A.) It is estimated that the mature Atlantic herring population today has a bio-mass (total weight of the population) of approximately 2 million metric tonnes (2 billion kg). If an average adult Atlantic herring weighs 0.125 kg, how many adult Atlantic herring are there in the entire population? Hint: kg /0.125 kg per fish = fish
There are fish in the entire population.

B.) An adult Atlantic herring consumes, on average, 10 g of plankton per day. How much plankton would the adult Atlantic herring population consume in a day?
The population would consume grams of plankton a day.

C.) If there were a severe reduction of plankton available to the Atlantic herring population, and therefore a 55% decrease in the herring, how many mature Atlantic herring would be supported by the ecosystem?
The ecosystem could support fish.

D.) How many kilograms would that equate to?
It would be kilograms.