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Pacific Threadfin

Pacific Threadfin. Polydactylus sexfilis. Commonly known as Pacific Threadfin or Six Finger Threadfin Also known by the common name moi , or the “fish of kings”

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Pacific Threadfin

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  1. Pacific Threadfin

  2. Polydactylussexfilis • Commonly known as Pacific Threadfin or Six Finger Threadfin • Also known by the common name moi, or the “fish of kings” • Fingerlings from aquaculture have been used to replenish depleted fisheries, now over 70% of all specimens caught were raised in aquaculture facilities • Modern aquaculture pioneered by Oceanic Institute in Waimanolo, HI

  3. Marketplace • $4-$7/lbs. • 1.3-1.5 FCR • $2.50-$4.25 production cost/lbs. • Still exclusively grown in Hawaii, but shipped to markets on the mainland, Asia, and Europe • Highly popular fish due to its taste and ability to be prepared essentially any way

  4. Lokoi’a • Ancient form of aquaculture used in Hawaii • Walled ponds built along the coast to trap and raise fish • At low tide nutrient-rich water drained from the pond and attracted additional fish to be trapped • So efficient that one pond could feed an entire community • Still utilized today by placing stock inside PVC cages within the original lokoi’a

  5. Reproduction • Protandrous hermaphrodites • Spawn for 3-6 nights 8-10 days after the full moon, year round in optimal conditions, with highest egg viability in the summer months • By dawn viable eggs reach the embryo stage • Known as prolarvauntil D3 when feeding begins, then postlarva until metamorphosis to juvenile form at D21-D25

  6. Current Aquaculture • 6-8 month grow-out period, >90% survival rate • Eggs are hatched and raised in recirculating aquaculture systems for the first 25 days • Moved to nursery tanks with a strong circular current and continuous feeding to prevent cannibalism until moving to grow-out at D60 • Grow-out techniques include: lokoi’a, intensive round tank (RAS), off-shore cages, and raceways

  7. Requirments • Larvae eat algae paste, rotifers, and Artemiasp. napuliibefore weaning to a dry diet • Dry diet needs 50% protein and 12% lipid content • Broodstock are fed a diet of frozen squid, smelt, and shrimp • DO: >5ppm • Salinity: >20ppt, preferable 33-36ppt • Temperature: 24-30°C

  8. Problems • Power outages cause population crashes in hatcheries and nurseries • Back up generators required, especially during peak spawning season • High losses due to cannibalism immediately after metamorphosis • Keeping nursery tanks shallow and a circular current moving prevents food stratification, which eliminates the size differential that prompts the cannibalism

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