From individual vital rates to population dynamics: An integral projection model for European native oysters in a marine protected area

• Published in: Aquatic conservation 2020-11, Vol.30 (11), p.2191-2206
• Main Authors: Lown, Alice E., Hepburn, Leanne J., Dyer, Rob, Cameron, Tom C.
• Format: Article
• Language: English
• Subjects: Biodiversity; Conservation; Elasticity; Environmental changes; Environmental restoration; Fecundity; Fisheries; integral projection models; Integrals; invertebrates; life histories; Marine conservation; Marine molluscs; Marine parks; Marine protected areas; Oysters; Parameter sensitivity; Population dynamics; Population growth; Projection model; Protected areas; Recovery; Recruitment; Recruitment (fisheries); Restoration; Sensitivity; Shellfish; Stocks; Survival; Translocation
• ISSN: 1052-7613; 1099-0755
• DOI: 10.1002/aqc.3445

Following an 85% decline in global oyster populations, there has been a recent resurgence in interest in the restoration of the European native oyster Ostrea edulis. Motivations for restoration from environmental stakeholders most often include recovering lost habitats and associated biodiversity and supporting ecosystem function. In coastal communities, another important justification is recovery of traditional and low‐impact fisheries but this has received less attention. Many restoration projects across Europe focus on the translocation of adult stocks, under the assumption that the limit to population growth and recovery is adult growth and survival. This may not necessarily be the case, especially where knowledge of large extant adult populations exists as in the Blackwater, Crouch, Roach and Colne Marine Conservation Zone in Essex, UK. Identifying what limits population growth for restoration and recovery is an important conservation tool. Here, the first size‐dependent survival, growth and fecundity data for free‐living O. edulis from a novel field experiment are used to parameterize an Integral Projection Model that examines the sensitivity of a flat oyster population to variation in individual vital rates and to potential harvesting – an original objective of a coastal community‐led restoration project. Given the high adult fecundity in this species, population recovery is most sensitive to changes in recruitment success; however, elasticity (proportional sensitivity of the population) is more evenly spread across other parameters when recruitment is already high. Based on locally agreed management objectives, recovery to double the current stock biomass should take 16–66 years (mean = 30 years) without active intervention. At that point, harvest rates could be sustained below 5% of the harvestable adult size whilst ensuring λs remains above 1.