Fish Populations and A River In Peril
As you may have seen already, in two recent Montana Standard articles from this year and last ( River in Peril, 2022 & Still in Peril, 2023 ), trout populations in the Big Hole have been struggling mightily. While the issue has appeared to be broadly occurring throughout southwest Montana, the Jefferson Basin and Big Hole in particular seem to be experiencing the worst of it. In fact, FWP has called it “a population crash” within a basin that encompasses the very headwaters of the Missouri River.
The short version: brown & rainbow trout populations have been on a downward trend for a number of years, but within the last few the decline has been dramatic and historic. In fact, the most recent fish counts conducted by MT FWP in the spring of 2023 showed a population that is the lowest on record since counts began in the 1960’s.
And we don’t know why.
Here are the most recent graphs from electroshocking surveys for the 3 surveyed sections of the Big Hole River:
*In the uppermost of section surveyed - MT FWP biologist Jim Olsen and his colleagues estimated less than 1,000 brown and rainbow trout per mile
*The middle section surveyed & overlayed on the established management goals (wherein populations dictate which angling regulations are adopted) - The Melrose section is estimated to have fewer than 500 brown and rainbow trout per mile.
*Lowermost section surveyed - The Hogback Section of the lower Big Hole is estimated to have between 500 and 700 brown and rainbow trout per mile.
That’s pretty alarming data.
But what’s most troubling for the folks that depend on a healthy Big Hole for their livelihoods, is the fact that biologists have also noted a lack of recruitment of young-of-the-year (i.e. juvenile) fish. Without strong recruitment of these next generation fish, the historically bad numbers may quite possibly continue to get worse until this problem is identified and addressed.
This is a crisis for the multitudes which depend on a healthy Big Hole. Jobs, businesses, and communities are on the line. In Beaverhead County, fly fishing, hunting and the outdoor economy generates more than $167 million annually and supports over 1,400 jobs. That doesn’t even account for the influx to Butte-Silver Bow, Anaconda, Deer Lodge.
An apparent bureaucratic shift away from prioritizing research and towards a focus on “customer service” has resulted in the inability to provide the data and support needed to ensure healthy ecosystems, while also making it impossible to provide good customer service to the folks who come here to recreate because of the quality of these rivers, and in doing so, support businesses and families in Beaverhead County through their spending.
So What the Hell is Going On?
Water quantity, water quality, eutrophication, rapid growth and development, climate change, increased recreational pressure…. these are all factors at play in this decline.
The effects of climate change are certainly having incontrovertible impacts on ecosystems throughout the Rocky Mountain West in the form of lower overall snowpacks, weakened & earlier runoff, lower flows & fewer bank-full days, higher water temps, higher spring temps & faster melt, lower soil moisture levels, and longer, more severe wildfire seasons, among many other well-documented and measurable effects. This is settled science.
*Trends in April Snowpack in the Western United States, 1955–2022
*Change in Peak Snowpack Timing in the Western United States, 1982–2021
We also know that eutrophication - excessive richness of nutrients in a body of water, frequently due to runoff from the land or wastewater, which can cause a dense growth of plant life and a resulting lack of dissolved oxygen - has a negative impact on the reproduction, respiration, and growth rates of both fish and macroinvertebrates.
*Top pictures of the Big Hole during a huge cladophora algae bloom in August 2020
*Bottom pictures of a toxic HAB (Harmful Algae Bloom) on the Beaverhead in the fall of 2019
What about T. bryo?
Tetracapsuloides bryosalmonae (T. bryo) is a myxozoan parasite of salmonid fish. It is the cause of proliferative kidney disease (PKD), one of the most serious parasitic diseases of salmonid populations in Europe and North America that can result in losses of up to 90% in infected populations.
This is a possible explanation for population decline. But it is only recently being studied in the Big Hole by a MT Tech graduate student, Paul Helfrich. We hope that his doctoral research is supported so that we might gain insight into the presence and extent of T. Bryo in the Big Hole and whether it is contributing to or driving this decline.
You may recall that the Yellowstone River experienced a major PKD outbreak in 2016. Though that situation affected mostly the native mountain whitefish, it was a large mortality event that saw a swift and robust response.
An interesting aspect of T. bryo is that infection and susceptibility seem to be exacerbated by eutrophication (i.e. nutrient pollution). And in the Big Hole, through laboratory analysis, we’ve documented regularly elevated levels of nitrogen & phosphorus, well over the numeric thresholds that indicate a negative impact on beneficial uses.
We’ve seen this trend for the last 3 years and it appears to be shifting aquatic communities and is contributing to a negative impact on recreation.
But, while all those things are having a clear impact and make fish populations more susceptible to stress and disease..... they don’t necessarily appear to be the primary driver of this basin-specific crash, which leads us to the probability of disease and the need for resources to get experts in to figure that out.
Certainly, the Big Hole has seen its share of troubling fungal outbreaks in the recent past, none more significant than in 2017 where there was a large die-off in brown trout. Those populations were well within the “ideal range” when they collided with a tough drought year and high water temps during the physiologically-burdensome spawning season. Many of us clearly remember the saprolegnia-plagued fish and the many large dead browns of spawning size that fall. Since then, we have only seen decline.
*A 26” dead brown from Oct. 2022, collected by a local guide
*Collected by FWP in the fall of 2022
Perhaps the most glaring oddity about this whole decline is two-fold:
1) Brown trout are widely understood to be the most temperature & pollution tolerant of the trout species, and
2) Why haven’t the rainbows or brookies or cutthroat increased and filled the void left by these declining browns?
This brings us to the conclusion that some kind of disease is a very possible driving factor in this decline. Something that is causing mortality, but more importantly, preventing survival of eggs or juvenile fish or both.
But, as noted in the MT Standard article, Montana has yet to provide additional resources to our frustrated biologists who lack direction, funds, and expertise to study and address a complicated issue of fish pathology. For nearly 1.5 years, during this population crash, Region 3 (which encompasses all of southwest Montana) is still without a permanent Fisheries Manager to give guidance to individual watershed biologists and direct resources to them.
Beginning two years ago, businesses, individuals, and conservation groups attempted to collectively persuade the Governor’s Office to create a multi-agency Cold Water Fisheries Task Force to “focus efforts on protecting and preserving Southwest Montana’s cold-water fisheries, water quality, and wild salmonid populations through identifying meaningful policy changes, seeking proactive agreements with landowners, and implementing science-based long-term solutions to address the declining health of Montana’s iconic cold water fisheries.”
So far, that call has gone unanswered.
It’s a stressful and frustrating situation we’re facing, and it demands immediate focus. So, let's hope that some attention to the matter can spur action to address this problem on the Big Hole, the greater Jefferson basin, and southwest Montana before it has a serious negative economic impact…. since it appears the ecological impact is already here.
We depend on the State to ensure that a clean and healthful environment is proactively maintained on our behalf, as is explicitly afforded us in the State Constitution.
Regardless, I’ll leave you with a final thought…..despite what is recklessly implied in some circles, either directly or indirectly, disparate user groups are not enemies of one another. We all depend on the same things for our lives, livelihoods, and enjoyment:
healthy water quality & quantity, robust riparian zones, public access, and healthy fish/game populations.
These are needs and, in fact, rights, that should cross the aisle.
As for us here at BHRF, we will continue to collect important baseline data and provide it to anyone interested so that good, well-informed management decisions can hopefully be made for the benefit of all users.
