An assessment of the use of the Jackass penguin as a sampler of the marine environment

Bibliography: leaves 68-83.In this thesis the use of the jackass penguin Spheniscus demersus as a sampler of the marine environment is assessed. Between February 1987 and July 1988, 638 monthly diet samples were obtained from adult jackass penguins at west - (Marcus and Jutten Islands) and southwest-coast (Dyer Island) colonies off South Africa, supplementing data collected since 1980. Penguin diet was compared over time and between colonies in order to establish the presence or absence of qualitative changes or quantified trends in the biology of pelagic schooling fish species important to the South African purseseine fishery, viz. anchovy Engraulis capensis, pilchard Sardinops ocellatus, maasbanker Trachurus trachurus and red-eye Etrumeus whiteheadii. The principal prey of jackass penguins and major contributor to commercial catches is anchovy and, consequently, the biology of this fish species was emphasized. Monthly and annual trends in prey composition and anchovy size-range were related to the availability, abundance and distribution of the penguins' prey species in the marine environment