Assessing the importance of cephalopods in the diets of marine mammals andother top predators: problems and solutions

The methodology typically used in the analysis of predator diets is subject to a range of errors and biases and these are reviewed in relation to esti mating the consumption of cephalopods by top predators. Further uncertainti es, relating to population size estimation, predator energy requirements an d sojourn time in the study area are encountered when estimating population consumption. We review the use of such data to predict consumption of cephalopods by cer tain top predators globally, in the Antarctic, the Azores and in the North Atlantic. The traditional approach is based on the derivation of "minimum" and "maximum" estimates. We illustrate an alternative approach for calculat ing confidence limits for estimates, based on bootstrap simulations, for sp erm whales in the northern Northeast Atlantic. While the resulting confidence limits may appear discouragingly wide, compu tations such as those used here are useful for showing where data are most imperfect and for setting future research priorities. Even at present, with in distinctly prescribed geographic areas, where populations are well known , such modelling of species interactions may be productive. (C) 2001 Elsevi er Science B.V. All rights reserved.