External spinal deformities in aquarium-reared grass carp Ctenopharyngodon idella (Cuvier & Valenciennes, 1844) from Kerala, India: an opportunistic observation

Abstract

Skeletal deformities are rarely documented in adult aquarium-reared grass carp (Ctenopharyngodon idella). This study reports an opportunistic observation of external spinal deformities in three adult individuals maintained in a public display aquarium in Kerala, India. Body curvature was consistent with kyphosis, lordosis, and kypho-lordosis. Despite these abnormalities, all affected fish were alive and exhibited routine swimming and feeding behavior. No radiographic or anatomical examinations were performed; therefore, the observations were limited to external examination and the underlying vertebral abnormalities could not be confirmed. This report expands the limited documentation of spinal deformities in captive adult grass carp and highlights the value of future radiological and anatomical investigations.