Post-release survival of marine gastropods: A review

Abstract

Marine gastropods support important artisanal, cultural, and commercial fisheries. However, overexploitation of abalone, conch, topshell, and limpets has resulted in population declines globally, with numerous species on the IUCN Red List of Threatened Species. Various efforts to supplement existing populations by either translocating wild or releasing hatchery-produced stock have suffered from low survival. To understand predictors influencing post-release survival, we conducted a systematic review and quantitative synthesis of literature on marine gastropod releases. Our global review identified 88 studies (575 unique release events) across 18 species. A similar number of releases were conducted in tropical (52 %) and temperate (48 %) regions, although most release events involved either Haliotidae (57 %) or Strombidae (26 %). Most releases used hatchery-produced stock (77 %), highlighting the prominent role of aquaculture. For seven species with sufficient data, we tested the effect of time since release, stock origin (hatchery, translocated), size at release, and density on post-release apparent survival (referred to as ‘survival’ hereafter), where applicable. Survival declined through time regardless of species. Hatchery-produced and translocated Haliotis fulgens had similar survival post-release, but hatchery-produced Aliger gigas had lower survival probability than translocated stock. Size at release increased survival probability for only two (Haliotis discus and A. gigas) of the seven species. Similarly, density had no effect on the post-release survival of Haliotis rubra, Haliotis rufescens, and A. gigas. Overall, we found low long-term predicted survival across the seven species. Our findings highlight that overcoming low post-release survival is a significant hurdle when rehabilitating depleted stocks of marine gastropods.