Do predators, handling stress or field acclimation periods influence the survivorship of hatchery‐reared abalone Haliotis kamtschatkana outplanted into natural habitats?

Abstract

ABSTRACT Northern abalone (Haliotis kamtschatkana) in British Columbia, Canada, are listed as endangered and are protected from fishing, yet their populations continue to decline. It is suspected that supplementation of wild populations with hatchery‐reared abalone will be necessary for the recovery of this species. This study examines the magnitude, timing, and causes of post‐outplanting mortality of hatchery‐reared late‐juvenile northern abalone. Abalone survivorship declined precipitously following outplanting, with 83% of abalone surviving 24 h after release and only 34% surviving 2 weeks in the wild. Handling, tagging, and temperature variations experienced during the outplanting procedure did not cause mortality. The majority of the abalone mortality in this study was attributable to predators. Additional factors accounted for only 1–2% mortality over 7 d. A 1‐week acclimatization period within predator exclosures did not improve subsequent survival of outplants. These results demonstrate that the ouplanting of hatchery‐reared abalone as a method of restoring wild populations of this endangered species is primarily constrained by high mortality during the first few days after outplanting, and that almost all of this early mortality is caused by predation. Predation mortality will therefore have to be overcome if outplanting of hatchery‐reared juvenile abalone is to be an effective restoration strategy.Copyright © 2013 John Wiley & Sons, Ltd.