Studies on southern Australian abalone (genus Haliotis) XVII. A chronology of H. laevigata

Abstract

The abalone Haliotis laevigata deposits 2 rings yr^-1 in the spire during the first 4–6 years of life at 11 sites in southern Australia. At two sites it deposits 3 rings yr^-1 , and at another, 3 rings yr^-1 for the first 3 years and 2 yr^-1 in the next 3 years. These rates of ring deposition appear to be dependent on the growth rate; they are not exact for every individual due to individual variation in growth but appear to be a statistical property of the population. The tendency for an integer number of rings to be deposited annually may be related to exogenous cues. Hence at one site where 3 rings yr^-1 are laid down they are deposited in about June, September and December each year, corresponding to winter, the spawning season and summer. Long term tag recaptures suggest that these rates of deposition persist in older shells but better validation is required. Erosion of the shell causes the loss of rings, and the attack of muricid and polydorid borers causes the deposition of adventitious rings as well as pigmented rings, called brown rings. These complications need to be considered in estimating the age of a shell from ring counts.

Key words:

• Haliotis laevigata
• growth
• shell aging
• chronology
• borers
• shell erosion
• brown rings