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The feeding habits of Makaira nigricans, Kajikia audax, Istiophorus platypterus (Istiophoridae), and Xiphias gladius (Xiphiidae) in the southeast Pacific Ocean were examined in Manta and Santa Rosa, Ecuador. This study describes the diets of these billfish species, evaluates dietary differences between species, and assesses seasonal differences in diet. A total of 274 M. nigricans, 321 K. audax, 267 I. platypterus, and 252 X. gladius were collected between February 2014 and April 2015. The scombrid Auxis spp. was the most important prey for M. nigricans, K. audax and I. platypterus, while the squid Dosidicus gigas was the most important prey for X. gladius. The results of the ANOSIM confirmed significant differences in feeding habits between the members of the family Istiophoridae and X. gladius. Seasonal differences for I. platypterus also were observed. Billfishes are specialist consumers with a narrow niche breadth (B a: M. nigricans and K. audax=0.1, I. platypterus=0.05, and X. gladius=0.04).

Mustelus lunulatus is the most important shark demersal species in the landings of the Ecuadorian artisanal fishery, this study was carried out to expand the knowledge about size, sex, type of growth (isometric or allometric) and reproductive aspects in males of the species. Biological traits of the sicklefin smooth-hound shark, M. lunulatus, caught in the Pacific coast of Ecuador were assessed by examining 199 individuals ranging from 41.2 to 135.0 cm in total length (TL). The means TL did not show significant differences between sexes. The sex ratio was not different from 1:1 and the weightlength relationship did not showed significant differences between males and females. Both sexes have a growth of isometric type (b males = 3.05 and b females = 3.15). Total length at sexual maturity (TL 50) of male M. lunulatus, calculated from the clasper condition, was estimated to be 97.2 cm. The present study provides new information regarding the biology of M. lunulatus in Ecuadorian waters.

El tiburón azul Prionace glauca es una especie importante en la pesquería de Ecuador. Se registraron un total de 577 organismos con tallas de 130 a 307 cm de longitud total (LT). La proporción entre sexos fue de 1.06 machos: 1 hembras. En los machos el clasper presentó medidas de entre 4 y 21.2 cm y el punto de inflexión fue estimado en 189.7 cm de LT. La talla media de madurez (LT 50) de los machos del tiburón azul fue de 187.1 cm LT.