Myoxocephalus jaok, the plain sculpin, is a species of marine ray-finned fish belonging to the family Cottidae, the typical sculpins. This species is found in the northern Pacific Ocean and adjacent Arctic Ocean. Taxonomy Myoxocephalus jaok was first formally described as Cottus jaok in 1820 by the French zoologist Georges Cuvier with its type locality given as the coast of Kamchatka. The specific name, jaok, is the local name for this species in Kamchatka. Description Myoxocephalus jaok has its dorsal fins supported by between 8 and 10 spines and between 14 and 17 soft rays while the anal fin has between 13 and 15 soft rays. The head depressed, with the upper surface having bony spines and ridges. There are rounded bony plates with serrated margins on the upper flanks. This species has a relatively narrow head with a u-shaped mouth when viewed from above. There are no cirri on the head and body and the top spine on the preoperculum is the longest and is straight and has no branches. There are many round bony spine bearing plates above the lateral line with a lesser number of smaller plates below the lateral line bearing rearward ponting spines. The lateral line is made up of three rows of pores. The overall colour is grey and brown with numerous small black spots and there may be indistinct dark bands. This species reaches a maximum publsihed total length of and a maximum weight of . Distribution and habitat Myoxocephalus jaok is found in the northern Pacific Ocean from the Sea of Japan and the Sea of Okhotsk through the Kuril Islands to southeastern Kamchatka and the western Bering Sea, including the eastern Aleutian Islands and from the Gulf of Alaska, north onto the eastern Chukchi Sea and the western Beaufort Sea. This species occurs in shallow waters where it is a demersal fish found on sandy and muddy substrates from the intertidal zone down to depths of typically less than ; rarely caught at depths greater than . Biology Myoxocephalus jaok has a catholic diet with over 100 differnt types of food item having been identified, although fish and decapods are the most important items. The fish taken include flatfishes, Alaska pollock (Theragra chalcogramma), Pacific sand lance (Ammodytes hexapterus) other cottids. The Decapoda include crabs such as Chionoecetes opilio, Hyas coarctatus and Telmessus cheiragonus as well as shrimps from the family Crangonidae.