fish have been removed from the lake's shoreline, and Healy said it's likely the rest sank to the bottom."

For Reno Gazette-Journal, Healy said that oxygen levels at depths of 10 and 25 feet measured between 1.1 and 1.9 parts per million on Monday. 'Fish, particularly trout, require much higher levels of dissolved oxygen to survive, really between 5 and 6 parts per million.'

Featured image: Screenshot from Reno Gazette-Journal interview with Chris Healy.