Ecotoxicological evaluations of common hatchery substances and procedures used in the production of Sydney rock oysters Saccostrea glomerata (Gould 1850).
Summary
Commercial hatchery supply of Sydney rock oyster spat has been hampered by production problems that have previously prevented faster growing and disease resistant stock being available to industry. As part of a larger Fisheries Research and Development Corporation funded study to identify problems and improve production techniques for this species, the toxicity of substances and the effects of handling procedures commonly used in bivalve hatcheries were investigated.
A broad range of substances commonly used for sterilisation, cleaning and other routine purposes in bivalve, fish and crustacean hatcheries were examined and included: chlorine; iodine; potassium permanganate; a commercial virucidal disinfectant; and, a commercial cleaning a sanitising agent. Tests were also used to target other sources of contamination for larval tanks including algae fed to larvae and the stored rainwater and bore water used for diluting seawater and cleaning. Chlorine, the virucidal disinfectant, bore water, rainwater, and algae were selected for further testing due to their regular use in the early stages of larval rearing in the bivalve hatchery.
Low concentrations of virucidal disinfectant in the 0.05-0.5 mg L-1 range were found to affect development of embryos as did low concentrations (0.83-1.66 mg L-1) of chlorine. Other notable findings were that rainwater and bore water caused abnormal development at concentrations of 1 and 10%, respectively. Abnormal development was attributed to contaminants contained in those waters. Algal cultures can contain by-products or harmful bacteria that impact on larval health, however tests showed that algae obtained from the hatchery did not affect larvae. The effects of screening fertilised eggs through a fine mesh screen to remove faeces and debris was examined and found not to affect the development of larvae. The results of the study highlighted the sensitivity of Sydney rock oyster embryos to small amounts of disinfectants. This study has identified several risk factors that have the potential to impact early development of Sydney rock oysters and has established a technique for examining new substances, materials and handling procedures introduced to the hatchery.