A cross-shelf gradient in delta 15N stable isotope values of krill and pollock indicates seabird foraging patterns in the Bering Sea

Concurrent measurements of predator and prey delta 15N isotope values demonstrated that a cross-shelf isotopic gradient can propagate through a marine food web from forage species to top-tier predators and indicate foraging areas at a scale of tens of kilometers. We measured delta 13C and delta 15N in muscle tissues of thick-billed murres (Uria lomvia) and black-legged kittiwakes (Rissa tridactyla), and in whole body tissues of walleye pollock (Gadus chalcogrammus) and krill (Thysanoessa spp), sampled across the continental shelf break in the Bering Sea in 2008 and in 2009. We found significant basin-shelf differences at fine scales (