What are bait balls?

What are bait balls?

• A. A large aggregation of plankton.
• B. A type of sonar signal.
• C. Light-emitting structures.
• D. Tightly packed groups of small fish that form a defensive formation.

Answer: (D)

Bait balls are tightly packed groups of small fish that form a defensive formation. When danger approaches, numerous small fish cluster into a dense, spherical-like ball and swim together as one. This makes it harder for a predator to pick out and catch an individual, and the rapid, confused motion can derail an attack. The dense grouping also helps reduce each fish’s individual risk by spreading the threat across many individuals. This behavior is different from plankton blooms, sonar signals, or light-emitting structures, which aren’t what bait balls describe. So the best description is a tightly packed school of small fish forming a defensive group.