The three-spined stickleback is one of the UK's most common and ecologically important small fish, serving as prey for many species and as an indicator of freshwater habitat quality.
Sticklebacks as small fish have welfare significance consistent with other teleost fish; research confirms they have nociceptive responses and stress physiology comparable to larger species. In the wild, their welfare depends on clean, structurally diverse freshwater habitat providing both food and refuge from predators. Agricultural and urban runoff degrades water quality and sediment structure, directly harming stickleback welfare. Their importance as prey species means that stickleback welfare improvements cascade through the food chain to predators including otters, kingfishers, and herons.