OBSERVATION ON SKELETAL DEFORMITY IN HATCHERY-REARED RED SPOTTED GROUPER, Epinephelus akaara (Temmick et Schlegel) FROM LARVAL TO JUVENILE STAGE

Abstract

Skeletal deformity is a significant problem in fish culture. The skeletal deformities in red spotted grouper from yolk-sac to juvenile stages were examined through clearing and staining of the cartilage and bone using Alcian Blue and Alizarin Red S. The overall results showed that the pattern of incidence of deformities showed an increase from preflexion to juvenile stages. The rate of deformities based on ten elements of bone from preflexion to juvenile stages were as follows: vertebral (42.6%—9.0%), dorsal proximal radials (4.8%—25.2%), neural spine (0%—8.4%), haemal spine (0%—6.8%), hypural (1.3%—5.4%), anal proximal radials (0%—5.4%), epural (1.3%—4.9%), arypural (2.0%—4.5%), lower jaw (1.3%—2.5%), and upper jaw (0%). Vertebral and dorsal proximal radials were recognized as the most susceptible parts to deformation. The main types of bone deformity were lordosis, scoliosis, fusion, shortening, branching, supernumerary elements, and saddleback syndrome. Development of saddleback syndrome was detected initially in preflexion stage, which was accompanied by deformity of the neural spines, dorsal proximal radials, and disposition of the distal radials and dorsal spines in later life stages. The skeletal deformity encountered during the larval rearing period could be caused by water surface tension.