Colorado Officials Report Massive Fish Die-Off: Here’s What Happened

by Amy Myers
colorado-officials-report-massive-fish-die-off-heres-what-happened

Recently, Colorado Parks & Wildlife (CPW) has been monitoring a massive fish die-off across multiple lakes, and the cause behind these aquatic deaths is nothing short of troubling.

The department first reported these die-offs on September 9, when the issue had hit Mann-Nyholt Lake in Adams County, about 20 miles north of Denver. According to officials, there were three parts to the equation that ultimately resulted in the death of “numerous fish.” The first was a recent algae bloom that took over the surface of the water. Acting as a detrimental shield, a large algae bloom can cut off the dissolved oxygen supply to the aquatic creatures below, leaving them to suffocate. Even worse, CPW reported that the area was also experiencing high water temperatures at the time. And to top it all off, the lake also had “lower levels of running water feeding into the lake.”

As a result, dead fish began to wash ashore.

CPW District Wildlife Manager Jerrie McKee stated in the release, “Some species are more susceptible as dissolved oxygen levels fall and include minnows and gizzard shad, which is the majority of the die-off at this time.”

Elaine T. Valente Lakes Has More Than 500 Dead Fish on Shoreline

Along with Mann-Nyholt Lake, Elaine T. Valente Lakes, a group of three lakes just northwest of the Rocky Mountain Arsenal, saw a much more detrimental situation. More than 500 dead fish collected along the shores of the east lake and hundreds more washed up along the north lake. Similar to the previous die-off, the cluster of lakes experienced a large algae bloom as well as high water temperatures. CPW stated that the event will directly impact aquatic life and fishing conditions “in the immediate future.”

On Twitter, the department shared photos of the distressing aquatic events. In them, several belly-up fish floated towards the edges of the water. Meanwhile, a green cloud of algae lurked below the water’s surface.

In particular, the Elaine T. Valente Lakes lost hundreds of gizzard shad, bluegill, crappie, bass and carp. At the very least, though, “There are no dead fish on the west lake, which is the most shallow of the three lakes.”

According to CPS Wildlife Manager Travis Harris, “conditions were caused by several factors. High water temperatures, lower levels of running water feeding into the lake, and an algae bloom have all resulted in lower levels of dissolved oxygen available for aquatic life. Some species are more susceptible as dissolved oxygen levels fall and include minnows and gizzard shad, which is the majority of the die-off at this time.”

As officials work to control the algae blooms and conditions of these two locations, CPW has also alerted staff at other state lakes and may “conduct additional monitoring and testing as they see necessary.”

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