Reproductive ecology of the witch guitarfish Zapteryx xyster Jordan & Evermann, 1896 (Chondrichtyes: Trygonorrhinidae) in the Gulf of Tehuantepec, Mexican Pacific

Abstract

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.