Proof of concept of a new technology for prolonged high-density live shellfish transportation: Brown crab as a case study

A new technology for live seafood transportation has been developed and tested at real conditions. The technology, whose purpose is to treat the water to allow for increased transportation periods and biomass loads, comprises the following steps: (i) pH control to maintain low NH3 concentration; (ii) electrochemical removal of ammonia; (iii) water disinfection; and (iv) separation of dissolved and particulate organic matter. A fraction of the rearing water is separated several times a day from the live seafood vessels and electrolyzed in a separate reactor to generate active chlorine, which oxidizes ammonia into nitrogen gas, in parallel to disinfecting the water. The electrolyzed water is then dechlorinated by a metabisulfite-based solution and pumped back to the holding tanks through an activated carbon column, applied to remove traces of both chlorine residuals and soluble organic matter. The water treatment process is thereafter repeated with a new portion of water, in a batch manner, as required to maintain the ammonia concentration at a predetermined value. The proposed technology was tested with European brown crab (Cancer pagurus). Four experiments were conducted to simulate transportation in cold aerated water using contemporary technology (two "control" tanks) and a similar setup was operated in parallel, but in which the rearing water was treated, using the tested technology. The tanks that were operated with the new system showed significant reduction in un-ionized ammonia and dissolved and particulate organic matter concentrations. Accordingly, the treatment resulted in much higher survival rates of the crabs, in experiments lasting for 16 days, conducted at a high crab density (~170 kg/m3). Economic analysis conducted using the data obtained in this Proof-of-concept study showed that the proposed technology has the potential to significantly increase the profitability of seafood producers and retailers and to decrease the price of live seafood to the consumer.