Which species are commonly recognized as nuisance species?

Nuisance species are typically non-native organisms that can disrupt local ecosystems, outcompete native species, or cause other environmental harm. The species identified in the selected answer—zebra mussels, quagga mussels, milfoil, and hydrilla—are well-documented examples of invasive species that pose significant threats to aquatic environments.

Zebra mussels and quagga mussels are particularly harmful due to their rapid reproduction and ability to clog waterways and damage infrastructure. They can also outcompete native mussel species for food and habitat. Similarly, milfoil and hydrilla are invasive aquatic plants that can create dense mats on the water surface, restricting light penetration and impacting oxygen levels, which can be detrimental to native fish and plant species.

In contrast, the other options list species that are either native, commonly occurring, or not typically associated with nuisance characteristics in the ecosystems where they thrive. For instance, species like bluegill or catfish are popular in recreational fishing and play a role in their ecosystems without causing the same kind of disruptive impacts that nuisance species do. Thus, the primary focus on the species in the correct choice underscores the ecological challenges posed by them.