Icelinus borealis has a very small antler-like uppermost spine on the preoperculum. There are 9 or 10 spines and between 15 and 17 soft rays supporting the dorsal fins, while the anal fin has between 12 and 14 soft rays. The caudal fin is clearly rounded and the pelvic fins are small and often curved. The overall color is dark olive gray or brown on the upper body, paler below. There are dark saddle marks, typically four, across the body and thin dark brown bars on the head and the finsexcept for the anal fin. In males the margin of the has black spots. This species has a maximum published standard length of.
Distribution and habitat
Icelinus borealis is found in the temperate eastern Pacific Ocean from the Bering Sea coast of Alaska south as far as Puget Sound, in Washington. It is a demersal fish found at depths between on soft or shell substrates.
Biology
Icelinus borealis feeds on crustaceans, especially shrimp. This species is common in waters near to rookeries of Steller's sea lions and so constitute part of the diverse prey hunted by that mammal.