How to estimate the biomass of a koi pond?
Knowledge of the fish population in a pond may be necessary when you want to know if you are feeding your fish sufficiently, or when you need to administer treatment via food.
The simplest and most precise method is to weigh each fish individually, but this ideal situation is only possible when the population is small and you have mastered the operations of capturing and tranquilizing the animals.
Most of the time, it is necessary to use an indirect method:
By sampling
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Divide the number of your fish into 2 to 4 groups according to their size;
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Catch one or two representative specimens from each group, then weigh them;
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For each group, multiply the average weight found by the number of individuals in the group.
By the size of the fish
- Divide the number of your fish into 2 to 4 groups according to their size;
- Catch one or two representative specimens from each group, then measure their total length;
- Evaluate the estimated weight of each fish captured using the table below;
- For each group, multiply the estimated average weight by the number of individuals in the group. | Total length | Estimated normal weight | Lean (-10%) | Heavy (+10%) | | — | — | — | — | | 10 cm | 21 g | 19 g | 23 g | | 15 cm | 67 g | 60 g | 74 g | | 20 cm | 154 g | 138 g | 169 g | | 25 cm | 292 g | 263 g | 321 g | | 30 cm | 494 g | 444 g | 543 g | | 35 cm | 770 g | 693 g | 847 g | | 40 cm | 1130 g | 1017 g | 1244 g | | 45 cm | 1587 g | 1428 g | 1746 g | | 50 cm | 2150 g | 1935 g | 2365 g | | 55 cm | 2829 g | 2546 g | 3112 g | | 60 cm | 3634 g | 3271 g | 3998 g | | 65 cm | 4576 g | 4119 g | 5034 g | | 70 cm | 5665 g | 5099 g | 6232 g | | 75 cm | 6910 g | 6219 g | 7602 g | | 80 cm | 8322 g | 7490 g | 9154 g |
Enter your fish counts and average weights in the biomass calculator.
By the quantity of food distributed
If you have a good idea of the rationing rate of your fish, you can make the following estimate :
Estimated weight (kg) = 0.1 x Quantity of feed distributed per day (g) / Rationing rate (%)
Example: if you distribute 600 g of food per day, with a rationing rate of 1.5%, then the fish biomass must be 40 kg.
Koi carp are generally fed between 0.5 and 2% per day (depending on fish age and season). This estimate should be based on a suitable feed; bread is not an appropriate koi ration. A clay product is not a ration either: the guide to bentonite in koi ponds distinguishes technological uses from unproven therapeutic claims.