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  1. #1

    Default liming a trout lake

    I fish a small trout lake and am concerned about the apparent lack of natural food. There seems to be snails, damselflies and small midges, but few sedges, olives, corixa and no shrimps or louse. The pH of the water is 6.8 and TDS 130ppm and very clear. This measurement was taken at the summer low level. The lake is enclosed and entirely sourced from rainwater, so the pH and TDS will probably drop with the winter rains. I've been wondering whether liming would help to improve the natural food supply and break up the silt.
    Does anyone have any suggestions?
    They stock the lake with ~150 trout every year, about 20 are removed or seen dead floating, but a lot seem too just disappear. We get the odd cormorant but no other predators. The remaining fish grow but may be just feeding on the dead trout that sink to the bottom?

  2. #2
    Join Date
    Mar 2013
    Location
    Sussex
    Posts
    593

    Default Re: liming a trout lake

    If it is an old, well established lake I would leave it alone. By altering the balance you may make things worse. With global warming small lakes are not going to sustain trout.
    https://sussex-trout-fishing.com/

  3. #3
    Join Date
    Feb 2012
    Location
    Helsby, Cheshire
    Posts
    204

    Default Re: liming a trout lake

    You do not say if there is plant life in the pond ? What the margin cover is ? Trees / bushes / grass ? It may be worth working on these before adding lime. If I were to put in lime I would use "Limestone" rather than lime powder. Added at water run in's in shallow areas.

  4. #4

    Default Re: liming a trout lake

    You can get in touch with your environmental regulator's fishery team who should be able to visit you and offer some advice - funding cuts allowing. It may be worth pushing your status as a community group. You'll get far better advice from a site visiting professional than any of us who'll only be able to offer general observations.

    My only experience of a limed lake is good, one of Tregaron AA's lakes,Llyn Berwyn, had become acidic due to its surrounding non indigenous conifers, the liming allowed the partially-stocked brown trout to thrive on its enhanced invertebrate population. It definitely works in the right situation but before any decisions are made get some qualified help rather than adopting a saloon-bar-science based approach.
    Musha rig um du rum da

  5. #5
    Join Date
    Jul 2010
    Location
    Scottish Borders
    Posts
    339

    Default Re: liming a trout lake

    I worked on this project as a student in 1989. I was involved with the fish counter side of things. Maybe some info here...

    https://www.fba.org.uk/journals/inde...ewFile/247/149
    Hidden Content

    One more cast.....

  6. #6
    Join Date
    Aug 2016
    Location
    Moray, Scotland
    Posts
    1,685

    Default Re: liming a trout lake

    Quote Originally Posted by kingf000 View Post
    We get the odd cormorant but no other predators. The remaining fish grow but may be just feeding on the dead trout that sink to the bottom?
    I was watching a heron with the owner of my local fishery this week. He reckons they will take on average, one fish a day. He thinks a single cormorant will kill or injure upto eight fish per day.
    Only when the last tree has been cut down, the last fish caught and the last river poisoned, will we realise, we cannot eat money.

  7. #7

    Default Re: liming a trout lake

    Many thanks for the replies. The lake is fairly open, the odd bush on the bank and lined with bullrushes around about 2/3rds of the lake. It has quite a lot of canadian pondweed that is being controlled by the addition of a blue dye. Away from the bank, the depth ranges from about 5 ft to 25 ft. It has been stocked with rainbow, brown, tiger and blue trout, but this year the blue trout seem to have totally disappeared. I have contacted the environmental agency, asking for advice, and look forward to their reply.

  8. #8
    Join Date
    Mar 2013
    Location
    Sussex
    Posts
    593

    Default Re: liming a trout lake

    If there is quite a lot of Canadian pond weed you have a problem that will be made worse by adding lime. During the day the weed photosynthesizes and produces oxygen which is good. At night the weed produces carbon dioxide as a result of respiration, the opposite of photosynthesis, which is bad. The pH of the water varies during this 24 hour cycle. Warm water has low dissolved oxygen. High, temperature, low dissolved oxygen and extreme pH kills trout. They sink into the weed never to be seen again. Distressed trout are picked off by Cormorants at dawn when the dissolved oxygen is at its lowest and when nobody is around to frighten them away.
    https://sussex-trout-fishing.com/

  9. #9

    Default Re: liming a trout lake

    Many thanks. The pondweed isn't too bad since adding the dye, which presumably blocks the UV light and so the weed doesn't grow so profusely. However, I shall now take pH measurements at different times of the day, especially in summer when the weed is at its worst. Could you please clarify why adding lime with the pondweed present would make the problem worse. Is it just the addition of more carbonate as a CO2 source? The last two years have been particularly bad due to the low rainfall and high temperatures, but as pointed out earlier, this may become the norm. with global warming. So regular stocking to replace dying fish may become the norm.

  10. #10
    Join Date
    Mar 2013
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    Sussex
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    593

    Default Re: liming a trout lake

    Lime will encourage the weed growth and make the problem worse. The best time to take readings for temperature, pH and dissolved oxygen (mg/L) is at dawn. It is the combination of these three metrics that tell you if trout will survive, they are interrelated. A digital pH meter is cheap, you can get one for under 10 from Amazon, the yellow and black one that looks like a highlighter pen. Digital dissolved oxygen meters are more expensive, buy one that gives a reading in mg/L because a reading of 'percentage of dissolved oxygen' varies with other factors (temperature, pressure etc.) and is not a good metric.
    https://sussex-trout-fishing.com/

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