Which two species were notably introduced in Michigan for biological control of aquatic weeds but are now prohibited?

The correct choice, which identifies grass carp and tilapia as the species introduced in Michigan for biological control of aquatic weeds but are now prohibited, highlights important aspects of aquatic pest management.

Grass carp (Ctenopharyngodon idella) were initially introduced into various water bodies to help control invasive aquatic plants. Although they are effective at consuming certain types of vegetation, they have also been known to disrupt local ecosystems by overgrazing and causing ecological imbalance. Due to their potential to spread and impact native species and habitats negatively, their use is regulated or banned in many areas.

Tilapia, on the other hand, was another species introduced for similar reasons. While they can help manage aquatic plant growth, tilapia can also thrive in various environments, leading to potential ecological issues such as competing with native fish for resources, altering habitat structures, and affecting local biodiversity when they establish wild populations.

In essence, both species were chosen for their potential benefits in controlling invasive plant species, but the unforeseen consequences of their introduction, such as ecological disruption and risks to native populations, have led to their prohibition in Michigan. The management of these species is crucial to maintaining ecological balance and protecting native aquatic environments.