Montana Anglers Urged to Report Fish Kills as Summer Heat Stresses Aquatic Life

As summer temperatures soar in Montana, fish populations face increasing stress from depleted oxygen levels in waterways. The Montana Fish, Wildlife and Parks (FWP) is now calling on anglers to be vigilant and report any fish kill events they observe.

Recent reports of dead or dying fish have emerged from several locations, including Thompson Falls, Noxon, and Cabinet Gorge reservoirs in Sanders County and Rogers Lake in Flathead County. FWP biologists have attributed these small-scale fish kills to a lack of dissolved oxygen, a common occurrence during the warmer months.

"Warm water holds less dissolved oxygen than cold water," explained an FWP spokesperson. "This makes it harder for fish to get enough oxygen, leading to stress and, in some cases, mortality."

The phenomenon, known as summer fish kills, typically affects shallow, productive waterbodies or bays of larger waters with abundant vegetation. As plants begin to die and decay, they further deplete oxygen levels, putting additional strain on fish populations.

While these events are often natural and may go unnoticed, the FWP emphasizes the importance of public reporting. Anglers are encouraged to contact their local FWP office with specific information about any fish kill events they witness. Details such as location, date, number and species of fish affected, and photographs can help biologists determine whether the event is natural or the result of human activity.

"Most of the time, these oxygen 'sags' do not occur in the whole waterbody and do not harm entire fish populations," the spokesperson added. "However, monitoring these events is crucial for maintaining the health of our aquatic ecosystems."

The FWP reminds the public that fish kills can occur year-round due to various factors, including extreme water temperatures, fish diseases, or the introduction of pollutants. By engaging anglers in the reporting process, the agency aims to gather comprehensive data to inform future conservation efforts and protect Montana's rich aquatic biodiversity.