Sustainable Farming of Ulva and Native Brown Shrimp in Mexico
Aonori Aquafarms is operating a pilot farm in San Quintin Mexico using a dual crop system producing Ulva clathrata and Farfantepenaeus californiensis (brown shrimp) together in seawater ponds, with the aim of producing shrimp in a sustainable fashion and with top quality. Our system achieves these goals. Ulva has value as a crop, primarily as human food for applications such as nori sheets, seaweed snacks or as a flavoring agent. In co-culture, Ulva has several roles: it is the principal source of nutrition for the shrimp, prevents ammonia accumulation and reduces the need for aeration. Water exchange requirements are low, typically less than 3% per day, determined by the need to control salinity.
This culture method conforms to sustainability standards. The impact of effluent is very low, since the extensive Ulva mat acts as a bioremediation agent, which absorbs nutrients from shrimp waste and also suppresses the growth of microalgae. Environmental impacts of farm construction are moderate because ponds are built on the dry coastal plain of Baja California, not in critical habitats such as mangroves. No antibiotics or chemicals are required, other than fertilizers to support Ulva biomass accumulation. Terrestrial and marine footprints are acceptable because Ulva can partially satisfy the nutritional needs of shrimp. We have identified feed mixes both with low and zero marine content that give good results as a complement to Ulva in the shrimp diet with feed conversion ratio between 0.7 and 1. A series of retention screens on the outflow and underground water discharge make the probability of escape of shrimp into the wild extremely low. In several years of trials, including in Sinaloa we have never seen evidence of disease in co-culture ponds. There are no signs of disease at the pilot project, which is regularly monitored, or in wild shrimp caught nearby which are checked annually. There are no other farms in the vicinity, because we work in a lower temperature range then L. vannamei. Ulva is known to have anti-viral and anti-bacterial properties, but at present the mode of action of these properties and their practical significance are not well known. A key element of our system is the reliable production of Farfantepenaeus californiensis post-larvae for stocking ponds, together with farm culture of breeding stock so production does not require using wild-caught breeding stock, technology we developed in collaboration with CIBNOR.
Farfantepenaeus californiensis is a desirable species. When raised with Ulva as a large fraction of the diet it has color, flavor and texture equal or superior to any shrimp, farmed or wild-caught.