title: Trophic ecology of yellownose skate Zearaja chilensis, a top predator in the south-western Atlantic Ocean.
abstract: The diet and trophic level (TL ) of the yellownose skate Zearaja chilensis in the south-western Atlantic Ocean (35°-54° S), and how these varied in relation to body size, sex, maturity stage, depth and region were determined by analysis of stomach contents. From 776 specimens analysed, 671 (86·5%) ranging from 180 to 1190 mm total length (LT ) had prey in their stomachs. The diet was dominated by fishes, mainly the notothenioid Patagonotothen ramsayi and the Argentine hake Merluccius hubbsi. The consumption of fishes and crabs increased with increasing predator size, and these preys were more important in the north than in the south. Isopods and other crustaceans were consumed more in the south and their consumption decreased as the size of Z. chilensis increased. The TL of Z. chilensis increased with LT from 4·29 to 4·59 (mean 4·53), confirming their ecological role as a top predator. The small and large size classes exhibited a low diet overlap and the highest spatial segregation, whereas medium and large specimens had higher co-occurrence and dietary overlap indices. A clear distinction in tooth shape was noted between sexes in adult specimens, with males having longer cusps. This sexual heterodonty may be related to reproductive behaviour, increasing the grasping ability of males during courtship, because there were no differences in diet between the sexes.
authors.affiliation: Instituto Nacional de Investigación y Desarrollo Pesquero, Paseo Victoria Ocampo s/n, Mar del Plata, B7602HSA, Argentina.|Laboratorio de Ictiología, Instituto de Investigaciones Marinas y Costeras, Universidad Nacional de Mar del Plata, Funes 3350, B7602AYL, Mar del Plata, Argentina.|Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Avenida Rivadavia 1917, C1033AAJ, Cuidad Autónoma de Buenos Aires, Argentina.
authors.forename: M
authors.initials: M
authors.lastname: Belleggia
authors.affiliation: Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, Buenos Aires, Argentina.
authors.forename: N
authors.initials: N
authors.lastname: Andrada
authors.affiliation: Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, Buenos Aires, Argentina.
authors.forename: S
authors.initials: S
authors.lastname: Paglieri
authors.affiliation: Instituto Nacional de Investigación y Desarrollo Pesquero, Paseo Victoria Ocampo s/n, Mar del Plata, B7602HSA, Argentina.
authors.forename: F
authors.initials: F
authors.lastname: Cortés
authors.affiliation: Instituto Nacional de Investigación y Desarrollo Pesquero, Paseo Victoria Ocampo s/n, Mar del Plata, B7602HSA, Argentina.
authors.forename: A M
authors.initials: AM
authors.lastname: Massa
authors.affiliation: Laboratorio de Ictiología, Instituto de Investigaciones Marinas y Costeras, Universidad Nacional de Mar del Plata, Funes 3350, B7602AYL, Mar del Plata, Argentina.
authors.forename: D E
authors.initials: DE
authors.lastname: Figueroa
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Avenida Rivadavia 1917, C1033AAJ, Cuidad Autónoma de Buenos Aires, Argentina.
authors.forename: C
authors.initials: C
authors.lastname: Bremec
mesh_terms: D000818:Animals; D001267:Atlantic Ocean; D049628:Body Size; D004032:Diet; D004463:Ecology; D005247:Feeding Behavior; D005399:Fishes; D005766:Gastrointestinal Contents; D016014:Linear Models; D008297:Male; D012737:Sex Factors; D012860:Skates, Fish / Q000033:anatomy & histology* / Q000502:physiology*; D014070:Tooth / Q000033:anatomy & histology
keywords: dentition; diet; elasmobranchs; trophic level