Food Habits of Some Commercially Important Groundfish off the Coasts

This report describes the food habits of some commercially important groundfish collected off the coasts of California, Oregon, Washington, and British Columbia. Generally, the groundfish reported on were sampled during three cruises the triennial groundfish survey of 1989 and the continental slope surveys of 1991 and 1992. Some young-of-the-year Pacific hake (also known as Pacific whiting, Merluccius productus) were examined from 1987 and 1988 surveys. Where possible, the diet of each groundfish species was examined for possible ontogenetic, latitudinal, depth, and seasonal changes. Typically, ontogenetic shifts in the diet of the predators examined on this study were based on the ability of the larger fish to eat larger prey. Effects of latitude, depth, and season were also detected for some of these species. The diet of age-0 Pacific hake shifted from copepods to euphausiids with increasing size (33-128 mm total length) in 1987, but not in 1988. Pacific hake became increasingly piscivorous with size, and cannibalism was an important diet component in 1991 in the Monterey INPFC (International North Pacific Fisheries Commission) statistical area. Sablefish (Anoplopoma fimbria) and shortspine thornyhead (Sebastolobus alascanus) consumed a wide variety of locally abundant prey items including large amounts of offal from fish-processing operations conducted at sea. The diet of juvenile sablefish captured over the continental shelf was similar to the diet of Pacific hake, but the diet of larger sablefish sampled from the upper continental slope was more similar to the shortspine thornyhead diet. Arrowtooth flounder (Atheresthes stomias) was the most piscivorous predator examined in this study, consuming mostly Pacific hake, Pacific herring (Clupea pallasi) and unidentified gadids. Longspine thornyhead (S. altivelis) consumed a variety of benthic crustaceans, and the presence of fishery offal in the diet indicated that longspine thornyhead also scavenged the slope bottom. Giant grenadier (Albatrossia pectoralis) consumed mostly deepwater crustaceans and fishes in this study, by weight. Pacific grenadier (Coryphaenoides acrolepis) stomachs contained mostly squid and a variety of crustaceans, by weight. A majority of the diet of Dover sole (Microstomuspaczjkus) and deepsea sole (Embassichthys bathybius) was polychaete worms and brittlestars.