Rearing fish during their larval stage is often the most difficult part of developing a new species for culture; however, for yellowfin tuna, this common difficulty is further complicated by the absence of a domestic population of breeding fish. Instead of setting up breeding tanks locally, which is expensive and logistically complex, researchers have been airfreighting tuna eggs and larvae from the Inter-American Tropical Tuna Commission’s facility at the Achotines Laboratory in Panama (one of the few research facilities in the world designed specifically to study the early-life history of tropical tunas) to their aquaculture facility at Hubbs-SeaWorld Research Institute in San Diego. The survivorship of these animals, though, has been so low that it has been basically impossible to carry out the necessary research on their early life history requirements (e.g., nutritional requirements). The first main goal of this project is to identify what is causing low survivorship among airfreighted fish and to fix the sources of harm, if feasible. In recent trials, project researchers found that larval survival in control groups retained in Panama and not subject to the stress of bagging for shipment survived better than those placed in bags for simulated shipments, which in turn survived better than those actually airfreighted. Survival upon arrival after 24 hour shipments was often high but mortality increased dramatically thereafter among all groups even before first feeding. Even control groups stocked directly into culture tanks (without bagging) failed to survive to a juvenile stage, suggesting that the quality of the larvae was impaired to start with or culture conditions were not optimized. Proliferation of bacteria during the shipping period was identified as a key impediment to success that was minimized by shipping eggs rather than larvae, sterilizing the water before adding it to the bags, and adding antimicrobial compounds to the water in the bags prior to shipment.
Development of Sustainable Tuna Aquaculture in the United States Using Yellowfin Tuna as a Model