Caligidae infestation in Asian seabass, Lates calcarifer, Bloch 1790 cultured at different salinity in Malaysia

The Asian seabass is euryhaline, therefore it is interesting to describe the infestation and survival of caligids at varying salinity on the host. In this study, two different brackish water culture systems with monoculture and polyculture practices were investigated for the occurrence of Caligus spp. on Lates calcarifer. Polyculture practices mainly consisted of snapper (Lutjanus spp.), grouper (Epinephelus spp.) and seabass (L. calcarifer), while the monoculture was stocked with only seabass. A total of 777 Caligus spp. specimens were isolated from the sampling in 2009, consisting of three species; Caligus chiastos, Caligus epidemicus and Caligus rotundigenitalis. In 2011, the total specimen was increased to 3110 and two additional species were found; Caligus punctatus and one unknown species (Caligus sp.). A 98.6% of the total examination was represented by C. epidemicus. Constant presence of C. epidemicus was observed throughout the study, regardless the differences in between culturing practices and systems. This species was able to survive within wide salinity range, from 5 to 28 ppt. The other isolated species (C. chiastos, C. punctatus, C. rotundigenitalis and Caligus sp.) were only found infesting in polyculture cages with the salinity ranging from 25 to 28 ppt. Despite accounts for less than 2% of the total specimens, these species may able to produce a challenge for L. calcarifer polyculture farming activity due to their capability for host switching. The present study revealed the potential risk for cross-species transmission in polyculture practices.