EVIDENCE OF DYSTOCIA IN A FREE-RANGING COWNOSE RAY Rhinoptera bonasus (ELASMOBRANCHII, RHINOPTERIDAE)

Abstract

Capture and handling can have sublethal consequences on elasmobranchs, even when individuals are quickly released to comply with legislation or fishermen's ethics on voluntary conservation. Dystocia is characterized by the physical inability to deliver the neonate, even when it is ready for birth. So far, this phenomenon has been reported only in Cownose rays kept under human care. The present study aimed to report the occurrence of dystocia in a free-living Cownose ray (Rhinoptera bonasus), possibly caused by capture stress. Allied to other sublethal effects, dystocia can compromise population recruitment and increase post-capture mortality, especially for older females. Still, considering that this phenomenon was observed and described only in captivity, reports of occurrence in the wild are essential to increase knowledge on the topic and adapt protocols used in captivity for free-ranging animals, as a way to reduce the negative impacts of dystocia.

The role of aquaria in the advancement of elasmobranch reproductive biology

“…Dystocia has been observed on multiple occasions for Cownose Rays in aquaria (Cavalcante et al, 2016;George et al, 2017), and it has also been suggested as a cause of mortality associated with capture for in situ rays (Leite et al, 2020). Procedures for cesarean delivery and monitoring have been developed for Cownose Rays, and, if adopted, should minimize neonate and female loss for animals in aquaria.…”