Seasonal Variation in Body Condition of Adult Barents

• Main Authors: Sea Harp Seals (phoca Groenl, K. T. Nilssen, T. Haug, P. E. Grotnes, V. Potelov
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Barents Sea; Phoca groenlandica
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.509.2074; http://journal.nafo.int/J22/Nilssen.pdf

In the period 1990–94, harp seals (Phoca groenlandica) were sampled for ecological studies in various areas and seasons in the Barents Sea. Data on total body weight, standard body length, axillary girth, dorsal and ventral blubber thickness were collected from all seals. Data from seals with standard body length 150 cm or more were analysed in order to evaluate the seasonal dynamics in body condition of the adult seals. Blubber thickness measurements and a condition index (C) expressed as C = L / W × d, where L is standard body length (cm), W is total body mass (kg) and d is dorsal blubber thickness (cm), showed the same seasonal patterns. The seals were in poor condition in spring and early summer (May–June), condition improved during the course of summer, and the animals were in good condition in September and in October when the mean dorsal blubber thickness was approximately 88 mm. The energy stores built up during the summer and autumn were maintained until February, whereafter the seals became thinner as the stores of blubber decreased rapidly during the breeding season (late February–March). A slight, but not significant increase in dorsal blubber thickness was observed in the short period between lactation and moult (late March–early April), but the stores of blubber decreased further during moult (late April–May) to a mean dorsal blubber thickness of less than 20 mm in mid-June. No significant difference was observed in blubber thickness or condition indices between the sexes in the various periods, except during April when the females were in significantly poorer condition than the males. Harp seals sampled during the seal invasions to North Norwegian coastal waters in February 1988 were in poorer condition than seals captured in the Barents Sea in February 1993. Key words: Barents Sea, body condition variations, harp seals.