Diet of Cape fur seals Arctocephalus pusillus pusillus at three mainland breeding colonies in Namibia. 2. Temporal variation

Abstract

Scat analysis was used to assess temporal variability in the diet composition of Cape fur seals Arctocephalus pusillus pusillus from three breeding colonies in Namibia (January 1994 to April 2002). The diet displayed significant inter- and intra-annual variation in composition at each of the study colonies. The diet was not predictable on an annual pattern, and little consistent seasonality was apparent at each of the study sites. However, some prey species tended to display some seasonality, possibly as a result of their life-history patterns. At the Cape Cross colony, small Cape hake Merluccius spp. in the diet coincided with their spawning season. At the Atlas-Wolf Bay and Van Reenen Bay colonies, lanternfish Lampanyctodes hectoris were most prevalent in the diet during the upwelling season (August–January). Outside that period, pelagic goby Sufflogobius bibarbatus were most abundant in the diet at those colonies. This pattern may be a result of the gobies' southwards migration from northern Namibian waters where smaller goby are dominant in the diet at the Cape Cross colony in the upwelling season. The prevalence of Cape horse mackerel Trachurus trachurus capensis in the diet at Cape Cross was coincident with the pelagic phase of juvenile horse mackerel.

Keywords: Arctocephalus pusillus pusillus, breeding colony, Cape fur seal, diet, Namibia, scat analysis, temporal variation

African Journal of Marine Science 2006, 28(1): 73–88