Malacological Society of Australasia

Molluscan Research

Volume 18, Issue 2 (Australasian Abalone): 30 April 1997
Edited by S.A. Shepherd, P.E.McShane and F.E.Wells

The shell microstructure and chronology of the abalone Haliotis corrugata.

S.A.Shepherd* and M. Avalos-Borja**.

*South Australian Research and Development Institute. PO Box 120, Henley Beach, SA 5022, Australia.
** Instituto de Fisica, UNAM, Apdo. Postal 2681, Ensenada 22800, Baja California, Mexico.

The abalone Haliotis corrugata deposits fine and dark rings in the shell near the spire and the dark rings can be used to age the shell. Each dark ring has two distinct microstructural elements; a layer of prismatic calcite, and a juxtaposed narrower layer of granular structure. The crystalline ultrastructure of aragonite between the rings shows seasonal changed in thickness of laminate apparently correlated with seasonal temperature changes. Examination of shells grown in culture showed that three fine rings deposited during the first year, the first dark ring at an age of about 20 months, and the second between 2 and 2.5 years; thereafter a dark ring is deposited annually. This aging technique was validated up to about 12 years of age by using growth checks laid down in the shell in about October 1991 during the El Nino as a time-stamp from which growth rates and age could be estimated. Using the aging technique the von Bertalanffy growth equation was fitted to age-length data from La Natividad, Baja California and the following parameters obtained: K = 0.33; L(infinity) = 160 mm. Catch curve analyses of commercial catch data gave Z = 0.28 for a sample in the late 1970s, and 0.66 for one in 1995.

pp. 197-207.