Size and age composition of the populations of abalone Haliotis fulgens and H. corrugata of Bahía Tortugas, Baja California Sur, Mexico

Abstract

The size and age composition was determined for pink abalone Haliotis corrugata and green abalone H. fulgens populations of Bahía Tortugas in the western coast of the Baja California Peninsula, Mexico, in October 1997. The biomass was estimated by means of a stratified random design using semiautonomous Hooka diving. The abalones were collected from 1 to 18 m of depth with a 10-m2 sampling unit. All shell lengths were measured and a subsample was taken to measure shell length, to weigh, to indentify sex and maturity stage and to collect the shells to determine the age in the rings of the spire. The size interval of the population accessible of H. corrugata was 55 to 180 mm for individuals 2+ to 16+ years old, with a mean length of 135.8 mm and mean age of 6.6 years. For H. fulgens, organism sizes ranged from 57 to 206 mm for individuals 1+ to 20+ years old, with a mean length of 154 mm and mean age of 5 years. Possible causes are discussed regading the difference in recruitment between H. fulgens and H. corrugata, the decrease of the oldest year class in both species, and the earlier spawning of H. corrugata to the light of the status of the resource and of the environmental conditions that prevailed during El Niño 1997-98.