Parasitic crustaceans infecting cultured striped trumpeter Latris lineata

Cultured striped trumpeter Latris lineata was held in sea cage systems or a land-based facility in south-eastern Tasmania. Visual checks of metazoan ectoparasites were conducted on six cohorts (T1 to T6) in the land-based facility from 2006 to 2007, and three cohorts (C1 to C3) held in cages from 2007 to 2008. Three parasite species were recorded; a cymothoid Ceratothoa banksii; a chondracanthid Chondracanthus goldsmidi; anda caligid Caligus nuenonnae. All three parasite species were present on the striped trumpeter in the sea cages with C. nuenonnae and C. goldsmidi found in very low prevalence on all cohorts. There was no significant effect of cohort or season on the parasites' prevalence or intensity. Cohort C1 had the highest numbers of C. nuenonnae with prevalence of 2.5% (intensity 1.0 ± 0.0 parasites fish−1), whilst cohort C3 had the highest prevalence of C. goldsmidi (3.3%, intensity 1.0 ± 0.0). The isopod C. banksii was recorded in increasing prevalence in cohorts C1 and C2 during 2008, cohort C1 had a prevalence ranging from 9.8% (intensity 1.0 ± 0.0) to 17.5% (intensity 1 ± 0.0) whereas prevalence in cohort C2 ranged from27.7% (intensity 1.21 ± 0.1) to 67.2% (intensity 1.8 ± 0.1). The two copepod species were recorded on the fish held in the land-based facility. C. nuenonnae was found on fish fromtwo cohorts at a prevalence of 22.3% (intensity 1.4 ± 0.1 parasites) in cohort T1 and 4.3% (1.0 ± 0.0) in cohort T2. In contrast, C. goldsmidiwas present during all parasite checks of cohorts T2 to T6with the percentage of infected fish ranging from 27.2% (intensity 1.3 ± 0.1) in cohort T2 to 100% (intensity 32.8 ± 1.9) in cohort T4. Treatments against C. goldsmidi were conducted on cohorts T2 to T6 including manual removal of adult parasites and Neguvon baths. There was no apparent reduction in the parasite prevalence within season during follow-up surveys after ~6 months. An eleven month re-infection experiment was conducted with C. goldsmidi; striped trumpeter from which parasites were removed showed significantly lower prevalence (F = 161.8, df 1,20, P b 0.001) than those fish from which parasites were not removed. The study suggests that effective control of parasitic crustaceans is likely to be an important factor in the successful culture of sea-caged striped trumpeter