Are deep-sea cephalopods really common preys for oceanic seabirds?

Abstract

VASKE JR., T. Are deep-sea cephalopods really common preys for oceanic seabirds? Biota Neotrop. 11(1): http://www.biotaneotropica.org.br/v11n1/en/abstract?article+bn02611012011.Abstract: An analysis of published data on oceanic seabirds diets, show the predominance of muscular cephalopods with superficial distribution in the oceanic layers, but also important are the gelatinous and ammoniacal species restrict to layers below 300 m from the surface. In principle, it could be not expected that deep-sea cephalopods are common prey for seabirds like several authors have been concluded. It is proposed in this study that an indirect source, important and easily attainable, have been appeared with the beginning of tuna longline operations. The habit to feed upon viscera of the fishes captured by tuna longliners, that discard the gut contents to the water, may explain the probable equivocal conclusions that deep dwelling cephalopods are natural prey of oceanic seabirds. Keywords: squid, octopus, seabirds, prey-predator. VASKE JR., T. Cefalópodes de profundidade são realmente presas comuns para aves marinhas oceânicas? Biota Neotrop. 11(1): http://www.biotaneotropica.org.br/v11n1/pt/abstract?article+bn02611012011.Resumo: Uma análise de dados publicados sobre dietas de aves marinhas oceânicas mostra a predominância de cefalópodes musculares e de distribuição mais superficial nas camadas oceânicas, mas também são importantes as espécies gelatinosas e amoniacais restritas a camadas abaixo dos 300 m da superfície. A princípio, não deveria se esperar que cefalópodes de profundidade fossem considerados presas comuns de aves marinhas oceânicas como reportados por muitos autores. É proposto neste estudo que uma fonte indireta, importante e de fácil obtenção, surgiu com o início das atividades dos barcos atuneiros que operam com espinhel. O hábito de ingerir restos de vísceras de peixes capturados em barcos espinheleiros pode explicar as prováveis conclusões equivocadas de que cefalópodes de profundidade são presas naturais de aves marinhas oceânicas. Palavras-chave: lula, polvo, aves marinhas, presa-predador. Biota Neotrop., vol. 11, no. 1 (37.9%) are deep-water dwellers, i.e., improbable as natural prey for oceanic seabirds. Scavenging is the main method of food search of seabirds, and then the seabirds are likely suited for daytime foraging. On the other hand, Imber (1992) calculated that 79% of the cephalopods found in the diet of Wandering albatross could be taken live at the surface, and 95% of them only or mainly at night, once some species are bioluminescent. Pitman et al. (2004) suggest that Laysan feed mainly on dead rather than live squid, once ommastrephids are their main food item. Moreover, ommastrephids are abundant at the sea surface