Predicting the impact of giant kelp restoration on food webs and fisheries production

1. Ecosystem restoration is gaining momentum as communities and policymakers increasingly appreciate the need to recover lost ecosystem services. However, more knowledge about the potential ecological outcomes of restoration for ecosystem services is needed to promote engagement of stakeholders with restoration targets. In Tasmania the giant kelp, Macrocystis pyrifera, is a productive canopy species that has declined by 95%. 2. We aimed to predict the effects of M. pyrifera restoration on foodwebs and fisheries production. The primary productivity multiple of M. pyrifera compared to the dominant understory species Ecklonia radiata was quantified and then incorporated into an Ecopath with Ecosim (EwE) model of Tasmanian waters. The model was fitted to catch per unit effort data to estimate the predator/prey interactions. Several scenarios were then simulated, representing uncertainty in predator/prey interactions and different areas of M. pyrifera restoration. 3. Restoration of degraded reefs with M. pyrifera was predicted to increase primary productivity by about 40 times per unit area compared to the existing habitat. 4. We predicted that restoring 30% of the degraded M. pyrifera area would increase abalone and coastal demersal fish catch rates by [~]7%. Rock lobster and reef-associated fisheries catch rates were predicted to increase by 1-2% respectively. 5. Model scale was hypothesized to underestimate the increases in biomass and catch. By modelling outcomes of ecological restoration, achievable targets can be set that are locally relevant and therefore more likely to attract support.