Responses to predators of cultured and wild red abalone, Haliotis rufescens, in laboratory experiments

Abstract

Hatchery-spawned and reared abalone that are placed onto subtidal reefs to enhance native populations often suffer a high mortality. A potential source of mortality is behavioral differences of cultured and wild abalone. Controlled observations and factorial experiments in the laboratory were used to examine abalone behavior and mortality rate due to three predators — crabs, sea stars and lobsters — on small reefs in laboratory tanks. Two abalone types — cultured and wild — and two age/size classes, 0+ (8–20 mm shell length) and 1+ (25–50 mm), were used. Abalone types differed in their movement patterns, with wild animals moving rapidlyto concealed positions within the reefs and most cultured abalones remaining in their original positions for several hours. Over all experiments, there were differences in predation rates by crabs, lobsters and sea stars, with crabs consuming the most abalone and sea stars the least. Significantly more cultured than wild abalone were consumed in an experiment in which different combinations of predators were present. No consistent differences were seen in the consumption of the two size classes of abalone. Animals fresh from the hatchery suffered significantly higher mortality and were more sluggish in their responses to predators than hatchery-reared abalone that had been acclimated to laboratory conditions. The results suggest, however, that cultured abalone may acclimate relatively quickly to a new environment, which may be useful for future attempts at transplanting these animals.