Which features make sticklebacks well protected from predators?

Sticklebacks are well-protected from predators through a combination of physical armor and behavioral adaptations.

Physically, these small, scaleless fishes are shielded by a row of hard, thin, bony plates along the sides of their bodies. Their defense is further bolstered by a series of sharp spines on their backs, positioned in front of the dorsal fin, as well as a sharp spine located in each of their pelvic fins.1

Behaviorally, most members of the order Gasterosteiformes enhance their safety by assuming a vertical position among plants or corals in their environment. This posture serves two defensive purposes: it provides camouflage and presents their protective body spines or shields toward predators that are typically oriented to the horizontal plane. Additionally, sticklebacks often inhabit a wide variety of aquatic environments where they can effectively find both food and shelter.2