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  1. #1

    Default Salmon size gene's or growth

    Is the size of a salmon determined by its gene's or by the amount of food available to it.
    For example if a 5lb grilse enters a river and spawns and is lucky enough to survive and returns to sea then a year or two later returns to the river to spawn again will that 5lb fish still be 5lb or will it then be say 10 or 12lb. Has anyone ever caught a fish that has being caught,recorded and tagged previously and found it was the same size or bigger,or are there any scale readers amongst us that could shed some light on this matter.

  2. #2

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    Quote Originally Posted by SOS View Post
    Is the size of a salmon determined by its gene's or by the amount of food available to it.
    For example if a 5lb grilse enters a river and spawns and is lucky enough to survive and returns to sea then a year or two later returns to the river to spawn again will that 5lb fish still be 5lb or will it then be say 10 or 12lb. Has anyone ever caught a fish that has being caught,recorded and tagged previously and found it was the same size or bigger,or are there any scale readers amongst us that could shed some light on this matter.
    Interesting question, I have no expertise or data to contribute, just the suggestion that with most animals (including humans !) size attained is normally a combination of genetics and food availability (quantity and quality).

  3. #3

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    Quote Originally Posted by SOS View Post
    Is the size of a salmon determined by its gene's or by the amount of food available to it.
    For example if a 5lb grilse enters a river and spawns and is lucky enough to survive and returns to sea then a year or two later returns to the river to spawn again will that 5lb fish still be 5lb or will it then be say 10 or 12lb. Has anyone ever caught a fish that has being caught,recorded and tagged previously and found it was the same size or bigger,or are there any scale readers amongst us that could shed some light on this matter.
    The size of a salmon returning to spawn is primarily genetically driven. Large powerful rivers produce large salmon to cope with these conditions. Smaller less powerful systems produce smaller salmon more fit for that system. That does not mean that you can't have large salmon in smaller rivers and vice versa as strays will always occur but if they are not fit for that particular environment then their genes will gradually be bred out.
    It is possible to estimate the size of a salmon from scale readings. In almost all instances they will have gained very little weight when they ascend a river on their second spawning. Very large salmon tend to have spent 3 or 4 years at sea before returning.
    The biggest second spawner I have caught was 16lb on the Tay and from scale and flesh samples submitted to The Freshwater Fishery Research lab at Pilochry it was found to have gained only about 2lb since its first spawning and was also incidentally identified as being of farmed stock.

  4. #4
    Join Date
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    Default Salmon Size

    I would say it is food availability - No one and nothing grows without sustenance otherwise we have discovered that the secret of perpetual motion is genetics?

  5. #5

    Default

    Size in length terms is likely to be at least partly driven by genetics and is the result of the number of years the fish spend at sea.

    Condition is the quality of the fish of a given length and is driven by feeding. For any given length we can get a wide range of weights, skinny grilse or porky small salmon.

    Just remember that genetics are plastic i.e. they are malleable and change over time in response to environmental factors, as well as parentage. When the conditions favour particular characteristics, ( in river and at sea). Those fish with those characteristics will predominate.

    A (poor) example of this is observable in Trout loves stocked with Leven fish. For a couple of years they generally see the Leven fish appearing in catches but over time the local strain tend to do better and in most places the stocked trout fail to change the long term situation.

    All IMHO and (over) simplified.

  6. #6
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    Stirling
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    Default

    I was always told that during the first sea feeding period that the smolt will grow to its maximum size be it a grilse or MSW fish. If it made it back to sea for another feeding period then this period would be for reconditioning and preparing for another journey to spawn and would not double in size say if it spent 2 years at sea. No scientific evidence just what i was told years ago from an old boy who taught me how to fish the devon. He described the first sea feeding period is like a humans teenage years where all the growth is achieved. I would be interested in someone with another theory or scientific explanation.

  7. #7
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    Default

    The OP is answered by Malloch, and a quick search on here will give evidence of the answer.

    But ultimately, who cares? Phenotypic plasticity and all that. Biggest UK salmon abounded when herring fisheries were at their peak.

    Cycles and plasticity. Mind I must admit I'd rather we were awash in 2 or 3SW fish than grilse, because they make a better meal.
    "...hooking mortality is higher than you'd expect: further evidence that as a numbers game, catch-and-release fishing isn't always as straightforward as it seems"
    John Gierach


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  8. #8
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    Default

    Salmon multiple spawners are rare so not too data much to go on. Large sea trout however do tend to be multiple spawners suggesting survival for another spawning run will tend to increase the size, certainly for sea trout.

  9. #9
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    Quote Originally Posted by Richardgw View Post
    Salmon multiple spawners are rare so not too data much to go on. Large sea trout however do tend to be multiple spawners suggesting survival for another spawning run will tend to increase the size, certainly for sea trout.
    On my one trip to fish in Norway it took me a while to realise that when they talked about MS fish they were not abbreviating MSW they meant multiple spawners and that their really big fish are multiple spawners.

    I bang on to anyone who will listen about big sea trout and how important they are. And they are mostly females and are multiple spawners.

  10. #10

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    Malloch has most of the answers.

    The genetics are not in anyway straightforward. In the UK 1,2and 3SW fish all happily interbreed as to fish that run from all times of the year. Their offspring tend to do the same. It seems highly likely that there must be some genetic influence and there is evidence that size at a certain age point has a large influence on wether a fish matured as a grilse or stayed at sea for another winter or 2. There is also some evidence that river temperatures can have an effect as well; from smolt size to smolt emigration times. It is worth remembering that the largest Delphi salmon in recent years was a 3 SW April fish both of whose parents were grilse.

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