1Fisheries Laboratory, Kinki University, Wakayama 649-5145, 2Kinki University Fish Nursery Center, Wakayama 649-5145, Japan
Red sea bream Pagrus major, red sea bream ×crimson sea bream Evynnis japonica (F1), and red sea bream ×F1 (RF1), with body length (BL) of 35~41cm and 2~5-year-old, and crimson sea bream, with BL of 25~33cm and 8-year-old, in attempt to develop new sea bream seedlings, were compared with their muscle fiber diameters. These fishes were fed on artificial diets commercially available and reared in net pens settled in the Uragami Bay, near the Peninsula of Shionomisaki. The RSB, RF1, and F1 had significantly lower relative head length, caudal peduncle length, body height, and eye diameter to the BL than those of CSB. Relative snout length and head hight to body length, lateral line scales, and gill rakers showed an increasing trend in the order of RSB·RF1, F1 and CSB. Fiber diameter frequency of white muscle under the tip of dorsal fin also slided to an increasing direction in the order of RSB, RF1, F1, and CSB. These results indicate that the backcross RF1 morphometrically approach to RSB more than F1 and CSB.