Restocking, stock enhancement, and sea ranching: Arenas of progress

There are concerns about the sustainability of the world's capture fisheries at the current total level of similar to 96 million tons per year. The warning signals are an increase in the proportion of depleted or recovering stocks, from about 10% in 1974 to 28% in 2004, and a corresponding decrease of under-to moderately exploited stocks from about 40% to 24%. It is widely acknowledged that reductions in fishing effort and restoration of fish habitats are needed to improve resilience of capture fisheries. Nevertheless, for some coastal fisheries, application of aquaculture technology through restocking, stock enhancement, and sea ranching also promises to help restore lost production and possibly increase harvests beyond historical levels. However, application of this technology still has a long way to go before integrated management systems are in place that successfully address all the biological, ecological, social, cultural, and economic issues. The main challenges include identifying when and where to use the interventions to add value to other forms of management; integrating these initiatives with institutional and fisheries management regimes; monitoring success of the interventions; producing cultured juveniles cost-effectively; and releasing them in the wild so that they survive in high proportions. We summarize progress to date by describing the main lessons learned from 30 years of research into the potential for releasing cultured juveniles into coastal fisheries, and from application of this technology at various scales. We also describe other lessons to be learned from stocking freshwater habitats and other emerging issues for enhanced coastal fisheries, such as market opportunities and the need to develop widely accepted definitions for "restocking," "stock enhancement," and "sea ranching." These definitions are needed so that nations can report and monitor different strategies used to improve productivity of capture fisheries.