Threespine sticklebacks are small, abundant, and slow swimmers, all of which combine to make them suitable prey for many different predators. However, they have evolved several predator defenses in their morphology and behavior. Anti-predator morphology includes dorsal spines, bony lateral plates, and a pelvic girdle that consists of a pair of anterior processes with ascending branches, posterior processes and pelvic spines. Behavioral responses to predation risk include schooling, remaining close to protective cover, and predator inspection. Anti-predator morphology and behaviors tend to be more well-developed in fish from environments that contain predators.
Known predators of threespine sticklebacks include fish in the families Percidae, Esocidae, and Salmonidae. Some lakes in Alaska and British Columbia have been stocked with rainbow trout (Oncorhynchus mykiss) and silver salmon (Oncorhynchus kisutch) for game, and these fish prey on sticklebacks in those lakes. Avian piscivores that prey on stickleback fish include loons (Gaviiformes), grebes (Podicipediformes), the common merganser (Mergus merganser), herons (Ardeidae), and kingfishers (Alcedinidae). Piscivorous macroinvertebrates, such as dragonfly naiads (Odonata) and beetles (Coleoptera) feed on eggs, fry and juvenile sticklebacks. Leeches (Hirudinea) prey on stickleback eggs and have also been found to consume adult sticklebacks stuck in traps.
- perch, (Percidae)
- trout and salmon, (Salmonidae)
- pike, (Esocidae)
- loons, (Gaviiformes)
- grebes, (Podicipediformes)
- common merganser, (Mergus merganser)
- herons, (Ardeidae)
- kingfishers, (Alcedinidae)
- dragonflies, (Odonata)
- beetles, (Coleoptera)
- leeches, (Hirudinea)
Anti-predator Adaptations: cryptic