Rapid infection and proliferation of dactylogyrid monogeneans on gills of spotted rose snapper (Lutjanus guttatus) after transfer to a sea-cage

•Three dactylogyrid species were found on gills of caged Lutjanus guttatus.•Dactylogyrids colonized caged fish since the first month of the farming period.•For each parasite species prevalence was 100% during most part of the farming period.•Mean intensity was higher from May to July.•Euryhaliotrema perezponcei was the most abundant parasite.

Finfish mariculture is typically threatened by parasite and disease outbreaks. Therefore, it is important to identify parasite species of potential risk for this activity. Snappers are valuable food fish worldwide. In the Eastern Pacific, spotted rose snapper (Lutjanus guttatus [Steindachner, 1869]) is a firm candidate for sea-cage aquaculture. In the current study, the parasitism of caged L. guttatus by dactylogyrids was evaluated for the first time during a complete farming period. Twenty five thousand juvenile fish produced at the Research Center for Food and Development (CIAD, Mazatlan Unit) were reared in a sentinel sea-cage from February to November 2012 in Mazatlan Bay, Mexico. A fish sample (n = 15) was obtained every month. Dactylogyrids from the left second gill arch were identified and quantified. A total of 18,704 dactylogyrids distributed in three species, Euryhaliotrema perezponcei García-Vargas, Fajer-Ávila and Lamothe-Argumedo, 2008, E. mehen (Soler-Jiménez, García-Gasca and Fajer-Ávila, 2012), and Haliotrematoides guttati García-Vargas, Fajer-Ávila and Lamothe-Argumedo, 2008 (Monogenea: Dactylogyridae) was found, which were able to infect caged L. guttatus since the first month of the farming period. Prevalence of these parasite species was 100% all the time, except for initial low values for E. mehen and H. guttati. The mean intensity of infection of each dactylogyrid species varied significantly between sampling months. Euryhaliotrema perezponcei was the most abundant parasite, reaching the highest mean intensity in May, June and July (154.3, 296.9 and 176.6 parasites/host, respectively). No clear seasonality of infection was observed; however, the influence of the water temperature on the observed infection levels is discussed. There was no mortality, change on behavior or pathological signs. However, given the rapid infection and proliferation of dactylogyrids, particularly E. perezponcei on L. guttaus reared in a sentinel sea-cage, outbreak of these parasites could be expected when this fish species is cultured on a large scale.

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