Which of the following is NOT a common type of aquatic pest?

The reasoning behind selecting salmon as the correct answer lies in the distinction between pests and non-pests in the context of aquatic ecosystems. Algae, invasive aquatic plants, and aquatic insects are all categorized as common aquatic pests because they can disrupt the balance of aquatic environments, cause harm to native species, block sunlight, and affect water quality.

Algae can proliferate excessively, leading to harmful algal blooms that deplete oxygen in the water and produce toxins, which can be detrimental to aquatic life. Invasive aquatic plants often outcompete native vegetation, altering habitats and ecosystems. Aquatic insects, while a natural component of many ecosystems, can sometimes become pests when they reproduce in excessive numbers, leading to negative impacts on both the environment and human health.

On the other hand, salmon are typically a natural and beneficial component of aquatic ecosystems. They play a crucial role in maintaining the ecological balance and are economically important both for ecosystems and communities. Thus, salmon do not fit the definition of a common type of aquatic pest, which is why this choice is correct.