Malacological Society of Australasia

Molluscan Research

Volume 18, Issue 2 (Australasian Abalone): 31 October 1997. Edited by S.A. Shepherd, P.E.McShane and F.E.Wells

Abalone stock enhancement by larval seeding: effect of larval density on settlement and survival.

P.A. Preece, S.A.Shepherd, S.M.Clarke and J.K.Keesing.

South Australian Research and Development Institute, PO Box 120, Henley Beach, South Australia 5022.

Abalone larvae of Haliotis rubra and Haliotis laevigata were released experimentally at sites in South Australia to determine the effect of density of larval release on subsequent survival. In one experiment, densities of post-larvae of Haliotis rubra, 19 days after release, were highest at intermediate release densities (16,000 larvae per metre squared) compared with low (1,600 per metre squared) and high (80,000 per metre squared) release densities. Highest post-larval densities were about 4.5 times background densities at control sites. In a second experiment, densities of post-larvae of Haliotis laevigata, 6 days after release, were three times higher (317 per metre squared) at high release densities of 120,000 larvae per metre squared than at low release densities of 2,000 per metre squared. After 49 days average survival of post-larvae across treatments was about 0.5% and mean density was 3.8 per metre squared. After 11 months the density of seed was about 0.6 per metre squared. In both experiments the most cost-efficient densities of larval release were the lowest in terms of the proportions of released larvae settling and surviving. Given the likely density-dependent mortality of post-larvae after settlement, larval release at even lower densities than those tried over larger areas is likely to be the optimal seeding strategy.

pp.265-273.