Trout are a diverse group of freshwater fish, valued by anglers and nature observers alike. Found in scenic aquatic environments, from clear mountain streams to expansive lakes, their beauty and the challenge of their pursuit make them a prominent and fascinating species.
Understanding What Defines a Trout
Trout belong to the Salmonidae family, which also includes salmon and graylings. “True trout” are primarily found in the Salmo and Oncorhynchus genera. Char, such as Brook Trout and Lake Trout, belong to the Salvelinus genus, though they are often called trout. All these fish share a streamlined body shape and an adipose fin, a small, fleshy fin located between the dorsal fin and the tail.
Major Trout Species and Their Identifiers
Rainbow Trout (Oncorhynchus mykiss)
Rainbow Trout (Oncorhynchus mykiss) are named for the distinctive iridescent pink or red band running along their sides. Their body coloration ranges from olive-green to blue-green on the back, fading to silvery-white on the belly. Small, dark spots are scattered over their back, sides, and all fins, including the tail. Freshwater adults commonly measure 15-40 centimeters (6-16 inches) and weigh up to 1 kilogram (2.2 pounds), though lake-dwelling or anadromous forms, known as steelhead, can grow significantly larger, exceeding 9 kilograms (20 pounds). Their caudal fin is typically squared with a slight fork.
Brown Trout (Salmo trutta)
Brown Trout (Salmo trutta) range from brassy brown to olive-brown on the back, transitioning to yellowish-brown or silvery on the sides, and a creamy white belly. They have large, dark spots, often outlined with pale halos, scattered across their sides and back. Reddish-orange spots, sometimes with pale borders, are also frequent, particularly on their lower sides. Unlike many other trout, their tail fin usually has few to no spots. Brown trout generally range from 1 to 2 pounds in smaller rivers but can grow much larger, exceeding 10 pounds in fertile lakes.
Brook Trout (Salvelinus fontinalis)
The Brook Trout (Salvelinus fontinalis) is technically a char, distinguished by light spots on a darker background. Their olive-green to dark brown bodies have distinctive wavy, worm-like patterns called vermiculations on their back and head. Along their sides, pale yellowish or greenish spots intermingle with small red spots, often encircled by blue halos. A prominent feature is the milk-white leading edge on their pectoral, pelvic, and anal fins, often followed by a black stripe. Typical lengths range from 25 to 65 centimeters (10 to 25 inches), with weights from 0.3 to 3 kilograms (0.7 to 6.6 pounds).
Lake Trout (Salvelinus namaycush)
Lake Trout (Salvelinus namaycush) are a char species, recognized by their dark brown to silvery-green body coloration. Their most striking feature is the irregular, cream-colored to yellowish spots or blotches covering their head, body, and fins. Unlike many other trout, they possess a deeply forked caudal (tail) fin. Lake trout are the largest members of the char genus, commonly ranging from 51-91 centimeters (20-36 inches) in total length and weighing between 1.8-10 kilograms (4-22 pounds).
Cutthroat Trout (Oncorhynchus clarkii)
Cutthroat Trout (Oncorhynchus clarkii) are named for the distinctive red, orange, or yellow slashes found on the underside of their lower jaw. Their body color varies widely by habitat, from olive to golden yellow or silvery-blue. Black spots are present, often sparse near the head and becoming more concentrated and larger towards the tail, extending onto the caudal fin. Freshwater-resident adults usually measure 15-40 centimeters (6-16 inches), though lake-dwelling forms can exceed 60 centimeters (24 inches).
Golden Trout (Oncorhynchus mykiss aguabonita)
The Golden Trout (Oncorhynchus mykiss aguabonita) is a Rainbow Trout subspecies known for its vibrant coloration. These fish display a brilliant golden-yellow on their lower sides, transitioning to an olive-green back. A prominent reddish-orange stripe runs along their lateral line. Black spots are confined to their back, above the lateral line, and on the tail. Their orange pectoral, pelvic, and anal fins often feature a black band with a white-yellow tip. Adults in native habitats range from 15 to 30 centimeters (6 to 12 inches).
Geographic Distribution and Preferred Habitats
Trout species require cold, clear, and well-oxygenated waters to thrive, favoring temperatures in the 50s to low 60s Fahrenheit. Adequate dissolved oxygen levels are crucial for their survival and growth. Diverse habitats offering a mix of riffles, pools, and cover, such as undercut banks and woody debris, are important. Clean gravel substrates are essential for successful spawning.
Rainbow Trout are native to the Pacific coast of North America and Asia, but are now established globally. Brown Trout, originating from Europe, Western Asia, and North Africa, are widespread due to their adaptability, inhabiting cool rivers, streams, and lakes with rocky bottoms and cover. Brook Trout, native to eastern North America, prefer clear, cool, spring-fed streams and ponds, with some populations migrating to and from marine environments.
Lake Trout are indigenous to deep, cold, and oxygen-rich lakes across northern North America, including the Great Lakes. Cutthroat Trout are found across western North America, occupying diverse habitats from coastal waters to high-elevation mountain streams and lakes, often seeking clear, cold headwaters. Golden Trout are native to the high-altitude streams and lakes of California’s southern Sierra Nevada, thriving in cold, clear, meandering waters with gravel or sandy bottoms.