Can We Restore Native Brook Trout?
As you read the title, your immediate answer probably depends a bit upon where you are and on what "restore" means to you. No doubt, there are some bright spots for Brook Trout (Salvelinus fontinalis) here in Wisconsin and throughout their native range. At the same time, over much of their native range, they have lost significant ground - mostly to Brown Trout (Salmo trutta) but in some places - like the Great Smoky Mountains - to Rainbow Trout (Oncorhynchus mykiss; Larson and Moore 1985).
Chris Collier images (above) - before and after of a fish passage project on a northeastern Wisconsin trout stream. Trout Unlimited in the Great Lakes watershed of Northern Wisconsin are doing great work restoring Brook Trout through improving fish passage and other efforts. I talked to Chris and reported on our conversation in an earlier post on restoring the neighborhood - read more. Even in Southeast Wisconsin - not exactly the "troutiest" part of Wisconsin - our Trout Unlimited chapter was doing work on Brook Trout streams but these were largely remnants and small spring runs. And the Coulee Region Chapter has supported a number of Brook Trout projects and studies. But in much of southern Wisconsin, Brook Trout are losing significant ground to Brown Trout (Maitland and Lanza 2022 and my recent post on that paper).
A recent paper out of the lab I earned Ph.D. many years ago, Huntsman et al. 2022, has a simple, declarative title, "Non-native species limit stream restoration benefits for Brook Trout". It is a question I have pondered - first before graduate school in the early and mid-1990s as I fished Wisconsin's Driftless Area and found few native Brook Trout. Then in West Virginia, my dissertation research was downstream in the Cheat River and its tributaries, but I did a lot of field work in the Shavers Fork where this paper is from. And upon returning to Wisconsin, the question remained but I came into it much more informed.
Shavers Fork is a large, complex system and the lab's research was in the headwaters which were largely in the Monongahela National Forest, what we always referred to as the Upper Shavers Fork. Despite the remoteness of this area, it is not without impacts, many of them historic. The forest was clearcut before being sold to the federal government, mining occurred in parts of the watershed, a railroad parallels the stream - providing access to the trees that were harvested but caused stream widening and thermal stress, and acid precipitation has plagued the watershed. But Upper Shavers Fork was once an angling destination for the rich and famous who traveled there for the river's large native Brook Trout.
This history of degradation, climate change, stocking and establishment of non-native Brown Trout and Rainbow Trout, and factors like perched culverts that prevented access to spawning grounds (Liller 2006) all contributed to a watershed that relied mostly upon stocking in the mainstem but Brook Trout remained in the tributaries - though often quite suppressed by acid precipitation. Limestone was added to some of the tributaries that were accessible by old forest roads or the railroad, largely with the goal of increasing the pH of the spring snowmelt to allow trout to be stocked into mainstem. However, liming also allowed for more successful spawning, giving fisheries managers hope that the watershed could be further restored.
My involvement at Shavers Fork was early in the process, our efforts were part of trying to better understand the watershed, the stream's habitats (Petty et al. 2001), and how fishes were distributed and interacted with the watershed (Petty et al. 2005, Petty and Thorne 2005, Liller 2006, Petty et al. 2012), even their genetics (Aunins et al. 2015). As science does, others built on that early work, allowed for the planning of watershed restoration, and eventually the assessment of those efforts (Merriam and Petty 2019, Trego et al. 2019, Huntsman et al. 2022).
Aerial photo showing j-hook structures designed to alleviate stream bank erosion and increase availability of pool habitat (Photo by P. Kinder; from Merriam and Petty 2019).
What we - and I use "we" very loosely as I had long since left West Virginia and was not involved in the restoration or the assessment of the restoration but I still feel part of the lab - found was that restoration was successful but non-native fishes, mostly Brown Trout, limited this success (Trego et al. 2019, Huntsman et al. 2022). Like many places, Brook Trout persist but they are often pushed to the margins and into suboptimal habitats. One of the lessons from this that is widely applicable elsewhere is that the main stem river is important not only to allow Brook Trout to move among tributaries but as an important foraging habitat. Huntsman et al. (2016) found that Brook Trout that had stable isotope signatures indicating that they foraged only in tributaries were smaller than those Brook Trout that fed in the main stem of Shavers Fork. Brook Trout in the main stem diets shifted to crayfish and small fishes and allowed for greater growth (Petty et al. 2014).
I spent the space and time talking about Shavers Fork in West Virginia as it, 1) is a great bit of nostalgia and was a lot of fun for me, 2) it was hopefully interesting to you, 3) it is as well a studied Brook Trout restoration project as there is, and 4) it is illustrative of the complexities behind our initial question, "can we restore Brook Trout when non-native trout are present?".
The above was the view from about 30,000 feet but hopefully you learned a little something about Brook Trout and Brown Trout interactions from another part of the Brook Trout's native range. More importantly, I had fun doing a bit of reminiscing.
Shavers Fork Links
Stewards of Shavers Fork - 48 minute video
Shavers Restoration & Fly Fishing - Fly Rod Chronicles - 21 minute video
Train Trip Up Shavers Fork Shows of Stream Restoration Project - 3 minute video
EBTJV - Upper Shavers Fork Instream and Riparian Habitat Restoration
What Does This Mean For Wisconsin and the Midwest?
Wisconsin and the Midwest faces many of the the same issues as does Shavers Fork. We suffer a similar history of degradation - the impacts of forestry, sedimentation, habitat alteration, large woody debris removal, fish passage barriers, invasive / non-native species, and others. And, of course, we too are working to try to preserve and protect - and restore when necessary - our native Brook Trout. And like Shavers Fork, our Brook Trout live in a riverscape (Fausch et al. 2004) that is often dominated by a non-native "invader", Brown Trout.
There are also some pretty significant differences between Wisconsin and West Virginia. Few of our streams suffer from acid precipitation as our bedrock and soils typically have greater buffering capacity. However, in an interesting twist, Brook Trout are typically less susceptible to low pH's (Grande et al. 1978) which may actually give them a bit of a foot up in West Virginia streams. Our streams tend to be lower in gradient, at least the tributaries to larger rivers. And due to our greater buffering capacity, Wisconsin streams are generally more productive. I do wonder if that in addition to less climatic warming in northern Wisconsin, tanic acids and lower pH's of northern streams allows for greater survival of Brook Trout compared to their Brown Trout competitors.
Back to the first paragraph and the original question; can Brook Trout be restored to Wisconsin watersheds? Without a question in my mind, yes they can but there are caveats. I mostly fish the streams of Vernon and Crawford Counties, western Richland County, and the southern parts of La Crosse and Monroe Counties. In this area, Brook Trout populations are unquestionably strongest where Brown Trout populations are absent or - for reasons I do not fully understand - Brown Trout are present but have remained at low densities. In my experiences, streams that have had habitat manipulation projects - call it restoration if you prefer - have seen increases in Brown Trout and decreases in Brook Trout populations. But this is not necessarily a cause and effect situation. While some have assumed that these improvements have changed streams to be "more Brown Trout friendly" and that other habitat manipulations may favor Brook Trout. In particular, it has often been repeated that Brown Trout prefer overhead cover and Brook Trout prefer instream cover. I have my doubts that eliminating overhead cover and increasing mid-channel current obstructions will benefit Brook Trout when Brown Trout are present. Similar improvements in Brown Trout populations occurred in streams that have not been manipulated and those that have been manipulated in what we think of a more "Brook Trout friendly" ways. This leads me to think that climatic and other large-scale factors are more responsible than are habitat preferences - but it does not rule out habitat changes as part of the explanation.
Then the second part is the question of what "restore" means as there are many different views on that word. From a "stream health" (Index of Biotic Integrity) perspective, restore typically means communities return to resemble those of pre-settlement communities or of the best current communities in the area (reference reaches). As I wrote about in an earlier post, those are two quite different end points. Pre-settlement conditions are quite a difficult and imperfect target and comparisons to the best reaches has its own flaws. Restoration to pre-settlement conditions means not having non-native (invasive?) species - namely Brown Trout in this case.
If we want to restore Brook Trout, removing Brown Trout or reducing their populations to a level where their impact on Brook Trout is greatly reduced is probably a necessity. This, of course, is quite difficult and in many places, nearly impossible. In so many Driftless watersheds, that ship has sailed - there are so many Brown Trout and the number of stream miles holding Brown Trout so vast that there is little chance of Brook Trout restoration. So we have restored Brook Trout in streams above barriers or those that drain into large, warmwater rivers - in tributaries to the Mississippi River, the Lower Wisconsin and Kickapoo Rivers - where large stretches of warm water greatly reduce the likelihood of Brown Trout colonization. By and large, this has been successful but are Brook Trout truly "restored" if they occupy only small headwater streams?
Back to lessons from Shavers Fork which tell us that access to larger streams allow Brook Trout to grow faster and larger (Petty et al. 2005, Petty and Thorne 2005, Merriam and Petty 2019, Trego et al. 2019, Huntsman et al. 2022) and that barriers alter the genetics of Brook Trout populations (Aunins et al. 2015) but Brook Trout showed a quick genetic response to barrier removal (Wood et al. 2018). We, of course, know the importance of access to larger, forage-rich habitats from coaster Brook Trout management on Lake Superior - access to the big lake is what "creates" coasters (Schreiner et al. 2008). If we are restoring Brook Trout to small, isolated stream reaches that protect them against competition and predation from Brown Trout, are we really restoring Brook Trout? I would argue we are not but we are doing the best we can given the circumstances and I would rather see some Brook Trout only streams than no Brook Trout or the occasional Brook Trout in a sea of Brown Trout.
In other parts of Wisconsin - like Chris Collier and Trout Unlimited's work in northern Wisconsin with the WDNR, US Forest Service, native tribes, and many others - we stand a better chance to restore Brook Trout into larger, intact watersheds. In these areas, the removal of barriers has allowed access to spawning grounds as well as access to better foraging habitats - and maybe better refugia - the three legs of Schlosser's (1991) dynamic landscape model (for a post on the topic).
So, can we restore Brook Trout to Wisconsin streams? My answer is, it depends. It depends on where - we have better chances in northern Wisconsin and more limited opportunities in the Central Sands and Driftless Area. And we have better chances where Brown Trout populations have not yet been established or are at levels were removal, increased harvest, and other management actions can reduce their impacts on Brook Trout. True restoration probably involves an intact riverscape (Fausch et al. 2004) where Brook Trout are able to access complementary habitats (Schlosser 1991). Maintaining this for Brook Trout in the presence of Brown Trout is difficult and maybe not possible. But it does not mean we should not try. It also means that our efforts in places where we have maintained but maybe not truly restored Brook Trout above barriers are still important as in many places, that is likely the best thing we can do for Brook Trout.
It is a complex question with few simple answers. While Shavers Fork is maybe not restored, it is in a better place than when we started our work around 2000. Brook Trout in a number of places in Wisconsin are also in a better place - though there is still a long way to go. Long live the native Brook Trout!
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Fausch, K. D., Torgersen, C. E., Baxter, C. V., & Li, H. W. (2002). Landscapes to riverscapes: bridging the gap between research and conservation of stream fishes: a continuous view of the river is needed to understand how processes interacting among scales set the context for stream fishes and their habitat. BioScience, 52(6), 483-498.
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