1Takehara Marine Science Station, Setouchi Field Science Center, Graduate School of Biosphere Science, Hiroshima University, Takehara, Hiroshima 725-0024, 2Field Science Education and Research Center, Kyoto University, Sakyo-ku, Kyoto 606-8502, 3Usa Marine Biological Institute, Kochi University, Tosa, Kochi 781-1164, Japan
Six species of parasitic copepods were found from the nasal, oral and gill cavities and gills of the temperate bass Lateolabrax japonicus collected from Ariake Sea during June 2000 to March 2001. Among them Caligus tanago, Naricolax atypicus, and Nothobomolochus lateolabracis were dominant, while Caligus epinepheli, Oribitacolax hapalogenyos, and Philichthyidae sp. rarely occurred. Lateolabrax japonicus was a new host for C. epinepheli, N. atypicus and O. hapalogenyos. Prevalence and intensity of the dominant three species were highest from January to March, although the seasonal fluctuations greatly differed among the parasite species. Reproductive activities of the dominant copepods were also high in this period. The number of eggs per paired egg-sacs highly fluctuated with season in N. atypicus and N. lateolabracis. Several host specimens were heavily infected by C. tanago (up to 30 adults) and N. atypicus (16) in February and March. Among the three dominant copepods, prevalence and intensity of C. tanago were not significantly correlated with increasing size of the host. These seasonal changes in the parasites seemed to be influenced by the migratory behavior and reproduction of the host in the sea.