Rockweed gunnel

The rockweed gunnel has a translucent body which varies in color from bright green to a reddish-brown and its color is determined by their environment. Fish living among green seaweed are green and fish living among brown seaweed are reddish brown. They can change colors depending on the type of seaweed surrounds them. The Rockweed Gunnels' colors are also determined by the color of the amphipods that it consumes. It has a long, anguilliform body (thin and eel-like) with small fins, each roughly equal in size to the diameter of their eye and too small to be used in swimming. The spine in the anal fin has a length which is 40% of the length of the head and has a sharp point, tilted forward. This fish has 83 or 84 spines in its dorsal fin and a single spine and between 32 and 38 soft rays in its anal fin. It has a rounded caudal fin. They have relatively big eyes as well as terminal mouths that are somewhat smaller than other gunnel species. Its maximum published total length is 23 cm (9.1 in).

The rockweed gunnel is found along the eastern Pacific Ocean from Banks Island, British Columbia in the north, to Punta Escarpada, central Baja California, Mexico in the south. The exact status of the species pertaining to each area is unknown as there has been no recent primary literature on this topic. This species lives in the demersal and intertidal zones at depths of up to 9 m (30 ft) which they use to migrate on. It commonly occurs in tide pools and inshore areas among masses of brown seaweed in the genus fucus, also known as 'rockweed'.