The data raises questions about the health of the Clark Fork fishery

David Brooks and Andrew Gorder

As anglers flock to the streams in the Clark Fork Basin for another fishing season, the hard-working staff at Montana Fish Wildlife & Parks (FWP) have grappled with a sobering question: Is it safe to eat fish anywhere in the Clark Fork River?

Fish problems in the Clark Fork aren't exactly breaking news. Previous FWP testing found high levels of three types of dangerous pollutants in some sections of the river: dioxins, furans and PCBs in rainbow trout and northern pike. This discovery led to a formal notice that the public should avoid consuming fish in certain sections of the river – from the confluence of the Bitterroot to the mouth of the Flathead – due to human health concerns.

But the Clark Fork is a large watershed, and the question remained whether fish in the headwaters or downstream should also be banned. These unknowns led Montana Trout Unlimited (MTU) to work with FWP and other stakeholders, the Clark Fork Coalition, the Montana Natural Resource Damage Program, the Missoula County Health Department and the Confederated Salish & Kootenai Tribes to pool resources to scale and the potential to investigate sources of pollution.

In 2022, MTU secured a federal grant from the EPA to fund water quality and fish tissue sampling at dozens of locations from the headwaters of the Clark Fork to the Idaho border. FWP staff spent the 2023 season deploying samplers in the river and catching fish to test for the presence of dioxins, furans and PCBs. The first results are now available and the picture is likely to be bleaker than before.

Equipment deployed last year detected elevated levels of PCBs, dioxins and furans at the headwaters, again near Bearmouth and downstream from Missoula. Although we await final analysis, initial results suggest that levels may approach or exceed safe limits for human consumption. It is now clear that this contamination is widespread. However, further work is needed to identify their specific causes and develop effective remediation strategies to protect human and ecological health.

What does this new data mean? We don't have a complete answer yet. Professionals with FWP and Montana DEQ must complete their quality control analysis before determining whether advanced advice is warranted. However, two things are certain:

First, anglers should proceed with caution on the Clark Fork. Even in very small amounts, these highly toxic pollutants are known to cause cancer, damage the immune system, and cause developmental and reproductive problems. While more needs to be done to fully understand the 2023 data, great caution would require avoiding fish consumption throughout the river.

Second, the public needs more information. These pollutants are highly toxic and extremely difficult to detect. Testing is expensive, time-consuming, and often leads to questions that require further investigation. In some areas we currently have the resources to investigate the issue.

At Smurfit Stone – a known source of all three types of pollutants – the EPA is studying the site and must do everything it can to quantify and mitigate Smurfit's contribution to the problem. In other areas, we may need to collect more data to identify and eliminate new sources of contamination.

We have gone too far to accept a permanently contaminated Clark Fork fishery, and FWP's findings require a strong response. This applies not only to Smurfit, but also to the upper reaches of the river, where hundreds of millions have already been invested in restoring a badly damaged waterway.

Through the ongoing and collaborative efforts of FWP, DEQ, and a broad range of community stakeholders, we are well positioned to identify and address threats to human and ecological health and work toward a cleaner, healthier Clark Fork.

David Brooks, Managing Director, Montana Trout Unlimited; Andrew Gorder, Director of Legal and Policy, Clark Fork Coalition

Anna Harden

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