Are there any wild steelhead left? Yes, there is no doubt. But it is up to us to ensure their future and the fisheries they provide.

In California, Idaho, Oregon, Science Friday, Steelhead Files, Washington by Nick Chambers

A topic that is commonly raised in the steelhead conservation world is whether there are any “pure” wild steelhead left.

Before I answer, I want to take a step back first. There are two types of hatcheries. We have integrated hatcheries, where fish used for broodstock are taken from the same population in which they are planted. These are typically referred to as “wild broodstock” hatcheries. There are also segregated hatcheries, where the fish used for broodstock were derived from a different population and then distributed broadly elsewhere. Examples include the Skamania summer run steelhead and the Chambers Creek winter run steelhead in Washington.

Generally, when people are concerned about hatchery genes being shared with wild fish, they focus on the segregated hatcheries because those fish carry some genes that are from outside populations. I think this is what you are referring to, so I will home in on that and all references hereafter are to segregated hatchery steelhead only – not wild broodstock.

What is regularly asked of us: Are there any wild fish remaining that do not have hatchery genes? This is a question often asked rhetorically by hatchery proponents in arguing that the alleged lack of “genetically pure” wild fish means that we should not try to conserve them and should not curtail hatchery operations. The logic being that the damage has already been done, so let‘s keep the hatchery programs in place.
Frankly, the answer varies by river system and species.




For steelhead, the answer is pretty clear: yes, we have lots of wild steelhead remaining with unique genes adapted to their native rivers — and their preservation is critical to both conservation and fishing opportunity.

One way to study the genetic effects of hatcheries is by measuring “introgression.” Introgression is the contribution of genetic material from one source to another, in this case from hatchery steelhead to wild steelhead. Because hatchery steelhead from segregated programs carry some different genetic markers than those in the wild population, scientists have developed techniques to distinguish a fish with “hatchery genes.” This means it does not matter whether the fish has an adipose fin or not. Scientists can tell the parents and origin from the DNA.

So let’s dive into the details of some research that has addressed this topic in rivers with long hatchery histories. In the Willamette River, where hatchery steelhead have been released for decades a recent study found that the native run of steelhead retained its genetic distinctiveness from the non-native hatchery steelhead. Here is the abstract:


Similarly, a recently published report on the extent of hatchery introgression in north Puget Sound rivers, which like the Willamette, have a decades-long history of hatchery releases found very low to non-existent levels (<2% in almost all cases, and <1% in many places) of hatchery introgression in wild fish. PugetSoundSteelhead_Introgression_TechnicalSummary_WarheitWDFW_Final_141010.
In the Clackamas River, a study found a substantial number of hatchery steelhead spawned in the wild and produced offspring. However, they also found little evidence of successful interbreeding between hatchery and wild fish. Here is the study abstract:


There is also work on rainbow trout (which are the same species as steelhead) indicating that retaining pure native genetics is possible despite extensive, long-term use of hatcheries. For instance, a study in Crane Prairie Reservoir in Oregon, which has been stocked with hatchery rainbow trout since 1955, found that genetically distinct native rainbow trout persisted despite the long history of stocking. Here is the paper:
In contrast, there are studies that have found substantial introgression of hatchery and wild steelhead. For example, research in California found introgression after decades of stocking:


Similarly, research on a small creek on the Washington coast – Forks Creek – found that up to 80% of the naturally produced steelhead in a given year were hatchery x wild hybrids. Here is the abstract:


So yes, there are populations where introgression with hatchery fish is a problem, with some data suggesting it might be worse for summer steelhead. Overall then, and typical of steelhead, there are no absolutes. There is a range. But introgression appears lower than one might think, and importantly, the data indicate that even in places like Puget Sound and the Willamette, a large component of “pure” wild steelhead remain.
So, how can there be minimal introgression in areas with extensive stocking histories?
The answer is simple. Segregated hatchery steelhead survive very poorly in nature relative to wild fish, and though they interbreed at times, few of those fish persist through the rigors of natural selection to reach adulthood. See abstracts for a few examples here, 1), 2)
One might logically conclude that poor survival of hatchery fish means that they don’t pose much of a threat to wild fish, but that conclusion would be wrong for the following reasons.

First, when hatchery fish mate with wild fish they produce offspring that survive poorly and do not return as adults at anywhere near the rate as wild fish. In other words, instead of getting, say, 2-5 adults returning from a wild x wild mating, you might get 0-2 adults returning from a hatchery x wild mating. That is not good for conservation or fishing.

But the problem goes deeper. Poor survival of hatchery x wild offspring means that some wild genes disappear from the population, lost in maladapted fish neither perfectly suited to survival in nature nor the hatchery. This can result in erosion of life history diversity, such as depletion of early-timed winter steelhead (fish that historically returned in December and January), and reduce the reservoir of genetic material that enables populations to withstand the fickle hand of Mother Nature (droughts, poor ocean conditions, floods, etc.)

Steelhead are resilient. But their resilience is codependent on life history diversity, which is reflected in their wide variety of freshwater and marine age classes. The multitude of life histories spreads risk of extinction and survival across a broad web of adaptability. Fewer age classes may work out great during a time of feast, but the risk is high when famine comes – and it always does. This is commonly referred to as the “portfolio effect”: you need genetic and life history diversity to have resilient, productive steelhead populations that can sustain themselves over time.


There is compelling research on this point. Jennifer Nielsen and co-authors examined the genetic structure of several steelhead populations in Idaho, including those that received hatchery plants and those that did not. They found that population size and genetic diversity was significantly greater in the populations that did not receive hatchery plants, and those rivers also had lower levels of introgression. Here is the paper:–Snake%20River%20Idaho.pdf






Of all the Puget Sound rivers, the Skagit River Basin has by far the greatest chance to rebuild and sustain an abundant, fishable wild steelhead population because it possesses both the habitat quality and quantity and population genetics necessary for a robust wild steelhead portfolio to exist.
So, circling back to the answer to the original question: yes, there are plenty of wild genes in many steelhead rivers. And the best thing we can do to both conserve wild steelhead and increase fishing opportunity is to make sure we manage steelhead to maintain and rebuild those wild populations where there is habitat to sustain them. If we don’t, and rely exclusively on hatcheries to support fisheries, we can expect both further declines in wild steelhead and more fishing closures over time as legally mandated protections go into effect.