World Aquaculture - September 2023

WWW.WAS.ORG • WORLD AQUACULTURE • SEPTEMBER 2023 15 the gear clean and, at the same time, promote oyster production and reduce labor associated with biofouling removal. Biofouling requires the frequent cleaning of farming gear to remove unwanted attached organisms and is a major cost to shellfish growers. The expectation is that urchins could assist in that task by feeding and moving around the gear, thus potentially lowering the need for biofouling management including commonly used methods on commercial farms such as freshwater baths, brine dips or periodic air drying techniques. For this project, local and native Atlantic purple urchins (Arbacia punctulacta) were cultured with native Eastern oysters (Crassostrea virginica). A. punctulacta is an omnivore and feeds on a variety of food, including algae when it is abundant and other animals when algae are less available (Gianguzza and Bonaviri 2013). For this project, urchins were stocked into bottom cages, either with or without grow-out bags (Figure 1), as this is the most common method of oyster culture in Virginia. The intention is to assess co-culture feasibility in commonly used methods and its possible positive effects, in order to provide an option of a farming strategy that could be adopted by the industry across a range of scales. The in-situ experiment was deployed in a shallow subtidal area in Bradford Bay close to VIMS Eastern Shore Laboratory, The US is the top seafood importer in the world and a big consumer of shellfish. Given this opportunity for domestic production, shellfish growers and related seafood businesses, including restaurants and chefs, have expressed interest in innovative forms of aquaculture that bridge farming efficiency and marine conservation spheres, such as restorative aquaculture or regenerative aquaculture. This has fueled interest in new aquaculture species for the national seafood market and the constant improvement of sustainability of farming management, both in environmental terms and social aspects. Combining new species with improved sustainability can be challenging, but co-culture could be one of the answers. Co-culture is the farming of more than one species in the same place and, in this case, farming in the same gear. Following the interest and bottom-up initiatives of many American farmers who strive to diversify their farming with more than one species, there has been enthusiasm to revisit the feasibility of growing grazer species, such as native urchins, with the long-standing traditional oyster industry. While previous projects have explored this possibility, they have not translated to the commercial industry. There was a need for evidence-based results in practical applications that can promote wide commercial adoption. A co-culture project, conducted at Virginia Institute of Marine Science (VIMS) and funded by the Atlantic States Marine Fisheries Commission (ASMFC) led by NOAA, is currently ongoing. The idea is simple: deploy urchins together with oysters inside farming bags or bottom cages to keep the urchins fed and keep Co-culture of Grazer Species and Bivalves: an Opportunity as a Nature-based Solution for Food Darien D. Mizuta, William Walton and Ricardo L. Cruz FIGURE 1. Atlantic purple urchins and Eastern oysters deployed a) in faming bags and b) directly in cages for a feasibility experiment of new species farming and farming management control of biofouling. (Photo credits: bag: William Walton; cage: Darien Mizuta). FIGURE 2. Sizes of urchins currently in use in the project: juveniles (25 mm to 40 mm shell diameter), and adults ( > 45 mm shell diameter). (Photo credit: Darien Mizuta). (CONTINUED ON PAGE 16) a b