Original sentence: Some commercially important diseases are VHS, ich and whirling disease
Edited sentence: Continued nourishment by the presence of the fish results in the zoospores secreting a neurotoxin.Fish kills by this dinoflagellate are common, and they may also have been responsible kills in the past which were thought to have occurred from other causes.Kills like these can be viewed as natural mechanisms for regulating the population of exceptionally abundant fish.Some commercially important fish diseases are VHS, ich and whirling disease.The dinoflagellates then eat the blood and flakes of tissue, and the affected fish die.The rate at which the kills occur increases as organically polluted land runoff increases.This toxin causes the fish to develop bleeding lesions, and their skin flake off in the wate.When large numbers of fish, like shoaling forage fish,  are in confined situations such as shallow bays, the excretions from the fish encourage this dinoflagellate, which is normally not toxic, to produce free-swimming zoospores