Rainbow Trout

The rainbow trout is a salmonid fish native to cold-water drainages of the Pacific coast of North America and eastern Asia, including a sea-run form known as steelhead. It belongs to genus Oncorhynchus, placing it taxonomically alongside the Pacific salmon rather than the true trout genus Salmo. Because of its popularity as a sport fish, rainbow trout have been introduced far beyond their native range and now occur on every continent except Antarctica. The species includes both resident freshwater populations that remain in rivers and lakes and anadromous steelhead populations that migrate to the ocean before returning to spawn.

Rainbow trout are identified by their coloration and spotting pattern along a streamlined body.

• Body: torpedo-shaped, laterally compressed, 30-80 cm typical length
• Back: olive-green to blue-gray
• Sides: silvery with a broad pink-to-red iridescent lateral stripe, most vivid in breeding males
• Spotting: dense small black spots on the back, dorsal fin, adipose fin, and tail
• Fins: small fleshy adipose fin present between the dorsal fin and tail, moderately forked caudal fin
• Head: relatively small with a terminal mouth lined with fine teeth

Steelhead (the anadromous, sea-run form) are more uniformly silvery with a fainter stripe, reflecting time spent at sea rather than in freshwater.

Rainbow trout inhabit cold, clear, well-oxygenated rivers, streams, and lakes with water temperatures generally between 10-18°C. Spawning requires clean gravel-bottomed streams with moderate current. The species is native to Pacific-draining watersheds of western North America and the Kamchatka Peninsula of Asia, but extensive stocking programs have established populations across six continents. Resident populations live entirely in freshwater rivers and lakes, while anadromous steelhead migrate from these same natal rivers to the open ocean to feed and grow before returning upstream to spawn.

Rainbow trout are opportunistic carnivores, feeding on aquatic and terrestrial insects, crustaceans, and smaller fish depending on their size and habitat. Resident freshwater fish typically spawn in spring, with females excavating gravel nests called redds where eggs are fertilized and buried for protection. Steelhead undertake extensive migrations, spending one to several years in the ocean before returning to freshwater to spawn, and unlike Pacific salmon, some steelhead survive spawning and can breed more than once. The species is territorial in streams, holding feeding positions in current, and is one of the most widely stocked and pursued recreational sport fish in the world.