New study on steelhead genes - "...up to 40% come from wild trout..."

Discussion in 'Steelhead' started by Luke77, Feb 1, 2011.

  1. Very interesting article:


    CORVALLIS, Ore. – Genetic research is showing that healthy steelhead runs in Pacific Northwest streams can depend heavily on the productivity of their stay-at-home counterparts, rainbow trout.

    Steelhead and rainbow trout look different, grow differently, and one heads off to sea while the other never leaves home. But the life histories and reproductive health of wild trout and steelhead are tightly linked and interdependent, more so than has been appreciated, a new Oregon State University study concludes.

    The research could raise new challenges for fishery managers to pay equally close attention to the health, stability and habitat of wild rainbow trout, the researchers say, because healthy steelhead populations may require healthy trout populations.

    In a field study in Hood River, Ore., researchers used DNA analysis to determine that up to 40 percent of the genes in returning steelhead came from wild rainbow trout, rather than other steelhead. And only 1 percent of the genes came from “residualized” hatchery fish – fish that had stayed in the stream and mated, but not gone to sea as intended by the hatchery program.

    “It used to be thought that coastal rainbow trout and steelhead were actually two different fish species, but we’ve known for some time that isn’t true,” said Mark Christie, an OSU postdoctoral research associate and expert in fish genetic analysis. “What’s remarkable about these findings is not just that these are the same fish species, but the extent to which they interbreed, and how important wild trout are to the health of steelhead populations.”

    This research, just published in the journal Molecular Ecology, was based on a 15-year analysis of 12,725 steelhead from Oregon’s Hood River, each of which was sampled to determine its genetic background and parentage. It was supported by funding from the Bonneville Power Administration.

    The study reveals a complex picture of wild trout and steelhead intermingling as they reproduce. A steelhead might be produced by the spawning of two steelhead, two wild trout, or a returning steelhead and a trout.

    Rainbow trout are small to moderate-sized fish in most rivers, but if that same fish migrates to the ocean it can return as a huge steelhead weighing 30 pounds or more, prized for sport fishing. Researchers still don’t know exactly why some trout choose to go to the ocean and others don’t, although they believe at least some part of the equation is genetic.

    Studies of rainbow trout and steelhead have been undertaken, in part, to better understand the implications of hatcheries. Including all salmonid species, more than one billion hatchery salmon are released into Pacific Northwest streams each year. And because hatcheries produce fish that are less able to survive and successfully reproduce in the wild, there is concern about hatchery fish mating with wild fish.

    “One implication of this study is that the genetic contribution by wild trout is diluting the input of genes from hatchery fish to the wild steelhead population,” said Michael Blouin, an OSU professor of zoology and co-author on this study.

    “The genetic influences of hatchery fish on wild steelhead populations are still a concern,” Blouin said. “But the good news from the Hood River is that the hatchery genes are being diluted more than we thought, and thus may not be having as much impact on dragging down the fitness of the wild steelhead.”

    The genetic influence of wild rainbow trout, the scientists said, is roughly cutting in half the genetic input of hatchery fish that reproduce in the wild – a mitigation of their impact that’s of some importance.

    The scientists cautioned that results from one river might not be representative of all steelhead populations. Nevertheless, Christie said, “The importance of trout in maintaining steelhead runs should not be underestimated.

    “They can act as a healthy genetic reservoir and preserve reproductive populations during years when ocean conditions make steelhead survival very difficult,” he said. “So a good way of looking at it is, whatever is good for wild rainbow trout is also good for steelhead.”

    Worth noting, the researchers said, is that most other salmonids, such as coho or chinook salmon, do not have this type of fall-back system to help produce fish with a higher capability of surviving. As such, they may be more vulnerable than steelhead to the concerns about genetic weaknesses produced by hatchery fish.
  2. This is exactly why all steelhead rivers should be Cand R only for ALL TROUT! I think that the 1% dilution of hatchery genetics is very interesting, And I would love...LOVE to see more studies on this race of fish, as well as others to further assess the validity of the study. I have suspected for a long time that the difference in spawning times between hatchery winter fish and native runs would minimize actual interbreeding of the two strains.
    Im not saying the hatchery fish don't spawn, I just think they most likely spawn with other hatchery fish in the system for the most part.
    I would also be interested to know if, when the steelhead and resident trout breed, if it is the case of male steelhead and female trout, or vice versa, or if there is even a propensity towards one or the other
  3. I've always been confused by the distinction between resident and anadromous versions of the same fish. After all, some rainbows live in the same watershed as steelhead but don't go to sea.

    In this study, Mark Christie says that resident fish act as a genetic reservoir in case of a poor ocean return. That is the best reason that I've heard.
  4. Have you ever watched the fish spawning. The little stay at home fish also get in on the action. A small male will actually throw out some sperm on the laid eggs.. So who's to say only the wild fish spawn. A hatchery fish came from a wild fish so spawning is in their genes. All this is beyond me so I don't try to figure any of it out.
  5. See thats what Im thinking old man. Do residents truly breed with steelhead, or is it resident trout males releasing their milt alongside a steelhead pair? Inquiring minds want to know. There are so many intriguing evolutionary adaptations for breeding in salmonids. I was very interested when I learned that some jack salmon imitate the coloring of females to allow them to slip in during paired breeding to release their milt.
  6. Interesting!
  7. The dilution may also be misreprsented because when wild winters spawn with hatchery winters none of the offspring survive to adulthood. You would not see dillution at all unless you studied parr. Even then it stands to reason that given their lack of genetic fitness these crosses would be sampled less frequently.

    WDFW is betting that you are correct with respect to spawn timing. This is only one issue though. It seems downright arrogent to me to think that we can engineer hatchery fish in such a manner that they do not effect wild fish. Further, the real issue with our PS populations is in the sound itself. I have never been given any possible realistic scenario where hatchery fish are aiding in wild fish survival in the PS. I can think of many possible scenario's whereby they have severe negative affects.

    Go Red Sox,
  8. Im not disagreeing with you. In my mind the PS is a pretty tough place to be a migratory fish. I don't think that carrying capacity is exceeded, but with degredation of habit an water quality it might be.
  9. An excellent summary of what has been know (though often ignored) for some time.

    The key sentence in regards to your question in what the life histories parents of those returning adult steelhead is -

    "A steelhead might be produced by the spawning of two steelhead, two wild trout, or a returning steelhead and a trout."

    It has been clear for some time that O. mykiss is a single species that in complex river systems like this region's anadromous waters have complex life histories that are often interwined. Those same complex life history interactions are also seen in our coastal cuttrhoat and bull trout.

    Those mature resident fish are at least as old as their larger anadromous cousins and often there are more repeat spawners in the resident population than the anadormous population. Regardless those resident fish represent a significant diversity of the species and should be consider important from both a genetic diversity and population stability view.

    The resident fish while similar in size to "Jacks" represent more than just age diversity.

    Stilly stalker -
    When an anadromous adult and resident adult interact during spawning by far the most common pairing is a larger anadromous female with a smaller resident male. And yes in those cases the resident male is actively spawning with the female. It is probably important to emphasis that when a female steelhead (or other salmonid) spawns those do so in a series of events. Rather than depositing her eggs all at one time the spawning with be divided into a number separate egg deopistion events. With steelhead the female will deposit her eggs in a dozen or so separate pockets with each separate deposit cover by gravel. The overall spawning process typically takes 1 to 3 days during which the female may construct more than one redd (which can be separated by significant distances).

    Anyway because each of the female's egg depositions are often separated by 1/2 hour to several hours it is not uncommon for a number of different males to fertilize portions of her eggs. While we tend to think of the spawning as a pair of fish it is often the case than more than one male maybe in the area of an active spawing female. When there is more than one male they typically engage in behavior ("fighting") to determine dominance or "spawning rights". That fighting typically includes chasing, butting, and even biting. The dominate male typcially slides along side of the female at the time she releases a portion of her eggs releasing his milt at the sametime. While that is the norm it is not uncommon for a second male to slip up on the opposite side and also contribute to the spawning.

    Have seen a resident male spawn with the large anadromous female under several scenarios. The first is when there are not anadromous males in the area; though there can be multiple resident males. The second is they can be that "sneaker" male that slips up on the opposite side of the female from the dominate male. And finally it sometimes the larger andromous males are so busy with their own battles for dominance they leave the "field' open for the opportunistic resident male.

    I'm in agreement with the importance of CnR of those resident rainbows for the over all health of our steelhead populations it is equally important that any CnR regulations include at least a bait ban (selective gear rules would be even better) whenever fishing occurs. The hooking mortality associated with CnR of bait caught trout quickly negates much of the value of CnR. The resident adults are subject to that hooking mortality whenever they are caught in the summer or winter.

    Tight lines
  10. So Curt, what about the situation of adult anadromous male spawning with a resident adult female? Not happening or just rare? In addition to this, are the chances better of the offspring being anadromous if both parents are as well?
  11. I knew that females had several spawning events. Thank you for the insight into the life history. Good stuff.

    Now imagine they remove the dams from the skagit and let all those resident rainbows re-steelheadify the Skagit!!!
  12. There's a good article about this in an issue of flyfishing & tying journal by John McMillian. I don't have it in front of me, but from what I can recall, steelhead will residualize if conditions are right. Temperature, food and stable flows are somre of the factors. It seems to be more prominent in males, as size is an evolutionary advatage in females. Their offspring may or may not go to sea, dependant on conditions. In that article there's a picture of a pair of steelhead ready to spawn with a "satelite" resident male right behind them ready to sneak in and fertalize.
  13. This is one of the best threads I've read here. Thanks for all your insights. I'm hoping to walk the shores of the Raging, Snoq and Tokul in the known spawning areas over the next couple months so I can watch them breed. Luckily, these are all very close to my house.

  14. ichthus voyeur... :clown:
  15. Luke -
    Whether with bull trout or O. mykiss I have not seen those larger anadromous males spawning with small resident females. While I don't know if anyone knows for sure why that is the case it seems to me that two factors may play a role. One is that those small females often construct their redds in locations (shallow water) that would make it difficult for those large males to be functional spawners. The other of course is that those large males may intimidate the smaller females. Of course both of those would be less of an issue with older/larger females. I have seen resident females well in excess of 20 inches.

    mbcracken -
    You should start seeing some wild steelhead spawning in early March continuing on into June on those streams. The peak spawning activity will be the later part of April.

    Tight lnes
  16. Curt's concern about the impact of bait fishing on preserving resident rainbows is likely to prove to be a sticking point for some. After all, salmon and steelhead eggs are a central part of the arsenal of many gear fishers, especially when fishing for hatchery salmon and steelhead. Expect to hear loud cries if a wide-spread ban on bait fishing is proposed; imagine if bait were outlawed on the Cowlitz.... [Actually, I can; I think that it would become a fabulous trout river - lots of bugs and productivity.]

  17. I think banning roe for bait woud cut WAAAAAAY down on poaching!!! Ive seen so many salmon poached on the Samish just for their eggs
  18. “The genetic influences of hatchery fish on wild steelhead populations are still a concern,” Blouin said. “But the good news from the Hood River is that the hatchery genes are being diluted more than we thought, and thus may not be having as much impact on dragging down the fitness of the wild steelhead.”

    Could this mean that everyone may have to re-think there adamant hatred for hatchery programs and hatchery fish and dams ? Wouldn't that be a bitch if every yuppy blog had to drop that mantra ?????????????
  19. That's one study from one river, most of the evidence points to hatchery fish having a negative impact on wild fish, there are other impacts aside from loss of fitness. I'm not saying that hatcheries don't have a place, but as they are run now they are not the answer.

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