Growth and feeding habits of grey seals ( Halichoerus grypus) in the northwestern Gulf of St. Lawrence, Canada

• Published in: Canadian Journal of Zoology
• Main Authors: Murie, D. J., Lavigne, D. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1992
• Subjects: Canada; Gadus morhua
• Online Access: http://dx.doi.org/10.1139/z92-221; http://www.nrcresearchpress.com/doi/pdf/10.1139/z92-221

Growth and feeding habits were determined for 82 grey seals (Halichoerus grypus) collected in the northwestern Gulf of St. Lawrence, Canada, between 3 July and 6 December 1983. Male grey seals reached an asymptotic standard length of 242 cm, whereas females attained a length of 201 cm. Most (96%) females 175 cm or longer and 5 years of age or older were pregnant. A larger proportion of grey seal stomachs contained food items in July than in the other months sampled, regardless of sex or maturity status. The diet consisted primarily of cod (Gadus morhua), herring (Clupea harengus harengus), and capelin (Mallotus villosus), which together contributed 72% of the wet mass and 76% of the gross energy of all the prey consumed. Invertebrates contributed negligible mass or gross energy to the diet. Grey seals primarily consumed fish ≤30 cm in length and ate only one or two different fish species during any one feeding bout. Based on our stomach content analyses, the food consumed daily by adult male and female grey seals provided an average gross energy of 3628 and 2925 kcal (1 kcal = 4.18 kJ), respectively, which is consistent with daily energy requirements estimated using bioenergetic models. However, the large percentage of empty stomachs (50%), together with differential digestion of fish species, suggests that grey seals may not feed every day.