Papers/Abstracts

Notes on the biology of the freshwater stingrays Paratrygon aiereba (Muller & Henle, 1841) and Potamotrygon orbignyi (Castelnau, 1855) (Chondrichthyes: Potamotrygonidae) in the Venezuelan llanos

Lasso, C. A., A. Rial B. and O. Lasso-Alcala

aqua, International Journal of Ichthyology, pp. 39-50, Volume 2, Issue 3 – April 1997

Abstract

The ontogenetic development, reproduction, feeding habits and habitat of the stingrays Paratrygon aiereba and Potamotrygon orbignyi from the Venezuelan Ilanos (Apure river basin) were studied.

According to the ontogenetic development, four stages were considered: fetuses, immatures, sexually maturing and mature individuals. The variation of 12 measurements and their development in relation to disk width are described. P. aiereba attained greater size (780 mm DW) and weight (25 kg) than P. orbignyi (325 mm DW) and weight (2 kg).

In P. aiereba males, sexual maturity is apparently reached at a size larger than 41 0 mm DW, whereas in P. orbignyi sexual maturity is attained at 230 mm DW. Females show signs of sexual maturation at 370 and 185 mm DW in P. aiereba and P. orbignyi respectively. Pregnancy and littering in both species goes on all year. Births seem to be more frequent during the rainy season. According to our data, the litter size varies between one and two young in each reproductive cycle in both species.

P. aiereba is a piscivore even though shrimps are important items in its diet. P. orbignyi is essentially an insect feeder.

P. aiereba has been observed only in the main channel of the Caño Guaritico (clear water) whereas P. orbigny is usually found in a wide range of habitats and water types.

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