Riainbow or steelhead?

Discussion in 'Steelhead' started by Smalma, Sep 3, 2007.

  1. Smalma

    Smalma Active Member

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    These topic seems to come up frequently - most recently on the "Tolt River reprot" and "Skookumchuck rainbow?"

    Below is a copy of a post I made in the Tolt discussion and thought that it might merit a thread/discussion of its own. Hope folks don't might and apologizes to the orginal posters on the other topics if I have "stolen" their threads; I encouorage interested readers to visit those dicussions as well. But thought that the topic might get a boarder reading in a separate thread.

    "First let's make it clear that resident rainbows and steelhead are the same species of fish and what we call rainbows and steelhead are just expressions of two different life histories for the same species. In fact it is very common for a single population of coastal O. mykiss (as well as interior pouations on anadromous waters) to express both life histories at the same time.

    There is a great plasticity between those two life histories with the two spawning togethter, steelhead spawners producing some resident fish and resident spawners producing steelhead smolts. The relative abundance of those life histories is typically determined by the relative survival of each life history. That survival often is a function of marine survival, freshwater habitat features, and fisheries management options. For example during periods of high smolt to adult survivals the balance is typically tipped towards steelhead the same happens in streams where management selects strongly against the resident life history (allowing the retention of resident adults, use of bait, etc).

    Typcially in western Washington steelhead smolts (those fish migrating to sea in the spring) are between 5 and 9 inches long. Obviously when those young fish are caught during the previous summer as parr/pre-smolts they are smaller as they have not fished that year's growth. As one catches O. mykiss in one of our western Washington streams the probability that it is a resident fish (fluvial lifehistory) increases for those fish over 9 inches and by the time they are 12 inches long probability that it will become a steelhead is quite low.

    Conservely as the fish get larger there is once again an over lap between what might be a steelhead and a resident rainbows. Based on scales I would say that on Western Washington anadromous streams most adult (sexually mature) resident fish are between 14 and 18 inches. However some may reach more than 2 feet long. Returing steelhead can be as small as 15 or 16 inches (winter run jacks and half-pounders) and some one salt summer steelhead may only be 19 inches long.

    Clearly there is considerable over lap between "rainbows" and "steelhead" both in size and population interactions. That said in regards to the Tolt I have personally caught fish from its anadromous waters that based on scales (fish 6 or 7 years old and having spawned several times) that were clearly "rainbows"/resident fish and were more than 18 inches long.

    If one is fishing anadromous waters and catching only fish that are less than 8 or 9 inches long you are likely catch parr that are mostly likely destine to smolt and become steelhead. If you are catching mostly fish over 12 inches you are catching fish that not likely to migrate to the salt. On some of our waters you will likely encounter a mix.

    I have found that I can tip the scale towards catching more "rainbows" and fewer "steelhead pre-smolts" by modifying my fishing methods. Avoid use of smaller flies if searching the water (using larger nymphs and streamers). If there is a hatch going on I closely watch the rising fish looking for one that appears to be larger and target only those fish. Generally I find more resident fish (at least ones that I can catch) in those more lightly fished areas and if looking for "bows" I like to hike a ways from access points and focus on the "high quality" holding water. Finally during the cooler water periods (from say late October to late May) the sub-adult fish are less active (mostly hiding in over-winter habiats) while the larger adult fish are out and about and by being observant one can stumble across opportunities to target those larger "bows".


    Tight lines
    Curt
     
  2. yuhina

    yuhina Tropical member

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    Very nice and interesting post, Curt.
    Any reference for the information you mentioned above? Is the life history form determined by the enviromental factors? I am very interested in these questions... thanks for the post...
    Sincerely,
    Mark
     
  3. Jim Fitz

    Jim Fitz Member

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    Quite interesting. Thanks for sharing.
     
  4. Milt Roe

    Milt Roe Active Member

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    The upper Tolt fish community is dominated by resident rainbows instead of the more typical resident cutthroat most often found in headwater systems on the west side. So there will be a fair number of resident rainbows drifting downstream into the anadromous zone compared to other systems.

    Rainbows, steelhead, and coho appear to restrict resident cutthroat population where they overlap, mostly as predation on the young of the year cutthroat. Once they reach 50 mm or so, cutthroat can hold their own with those species.

    Interestingly, there are a few westslope cutts on the S fk Tolt.
     
  5. Josh

    Josh dead in the water

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    Where do hatchery fish fit into this equation? Two weeks ago on the Methow, I caught a few 12+ inch fin-clipped hatchery fish. The answer might be that I am off on the size, since I didn't take the time to measure them perfectly.
     
  6. jackchinook

    jackchinook Member

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    Josh, that's an interesting question.

    I used to work with WDFW hatchery evaluation in Twisp with steelhead and Chinook and that was one of the main uncertainties that we investigated. Specifically, the proportion of the stocked SH population that residualized...basically deciding to become 'rainbows' rather than 'steelhead'. These are fish that were reared from anadromous steelhead gametes, raised to smolts size in the hatchery, then released in the spring with the managers' objective of heading directly out to sea as steelhead.

    There are a number of theories for why residualism may be taking place, or increasing, or whether it's natural, but the fish may be getting mixed messages by being raised in a hatchery where they have high juvenile survival, plenty of food, and stable environmental conditions....then they're stocked into a system in the beginning of the summer and they think it's pretty darned nice...maybe we'll stay around a while. Granted I'm totally anthropomorphizing the smolts, but on a population level this is sort of what's happening. As Curt said, O. mykiss is a very plastic species, able to exhibit a high degree of variation in life history, even within a population. The issue may even be exacerbated by adding these residualizing fish into the mix since they may be adopting the 'sneaker male' technique to pass their genetics along to the population.

    Using PIT tags and some hook 'n line survey effort (tough job!), we found that almost all of the O. mykiss sampled in the lower 8 miles of the Twisp River were hatchery released smolts. Since I left, I know there was some work done elsewhere in the system but I'm not up to speed on the results. Most of the 'rainbows' I took personally from the lower Methow were also hatchery releases. (There are some wild fish in the mix as well, but they weren't the notorious Method Megatrout; there are a hell of a lot of unclipped-hatchery-origin residuals in that system).

    Interestingly, the PIT results also showed that some of those fish that residualized did in fact head out to sea the next year...they just weren't quite ready to go when stocked. It's in the interest of the wild fish, of course, to minimize this residualism which manifests itself in the form of competition for food, habitat, etc. etc.

    On a side note, I also caught a number of residual rainbows that were over 12" so your measurements may not be too far off;)
     
  7. Josh

    Josh dead in the water

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    jackchinook,

    Thanks for that info. Makes sense to me.

    Most interesting is that some of those fish decide to head out the year after they are stocked.
     
  8. Will Atlas

    Will Atlas Guest

    yeah, can't remember who did the work, but there is some scientific literature out there on residualization in O. mykiss. In hatcheries, fry grow to smolt size in one year, while in the wild they're typically smolting as age-2s. Looks like those increased growth rates may lead to higher numbers of residuals as well as more early sexual maturity in males (precocious parr).

    Milt, how do you come by all your info on the tolt system? pretty interesting.
     
  9. Old Man

    Old Man Just an Old Man

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    You can lead a horse to water but you can't make him drink. I think you can do the same with people that fish in general. You can tell them what is right and what is wrong but then they make up their own minds as to what it right or wrong. It's almost like pissing in the wind.

    But that is the way I see it.

    Jim
     
  10. Smalma

    Smalma Active Member

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    Yuhina -
    I don't have a handy reference for you however in recent years there has been quite a bit of work in this area with much of the results just now making its way into the published literature. There has been some work in the Columbia basin and Hood River and I believe the lead author was K. Kostow.

    The most interesting thing is that nearly everyone that has taken the time to look closely are finding some sort of interactions between the various life histories. If the rainbow form was not so heavily selected against in anadormous waters by fisheries management actions I pretty confident that we would be seeing even more interactions.

    The relative abundance of the two life histories are influenced by the relative survival the two strategies encounter. That survival of course has an environment factor with the dominating fact being how well the anadromous fish are doing - not uncommon over a thirty year period to see a 10 fold difference in marine survival. Obviously young fish (smolts) that experience the higher end of that survival are much more successful than the resident fish and those smolts that experiecne the lower survival rates.

    One of the big advantages that the resident fish may have is an increased survival rate between spawnings. In Washington it would be uncommon to see much more than 15% of the spawning adults to survive to spawn again (much lower for summer steelhead on the Columbia. While in lack of fishing it would not be uncommon to see something like 50% of the rainbows to survive to spawn again. While the feccundity (# of eggs) of the steelhead is much higher the rainbows hav more chances to successfully spawn. In situations with low freshwater survivals (floods, etc) having several chances to high favorable survival conditions may be more important than putting more eggs in the gravel.

    Milt Roe -
    I believe the sort of those westslope cuttrhoat above the SF Tolt resrevoir was from an alpine lake in the headwaters that recieved a plant of westslopes 20 or so years ago.

    Your are correct in that the dominate fish in the Tolt and the rest of its forks are O. mykiss. That is typical of what I see in most western Washington streams. There is a definite partitioning of habitats between the rainbow and cuttrhoat. Generally speaking the rainbows dominate in the larger and higher gradient streams while the cutts become the dominate in the smaller and lower gradient streams. Occassionally see a larger streams (MF and SF Snoqualmie) where the cutts are dominant however it seems to me that the major spawning areas in those areas are typcially cutthroat type waters.

    Josh -
    It isn't a surprise that you found rainbows in the Methow that were clipped. It has long been recognized that some "smolts" will stay in the stream rather than migrate. That is a larger problem with summer steelhead than winters and the rate at which the fish residaulize seems also depend on the quality of the fish released (sufficent siz, timing, etc) as well as the flows at the time of the release. One of the fish management problems I referred to above.

    However those are not the rainbows that I'm speaking of. Many of the rainbows we see are not clipped and in some cases the rainbows are streams that have not been planted years - just one example would be the Cedar near Seattle where planting ended in 1994.

    Tight lines
    Curt
     
  11. yuhina

    yuhina Tropical member

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    Thanks a lot for the detailed information, Curt, I will check them out.

    It is amazing that fish just can do whatever they want... wish they score the key factor that switch life history strategies around... it would be a great discovery for evolutionist and conservationist.
    I appreciate your information and looking forward to your post. Sincerely, Mark
     
  12. Smalma

    Smalma Active Member

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    Yuhina -
    A decent place to start your research would be -

    http://www.nwr.noaa.gov/ESA-Salmon-...ations/Steelhead/Steelhead-Status-Reviews.cfm

    Go to the 2005 Puget Sound review. On page 19 you will find a discussion of this issue include various literature cites. A couple of the interesting ones that are just hitting the literature include those by A. Marshall and J. McMillian.

    I'm sure that you find a literature trail to keep you busy for a while. More recent reviews may have additional information.

    I found it both interesting and distressing that NOAA fisheries decided to exclude rainbows from the steelhead listing. Shows what happens what politics trumps biology.

    Tight lines
    Curt
     
  13. Josh

    Josh dead in the water

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    Lots of cool info here. Thanks everyone.

    I was a little bummed when I landed those fin-clipped fish. They were the right size to be rainbows, and I couldn't tell until I got them in that they weren't. After that I just hustled to get them off the line as fast as possible. I was trying to catch rainbows, not hassle young steelhead.

    However, if they were sticking around when they should have been 'out to sea' then I don't feel quite so bad.
     
  14. Richard Olmstead

    Richard Olmstead BigDog

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    Curt -
    I and a friend fished the North Fork Stilly one morning last week for SRC. The fishing was slow (as others have reported) with only a few fish caught. However, we each caught one fish in the 16-18" range that was sea-bright, had a definite pink stripe down its side, and not a hint of orange on its throat. I realize that fresh SRC often have fainter orange slashes than resident cutts, but these looked for all the world like rainbow trout that had just returned from the salt. They were too small for steelhead, in my limited experience on the Stilly, but you indicate that there may be some jacks or half-pounders in the mix. Do you suppose this is what we caught?

    If, in fact, they were small steelhead, this probably means that they were in the salt for just one season and perhaps didn't travel as far asea. If conditions in the North Pacific are in part to blame for the decline in Puget Sound Steelhead, do you suppose that we may start to see more fish taking on this life history in the future?

    Dick
     
  15. Paul Huffman

    Paul Huffman Driven by irrational exuberance.

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