Seasonal occurrence of Caligus spinosus and Parabrachiella seriolae (Copepoda) parasitic on cage-cultured yellowtail (Seriola quinqueradiata) at a fish farm in western Japan.

摘要

The occurrence of Caligus spinosus Yamaguti, 1939 (Caligidae) and Parabrachiella seriolae (Yamaguti and Yamasu, 1960) (Lernaeopodidae) parasitic on yellowtail, Seriola quinqueradiata Temminck and Schlegel, 1845, cultured at a fish farm in Nagashima, Kagoshima Prefecture, Japan, was examined. Both parasites were absent on wild-caught juvenile yellowtail ("mojako") (length=6.5-13 cm; weight=5.4-16 g) at the time of stocking in net cages. Prevalence and median intensity of C. spinosus infection on the gill rakers were strongly and positively correlated with seawater temperature. Most of the C. spinosus population was adult females (45-100%). Prevalence of P. seriolae found attached at the base of the pectoral fin showed a high and positive correlation with seawater temperature. Most of the P. seriolae population comprised of adult females (78%). No gross pathological changes or host mortality were associated with the presence of either C. spinosus or P. seriolae.