Food habit variability of arrowtooth flounder (Atheresthes stomias) along the US west coast

A diet study of arrowtooth flounder (Atheresthes stomias) was undertaken to provide current information on their food habits and predator-prey relationships in the California Current Ecosystem. Arrowtooth flounder stomachs (n = 573) were collected between 2013 and 2018 from 397 trawls during the Northwest Fisheries Science Center's West Coast Groundfish Bottom Trawl Survey. A total of 357 stomachs (62.3%) contained prey, which revealed a highly piscivorous diet across all lengths examined (14 - 77 cm) and described a regionalized and opportunistic feeding behavior. Increased predator length correlated both with an increase in percentage of fish prey consumed and an increase in depth of capture. Smaller (< 43 cm) and shallower (<= 183 m) arrowtooth flounder consumed a relatively high percentage of euphausiids and shrimp, while larger arrowtooth flounder (>= 43 cm) captured at greater depths (> 183 m) consumed more fish and fewer shrimp and euphausiids. Arrowtooth flounder diet varied by geographic area, likely resulting from regional differences in prey availability. North of the mean latitude of capture (44.45 degrees N), Pacific hake (Merluccius productus) and Pacific herring (Clupea pallasii) were the predominant fish in arrowtooth flounder diets, while arrowtooth flounder caught south of the mean latitude consumed mostly Pacific hake and rockfishes (Scorpaenidae). Unidentified teleost fish contributed much to the diet across all size, depth, and latitude ranges.