We had the privilege of catching up with Trout Unlimited Biologist, John McMillan, to talk about his work in the Pacific Northwest. While he is typically diving deep into steelhead research, he also has an immense amount of knowledge on trout populations. In addition to this amazing interview, tune into the Flylords Instagram for an Instagram live with John, tonight at 5:00 PM MT.
FL: How are climate change and warming ocean conditions impacting anadromous fish populations?
John: Great question, and given the poor returns of steelhead across much of the West Coast this year – from BC down through much of Oregon – it is also timely. There are several ways climate change can and has impacted anadromous fish.
Salmon, trout, and char (here on referred to as “salmonids”) all have a range of temperatures they can live in before things become highly stressful and eventually, lethal, which means that the spatial distribution of fish is likely to change depending on the species-specific tolerances for water temperature. Generally, climate change is predicted to increase water temperatures both in freshwater and the oceans, and if the temperatures get too warm, a fish must move or die.
In freshwater, this could eventually push the distribution of salmonids further north in latitude and/or higher up in elevation. For example, salmonid species that are partly or wholly resident, such as inland cutthroat and rainbow trout, may need to spend larger portions of their life in higher elevation habitats to avoid warmer water temperatures in lower elevation locations. They could also alter their life history by only utilizing the lower elevation habitats during the coolest periods of the year, and then relying on the higher elevation, cooler habitats during the hottest times of year. In both cases, fish will have to adapt to keep pace with a changing climate.
If the ocean does become too warm and/or we continue to experience warm “blobs” of water holding in the North Pacific, the impacts will likely depend on the species. A warming ocean could eliminate some species that do not have a freshwater life history, such as pink salmon and chum Salmon. On the other hand, steelhead and rainbow trout are the same species and can give rise to one another, and there is evidence that declines in survival of steelhead can lead to increases in resident rainbow trout. It is therefore possible that the anadromous steelhead life history could be dramatically reduced or extirpated, but the species as a whole could persist as resident rainbow trout if freshwater conditions are sufficient. The same is true for coastal cutthroat trout.
“As my dad loves to say, Nature will bat last.”
These are very general answers, of course, because it is very difficult to predict how quickly and broadly temperatures may become unsuitable for salmonids. From a process perspective, there is some interesting science on the strength of the ocean currents that circulate water from north to south. These ocean currents are also critical to creating upwelling, which provides cool water and rich sources of food for juvenile salmonids entering the ocean. If the circulation system continues to weaken and eventually break down, it could be devastating for salmonids. That said, if things get that bad, some models predict the warming phase will be relatively short-lived and we could revert back into another ice age, which would be very challenging for humans, but awesome for salmonids. In other words, just because things are heating up now, doesn’t mean our climate will continue to warm without an equal reaction back the other way at some point in time. As my dad loves to say, Nature will bat last.
FL: With steelhead numbers on the decline in most places, how is this impacting local trout populations in some of these rivers?
John: Oncorhynchus mykiss, the scientific name for steelhead/rainbow trout, are my favorite species, both as scientists and anglers. I love them for their remarkable diversity. O. mykiss occupies the broadest range of habitats across the Pacific Coast, from Baja California up to the Aleutian Islands. One reason they do so is because of their ability to withstand warmer and cooler temperatures and because they have both resident and anadromous life histories in their evolutionary tool-belt. Therefore, it is possible, as I mentioned earlier, that as steelhead declines, resident rainbow trout could become more prevalent.
The data I am familiar with suggests it will take a longer period of poor ocean survival to dramatically shift the population away from anadromy and more towards residency. In Russia for instance, it took at least a few generations of poor steelhead returns before rainbow became more prevalent. The latest period of poor ocean survival started around 2016. If this continues for another 5-years, there could be some measurable changes. Unfortunately, though, very little data exists on rainbow trout compared to steelhead, and in many rivers, the number of steelheads returning each year is not monitored. For instance, I live on the Olympic Peninsula, and we have data on the abundance and distribution of returning steelhead, but we don’t have any data on rainbow trout. The same is true for most of the steelhead populations from Alaska down to California and inland to Idaho. Unless we begin collecting that type of information, it will be difficult to track how populations change.
FL: Can you talk about the work that has been done on the Elwha River?
The Elwha River has been front and center for a tremendous amount of monitoring. I would be remiss then not to mention that a great deal of work has and is done by Lower Elwha Tribe, NOAA/NMFS, Olympic National Park, USGS, USFWS, WDFW, and many other agencies. Basically, a lot of really cool work has been done so far, and that work, though it has slowed a bit, continues to track various aspects of dam removal.
I’ll try to nail it down to a few major points.
First, dam removal had a clear impact on the river, fish, and insects. The main-stem Elwha below the dams became choked with fine sediment during and following dam removal, though sediment loads are now at what scientists consider to be fairly normative levels. That is good for the fish and the other types of life in the river. Nonetheless, research indicated that the high levels of sediment dramatically reduced the abundance of fish and insects in the river below the dams, up to as much as 95% depending on the year and location. Now, 10-years after dam removal started, we are seeing a sharp resurgence in many salmonids and a big increase in insect production. Essentially, the river is back to looking like a normal river, and the fish and insects are taking advantage of the more stable environment.
Second, among species, bull trout and summer steelhead have shown a remarkable increase in abundance since dam removal. Not only are bull trout more abundant, but they are also larger, and many fish are now migrating to the ocean and then back up above both dams into the headwaters where they spawn. Summer steelhead nearly became extinct prior to dam removal. Each year, I counted only 1-3 adult summer runs below the dams. Some were stray hatchery fish, others were unclipped, but we were unsure of whether they were originally from the Elwha or from somewhere else. The cool part is that the summer run population in the Elwha is now the largest population of summer runs on the Olympic Peninsula and is likely the largest population along the entire Washington Coast. Pretty amazing for that to happen within a few years of dam removal, and that is one reason that Trout Unlimited partnered with film-maker Shane Anderson to produce a short movie on Elwha summer steelhead, which can be found HERE. The response of both species underscores that dam removal can be a critical strategy for increasing the survival and resilience of formerly depleted stocks of fish.
Third, much of dam removal was focused on restoring the fabled runs of large-bodied Elwha River Chinook Salmon. The fish were rumored to exceed 100lbs, and discussions with members of the Elwha Tribe indeed suggest the river once supported a very large Chinook. Since dam removal, they have produced very few natural offspring, presumably because they mostly spawn in the main-stem Elwha below the dams, and their redds and juveniles experienced very difficult conditions. Recently, however, the fish have started to turn things around. The abundance of naturally produced Chinook smolts has sharply increased, and we are starting to see more diverse juvenile life histories than we did prior to dam removal.
Last, while the river conditions and fish are generally improving, the fish are still not out of the woods yet, so to say. Some species, such as chum salmon, pink salmon, and sockeye salmon have not responded with similar gusto, likely for a variety of reasons. This is not surprising. That said, the Elwha provides a beacon of hope in an otherwise challenging climate.
FL: What were the steelhead counts when the dam was there and what are they are today?
John: Before the dams were removed there was about 100-300 wild winter steelhead below the dams, though the population may have occasionally reached larger numbers in years when ocean survival was good. We only documented 1-3 summer runs a year.
Since dam removal, the number of winter runs, which includes a hatchery broodstock program (a program where wild fish are used as broodstock) run by the Lower Elwha Tribe, has increased up to 1,500-1,600 fish in the best years. The summer run population, for which hatchery fish are not released, has ramped up to as many as 900 fish in a year. It’s great to see this kind of trajectory, though I believe there is still room for many more winter and summer-run steelhead in the Elwha. This is just the beginning.
FL: Why are dams so bad for fish species?
John: Dams have a number of bad effects, but I tend to think there are two major ones.
First, dams without fish passage block migration within rivers and to and from the ocean. There is nothing worse than blocking the pathway of migratory species like salmon and steelhead. It essentially eliminates the fish that were formerly produced above the dams.
Second, dams dramatically change streamflow and temperature regimes. For example, both dams on the Elwha blocked the downstream transport of sediment, so the main-stem Elwha contained a higher frequency of larger boulders and cobbles below the dams. This limited the amount of spawning-size gravel for salmon and steelhead, and almost eliminated the potential for smaller-bodied fish that use even smaller-sized gravel when spawning. In places like the Snake and Klamath Rivers, water temperatures tend to get warmer in the long, stagnant pools formed behind the dams. The combination of slower water and warmer water temperatures can also lead to greater productivity of invasive warm-water species, such as small-mouth bass and catfish, both of which are known to prey on juvenile salmon and steelhead. Essentially, salmon and steelhead have evolved to live in free-flowing rivers, and while they also take advantage of lakes and beaver ponds, free-flowing rivers create a myriad of diverse habitats and niches that favor different species in different locations of the river. Dam construction homogenizes the habitat, usually worsening conditions for salmon while simultaneously improving conditions for invasive competitors.
Further, there is an interaction between fish migration and the lakes formed behind dams. For instance, juvenile salmon and steelhead tend to use the river’s current to help them migrate downstream to the ocean. With dams in place, they are forced to swim without any assistance, sometimes for hundreds of miles, resulting in reduced survival. And even if passage is available for adults, as we see in the Columbia and Snake Rivers, the stagnant, warm impoundments that form behind the dams can result in stressful and lethal temperatures for upstream migrating adults, leading to high mortality rates in warm years.
FL: A unique species that you study is coastal cutthroats, how are they different than your normal resident cutthroat trout?
John: I do love cutthroat. Like steelhead, they display a lot of life history diversity, and they also love the rainforest rivers that I call home. The main difference with coastal cutthroat is that some of them go to the ocean, while our inland sub-species, such as Westlope and Yellowstone cutthroat, do not because they can’t access the ocean. That said, Yellowstone cutthroat can attain larger sizes than our coastal cutthroat, even the anadromous ones because they also undertake migrations to and from lakes. In those situations, the lake basically acts like an ocean.
The Elwha is somewhat unique among our coastal watersheds in that it doesn’t have many coastal cutthroat trout. The Elwha is predominantly a rainbow trout/steelhead stream. There is however one small creek in the Elwha that is home to a very cool population of cutthroat.
Both fall and spring spawning fish have persisted through and after dam removal, and we are collecting DNA to evaluate the genetics of fish in different locations. I’ll try to provide you an update on that once the research is suitable for publication.
FL: What can someone who doesn’t live in the PNW do to make a difference for these fisheries?
John: Absolutely, there are many ways that people can get involved and try to help the fish and the fisheries they support. One way is to join a group or organization that is focused on conservation, like Trout Unlimited. We have a presence in every state where there are salmonids in the USA, and we have a large number of local chapters where people can get to know their watersheds and learn about ways to help conserve the fish and their habitat. We also have a series of blog posts that people can read to learn more about fish and conservation, and there are a lot of ways for members to learn from TU staff and scientists.
I would also recommend getting to know one’s own favorite fish and watershed, especially local ones. Improving knowledge about local fish and science is critical because more informed people make better advocates. If you have a favorite fish or river, look for opportunities to learn more about those places. Additionally, it’s important for anglers to keep abreast of fish runs because as we see this summer, many populations of steelhead are struggling. One way to be conservative is to try and reduce our impacts individually, either by catching fewer fish or by using more difficult methods. Essentially, don’t focus on fishing as a numbers game, try to enjoy the whole experience, our fish populations are under a lot of stress trying to keep pace with climate change, and if we want the next generation of anglers to have a chance at these fish, we will have to make some sacrifices in our life.
Last, but not least, I suggest reaching out to local biologists that work in a person’s home watersheds. TU has many local biologists working across the USA, but so do agencies and other groups. Biologists can help anglers better understand the fish, their habitat, and their challenges, and it is fun because anglers often learn new things to help them become more effective stewards.
FL: Are their takeaways from the Elwha we can apply to other struggling river systems?
John: I think so. The project underscores how valuable dam removal is. I understand that some dams are unlikely to be removed to breached. But there are also dams that, like the Elwha, are aging, outdated, and if not unsafe, they simply aren’t providing the services they once did. Further, given the effects of climate change and the depleted status of salmonids, dam removal may be more critical than ever.
Dam removal or breaching can restore natural river processes, including thermal and flow regimes, transport of sediment, and formation of habitats – like riffles, pools, and side-channels. That is something that should happen in almost all rivers where dams are removed. In the Elwha, the former lake beds have become some of the most important habitats for spawning and rearing salmon, steelhead, trout, and char. They have extensive floodplains, which are low gradient reaches where the river can spread over and across the terrain as the river flow increases. This helps disperse energy and store sediment, and it establishes the types of lower energy habitats that fish need during floods. And it has helped increase the diversity of gravel and cobble in areas below the dams, dramatically increasing the amount of spawning habitat.
“Breaching dams is the only way to improve the migration corridor sufficiently to ensure that fish remain healthy enough to get in and out of those high-quality upstream habitats.”
There are floodplain habitats underneath the reservoirs behind the four dams in the lower Snake River, and if the dams were breached, the floodplains and side-channels could offer similar benefits to fish as we have observed in the Elwha River. Such habitats will likely help expand the distribution of spawning and rearing salmon and steelhead, and they could provide pitstops for juveniles and adults that are migrating through the system, either downstream to the ocean or upstream to their spawning grounds.
Dam removal in the Elwha also renewed access to high-quality, protected habitat in the Olympic National Park. There is also an abundance of high-quality habitat in the upper Snake River basin, and while the four lower dams have passage, an abundance of salmon and steelhead reaching those habitats has declined since the dams were constructed. In the Snake, getting to and from that habitat requires one of the longest salmon migrations in the world, and it is made all the more difficult by the long series of stagnant impoundments. Breaching dams is the only way to improve the migration corridor sufficiently to ensure that fish remain healthy enough to get in and out of those high-quality upstream habitats.