Body shape :  Elongate and spindle-shaped, somewhat laterally compressed

Average size :  20 to 30 cm (8 to 12 in)

Coloration :  Varies with habitat; dark with pale spots; marbled olive-green to black back; paler flanks with light spots and small, red spots surrounded by bluish halo; marbled dorsal and caudal fins; pectoral and pelvic fins with black band and white margin; coloration more intense during spawning with males showing bright orange abdomens.

Anadromous brook trout (sea trout, living at sea but spawning in fresh water) more silvery with a few faint, red spots.

External characteristics :  Large mouth with well-developed teeth; hooked lower jaw sometimes visible in spawning males; adipose fin far beyond dorsal fin; dorsal and pelvic fins at mid-body length; square or slightly forked caudal fin.