Vertebral deformities in triploid Atlantic salmon (Salmo salar L.) underyearling smolts

This study investigated the prevalence of vertebral deformities in triploid and diploid Atlantic salmon smolts. Four full-sibling families were either subjected to hydrostatic pressure (655 bar, 6.25 min, 8 °C) (triploid) 37 min post-fertilization, or were maintained as untreated controls (diploid), and then reared to the smolt stage. Some 800 fish (100 per ploidy/family group) were palpated for vertebral deformities, and 480 (60 per ploidy/family group) of these were selected at random for radiography and evaluation for vertebral deformities. There was a significantly higher prevalence of triploid individuals classified as spinally deformed during palpation (triploids; 1–3%, diploids; 0–1%), and of individuals with one or more deformed vertebrae on radiographs (triploids; 30–35%, diploids; 8–13%). The trunk region (V9-30) of the vertebral column was the predominant location for deformities in triploids, with vertebra number 24 being the most often affected. Of the triploids, 7.6% had a malformation in this particular vertebra, which is located beneath the dorsal fin.