Research Document - 2004/093
Estimated Consumption of Atlantic cod (Gadus morhua), by Harp seals (Phoca groenlandica), in NAFO Zone 4RS.
By M. O. Hammill, Stenson, G.B.
Abstract
Consumption of Atlantic cod, by harp seals in the northern Gulf of St Lawrence (NAFO zone 4RS3Pn) was estimated for the period 1985-2003. Estimates were obtained by combining information on harp seal abundance, energy requirements, diet composition and the distribution of animals. Estimated consumption of 4RS Atlantic cod, in 2003 was in the order of 27,700 (SD=7,100) tonnes. Harp seals appear to feed primarily on cod less than 30 cm in length, but variability in prey length in this study and elsewhere have been observed. Overall, fifty-six percent of the estimated consumption consists of cod ≤ 3 years of age. Considerable uncertainty in the distribution of animals and diet composition at the population level affect both the magnitude and the direction of the bias in current estimates of cod consumption. These estimates differ from earlier studies by attempting to incorporate variability in estimates of population size, energy requirements, seal distribution, and diet composition.
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