Reproductive Aspects of Poecilia sphenops in a Reservoir at Morelos State, Mexico

Poecilia sphenops is a native species recently recorded in the Balsas basin and the Amacuzac River
in Morelos (Mexico), in which it is abundant and widely distributed. This study analyzed some aspects
of the reproductive biology of Poecilia sphenops from the Emiliano Zapata reservoir, in Central
Mexico. Specimens were collected using a 20 m-long seine with a 5 mm mesh size, from January to
December 2006. A total of 581 specimens were collected: 407 females (70.0%), 83 males (14.3%)
and 91 individuals with no differentiated sex (15.7%). Fish ranged from 20 to 96 mm in total length
and 0.01 to 13.07 g in body weight. The female to male sex ratio (4.9:1) deviated significantly from the
unity (χ²= 214.2, p<0.05). Monthly variations in gonadosomatic (GSI) and hepatosomatic (HSI)
indexes and ovarian development stages showed that P. sphenops spawning season occurred
between July and October, concurring with the rainy season. Another reproduction peak was
registered in February. The largest length registered for males and females was 96 mm and 83 mm,
respectively. Temperature, and food abundance and quality were some of the factors that could limit
fish reproduction in the reservoir. The reproductive information obtained in this study of P. sphenops
will enable fisheries to be regulated. To this date there are no specific measures implemented to
regulate this resource. The size at first maturity should be considered in the exploitation.