Feeding, growth and survival of abalone (Haliotis asinina Linnaeus 1758) reared at different stocking densities in suspended mesh cages in flow-through tanks

Abstract

Feeding, growth and survival of hatchery-bred juvenile abalone, <i>Haliotis asinina</i> (mean initial shell lengths: 32 mm) stocked at 25, 50 and 100 m^-2 of shelter surface area in mesh cages suspended in indoor tanks were determined. Animals were fed the seaweed, <i>Gracilariopsis bailinae</i>, to excess given at weekly intervals. After 250 d, avereage daily growth rate (mean: 122 µm d^-1 shell length, 156 mg d^-1 body weight) was highest in abalone reared at the lowest stocking density (25 m^-2 ). Abalone stocked at 50 and 100 m^-2 had similar growth rates that ranged from 96 to 98 µm d^-1 SL and 123 to 131 mg d^-1 BW). Daily feeding rates of 29 and 30% were not significantly different for abalone stocked at 25 and 50 m^-2, respectively, but were higher than abalone stocked at 100 m^-2. The higher feeding rates of 24-28% day^-1 of abalone in all treatments starting day-129 until day-160 could be due to the onset of sexual maturation as most abalone are already mature at this size. Survival rates were generally high (91-98%) and were not significantly different among treatments. However, body size (range: 59.3 mm SL, 57-58.4 g BW) at harvest was bigger in animal stocked at 25 m^-2 than those stocked at 100 m^-2. Sexual maturation during culture did not hamper growth of abalone. <i>G. bailinae</i> proved to be a sufficient food source for abalone grow-out. A stocking density between 50-100 m^-2 is recommended for tank grow-out of <i>H. asinina</i>.