Ocean pout (Macrozoarces americanus (Bloch and Schneider) (Pisces: Zoarcidae)) predation on green sea urchins (Strongylocentrotus droebachiensis (O.F. Mull.) (Echinodermata: Echinoidea)) in eastern Newfoundland

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Abstract
The diet of ocean pout was studied by analysis of the contents of the gastrointestinal tracts of 151 individuals collected from the green sea urchin dominated rocky subtidal in eastern Newfoundland. Green sea urchins constituted 62% of the overall diet by weight. The brittle star, Ophiopholus aculeata, constituted 7% of the diet, while the remainder was miscellaneous invertebrates and fish (mainly capelin and billfish). From April to July, when the fish are inshore and feeding, before breeding, the average ocean pout contained 56.3 g of urchins. This is a biomass of urchins equivalent to that in 0.106 m2 of the middle of the urchin-dominated zone. During the inshore feeding period, the average male ocean pout contained 65.0 g of urchins, and the average female contained 47.5 g, biomass values representing 0.122 and 0.089 m2, respectively. Assuming that the contents of the gastrointestinal tract turn over every 3 days, and assuming a 1:1 sex ratio, it is calculated that while inshore, before a seasonal reduction in feeding associated with the spawning season, each ocean pout consumes on average 2.29 kg of urchins (males 2.64 kg, females 1.93 kg). Based on these figures, a density of one ocean pout pair per 8.6 m2 would be required to completely consume the mean biomass (532 g m−2) of urchins present in the urchin-dominated zone in one season.

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