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  1. #101
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    Quote Originally Posted by Colin M View Post
    I doubt it very much Roag fisher, the loch was first used for abstraction in 1971 (50+ years ago) when the barrage was built so surely any effect related to that would have been evident long before now.
    The regime for raising and lowering the gates has been tampered with over the years and we always worry that after a spell of low water when a flood does come and the gates are not opened to give a freshet that our fish may well elect to run one of the other rivers that is experiencing a natural spate - in fact we are currently experiencing just such an extended period of low water.

    Colin
    A lot of the rearing of surplus (to the spawning burns) juveniles takes place in lochs. It takes time for sediment to build up on the bottom of the loch to a point where the food chain gets altered, possibly in a negative way to juvenile salmonids. That point may well have been reached.

  2. #102
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    Quote Originally Posted by Roag Fisher View Post
    A lot of the rearing of surplus (to the spawning burns) juveniles takes place in lochs. It takes time for sediment to build up on the bottom of the loch to a point where the food chain gets altered, possibly in a negative way to juvenile salmonids. That point may well have been reached.
    I may well be wrong but like you say that sort of thing takes time but what we are seeing is a significant drop in number over a very short period of three years
    No solution fits all!!

  3. #103
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    Sep 2017
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    Default Dismiss nowt

    I would dismiss nothing from the argument. But your argument is more likely to involve predation on those dropping juveniles IMO. Below is the alien species argument, just found one near me:

    " Alien invasive species have a great edge over native species, be they plant or animal, largely because the invasive or introduced species generally arrives in a new land without its predators, pests and diseases in tow. They have an unfair advantage over native species which have an extensive array of things that like to eat or kill them that have evolved in place with the natives. "

    This is my alien; what the hell is this: a dandelion or Whickham Grass ? And why won't the pic load in the correct orientation please ?

    Quote Originally Posted by Roag Fisher View Post
    A lot of the rearing of surplus (to the spawning burns) juveniles takes place in lochs. It takes time for sediment to build up on the bottom of the loch to a point where the food chain gets altered, possibly in a negative way to juvenile salmonids. That point may well have been reached.
    Attached Images Attached Images fullsizeoutput_d-jpeg 
    Last edited by Dave Wilkinson; 10-07-2018 at 12:54 PM.

  4. #104
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    Nov 2009
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    In a cooling North Atlantic...
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    Quote Originally Posted by Dave Wilkinson View Post
    I would dismiss nothing from the argument. But your argument is more likely to involve predation on those dropping juveniles IMO. Below is the alien species argument, just found one near me:

    " Alien invasive species have a great edge over native species, be they plant or animal, largely because the invasive or introduced species generally arrives in a new land without its predators, pests and diseases in tow. They have an unfair advantage over native species which have an extensive array of things that like to eat or kill them that have evolved in place with the natives. "

    This is my alien; what the hell is this: a dandelion or Whickham Grass ? And why won't the pic load in the correct orientation please ?
    It's a spiralised dandelion seedhead so not entirely ironic.

  5. #105

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    Quote Originally Posted by Dave Wilkinson View Post
    I would dismiss nothing from the argument. But your argument is more likely to involve predation on those dropping juveniles IMO. Below is the alien species argument, just found one near me:

    " Alien invasive species have a great edge over native species, be they plant or animal, largely because the invasive or introduced species generally arrives in a new land without its predators, pests and diseases in tow. They have an unfair advantage over native species which have an extensive array of things that like to eat or kill them that have evolved in place with the natives. "

    This is my alien; what the hell is this: a dandelion or Whickham Grass ? And why won't the pic load in the correct orientation please ?
    It's goat's beard Tragopogon pratensis - a native to the UK

  6. #106
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    Aug 2008
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    Yorkshire (were there a god it'd be god's own country) & Afrique
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    Quote Originally Posted by Dave Wilkinson View Post
    ...

    But if you look at Lomond's cohort in the Lakes, Windermere, and indeed most of other lakes there, they are a Canary for you. They are silting and warming, full of perch with few trout and have been doing this for years. There is a gradient of salmonid mortality which increases from North to South in the Northern Hemisphere which appears to be increasing...
    That's a fair point, but the one unspoken issue with that is the cause? Whilst it's easy for some to jump on the, to my mind way too glib, "global warming" bandwagon (despite the cooler winters this last decade.) Abstraction, draining the bogs (forestry etc) groundwater poisoning, and of course the increased eutrophicationand other poisoning through too many anthropogenic inputs to surface waters. Basins like this with massive tourism on the up, and ever increasing (human) resident populations, the impacts are poorly understood, but just like it takes 50+ years for a regulated (damed) channel to equilibrate, this is a decadal issue.

    It took about 10 years for the biology of one (restricted catchment) lake I know to change once about 30 homes were built around it... but now there's no turning back and the crustaceans and fish etc. are a pale shadow of what they were. But of course they blame the chappers..

    Just as sure as the overfed ducks changed the biology of Kilton and Tebay lakes, then vendace, powan etc. suffer more as a barometer of change than the ultimate survivor Salmo. Bass' lake is surely a totally different animal to 50 years ago...
    "...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

  7. #107
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    Nov 2017
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    Default Encouragement

    sorry for the absence recently - I've been on a fishing holiday on the north coast.

    Before I went on holiday I met with Andy walker as suggested by a couple of you and spent a couple of hours with him in Pitlochry talking about all things sea trout.
    The upshot was that he felt without seeing it and being able to study it in detail, that the Luss water was a good candidate for a studied stocking programme. On the subject of sea trout producing brown trout or sea trout he told me that he had conducted a study on an Earn tributary using sea trout progeny from lower down the catchment to stock a fishless burn above an impassable fall. He stocked them as first fed fry which are almost impossible to mark. In order to mark them he went back later in the year and recaptured them to fin clip and dye mark the fingerlings. The result was that from these stocked fry the burn re-established a native brown trout population which stayed in the burn. It also produced a native brown trout population which migrated locally into the Earn but the important point to me was that 50% of the recaptured adults returned as sea trout. Like some of you have said there are no guarantees that you'll get sea trout back but this study gives me some hope that you may well do.
    Andy still has a strong passion for sea trout and it was a privilege to speak with such a knowledgeable man in the field.
    He recommended a book to me which I have now bought which contains his paper along with lots of others published papers on sea trout:
    Sea Trout : Biology, conservation and management - Graeme Harris and Nigel Milner.
    It's a mine of information on all things sea trout.
    This along with the Adams et al paper that I mentioned earlier studying the anadromous nature of Lomond trout in particular strengthen my belief that sea trout stocking in certain circumstances is a viable option.
    Things (who knows what things?) in the catchment may have changed beyond recovery but do we just accept that as being the case or do we try to do something to address the problems?
    I'm told that there are lots of sea trout in the inner Clyde estuary so hopefully I'm completely wrong about the demise of the sea trout and they will turn out to be Lomond fish and this back end will show a recovery once the water cools. Even if that's the case I still think the Luss Water needs attention.

    Colin
    No solution fits all!!

  8. #108

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    Colin M,

    Thanks again for this fascinating thread. I really do hope you succeed in achieving what you have started. With fish now starting to show in the system many might put their thoughts on this on the back burner. Please keep this thread alive with any information you collect. I was wondering if the LLAIA have been in touch with you?.

    Regards
    Lee

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