In the worst-case scenario, it will take 6 years for the lake to have no more trout.
The lake has an average trout population of 20,000, with a natural oscillation above and below the average by 2,000 every year. This means the range is between 18,000 and 22,000.
Fishermen catch 3,000 fish every year. To find out how long it will take for the lake to have no more trout, let's consider the worst-case scenario: starting at the minimum population of 18,000, and the fishermen catching 3,000 fish every year.
The time it will take is calculated by dividing the initial population (18,000) by the population decrease per year (3,000):
Time = Initial population / Population decrease per year
Time = 18,000 / 3,000
Time = 6 years
Therefore, in the worst-case scenario, it will take 6 years for the lake to have no more trout.