Parasitism of Argulus japonicus in cultured and wild fish of Guangdong, China with new record of three hosts

This study aimed to demonstrate the ability of Argulus japonicus to infect a wide range of freshwater fishes, as well as to understand the effects of fish origin and host body size on the incidence of A. japonicus. Samples of cultured and wild fish were collected randomly from July 2010 to March 2013, using angling, long-lining, gill-netting, and trapping from rivers and fish farms in Guangdong province, South China. Eight fish species were found to be heavily infected including the common carp, the goldfish, the black carp, the silver carp, the brown trout, the rainbow trout, the mandarin fish, and the perch. Furthermore, the black carp, the brown trout, and the mandarin fish were recorded as new hosts for the first time. During the present study, a total of 2,271 fishes were examined, out of which 712 fishes were found to be infected by a total of 1,443 A. japonicus. Abundance and intensity of A. japonicus infection were significantly influenced by origin of fishes (cultured and wild) and total length (class I, <250 mm; class II, 250–350 mm; and class III, >350 mm) of fish species, whereas varied impacts on prevalence of infection were observed. The correlation between total length of fishes and prevalence of A. japonicus infection was variable, where no significant correlation was observed in the black carp, the silver carp, the mandarin fish, and the perch. In spite of the weak negative correlation between body size of the silver carp and prevalence of infection, A. japonicus was the most abundant and intensive in the silver carp. Thus, aquaculturists should pay particular attention to the control of these fish lice due to its host biodiversity.