The 3-million-gallon blowout of mine waste last month didn’t cause a massive die-off of trout in the Animas River, but wildlife officials are concerned about the steady decline of fish populations in the past decade.
In August and early September, Colorado Parks and Wildlife crews conducted a survey of trout numbers in sections of the Animas near Durango and Silverton.
“We did it last year, and normally we skip a year,” Parks and Wildlife spokesman Joe Lewandowski said at the time. “But because of the spill, our biologists decided it’d be a good time to do it again, and see what’s going on.”
A statement from the Parks and Wildlife on Tuesday said the survey did not show effects on fish from the mine spill, but the results did provide a “mixed picture” for trout.
In Durango, officials saw an increase in the overall biomass of fish, but aquatic biologist Jim White said that’s because Parks and Wildlife stocks about 40,000 fingerling trout every year.
Two segments – from the La Plata County Fairgrounds to the Ninth Street Bridge, and from Cundiff Park to the High Bridge – met the “Gold Medal” water status for biomass, a standard of 60 pounds of fish per surface area.
But overall, the river did not meet the Gold Medal status.
Fish greater than 14 inches improved slightly from 2014 – from nine to 11 fish per acre – but the Gold Medal standard is 12 fish longer than 14 inches or more per acre.
Parks and Wildlife officials said the number of large fish remains low, and trout have shown little signs of natural reproduction, issues that wildlife experts have been combating for almost 10 years.
White told The Durango Herald last month a number of factors – less water in the river because of irrigation and less snowfall, urban runoff and higher water temperatures – are the leading cause of the fish population decline.