Studies related to the artificial spawning and culture of the Abalone, Haliotis midae linne, 1785

Master Thesis


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University of Cape Town

The successful aquaculture of the abalone Haliotis midae requires a multi-disciplinary approach. Experiments were designed to provide insight into various aspects of abalone biology and seawater system design. A comparative evaluation of a closed and open seawater system for an H. midae hatchery was performed. Monthly seawater temperatures and nitrite levels were higher in the closed system. The salinity of the closed system seawater varied more than that of the open system. The pH of seawater in the closed system varied between 7.7 and 8.2. This was lower than the 7.9 to 8.35 pH range of the open system seawater. An open system is thus clearly preferable to a closed system. Haliotis midae reproductive condition can be assessed visually by examining the shape and colour of the broodstock gonads. Spawning experiments showed that abalone should be starved for at least 24 hours prior to spawning induction. Haliotis midae can be induced to spawn by treatment with hydrogen peroxide when exposed to seawater at a pH of between 9.0 and 9.9 (males and females) Spawning can reliably be induced by using final hydrogen peroxide concentrations in the range of 7 to 25 mM for male and female H. midae. Gravid broodstock should be exposed to hydrogen peroxide for 100 to 300 minutes during spawning induction. There was no significant impact observed for prior conditioning of the brood-stock to the spawning tanks, lunar phase and timing of spawning induction relative to sunset. Haliotis midae larval toxicity to chlorine, copper and ammonia was investigated. The LT50 to a chlorine concentration of 0.06 mg/l was 170 minutes. For copper the LT50 of larvae exposed to 0.12 mg/l was 53 minutes. The LT50 of ammonia at 5 mg/l was 600 minutes. A brief synopsis of the major findings is presented in the last chapter. Some discussion on the future prospects of the abalone industry is also provided.

Bibliography: leaves 122-135.