By Montana Grant

Posted: May 11, 2023

Brown trout populations in Montana are on the decline. The Bighole, Bighorn, and now the upper Clarks Fork are all showing dramatic changes in Brown trout. There seem to be several reasons why the Browns are in trouble.

Brown trout are not native to North America. They were introduced to the continent from Europe. Montana’s Brown population are a result of stocking. Hatchery programs promoted this species since they could withstand warmer waters and spawned in the Fall, as do Brook trout. Rainbows and Cutthroats spawn in the spring.

Browns are more aggressive than other trout and can quickly take over a trout watershed. Last year, a Dam malfunction caused the Madison River to lose most of the year’s class. Dewatered spawning gravels were impacted by low flows.

The Upper Clark Fork’s brown population began to decline when the Berkeley Pit water was treated and released at the Horseshoe Bend Treatment Plant in Butte. The EPA set water quality requirements and allowed treated water to flow into the Clark Fork’s headwaters. The human disturbance is releasing dissolved solids downstream. The toxins are in the mine waste and in the remediated watershed soils. The Anaconda smelter discharge flows into 3 settling ponds at Warm Springs. They used to isolate/collect/settle much of the pollution. This is no longer the case.

The Brown trout population went from 1,800 trout per mile down to 25! Biologists are surprised but the water being released appears to be the Smoking Gun. This treated water still contains high quantities of heavy metals, Selenium, and Strontium. Studies show that reproduction failure is a result of contact with these elements.

Other watersheds and the Clark Fork are also being impacted by dewatering, raised water temperatures, increased conductivity, and PKD, (Proliferative Kidney Disease). As variables change, fish populations are the first to show signs of a problem. Whitefish are also being impacted. Habitat destruction is also a concern. Loss of shoreline vegetation means less shade and cover for fish.

The final nail in the trout’s coffin is the dramatic increase of fishing pressure. Record numbers of fishermen are also causing higher mortality due to poor Catch and Release skills. Trout can only be caught and handled so many times before the stress kills them. Cell phone selfies and catch records take time to photograph and film. Some anglers film every fish that they catch for bragging rights. Improper nets, long fighting times, dropping and squeezing fish, and excessive pressure are taking their toll.

Browns are the canary in the coal mine!

Montana Grant

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