The diet of the Atlantic wolffish was studied by examining the contents of the gastrointestinal tracts of 90 individuals collected from the sea urchin dominated rocky subtidal in eastern Newfoundland. Green sea urchins comprised 75% of the overall diet by weight. Horse mussels ranked second but comprised only 9.5% of the diet. The remainder of the diet consisted of several species of invertebrates and fish. The average (over the whole season) wolffish contained 120 g of urchins, equivalent to the biomass of urchins on 0.23 m2 in the middle of the urchin-dominated zone. During April–September, prior to breeding, the average male wolffish contained 174 g of urchins, and the average female contained 85 g of urchins, biomass values representing, respectively, 0.33 and 0.16 m2. Assuming that the contents of the gastrointestinal tract turn over every 3 days, it was calculated that during May through August each wolffish consumes on average 5.29 kg of urchins (males, 7.09 kg; females, 3.50 kg). Based on these figures, a density of 1 wolffish pair per 20 m2 would be required to consume the mean biomass (532 g m−2) of urchins present in the urchin-dominated zone in 1 year.
Spring feeding of Atlantic wolffish (Anarhichas lupus) on Stellwagen Bank, Massachusetts
