What is a necessary step when applying a toxicant to manage fish populations?

Lowering the water level when applying a toxicant to manage fish populations is a necessary step for several reasons. Reducing the water level can concentrate toxicants within a smaller volume of water, making them more effective against the target fish populations. Additionally, by lowering the water level, there is less aquatic habitat for non-target species, which may help to minimize unintended consequences on other wildlife or plant life.

This step also ensures that the area can be effectively monitored post-application. With a reduced water level, it becomes easier to assess the efficacy of the toxicant and to manage any potential runoff or degradation of the treatment site.

In contrast, increasing water levels or adding more fish would dilute the effect of the toxicant, complicate the management process, or inadvertently increase the population of undesirable species. Removing all vegetation would not be suitable as some plants can help absorb toxins, whereas the management goal focuses on the fish population specifically.