First report of skeletal deformity in Schizothorax plagiostomus (Heckel, 1838) from Kashmir valley, India

Abstract

Schizothorax plagiostomus (Heckel, 1838) is a native cyprinid fish, commonly known as 'khont' in Kashmir. It is a commercially important herbivorous freshwater snow trout species that inhabit cold-waters in snow-fed rivers with temperatures ranging from 8 to 19 °C, considering great aquaculture potential (Rayal, 2020). This species breeds in streams and rivers and reaches a maximum body length of 41.5 cm (Khan and Sabah 2013). It is frequently difficult to differentiate from Schizothorax richardsonii (Gray, 1832) due to its close resemblance (Pandey and Nautiyal 1997). Schizothorax plagiostomus is commonly distributed in the Himalayan foothills, but recent observations indicate that Schizothorax plagiostomus has declined significantly in many parts of its range due to the introduction of invasive species, overfishing, and damming. (Ganai et al., 2011). The IUCN classifies this species as vulnerable (Jan and Daniels, 2022). Skeletal deformity has a significant impact on the biological performance of all fish (Raja et al., 2016). However, skeletal deformation has been used by fisheries biologists to monitor fish health under existing water conditions (Lindesjoo and Thulin, 1992). Skeletal deformity is a complex combination of various bone diseases, including spinal and vertebral deformities such as kyphosis, scoliosis, lordosis, platysma, and spinal fusion. Other deformities include crooked jaw, crooked neck, and forward and downward protrusion of the lips and jaw, reduction of the lower jaw, reduction or asymmetry of the fins, shortening of the gill cover, etc. (Berillis, 2015).