Microstructure, chronology and growth of the pinto abalone, Haliotis kamtschatkana, in Alaska

Abstract

The microstructure, deposition of rings, and growth checks in the pinto abalone, Haliotis kamtschatkana Jonas, were examined at seven sites in southeast Alaska. Rings were of calcium carbonate with prismatic or block-like structure or were of organic material (called brown rings); sometimes both types were juxtaposed in a compound ring. Rings alternated with nacreous layers having a brick-like or laminar structure. Laminar thickness was correlated with ambient sea temperatures and provided internal evidence of periodicity of ring deposition. One ring a year appears to be deposited in the spire of this abalone in about mid-summer, and a growth check is laid down at the growing edge of the shell in about mid-winter. Rates of deposition of the rings and growth checks were validated by comparison with known growth rates from mark-recapture experiments at one site, and modal analysis of length frequency data at others. Examination of a sample of shells of known age confirmed a deposition rate of one ring a year. Brown rings appear to be laid down adventitiously and were excluded from ring counts for aging purposes. The three independent techniques, rings, growth checks, and modal analysis, gave consistent juvenile growth rates at 7 sites of 14-18 mm/y during the first 4 y. Thereafter, growth rates followed a declining exponential curve. Growth rates differed little between sites, and mean parameters of fitted von Bertalanffy growth parameters for seven sites were: K = 0.20: L(∞) = 125.9 mm.