Fur Seal Diving Behaviour in Relation to Vertical Distribution of Krill
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Continuous records of diving depths of female Antarctic fur seal Arctocephalus gazella on 3-8 day feeding trips to sea from South Georgia were analyzed in conjunction with data on diel changes in the abundance and distribution of their main prey, krill. In 36 complete days foraging by 7 seals, 75% of 4273 dives were at night. Dives then were consistently shallower (dive depth <30 m) than in daytime (mostly 40-75 m). This closely matched changes in the vertical distribution of krill, nearly all of which was below a depth of 50 m from 09.00-15.00 h, with substantial quantities >40 m only between 21.00-06.00 h. Although over 40% of the krill in water column at any time of day was <75 m, only 3% of dives exceeded this depth. Because krill migrate vertically fur seals are able to exploit them most efficiently during shallow dives at night.-from Authors
author list (cited authors)
Croxall, J. P., Everson, I., Kooyman, G. L., Ricketts, C., & Davis, R. W.