Abstract
Vertebral deformity including kyphosis and lordosis was observed in cultured yellowtail (Seriola quinqueradiata) and amberjack (Seriola dumerili) in farms at Kagoshima Bay, Japan in 1999 (Takemaru et al. 2009). In this paper, the process of the deformity and relationship with maturity of fish was examined to clarify the cause of this disease in 2000. Yellowtail collected at the same location mentioned above showed more serious deformities than before when the fish mature in May and their gonads atrophied in June. The delay of growth and remarkable individual fluctuation in the weight of viscus were also observed. Moreover, in this period showing the atrophy of gonads, the hyperplasia-like osteoma, which was observed in deformed yellowtail in 1999, appeared on the spines of vertebra. A cause of deformity showing kyphosis and lordosis in cultured yellowtail can be attributed to their maturity.
