Which of the following is a common method for assessing biological water quality?

Surveying fish populations and diversity is a common method for assessing biological water quality because fish are key indicators of the health of aquatic ecosystems. They are sensitive to changes in their environment, including water temperature, oxygen levels, and the presence of pollutants. Fish communities can reflect overall ecosystem conditions, such as habitat quality and the availability of food resources. Therefore, by studying the diversity and abundance of fish species, researchers can gather important information on the biological health of a water body, which can indicate the presence of pollutants or changes in habitat.

In contrast, other methods mentioned focus more on chemical or physical aspects of water quality. Methods that rely solely on chemical analysis or monitoring pollutants do not provide a complete picture of biological conditions. Analyzing algae growth patterns, while relevant for assessing certain aspects of water quality, does not offer a comprehensive evaluation of biological health since algae proliferation can also indicate harmful conditions like nutrient pollution but does not inherently reflect animal community health.