Measuring oxygen levels in the lake for two months Checking the lake water for nutrient levels on one day Sampling fish populations in the lake over several years Observing the surface of the lake for signs of the new fish after one week
I gave my students this multiple choice question: A group of fish was released into a local lake. This species of fish had never lived in the lake before. Scientists want to collect data on how the lake's ecosystem is affected by the new fish. Which method of data collection will give the most accurate results?

Only one answer is correct among these 4 choices:
- Measuring oxygen levels in the lake for two months
- Checking the lake water for nutrient levels on one day
- Sampling fish populations in the lake over several years
- Observing the surface of the lake for signs of the new fish after one week

Could you tell me which one is correct?

Sampling fish populations in the lake over several years