Mate finding in the isopod parasite Ceratothoa oestroides (Risso, 1816) in an aquaculture environment: A case study in the sea bass Dicentrarchus labrax (Linnaeus, 1758)

•There was no mature female parasite found after 865. 47 °DD, which imply that maturity of C. oestrodes requires more °DD.•Female parasite C. oestroides uses some way of communication to attract the pulli II i.e., the future male parasite.•In aquaculture health management communication between C. oestroides pairs could be used to lure parasites into traps. The purpose of this in situ study was to determine the pattern of protandrous hermaphrodite Ceratothoa oestroides infestation in sea bass with respect to parasite sexual behaviour. Sea bass (N = 618) were divided into six net cages which presented three experimental groups. Group 1 represented infected fish, where female parasites were manually removed and male parasites were left in the buccal cavity of fish. Group 2 represented infected fish where both female and male parasites were removed, and group 3 represented uninfected fish (i.e., the control group). The duration of the experiment was 865.47 degree days (ºD), and average sea bass mortality rate was 11.97 %. No mature C. oestroides females were found at the end of the experiment. Fish in cages with removed female parasites (group 1) had a statistically higher number of parasites in pairs at the end of the experiment, compared to the group where all parasites - both males and females - were removed (group 2) and control group (group 3) (P