Copper sulfate treatment decreases hatchery mortality of larval white seabass Atractoscion nobilis

Culture of white seabass Atractoscion nobilis larvae was repeatedly limited by severe mortality during the first 18 days posthatch (dph). Affected larvae examined by phase-contrast and scanning electron microscopy, and by conventional histopathology had numerous bacteria on the epidermal surface, especially on the primordial fin. The bacteria were associated with microscopic epidermal lesions that progressed to fin fraying and ulceration. No other cause of death was found by histopathology. Bacteria cultured from the skin surface included Vibrio and Psuedomonas spp. White seabass at 12, 15, and 52 dph were given 2 h exposures of 0.1–1.0 mg l− 1 total copper ion to develop a disease treatment for larval and juvenile fish. Production lots of white seabass were experimentally treated with 0.1 mg l− 1 total copper ion as a 1 h static bath between 7 and 16 dph. Although all treatments significantly (P = 0.00) increased survival, a standardized treatment at 10 and 12 dph increased larval survival at 18 dph harvest from under 1% in untreated larvae to 32–66% in treated groups (P < 0.0001). Copper sulfate treatments significantly reduced bacterial colonization of the epidermis (P = 0.00) and treated fish had fewer microscopic lesions (P = 0.00). Fish had no microscopic evidence of toxicity due to treatment at 0.1 mg l− 1. One h bath treatments of 0.1 mg l− 1 copper sulfate increase survival of intensively cultured white seabass larvae.