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Abstract
The abalone Haliotis fulgens deposits fine (non-pigmented) and dark (pigmented) rings in the spire that are useful for aging the shell. A dark ring is deposited annually, and in the first 4–5 years is preceded by one or more fine rings which are deposited with decreasing frequency over time. External shell erosion causes the loss of about one ring per 32 mm shell length over about 80 mm length. The El Niño events of 1982–3 and 1991–2 caused growth checks in shells of H. fulgens at La Natividad and Bahia Tortugas, Baja California and were used as a time-stamp to validate the rate of deposition of dark rings in the shell. In about 9% of the shells examined more or less dark rings are deposited than expected. In these cases counts of fine rings as well as dark rings can reduce the chance of error.