Morphological abnormality in thornback ray Raja clavata in the Irish Sea

Abstract

A free-swimming thornback ray Raja clavata specimen demonstrating significant morphological abnormality is reported, captured by beam trawl in the Irish Sea off north Wales, UK. The anterior sections of both pectoral fins were separated from the head section for a length of approximately 140 mm extending from the rostrum tip to a point posterior of the spiracles, along with abnormal morphology of the gill slits. This phenomenon has been observed elsewhere but is the first documented example of this abnormality in the eastern Irish Sea, despite widespread targeting of the species across the region by commercial and recreational fishers. Possible causes and consequences of the observed abnormality are discussed.

RETRACTED: Aerial imagery reveals abnormal stingrays, Taeniura lymma (Myliobatiformes: Dasyatidae), in the central Red Sea

“…Perhaps, the most similar deformity previously reported is a Chilean eagle ray, Myliobatis chilensis Philippi, 1892, whose pectoral fin was symmetrically split in the middle (Valderrama‐Herrera et al., 2022). Somewhat similar are the most severe, symmetrical cases of an incomplete fusion of the pectoral fin to the head, which is relatively common in batomorphs (Bureau, 1889; Clarke, 2021; Ehemann et al., 2022; Legendre, 1935; Ribeiro‐Prado et al., 2008; Templeman, 1965; Valderrama‐Herrera et al., 2022). The prevalence of incomplete disk closures in batomorphs is likely a result of the fact that the pectoral disk develops out of two separate pectoral fins that first grow in length and width and then gradually fuse with the body (Thorson et al., 1983).…”