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  1. #11

    Default Re: liming a trout lake

    Quote Originally Posted by sofasurfer View Post
    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.
    I fish a small local rain fed lake and have experienced some of the same issues. It has been stocked with rainbow and brown trout but has an indigenous population of carp. Over the last two years most of the trout have died and the carp have survived and thrived. Our local EA rivers inspector lent us the equipment for monitoring pH and dissolved Oxygen. We found that pH levels were relatively stable at around 6.2, however dissolved oxygen levels measured as "percentage" where as low as 45%. We were advised that levels of 90% or above were essential to maintain a healthy stock of trout. Carp will tolerate very low oxygen levels. The EA guy lent us a petrol driven aeration system which we ran throughout the day and night for several days. The resulting d02 levels were well within the required range and the lake was declared "fit again" Subsequently we have purchased our own pH and d02 meters and we have also invested in an aeration system. This year we have had no apparent losses and catch levels have been good. As suggested above, talk to the EA and try to get help and advice from them. We found them very helpful. Good luck

  2. #12
    Join Date
    Mar 2013
    Location
    Sussex
    Posts
    398

    Default Re: liming a trout lake

    Percentage of dissolved oxygen is not a good metric. At a temperature of 26 degrees the percentage of oxygen might be 100% but would be too low to support trout. Conversely, a 50% saturation at 15 degrees would be OK. The relationship between dissolved oxygen temperature and pressure is complex.

    "Two bodies of water that are both 100% air-saturated do not necessarily have the same concentration of dissolved oxygen. The actual amount of dissolved oxygen (in mg/L) will vary depending on temperature, pressure and salinity .

    First, the solubility of oxygen decreases as temperature increases . This means that warmer surface water requires less dissolved oxygen to reach 100% air saturation than does deeper, cooler water. For example, at sea level (1 atm or 760 mmHg) and 4C (39F), 100% air-saturated water would hold 10.92 mg/L of dissolved oxygen. But if the temperature were raised to room temperature, 21C (70F), there would only be 8.68 mg/L DO at 100% air saturation ."

    Look at this link for a good explanation....
    Dissolved Oxygen - Environmental Measurement Systems

    If you are going to buy a dissolved oxygen meter, get one that reads mg/L or you are going to have to do some complex maths :-)
    https://leconfieldflyfishingclub.com/

  3. #13

    Default Re: liming a trout lake

    A pH of 6.2 seems very low. The majority of recommendations for trout fisheries states 6.5-8.5. The lower the pH, there seems to be a lower diversity of aquatic insects. There is a very interesting government report:
    Management advice for trout grayling and arctic char fisheries - GOV.UK.

    The hot summer this year seems to have taken a toll. Our lake has a deep channel and so many of the fish seem to have survived the low oxygen. From July to September the margins had so little oxygen that it took ages for the caught and returned fish to recover. Catch rates dropped dramatically from July - September, with only the odd fish caught. You could see lots of fish but they just weren't feeding. Unfortunately our club cannot afford an aerator.

  4. #14
    Join Date
    Mar 2013
    Location
    Sussex
    Posts
    398

    Default Re: liming a trout lake

    In lakes pH varies throughout the day. One day in June 2018 I took early morning pH readings at 9 different lakes with water temperature varying from 17 degrees to 21 degrees. The corresponding pH ranged from 6.36 to 9.10. Temperature, pH and dissolved oxygen (mg/L) need to be measured at dawn and 1:00pm over a few days to get an accurate assessment of the problem.
    https://leconfieldflyfishingclub.com/

  5. #15

    Default Re: liming a trout lake

    Interesting to know whether the more acidic lakes had less aquatic insects than the more basic, and whether the fishing in the more basic lakes was better?

  6. #16

    Default Re: liming a trout lake

    There's a stack of easily read stuff on the net, Google "How does ph affect aquatic life"
    Musha rig um du rum da

  7. #17

    Default Re: liming a trout lake

    Horse Manure. Visit your local horse stables and get a few bags of raw manure. Your problem will be lack of Daphnia (water flea) that fish and aquatic insects, especially Damsels like to feed on. Put the manure around the margins in the sunniest spots during the spring and summer and this will quickly increase the Daphnia population. Be careful not to put in too much (1 - 2 cwt per acre) is more than enough, otherwise you could alter the ph value of the water. Also the manure will release nutrients which could increase weed growth.

  8. #18
    Join Date
    Feb 2010
    Location
    Dumfries, South West Scotland
    Posts
    678

    Default Re: liming a trout lake

    Would horse manure not put too much nitrogen in? Next thing would be algal blooms?

  9. #19

    Default Re: liming a trout lake

    Yes, if too much is thrown in, that is why I said no more than 1-2 cwt per acre around the margins and not tossed in the pond. More than that will cause an imbalance of nutrients and create other problems

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