Seasonal abundances of Prosomicrocotyla gotoi (Monogenea) and Opecoelus sphaericus (Digenea) from greenlings Hexagrammos otakii in a southern coastal area in Korea

Abstract

Seasonal fluctuations in prevalence and abundance of Prosomicrocotyla gotoi (Monogenea) and Opecoelus sphaericus (Digenea) infecting greenlings Hexagrammos otakii were investigated in a southern coastal area of Korea from June 1998 to October 1999. P. gotoi was found on the gills of 70 (34.5%) greenlings; 1 to 14 parasites per fish. Prevalence values of P. gotoi ranged from 0% (May 1999) to 61.9% (September 1998). Abundance of P. gotoi sharply increased to a peak in late fall (November), then it declined gradually to May in 1999. O. sphaericus occurred in the intestines of 42 (20.7%) greenlings and ranged from one to eight trematodes per fish. Prevalence values of O. sphaericus ranged from 0% (May, June and July 1999) to 71.4% (October 1998). Abundance of O. sphaericus peaked in October 1998, then remained at a low level. Weak positive correlations were observed between intensities of each parasite species and host body length. The period of peak abundances of both P. gotoi and O. sphaericus infections were well corresponded to the spawning season of greenlings.