Heritage Stewardship – Long-term Evidence/Sustainability
MacArthur Foundation [to 21 Jul 2018]
July 16, 2018 – Grantee Research
Research Finds Model for Sustainable Fishing in Coral Reefs
A 20-year study of Kenyan reefs generated a mathematical model for sustainable fishing to maintain reef ecology, which helps mitigate the threat reefs face from climate change. The study by the Wildlife Conservation Society, supported by MacArthur, found an ideal target of 50 tons of living fish per square kilometer to maintain productive harvests and sustainable recovery rates of coral reef fish without comprising the ecosystem. The results constitute a standard that researchers hope to test and apply in other reefs around the globe.
Fish and Fisheries
Early View – Online Version of Record before inclusion in an issue
Multicriteria estimate of coral reef fishery sustainability
Timothy R McClanahan
First published: 10 May 2018
A holistic basis for achieving ecosystem‐based management is needed to counter the continuing degradation of coral reefs. The high variation in recovery rates of fish, corresponding to fisheries yields, and the ecological complexity of coral reefs have challenged efforts to estimate fisheries sustainability. Yet, estimating stable yields can be determined when biomass, recovery, changes in per area yields and ecological change are evaluated together. Long‐term rates of change in yields and fishable biomass‐yield ratios have been the key missing variables for most coral reef assessments. Calibrating a fishery yield model using independently collected fishable biomass and recovery data produced large confidence intervals driven by high variability in biomass recovery rates that precluded accurate or universal yields for coral reefs. To test the model’s predictions, I present changes in Kenyan reef fisheries for >20 years. Here, exceeding yields above 6 tonnes km−2 year−1 when fishable biomass was ~20 tonnes/km2 (~20% of unfished biomass) resulted in a >2.4% annual decline. Therefore, rates of decline fit the mean settings well and model predictions may therefore be used as a benchmark in reefs with mean recovery rates (i.e. r = 0.20–0.25). The mean model settings indicate a maximum sustained yield (MSY) of ~6 tonnes km−2 year−1 when fishable biomass was ~50 tonnes/km2. Variable reported recovery rates indicate that high sustainable yields will depend greatly on maintaining these rates, which can be reduced if productivity declines and management of stocks and functional diversity are ineffective. A number of ecological state‐yield trade‐off occurs as abrupt ecological changes prior to biomass levels that produce MSY.