Important prey species of marine vertebrate predators in the northwest Atlantic:proximate composition and energy density

Abstract

Prey energy density values are crucial inputs to bioenergetic consumption models. Vertebrate predators in the northwest Atlantic consume a variety of prey species, but the proximate composition (PC; proportions of lipid, protein, ash and water) and energy density (ED; kJ g-l) of prey, and their variability, are known poorly. In this study, key prey species from Newfoundland and Labrador were studied: Atlantic cod Gadus morhua, American plaice Hippoglossoides platessoides, sand lance Ammodytes dubius, Arctic cod Boreogadus saida, northern shrimp Pandalus borealis, redfish Sebastes spp., Greenland halibut ReiDhardtius hippoglossoides, squid Illex lllecebrosus and Gonatus fabricji, capelin Mallotus villosus, Atlantic herring Clupea harengus and daubed shanny Lumpenus maculatus. PC and ED varied greatly among species and were influenced by size, season, geography and year. Herring, capelin and G. fabricii had the highest ED, whereas Atlantic cod, plaice, sand lance and shrimp had the lowest. Halibut and I. illecebrosusincreased in ED with size. EDs of capelin and redfish varied seasonally; that of plaice and sand lance did not, Herring and halibut had higher ED in the early 1990s than in recent years. Such variation in prey ED has important imphcations for digestive efficiency, foraging energetics, and dietary preferences of vertebrate predators.