What is the primary cause of fish kills due to water pollution?

The primary cause of fish kills due to water pollution is often linked to insecticides. These chemicals can enter water bodies through agricultural runoff, seepage, or accidental spills. Once in the water, insecticides can exhibit toxic effects on aquatic life, including fish.

Insecticides are designed to target specific pests but can inadvertently affect non-target organisms, including fish. The toxicity can manifest in various ways, such as causing respiratory distress, impairing reproduction, or leading to decreased immune function. As a result, these chemicals can ultimately lead to significant declines in fish populations and even large-scale fish kills in contaminated waters.

In contrast, while herbicides, fungicides, and rodenticides can also contribute to water pollution, their primary impacts are not usually direct fish kills. Herbicides primarily target plants, while fungicides target fungal pathogens and may have less pronounced effects on fish. Rodenticides are designed to control rodent populations and their effects on aquatic ecosystems are generally indirect, typically leading to secondary poisoning rather than immediate toxic impacts. Understanding the different pathways and effects of these substances helps clarify the significant role insecticides play in fish kills.