Journal of the Marine Biological Association of the United Kingdom

Research Article

Food and feeding habits of the blue shark Prionace glauca caught off Ensenada, Baja California, Mexico, with a review on its feeding

Unai Markaidaa1 p1 c1 and Oscar Sosa-Nishizakia1

a1 Laboratorio de Ecología Pesquera, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, 22800 Baja California, Mexico

Abstract

Stomach contents of 893 blue shark (Prionace glauca) caught off Ensenada, Todos Santos Bay, Baja California, from 1995 to 1997 were analysed. 614 had identifiable food remains. A large variety of pelagic cephalopods occurred in 55.5% of all stomachs and accounted for 46.2% of all prey and 84% by estimated weight of stomach contents. The most abundant (17%) and frequent (32%) was Histioteuthis heteropsis and the most important by estimated weight (22%) was ‘Gonatus californiensis’. Argonauta spp. and Vampyroteuthis infernalis were also abundant prey. A pair of beaks of giant squid Architeuthis sp. constitutes the first record for Mexican waters. Feeding habits and the probability of scavenging on mesopelagic cephalopods is discussed. The single most abundant prey was the pelagic, red crab Pleuroncodes planipes (41.7%). Other prey included teleost fish, amniotes and floating items. Diet varied greatly between months with no clear seasonal pattern. Tiny diet differences due to shark size or sex were inconclusive. A thorough review of studies on blue sharks stomach contents analysis is given. Blue shark feed on a large variety of passive pelagic prey, mainly mesopelagic cephalopods, that could be preyed upon as well as scavenged. Depletion of this predator due to overfishing may be leading to unknown cascading top-down effects in the mesopelagic realm.

(Received June 04 2009)

(Accepted November 10 2009)

(Online publication February 12 2010)

Correspondence:

c1 Correspondence should be addressed to: U. Markaida, Laboratorio de Pesquerías Artesanales, El Colegio de la Frontera Sur (ECOSUR), Unidad Campeche, Calle 10 # 264, Col. Centro, 24000 Campeche, Mexico email: umarkaida@ecosur.mx

p1 Present address: Laboratorio de Pesquerías Artesanales, El Colegio de la Frontera Sur (ECOSUR), Unidad Campeche, Calle 10 # 264, Col. Centro, 24000 Campeche, Mexico