A. Berruti et al., SEASONAL AND INTERANNUAL VARIATION IN THE DIET OF 2 COLONIES OF THE CAPE GANNET (MORUS-CAPENSIS) BETWEEN 1977-78 AND 1989, Colonial waterbirds, 16(2), 1993, pp. 158-175
The species composition of the prey of the Cape Gannet (Morus capensis
) was monitored monthly at colonies at Lambert's Bay and Malgas Island
in th, southern Benguela system off western South Africa from 1977-78
to 1989. A modified form of the biplot procedure gave a parsimonious,
descriptive summary of this time-series. The diet at Malgas Island sh
owed much greater seasonality than at Lambert's Bay. Seasonal variatio
ns in the anchovy (Engraulis japonicus) and sardine (Sardinops sagax)
components of gannet diet conformed largely to the known distribution
of these species. However, the gannet diets demonstrated a previously
undocumented presence of adult anchovy off the western Cape, particula
rly in summer. The contribution of sardines to the diet increased from
late 1984 at Malgas Island, and from late 1985 at Lambert's Bay, with
corresponding decreases in anchovy and hake (Merluccius spp.) at Malg
as Island and anchovy at Lambert's Bay. The occurrence of hake in gann
et diets, available as trawler offal throughout the year in deeper wat
ers, seems to be associated with a lack of shoaling fish inshore.