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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI:

    Sea lice Lepeophtheirus spinifer, Tuxophorus sp. and Caligus sp. (Copepoda: Caligidae) infections on wild-caught queenfish Scomberoides commersonnianus (Pisces: Carangidae) from northern Australia

    B. K. Diggles*, L. Barnes, M. Landos, M. M. Dennis, J. P. J. O'Carroll

    *Corresponding author:

    ABSTRACT: Studies of ectoparasites of wild-caught queenfish Scomberoides commersonnianus from several areas of northern Australia were reviewed to investigate relationships between parasite burdens, environmental conditions and external lesions. A sample of 27 queenfish captured near a dredge spoil disposal site in Gladstone Harbour, Queensland, Australia, in January 2012 was anomalous with a high percentage of fish (66.6%) exhibiting grossly visible skin lesions including foci of erythema and petechial haemorrhages, particularly on the pectoral girdle and ventrolateral surfaces. Microscopically, lesions comprised acute epidermal erosion, ulceration, and/or perivascular dermatitis with dermal oedema and depigmentation. Skin lesions were associated with high prevalence (100%) and intensity (mean intensity = 21.2 copepods/fish, range 4-46) of infection by sea lice Lepeophtheirus spinifer. Only queenfish infected with more than 10 L. spinifer presented with skin lesions. This was the first record of L. spinifer from Australia. In contrast, grossly visible skin lesions were not reported from queenfish (n = 152) sampled from other sites in the Northern Territory and Queensland where the sampled fish had a much lower prevalence (51.3%) and intensity (mean intensity = 3.54, range 0-26) of copepod (L. spinifer, Caligus spp. and Tuxophorus sp.) infections. Copepods from queenfish in studies undertaken outside Gladstone Harbour exhibited an overdispersed pattern of infection, with the vast majority (n = 137, or 90.1%) of fish infected with less than 5 copepods. These data demonstrate that heavy L. spinifer infections, combined with poor water quality and/or direct exposure to contaminated dredge spoil and blooms of the cyanobacterium Lyngbya majuscula, can be associated with cutaneous disease in wild-caught queenfish.