Factors affecting proximate composition of prey species important to marine vertebrate predators in the Northwestern Atlantic

Magalhães, Alexandra M. (1999) Factors affecting proximate composition of prey species important to marine vertebrate predators in the Northwestern Atlantic. Masters thesis, Memorial University of Newfoundland.

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Abstract

Energy-density values of prey species are essential inputs for bioenergetic models of consumption. Diets of marine vertebrate predators in the northwestern Atlantic are reasonably well described, but the proximate composition (PC) and energy density (ED) of these prey species, and the factors affecting them, are poorly known, particularly tor those prey sizes commonly eaten. The purpose of this study was to estimate PC and ED of important prey species, and investigate important sources of variation. -- Twelve species were collected in waters near Newfoundland and Labrador: 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 (Reinhardtius hippoglossoides), squid (Illex illecebrosus and Gonatus fabrici), capelin (Mallotus villosus), Atlantic herring (Clupea harengus) and daubed shanny (Lumpenus maculatus). ED was estimated from replicates of all samples by determining moisture, lipid, protein and inorganic content. ED differed among species and was influenced by body size, season, geography, and year of collecting. Herring, capelin and Gonatus squid had the highest ED; Atlantic cod, American plaice, sand lance, Arctic cod and northern shrimp had the lowest. ED increased greatly with size (age) in capelin, and also in Greenland halibut and Illex squid. Other species showed no strong relationships of ED to body size. ED was greater in male than female northern shrimp. ED in capelin was highest in winter. Arctic cod had higher ED offshore than nearshore in eastern Newfoundland. Interannual variation in ED was found in Greenland halibut and Atlantic herring. Levels and variation in ED are discussed in relation to predator physiology, ecology, and life history.

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