Identification of a nursery area for the critically endangered hammerhead shark (Sphyrna lewini) amid intense fisheries in the southern Gulf of Mexico.

Since the 1980s, there has been growing concern in the Mexican Atlantic regarding high catches of neonate and juvenile sharks in small-scale fisheries. Fishery-dependent data from 1993 to 1994 and 2007 to 2017 and fishers' ecological knowledge from 2017 were used to identify nursery areas for scalloped hammerhead, Sphyrna lewini, in the southern Gulf of Mexico. Catch records and fishing areas of neonates, YOYs, juveniles and adults of S. lewini (N = 1885) were obtained from calcareous and terrigenous regions in the western Yucatan Peninsula. The results suggest that a nursery for scalloped hammerhead is found in the terrigenous region, characterized by relatively shallow and turbid waters due to rivers' discharges. Neonates and YOYs (96% and 86% of their total records, respectively) were commonly found there over the years in May-August in multiple fishing areas identified by fishers, although mainly between isobaths 10-30 m. The enforcement of management measures is necessary because the nursery is located in a region with intense fishing effort.

Reproductive characteristics and reproductive tract anatomy of the California butterfly ray Gymnura marmorata (Myliobatiformes: Gymnuridae).

The California butterfly ray Gymnura marmorata is frequently caught by artisanal fisheries in north-western Mexico (Baja California Sur; BCS). The aim of this study was to estimate reproductive characteristics and describe the micro and macroscopic reproductive structures of female and male G. marmorata. Sampling was carried out at two fisheries landing sites located on the west coast BCS, from 2008 to 2012. The largest disc width (WD ) ever recorded for this species was 131.0 cm and females were larger than males. The male sample was composed exclusively of adult specimens, with a median size at 50% maturity (WD50 ) estimated at 44.9 cm WD . For females, size at onset of maturity was estimated at 63.0 cm WD ; WD50 , at 64.7 cm WD ; and size at pregnancy at 80.1 cm WD . Gonadal asymmetry was observed for the first time in this species. Indeed, in males only the left testis was functional (testicular asymmetry), while in females, only the left ovary was functional (ovarian asymmetry).

Feeding habits of billfishes (Carangaria: Istiophoriformes) in the Ecuadorian Pacific Ocean

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).(AU)

Los hábitos alimentarios de Makaira nigricans, Kajikia audax, Istiophorus platypterus (Istiophoridae) y Xiphias gladius (Xiphiidae) en el Océano Pacífico sudeste se examinaron en Manta y Santa Rosa, Ecuador. Este estudio describe las dietas de estas especies de peces de pico, evalúa las diferencias de la dieta entre especies y las diferencias estacionales en la dieta. Se obtuvo un total de 274 M. nigricans, 321 K. audax, 267 I. platypterus y 252 X. gladius entre febrero 2014 y abril 2015. El escómbrido Auxis spp. fue la presa más importante para M. nigricans, K. audax y I. platypterus, mientras que el calamar Dosidicus gigas fue la presa más importante para X. gladius. Los resultados de ANOSIM confirmaron diferencias significativas en los hábitos alimentarios entre los miembros de la familia Istiophoridae y X. gladius. También se observaron diferencias estacionales para I. platypterus. Los peces de pico son consumidores especialistas con una amplitud de nicho estrecha (B a: M. nigricans y K. audax=0.1, I. platypterus=0.05 y X.gladius=0.04).(AU)