Fish

Pisces

Fish is a broad common term for aquatic vertebrates with gills, fins, and bodies adapted to life in water, from tiny reef gobies to salmon, carp, catfish, sharks, rays, and deep-sea forms. It is not a single narrow biological group in the way one species is; the name covers many ancient and modern lineages. Fish live in freshwater, brackish water, and marine systems, and their shapes reflect swimming style, feeding method, habitat, and life cycle.

Human relationships with fish are equally varied. People keep them in home aquariums and public aquaria, raise them in aquaculture, manage them in ponds and hatcheries, harvest them through commercial and recreational fisheries, and monitor them as indicators of water quality. Practical care starts with the species rather than the word fish: temperature, salinity, oxygen, diet, tank size, schooling needs, disease risk, and legal collection rules differ widely. Good records can help track origin, strain, stocking history, and health treatments in managed systems.