Recruitment of juvenile abalone (Haliotis spp.) measured in artificial habitats.

Abstract

In September 1989, 45 concrete block habitats were deployed at three sites 25 km apart along the southern shores of Santa Rosa and Santa Cruz Islands, California, at depths of 10-16 m. In October 1989, 7200 small (≈ 41 mm) hatchery-reared red abalone, Haliotis rufescens, were introduced into 36 of the habitats. Nine habitats remained empty as controls. The habitats were surveyed in situ periodically for two years. Sufficient numbers of native abalone, H. rufescens and H. corrugata, were detected (315) to identify spring recruitment events. Habitats with introduced abalone contained more than twice as many native abalone as did empty control habitats during the first year. Average densities of native abalone in the artificial habitats (0.011 m^-2) approximated densities of young-of-the-year abalone discovered by previous destructive sampling in natural habitat. Approximately 32% of the introduced abalone survived one year and 24% survived two years. Three to eight artificial habitats were sufficient to detect 20% differences in mean abalone densities during peak spring recruitment events.