Purple sea urchin Strongylocentrotus purpuratus populations have increased dramatically along the west coast of the United States, resulting in areas known as “urchin barrens” with little to no kelp due to grazing pressure. Concurrently, ocean warming and marine heat waves have further stressed kelp populations. These factors have contributed to a >95% decline in bul l kelp Nereocystis luetkeana forests off the Northern California coastline since 2014. These habitats are critical to supporting California’s coastal ecosystem and fisheries.
Urchin roe, or uni, is a high-value food item for which there is a global shortage and high demand. Urchins in barrens can persist for decades without food and are left with inedible gonads. Establishing an aquaculture industry to remove adult urchins from the wild to enhance and sell their roe incentivizes the restoration of both the kelp forests and local urchin fishing communities which have been in decline since the c ontraction of the red urchin Mesocentrotus franciscanus fishery in the 1990s.
Over the past 5 years, we conducted a series of experimental ranching trials to test the feasibility of and develop techniques for roe enhancement, also known as urchin ranching. Based on this experience, we created a manual intended to jump-start the ranching industry and help future urchin ranchers quickly develop and scale their businesses. It is focused on pract ical applications of the existing literature and recommendations for aquaculture system design, collection, transportation, maintenance, feeding, and managing urchin health, growth, and mortality. Additionally, it details the design of a low-cost urchin ranching bin system using readily available materials which we developed to further facilitate the adoption of urchin ranching. Rather than a definitive rulebook, this manual serves as a best practices guide that mitigates the risk shouldered by ranchers developing a novel restorative aquaculture industry by identifying key points of failure in the ranching process. It will also be available online as a living document that is continually updated as insights from future research trials and commercial-scale operations are gathered and tested. Given that urchin barrens can occur in many areas globally, this manual may also serve as a useful reference for urchin ranchers working to solve the urchin barren problem with other species around the world.