1 Introduction The feeding ecology of marine predator populations, and therefore their trophic niche, is defined by a combination of biotic and abiotic factors. Biotic factors refer to all living organisms in an ecosystem, which together constitute the food web. Abiotic factors, such as temperature and salinity, determine in part the presence, distribution, and abundance of prey and their consumers within an ecosystem (Castillo et al. 1996; Harrison and Whitfield 2006; Bailleul et al.
