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  1. #41

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    Quote Originally Posted by mows View Post
    If you looked at that graph in isolation, you could easily argue "its all at sea"
    Its only when you see that 25% of these smolts will be missing within a week of leaving that it gets interesting again.
    That and the change in age of the smolts and possible health and strength of them.

    Cheers

    Mows
    True

    Another factor at play could be run timing changes and the relative lack of spring fish when compared with the early years of the trap.

    I'm not convinced that all the returning Girnock fish return to the Girnock; but see no reason to argue with the MSS assessment that the burn is primarily spring fish spawning habitat. Less springers = less returning fish to this particular area.

  2. #42
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    Quote Originally Posted by mows View Post
    1. If you looked at that graph in isolation, you could easily argue "its all at sea"
    Its only when you see that 25% of these smolts will be missing within a week of leaving that it gets interesting again.
    That and the change in age of the smolts and possible health and strength of them.

    Cheers

    Mows
    1. Good point. Pretty sure that's how many sections of the SCS look at it, as if there's some causal rather than coincidental connection. As noted above, there is a tendency to disregard straying (at least 30-odd percent of tagged smolts strayed all around Scotland from the available Girnock evidence).

    So the mantra may be "look the smolts are being sent out and they're not returning must be problems in the Salsea" It needs to be looked at from the other way as well. Unfortunately there's a baseline study of 1 year for the in-river outmigration survival of smolts

    Perhaps the point is that as long as 5-10 adults get in annually, no worries... they'll send out roughly as many smolts into the river as if there were 100 adults there.

    Having looked at bit closer at the spatial analysis of the catchment it's pretty clear it's degraded now (mainly forestry) versus when monitoring started 50 years ago, again not something you see in the published data or any analysis.

    Perhaps it's as simple as the adults keep straying more now, but those that time it just right can cope with the smell or taste or whatever. Seems not to have a massive effect on smolt productivity from those adults that get in but of course, an acidification event can have a big impact. Perhaps that's what the lows in smolt production mean, for a number of the lowest smolt emigrant counts on record, the previous year tends to be a very wet one (based on Braemar's average annual rainfall) - if there were pH readings for the burn it would be interesting to research more.

    As mentioned previously (?AST AGM presentation thread) it seems to knock the traditional Stock-Recruitment relationship into a cocked hat.
    "...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

  3. #43

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    Quote Originally Posted by Grassy_Knollington View Post
    Loxie

    I meant to ask MSS when I asked about the smolt counts. It would be very interesting if the pan-jetted every smolt in a recognisable place and then counted how many adults coming back in had the panjet mark. In an ideal world I'd take the Halladale, Strathy, Forss and Thurso, smolt trap, panjet each river a different colour and then sweep net to check the returning adults. But it's not an ideal world so I refer to MSS for the reverse of that experiment: Girnock smolts tagged on their migration then recaptured elsewhere.

    Girnock smolt recaptures by rod& line = 110

    River Dee: 83
    N Esk & Bervie: 3
    S Esk: 5
    Don: 8
    Deveron: 4
    Spey: 7

    20% certainly strays to other rivers, they've run into fresh.

    Girnock smolt recaptures by Net & Coble = 72

    Dee: 28
    N Esk & Bervie: 37
    Tay: 6
    Spey 1

    60% likely strays into other rivers i.e. they're in the lower reaches.

    Girnock smolt recaptures by Fixed Engine = 161

    Dee: 82
    N Esk & Bervie: 51
    S Esk: 15
    Don: 2
    Spey: 3
    Findhorn: 2
    Connon & Alness: 1
    Unattributable: 4
    Nith 1

    50% cruising around the coast and not homing straight into the Dee; the others may have done this too of course and fish will go up and take a look in a river before leaving. Likely not in the numbers in the first 2 serials above though. N Esk smolts strayed far wider down the west coast BTW.

    WRT the Dee I would be more interested in what happens to the Autumn Parr.

    It's all here: I wonder why 'count them all out and count them all back' didn't read this:

    Report of the Mixed Stock Fisheries Working Group
    Section 2
    It would be interesting to know what percentage of Girnock spawners were themselves spawned in Girnock and indeed how many spawners not spawning in Girnock were spawned there.

  4. #44

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    Quote Originally Posted by seeking View Post
    Hi Seeking,
    those charts are a misrepresentation of the data.

    To plot a mean on a chart will never show any trend even though there is an obvious trend in the returning adults.

    You also need to plot "Count of total emigrants" like MSS do here.

    Juvenile Emigrants.

  5. #45
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    Quote Originally Posted by Walleye View Post
    Hi Seeking,
    1. those charts are a misrepresentation of the data.

    To plot a mean on a chart will never show any trend even though there is an obvious trend in the returning adults.

    2. You also need to plot "Count of total emigrants" like MSS do here.

    Juvenile Emigrants.
    Hello Walleye

    1. No they are not. They are the data They make the trend as obvious as a 5ya-running average. From the data it's clear that adult returns are well below average since the late 1980s, whereas smolt production remains within range and varies around the average.

    2. No I don't. Smolts are the important output of the burn. Smolt production is what fundamentally matters. Oversupply of losers and strays that get displaced are welcome to try and find a niche somewhere else, or feed the goosanders.

    Thanks for your input.

    Regards
    Last edited by seeking; 13-09-2017 at 05:48 PM.
    "...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

  6. #46

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    Quote Originally Posted by seeking View Post
    Hello Walleye

    1. No they are not. They are the data They make the trend as obvious as a 5ya-running average. From the data it's clear that adult returns are well below average since the late 1980s, whereas smolt production remains within range and varies around the average.

    2. No I don't. Smolts are the important output of the burn. Smolt production is what fundamentally matters. Oversupply of losers and strays that get displaced are welcome to try and find a niche somewhere else, or feed the goosanders.

    Thanks for your input.

    Regards
    Fair enough. Your last mention was of trend lines then charts with no explanation so I jumped to the wrong conclusion.

    What does the reducing surplus tell you in the context of 80% lower spawner numbers? Is the Girnock close to a situation where there may be no surplus to ensure maximum production of smolts?
    In addition, what if those parr that migrate downstream to avoid overpopulation in the Girnock burn actually thrive further downstream in areas where there is lower spawning and smolt density? Could this parr migration be a natural way of maximising whole river smolt production?

  7. #47

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    Quote Originally Posted by Walleye View Post
    Fair enough. Your last mention was of trend lines then charts with no explanation so I jumped to the wrong conclusion.

    What does the reducing surplus tell you in the context of 80% lower spawner numbers? Is the Girnock close to a situation where there may be no surplus to ensure maximum production of smolts?
    In addition, what if those parr that migrate downstream to avoid overpopulation in the Girnock burn actually thrive further downstream in areas where there is lower spawning and smolt density? Could this parr migration be a natural way of maximising whole river smolt production?
    As covered earlier, the Autumn Parr could make a contribution to the total smolt run and I think there are studies which document how significant this is. However they are 6-7 months away from the real deal and aren't actually smolts.

    They move for a variety of reasons, food availability is one, another is the lack of available habitat for large parr - they need bigger substrate to hide in.

    Don't forget that once in the main stem their life continues to face most of the same pressures they did in the burn. Survival there is also likely to be a complex mix of factors where lower numbers are compensated for by higher survival.

    Finally, if you look at the Baddoch counts you will see rising Trend of Autumn emigrants against declining adults and stable (within range) smolt counts. I'm not sure this is consistent with the theory of lower main stem production due to less eggs in the headwaters.

  8. #48

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    Quote Originally Posted by Grassy_Knollington View Post
    As covered earlier, the Autumn Parr could make a contribution to the total smolt run and I think there are studies which document how significant this is. However they are 6-7 months away from the real deal and aren't actually smolts.

    They move for a variety of reasons, food availability is one, another is the lack of available habitat for large parr - they need bigger substrate to hide in.

    Don't forget that once in the main stem their life continues to face most of the same pressures they did in the burn. Survival there is also likely to be a complex mix of factors where lower numbers are compensated for by higher survival.

    Finally, if you look at the Baddoch counts you will see rising Trend of Autumn emigrants against declining adults and stable (within range) smolt counts. I'm not sure this is consistent with the theory of lower main stem production due to less eggs in the headwaters.
    I have to agree. Two data points (Girnock and Baddoch) really isn't enough to draw any firm conclusions from. My old boss would happily shout "need more data!". He would also tell us "in God we trust, everyone else bring good data!" And on that note, I will try from now on to avoid trying to make conclusions from bad / insufficient data! :-) at least for a while anyway.

  9. #49
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    Quote Originally Posted by Loxie View Post
    It would be interesting to know what percentage of Girnock spawners were themselves spawned in Girnock and indeed how many spawners not spawning in Girnock were spawned there.
    About 3 years ago I met Salar35 on the Dee. He showed me some PowerPoint slide prints, one of which showed the return to natal stream rates. As far as I can recall they were something around or just over 30%, which led me to point out that this was far from indicative of certainty, least of all supportive of the notion that springers beget springers.

  10. #50
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    Default Cod

    Well it started with herrings,which led to the demise of blue fin tuna on the north east coast,then the mackeral were hammered and have never ever recovered to what numbers were like back then,houting a migratory herring/whitefish a memeber of the salmon family went extinct in the 40s i think...so they is lessons to be learnt unfortunatly they aint been learnt in HURRY.

    PS smelts also a salmon family member have well declined also,both species of shad allis and twaite,and sturgeon well say no more.....though for the past few yr blue fins are making a appearence from time to time.But ingeneral the bait species like herrings were fished out which led to the demise of the NORTH SEA TUNNY.-----shame.
    "Don't hate the black, don't hate the white,if you get bitten just hate the bite"

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