Which gasterosteiform fishes are found in freshwater habitats?

Within the order Gasterosteiformes, the family Gasterosteidae, commonly known as sticklebacks, is the primary group noted for inhabiting freshwater environments, alongside brackish and marine waters.12

Specific freshwater-dwelling species include:

• Three-spined stickleback (Gasterosteus aculeatus): A widespread species found in both fresh and salt water throughout the Northern Hemisphere.2
• Nine-spined stickleback (Pungitius pungitius): A widely distributed form found in the Northern Hemisphere.2
• Brook stickleback (Culaea inconstans): Specifically noted as an inhabitant of North American fresh waters.2
• Four-spined stickleback (Apeltes quadracus): Found in both marine and freshwater environments of North America.2

While many gasterosteiforms are primarily marine, certain pipefishes, seahorses, and sticklebacks possess the physiological ability to tolerate a wide range of salinity, allowing them to occupy diverse aquatic habitats.3