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Thread: This might explain a lot....anyone with an interest in salmon should watch this video

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    Default This might explain a lot....anyone with an interest in salmon should watch this video



    This may have already been posted on here but I cannot stress enough the potential importance of these new findings for Scottish salmon described in this presentation by eminent Norwegian fisheries scientist Jens Christian Holst. The presentation is an hour long but in my opinion if you really want to understand why grilse are declining and big spring salmon seem to be thriving this is time well spent. It also explains why some seabirds like gannets are exploding but others like puffins and kittiwakes are collapsing. The reason is the same.
    The theory is called the underfishing/overgrazing pelagic fish theory and is actually very simple. Best of all - unlike most of things us fishery managers look at - there is also a fairly simple solution.
    While this new theory doesn't mean that fish farms, seals or mergansers are still not an issue, the scale of this new impact is on a completely different level.
    It's time for all the fisheries management bodies to stop doing yet more research in freshwater when its clear the problem lies in the high seas and, unlike what we have all been told, there may be something we can do about it.

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    Right then everybody has to go out and catch as many mackerel and herring as possible to cut down the competition. On the other hand that is probably why we are seeing more 3 and 4 SW fish this year so far. They are having to stay at sea a lot longer due to the lack of food as post smolts and then the abundance of food once they are big enough to feed on the young mackerel and herring shoals.

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    SOS
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    This cant be right as it goes along with what i have said in other posts and threads and goes against what the experts on SFF have being arguing with me about since i started posting.

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    Many thanks for posting that runningsilver. It is an interesting presentation, marred by disastrous sound, and lots of coughing.

    Interestingly we recently had a bit of banter on SFF about related issues here:

    Changes in Tweed salmon runs

    It is of course worth pointing out that the presenter tells the audience he was the Scientific Coordinator of SALSEA Merge. Since we know all about SALSEA and it's background and results and limitations, then it is hardly surprising that this presentation may be a little "Ocean-centric" in it's approach. But no matter.

    The theory is interesting but, IMHO, unfortunately the soundness of it seems to be undermined by a number of basic errors and omissions.

    One is the presenter at the onset admits that the hypothesis he's about to present, which to stress again, IS interesting, says it’s “not a hypothesis”, to him it’s “more than that”. I’d personally chalk that down to “confirmatory bias”.

    The first glaring issue is that despite being a man with a lot of fisheries experience, there is no mention of the public health warning that should accompany the ICES Guestimates of PFA that feature prominently as the groundwork for his presentation. The whole thing appears a house of cards, built on the foundations of the lie that is the assumption that ICES PFA “guesstimates” mean anything. He uses lots of data for netting but at no stage (even when applying it to Norwegian sprats) does he state that catches are down because effort is hugely down. No surprise there then.

    The Irish data is banded around likewise – Irish salmon catch has declined by 97% since 1973. Surely he means the net catch? And surely that’s also because of a collapse in netting effort and banning of drift nets and outcompetition by cheap farmed rubbish… Ironic really given the minor focus of Aquaculture in the presentation. The overreliance of many theories on ICES PFA Guesstimates does salmon science a disservice IMHO.

    [Funnily enough there's no mention of the best stock assessments available (Tyne and N Esk counters) which data are coincidentally at variance with ICES PFA Guesstimates.]

    Of course the ocean is in a state of equilibration and re-equilibration. It’s an ocean. There’s lots going on. Just as (obvious) subaerial volcanism adds nutrients that can help fish stocks, what about (unobvious) subsea volcanism that do the same. Can’t measure that or even guess at it. Also I’d be interested to see what their plankton trawls showed about microplastic particle abundance changes, since that is likely to be a significant driver in trophic collapse in the future. Can we do anything about it? Yes probably. Starts on land and in the rivers...

    He uses the examples of a trophic collapse in seabird numbers and divorces kittiwakes and puffins (dramatically declining according to some estimates) from gannets (increasing in some). If true there may be many different issues responsible. But is there actually a collapse in their numbers?

    For the UK, these are the actual estimates:

    Puffin up 37% since the late 1960s
    Atlantic Puffin Status and Trends

    Kittiwake down 7% since the late 1960s
    Black-legged Kittiwake Status and Trends

    Gannet up 150% since the late 1960s
    Northern Gannet Status and Trends

    Maybe the different bits of the far off ocean are having different differential effects on seabird numbers?

    Some of the hypotheses about good and bad years for grilse don’t really find support in UK data either. He shows a graph toward the end showing catch vs. growth, and states that 2004 was a good year and 2008 a bad one. Coincidentally 2010 is close to 2008. However, those three years had the top rod catches for GB. Much of that from the Tweed. So clearly our fish don’t all necessarily feed per his theory.

    All interesting stuff though, and lots more to mull over.

    Finally, the presentation states with total certainty that the rivers are fine and that there is no variance in smolt production!

    This despite the cast iron FACT that annual variances change by up to over 400% in UK examples (Girnock, Baddoch and N Esk) and the fact that a good year for smolts on the North Esk is not often a good year for them on the Dee (and even that within the Dee, a good year on Girnock may not be a good one on the Baddoch).

    All that suggests is that the fundamental control on salmon returns (smolt output) is catchment (and even sub-catchment) specific…

    So no real danger in focusing effort there, on the rivers, methinks. All IMHO and could be wrong mind.


    PS – personally it boils my blood that this presentation does not address the near-shore environment where massive damage is done to smolts (before they become high-seas post-smolts) going out. The focus of the “all at sea” hypothesis, right to SALSEA and beyond, has been the high seas, not the rivers and near-shore where the major mortality drivers can be shown to be.
    "...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


    Fed up of debating C&R - see Hidden Content

    Unless otherwise stated, data used in any graph/figure/table are Crown copyright, used with the permission of MSS and/or EA and/or ICES. MSS / EA / ICES are not responsible for interpretation of these data by third parties

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    SOS
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    YEP just as i said cant be right must be another red herring as one of the experts has already disputed it.


    P.S love the arguments
    westie4566 likes this.

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    Quote Originally Posted by SOS View Post
    YEP just as i said cant be right must be another red herring as one of the experts has already disputed it.


    P.S love the arguments
    Just listened to it again and there was no reference to red ones just silver herrings.
    westie4566 likes this.

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    It seems to me that yet again some " well respected" scientist has come up with a pet theory that explains everything in a nice neat little box. Figures and facts are then manipulated to "prove" the hypothesis.

    Are there really too many sea fish in the sea compared to decades or even centuries ago, before mankind developed industrial scale fishing, I doubt it very much.

    I recall back in the 60's that the amount of sea fish in Scotlands west coast was simply awe inspiring. Looking over local piers on a clear day was like looking into an aquarium at times. That's what got me into fishing. Mackerel shoals were so large that at times huge areas of the seas surface bubbled with them. Now these same areas are like fish deserts and mackerel shoals are a small fraction of what they once were.
    westie4566 and shucky4salmon like this.

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    So just to clear,
    There's enough food in sea for more mackerel and herring than there has been for a long time, and this means there isn't enough food for salmon.
    westie4566 and phil.b like this.

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    Quote Originally Posted by mows View Post
    So just to clear,
    There's enough food in sea for more mackerel and herring than there has been for a long time, and this means there isn't enough food for salmon.
    When you put it like that...
    westie4566 likes this.

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    Quote Originally Posted by mows View Post
    So just to clear,
    There's enough food in sea for more mackerel and herring than there has been for a long time, and this means there isn't enough food for salmon.
    Could be a numbers game here?

    Far more mackerel and herring than our smolts so out competing them in the food chain....or maybe just gobbling them up?

    Just another question in the myriad when it comes to salmon and some of their problems.
    ..........so many flies, so little time!

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