THE FATE OF NORTH UMPQUA SUMMER STEELHEAD: The Problem and the Solution
In 2021, 347 summer steelhead crossed the Winchester Dam to head up to their ancestral spawning streams in the upper reaches of the North Umpqua River. When settlers first arrived, a man could catch a wagon load with a net in one morning. Even when accurate counts began in 1948, after decades of habitat loss and dam building, summer steelhead consistently numbered in the thousands through most of the late 20th century. Now, these 347 fish are all that stand between this iconic run and extinction.
In recent decades, winter steelhead have done comparatively well, with numbers typically in the six to twelve thousand range. Why have these two very similar runs fared so differently? The graph below tells a compelling story.
First, a bit of background: There’s an old saying among fish biologists that the abundance of anadromous fish (fish that hatch in freshwater streams, migrate to the ocean, and return to their home streams to spawn) is affected by the four Hs: habitat, harvest, hydropower, and hatcheries. I would add a fifth H for “heredity”. Although all of these factors are operating in the North Umpqua, the different fates of summer and winter steelhead runs can largely be explained by looking at how the last two Hs – hatcheries and heredity – interact.
In the last few decades, geneticists have discovered that the traits inherited from a pair of parents are affected not only by the information encoded in the DNA of each set of genes, but also by environmental signals that can turn those genes on or off. This phenomenon is referred to as epigenetics, and epigenetic changes can be passed to offspring for at least two generations. For example, a 2013 study found that when mice were exposed to the scent of cherry blossoms (something they had never encountered in their laboratory cages) and were then shocked, their offspring and their offspring exhibited fearful behavior when exposed to the same scent (1).
A more recent study has shown that hatchery conditions, including feeding practices that accelerate growth and result in early maturation, can alter the epigenetic developmental programming of steelhead trout(2). This epigenetic re-programming happens when steelhead are raised in concrete tanks and fed artificial diets. Crowded conditions and numerous small injuries also contribute to changes in gene expression in hatchery steelhead. These epigenetic changes result in “…decreased fitness of hatchery-reared fish and offspring in the wild, and changes in age at spawning, morphology, growth rate, brain morphology, anti-predator behavior, and migration” leading to reduced reproductive success in the wild. The authors conclude that “The impacts of hatchery exposures are not only important to consider on the fish exposed, but also on future generations and on the evolutionary trajectory of fish in the river populations.”
So, what happens when wild fish cross with hatchery-reared fish? A study published last month that looked at the relative biological fitness of hatchery vs wild (natural-origin) pink salmon (closely related to steelhead) in Prince William Sound concluded that reproductive success was significantly lower for hatchery vs natural-origin fish(3). The data suggested that the offspring of two hatchery-origin parents have the lowest reproductive success, with hybrid offspring having intermediate success. Epigenetically altered genes are potentially heritable in salmonids, with alterations found to extend to the sperm of adult male steelhead and salmon(2,4). Although this is not the only factor affecting the fitness of hatchery-raised fish and their offspring – heritable genetic traits, as well as behavioral, phenotypic, and ecological differences, are also influential – it clearly has serious implications for wild runs that spawn concurrently with hatchery-reared fish.
Hatchery managers attempt to keep wild and hatchery stock separated – hatchery-reared fish theoretically should return directly back to their hatchery rather than moving upstream to where wild steelhead spawn. But this is often not the case, possibly due in part to epigenetic modifications affecting migration behavior. In fact, the Oregon Department of Fish and Wildlife has documented that nearly one-third of summer steelhead spawning in North Umpqua upland streams are of hatchery origin.
So, what is the solution to the precipitous decline in North Umpqua summer steelhead? Another look at the graph reveals the answer.
Notice that the winter steelhead hatchery program was discontinued in the early 1990s. Interestingly, two generations later wild winter steelhead populations rebounded to their highest abundance since counts began in 1948, while wild summer steelhead continued to decline. This is strong evidence that hatchery fish are detrimentally impacting the wild run by reducing biological fitness and increasing direct competition for food and habitat.
Based on these fish counts and the latest science, the North Umpqua Coalition (a partnership that includes Umpqua Watersheds, the Native Fish Society, the Steamboaters, The North Umpqua Foundation, the Conservation Angler, and Trout Unlimited) is demanding that the Oregon Fish and Wildlife Commission direct the Oregon Dept. of Fish and Wildlife to immediately discontinue the summer steelhead hatchery program on the North Umpqua. Beyond the failure of the program to support wild fish, there is no economic reason to continue rearing hatchery steelhead. They do not make up a significant proportion of salmon species caught by the commercial fishing industry, and they are rarely caught by any but the most skilled sport fishers. The North Umpqua is a world-renowned steelhead river, and anglers come from all over the world to test their skill against these wily creatures. An all-wild steelhead river with healthy year-round runs would drive even more sport fishing dollars to our economy.
Discontinuing the summer steelhead hatchery program will give the remaining wild run a fighting chance to survive and once again thrive in the North Umpqua. We owe nothing less to this iconic natural treasure. Look for ways to help in upcoming issues of our online Watershed Moments.
1 Callaway, E. Fearful memories haunt mouse descendants. Nature (2013). doi.org/10.1038/nature.2013.14272
2 Nilsson, E, Sadler-Riggleman, I, Beck, D, Skinner, MK. Differential DNA methylation in somatic and sperm cells of hatchery vs wild (natural-origin) steelhead trout populations. Environ Epigenetics (2021). doi: 10.1093/eep/dvab002.
3 Shedd, KR, Lescak, EA, Habicht, C, Knudsen, EE, Dann, TH, Hoyt, HA, Prince, D. J., Templin, W. D. Reduced relative fitness in hatchery-origin Pink Salmon in two streams in Prince William Sound, Alaska. Evolutionary Applications (2022). doi.org/10.1111/eva.13356
4 Leitwein, M., Laporte, M., Le Luyer, J., Mohns, K., Normandeau, E., Withler, R., Bernatchez, L. Epigenomic modifications induced by hatchery rearing persist in germ line cells of adult salmon after their oceanic migration. Evolutionary Applications (2021). doi.org/10.1111/eva.13235