Combining a novel outplant module with metareplication to further abalone restoration capacity in California

Abstract

ABSTRACT Species reintroductions require large resource investments for rearing and placement and are further complicated by the paucity of robust monitoring regimes. Nonetheless, continued population declines in many species necessitate such actions. The white abalone (Haliotis sorenseni) in California has experienced steep population declines and a reintroduction programme through outplanting juvenile, captive-bred abalone is considered necessary for its recovery. A novel module known as the Short-term Abalone Fixed Enclosure (SAFE) was developed to allow red abalone (H. rufescens), a surrogate species that is not endangered and co-occurs with white abalone, a period of adjustment before dispersing. Outplant events were conducted at multiple sites in California, USA and monitored regularly for shells and live animals in a process known as metareplication, considered essential for robust outplant reporting. Time-lapse cameras were also placed on SAFEs to document predator visitation. Live animals and shells both increased on-site throughout the first six months and declined thereafter, with most animals unaccounted for. Empty shells on site were considered a proxy for the mortality rate and the lack of encounters after a short period suggests successful emigration from modules into the reef habitat. Predator visitation was generally low, and no significant differences were found across outplant periods. Results from this study indicate outplant mortality may peak early and predator activity is generally low and unrelated to abalone introduction. This vital step illustrates this outplant method may be an effective tool in restoring abalone to subtidal rocky reefs.