From January 2008 to December 2009, 451 specimens of witch guitarfish Zapteryx xyster were caught in the Gulf of Tehuantepec. Total weight, total length (TL), sex, maturity stage and catch depth were recorded for each specimen. Maturity stage distribution exhibited significant differences with respect to depth. The data indicated that adults migrated towards shallow waters (25–37m) to reproduce, starting in February. Males reached maturity at 44cmTL, whereas females reached maturity at 48cmTL. Witch guitarfish females are synchronous; therefore, ovulation and mating begin in March and parturition begins in April. Females showed a 2-year cycle with consecutive vitellogenesis and gestation. Fecundity was five to eight embryos (mean six embryos) and the sex ratio of embryos was 1:1. Birth occurred in April and May, with an average size at parturition of 17.3cmTL. There was sexual dichromatism between males and females during the breeding period, and sexual polymorphism in adult females. The incidental catch of the witch guitarfish during courtship and mating threatens the survival of this species.

In the study, the authors evaluate the spatial distribution pattern of vermiculate electric-ray Narcine vermiculatus using geostatistical techniques to predict its spatial distribution and indicate its reproduction strategy. From January 2008 to December 2009, 3333 specimens of vermiculate electric-ray were caught. Total length (L T ), sex, maturity stage, catch location and depth were recorded for each specimen. The L T of vermiculate electric-ray ranged from 6.7-24.6 cm. The authors estimate an irregular spatial structure, with a high-density patch ( x = 53 ind. ha −1 ) located on the east coast, which concentrates 65.2% of the specimens. The high-density patch consists mainly of large juveniles (13.3-19.5 cm L T ), sub-adults (14.0-19.8 cm L T ) and young adults (14.7-21.3 cm L T ). Data indicate that adults migrate to the high-density patch to reproduce. Males reached maturity at 14.5 cm L T , whereas females reached maturity at 19.3 cm L T . Vitellogenesis in female vermiculate electric-ray begins in June; ovulation, mating, fertilization and gestation in October and birth begins in February. This indicates an annual cycle with vitellogenesis and consecutive gestation, in females synchronized in reproduction. Fecundity was 1-8 ( x = 4), and the sex ratio of embryos was 1:1. The birth occurred between February and April, with an average size at parturition of 6.3 cm L T . Incidental capture of sub-adults and adults of N. vermiculatus by bottom trawls threatens the survival of this species.

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