In the river, the pike population per season forms 20 kg of biomass. What should be the average

In the river, the pike population per season forms 20 kg of biomass. What should be the average increase in the biomass of plankton (in tonnes) per season in accordance with the 10% rule so that it can provide food for small fish, which makes up 80% of the pike ration? The volume of zooplankton consumption by small fish is 40 %

Because small fish make up 80% of the total pike diet, then it forms 80% of the pike biomass.

20 * 0.8 = 16 kg.

In accordance with the 10% rule (only 10% of the energy goes to the next trophic level), the pike must eat 10 times more to gain this mass to get 100%:

16 * 10 = 160 kg of small fish.

In turn, 40% of the biomass of this fish is formed by plankton:

160 * 0.4 = 64 kg.

This means that to gain this mass, you need to eat 10 times more:

64 * 10 = 640 kg of plankton, or 0.64 tons – this is exactly the increase in the biomass of plankton should be.