Larval nutrition strategies for improved tuna hatchery production

Tuna are among the most highly valued fish worldwide. Due to this value and high demand, tuna are being fished beyond sustainable levels in many parts of the world. Replacing or supplementing wild catch with hatchery raised tuna makes sense, but this is technically difficult with current technology. Hatchery efforts since the 1970s have made progress in capture and spawning of tuna to provide eggs for culture. Institutes in Japan, Australia, Panama, Indonesia, Spain and several other European countries now have spawning tuna broodstock in captivity, and a similar effort is under way in Hawaii and other parts of the USA. The major obstacle to successful hatchery production now is survival of young tuna larvae. Decades of research in Japan and elsewhere indicate that tuna larvae have special needs that are difficult to provide in captivity. The most advanced hatcheries now produce only a few thousand juvenile tuna per year at high cost. Pacific Planktonics has resources that may improve tuna hatchery culture, based on the current hypothesis that nutritional deficiency may be the problem. Previous research at Pacific Planktonics resulted in successful production of several marine fish species that were difficult to raise. Much of this success was due to our ability to provide the best nutrition to fish larvae (i.e., natural feeds such as marine copepods), and to provide this nutrition efficiently and effectively in quantities adequate to support large scale fish culture. This project aims to determine if natural marine feeds will improve larval tuna survival, and to estimate the costs to produce these feeds to support commercial tuna aquaculture. Biochemical assays will help us to assess the nature of our results, and to continue improving standard hatchery feeds. Based on previous USDA-SBIR work at Pacific Planktonics, we hypothesize that our cultured feeds will satisfy that need, as found in successful feeds (yolk sac larvae of various fish). Our objectives will be accomplished by comparing survival of young larval tuna fed standard hatchery feeds (i.e., enriched rotifers and brine shrimp) versus copepods. Successful results will help tuna aquaculture to expand to commercial scale. This project is endorsed by Hawaii Oceanic Technology, Inc. (http://www.hioceantech.com) a company that intends to build a commercial offshore tuna cage farm in Hawaii. HOT intends to raise bigeye and yellowfin tuna in very large cages off the Kohala coast of the island of Hawaii, and has a successful broodstock husbandry program in place at Pacific Planktonics. This broodstock is the founding basis of our commercialization plan to provide a dependable supply of fingerling tuna to HOT. HOT will eventually build their own tuna hatchery, but Pacific Planktonics will continue to provide backup broodstock and fingerlings.