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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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    Nov 2017
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    Scotland
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    84

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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

    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
    Join Date
    Nov 2009
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    In a cooling North Atlantic...
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    1,053

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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
    Join Date
    Aug 2008
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    Yorkshire (were there a god it'd be god's own country)
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    3,446

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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

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