Krill caught by predators and nets revisited: interpreting prey selection in proper temporal–spatial scales

Krill demography and recruitment are tracked through time using scientific net sampling and predator diet sampling. Comparisons of these two methods show broadly coherent results but also frequently show differences that have fueled speculation of prey selectivity by predators. Krill, however, are not homogenously distributed and matching temporal-spatial scales of sample collections can be problematic. In this paper we use ARGOS satellite location data from foraging female fur seals to first identify foraging habitat and its proximity to breeding colonies where diet studies are conducted. We compare krill length frequency data collected over the entire West area of the U.S. AMLR survey grid with that collected only in fur seal foraging habitat. Both are compared to krill in fur seal diet. When spatial temporal scales for the two data sets are approximated as close as possible we found no difference in krill length frequency distributions. We suggest that fur seals are not selecting large krill while foraging but are instead selecting foraging locations that have larger krill in densities that maximize energy gain.