What is one potential contributor to fish kills that occurs from agricultural practices?

Insecticide runoff is a significant factor that can contribute to fish kills resulting from agricultural practices. When agricultural fields are treated with insecticides, rain or irrigation can wash these chemicals into nearby water bodies. The runoff may contain high concentrations of toxic substances that can be harmful to aquatic life.

Insecticides are designed to target pests, but they can also negatively affect non-target species, including fish and other aquatic organisms. The introduction of these chemicals into water bodies can disrupt physiological processes, affect reproduction, and lead to acute or chronic toxicity, ultimately resulting in fish kills. Moreover, these substances can have broader ecological impacts by altering food webs and water quality.

While the other choices may relate to environmental conditions, they do not directly link to the specific impact of agricultural practices on aquatic ecosystems as strongly as insecticide runoff does. High water levels could indeed stress fish populations or create different ecological conditions, but they are not specifically tied to agricultural practices. Excessive sunlight generally leads to increased plant growth rather than direct fish kills. Overfishing pertains to the removal of fish populations rather than an environmental or chemical impact from agricultural practices.