What is a sign of zebra mussel infestation on a boat?

The presence of darkened spots or growths on hard surfaces is a clear indicator of zebra mussel infestation on a boat. Zebra mussels attach themselves firmly to various surfaces, including boat hulls, motors, and trailers, creating these distinct growths. This is a characteristic feature of their presence, as they typically form clusters that may appear slimy or rough, contrasting with the underlying material of the boat.

The other options, while potentially pertaining to aquatic environments or issues related to boats, do not specifically indicate a zebra mussel infestation. Brightly colored stripes on the hull are not a recognized sign of these mussels, as their attachment patterns do not result in vibrant coloration. Unusual fish behavior may suggest changes in the local environment but does not directly reveal the presence of zebra mussels. Similarly, increased water flow is generally not a direct consequence of zebra mussel activity; rather, it might be influenced by other factors such as design and water conditions. Understanding these distinctions is crucial for effective monitoring and management of invasive species like zebra mussels.