Wild steelhead vs Native vs ?

Discussion in 'Steelhead' started by generic, Oct 28, 2011.

  1. cabezon

    cabezon Sculpin Enterprises

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    Here is a scenario, a thought experiment. Let's take the brood from a single pair of parents and split it in half. Half is deposited in the gravel exactly as normal; half is deposited into an egg-tray at a hatchery. The wild eggs are exposed to variation in temperature, oxygen, exposure to pathogens; many eggs do not complete development (die) and some genes are turned on and others permanently turned off among the survivors (a topic called epigenetics). The hatchery eggs experience relatively constant temperature and oxygen and minimal exposure to pathogens (but they may have exposure to antibiotics); most hatch. For the next year, the overwhelming majority of the wild steelhead will die; some from chance events, some because they are not as well-adapted to their environment as the survivors. The survivors learn what is (and isn't) food (or die) and where to hide to avoid predators or adverse water flows (too much or too little) (or die). They become territorial to preserve their food. More genes are turned on and others turned off. The hatchery survivors also learn what is food (pellets), but they do not have to do much to avoid predators and they tolerate tight packing. Some genes are turned on and others turned off, but these patterns are different from those whose regulation was adjusted in the wild fish. After a year, the hatchery fish are now released to the same environment as the wild fish. But these fish are not the same. Yes, the basic DNA may be similar (although selection has likely changed the gene frequencies between the two groups - a concrete raceway is not equivalent to a stream). The control of genes is likely to be dramatically different too. This may impact growth, survival, and reproductive success when the survivors from each group returns. Now the returnees of both groups spawn in the gravel. But epigenetic effects can persist for generations afterward. Bottom line. 1) Rearing wild fish in the hatchery environment certainly selects for genes that are different than those selected for in fish growing in the wild. 2) Changes in epigenetic effects can last for multiple generations, becoming less important with increasing number of generations.

    Epigenetics (beyond the genome) is the study factors that impact the regulation of genes (DNA). It is a very active area of research and the picture is far from complete. Here is a link to wikipedia's entry on epigenetics: http://en.wikipedia.org/wiki/Epigenetics and a great PBS program on the subject: http://www.pbs.org/wgbh/nova/body/epigenetics.html. There are well-known studies of human epigenetic effects that impacted multiple generations. One study traced the survival and health of Dutch children conceived in 1944 during a period when the Germans denied food to some towns because of partisan activity; individuals who were developing in utero during this period were smaller than those in other towns outside German control and these effects were passed on to their children as well as an increased risk of schizophrenia (see http://en.wikipedia.org/wiki/Dutch_famine_of_1944#Scientific_legacy). Similarly, a study of the population of a small isolated town in Sweden (Overkalix) demonstrated that epigenetic effects impacted daughters differently from sons and varied depending on available food (see http://en.wikipedia.org/wiki/Överkalix_study).

    Of course, salmon have not been studied for epigenetic effects..... yet. But epigenetic effects are well-documented in many species. Generally, they are driven by environmental factors (stresses), they impact the biology of the individuals who experience them, and the effects can impact future generations. Thus ends today's biology lesson.

    Steve
     
  2. Chris Johnson

    Chris Johnson Member: Native Fish Society

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    It sounds good but this study shows no benefit to broodstock programs. They have been doing this on the north fork Nooksack for years with spring chinook, they get a good return but they don't seem to reproduce(0.128 fecundity). Mining wild fish to make hatchery fish is a bad idea in most cases(IMVHO). If you have some literature that show a different result I'd like to read it.
    I can send you the Chilcote study or you can see it on the nativefishsociety.org

    Chris
     
  3. Smalma

    Smalma Active Member

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    Cabezon-
    While not as detailed as some human studies I believe that epigenetic effects have been demostrated in salmonid. For example it has been know for decades that the water temperature during the incudbation of trout eggs can influence such mertistic counts as vertebrae or scale numbers. More recently there is developing information that O. mykiss fry/parr are more likley to adopt the resident life history rather than the anadromous life history when rearing temperatures are higher.

    Chris -
    While it is correct that those natural spawning NF Nooksack spring Chinook are not very productive that productivity maybe limited more the carry capcity of that system than the origin of the spawners. It seems regardless of the numbers of spawners the systems seems to be capable of producing only a few hundred adults.

    As always when it comes fish and their genetics issues can be very complex. The role of the exteme natural selection that takes place in salmonid populatins can not be over looked.

    Tight lines
    Curt
     
  4. Chris Johnson

    Chris Johnson Member: Native Fish Society

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    Curt, thanks for your response, having very limited knowledge on the subject I always appreciate educated answers. In respect to N.F. Nooksack spring chinook, If carrying capacity is the limiting factor, it begs the question, why continue the program?
     
  5. Paul Huffman

    Paul Huffman Driven by irrational exuberance.

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    Yes, but here's another thought experiment. Half the eggs are deposited in the gravel exactly as normal. A duck finds the nest and eats 95% of them. Or a skulpin. Or a big winter flood. There's no selection for the fittest egg. It's just bad luck. No chance for the most adaptive, fast, or smart fry to survive the selection process to pass on their superior genes to the next generation, because they died as eggs. On the other hand, the eggs in the hatchery have 90 times the egg to fry survival, thanks to improvements in hatchery design and practice: redundant water systems, flow alarms, disease management.
     
  6. Chris Johnson

    Chris Johnson Member: Native Fish Society

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    Here is another line of thought: the strongest most fit wild fish get the best spawning habitat, insuring the best chance of suvival for their offspring. 90% of hatchery eggs survive, insuring the weak as well as the strong suvive to fry stage, delute the gene pool and take limited food and habitat resources from an already strained population.