Pacific Threadfin
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Transcript of Pacific Threadfin
Pacific Threadfin
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
Polydactylus sexfilis
$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
Marketplace
Loko i’aAncient 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 loko i’a
ReproductionProtandrous 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 prolarva until D3 when feeding begins, then postlarva until metamorphosis to juvenile form at D21-D25
Current Aquaculture6-8 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: loko i’a, intensive round tank (RAS), off-shore cages, and raceways
RequirmentsLarvae eat algae paste, rotifers, and Artemia sp. napulii
before 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
ProblemsPower outages cause population crashes in hatcheries and
nurseriesBack up generators required, especially during peak spawning
season
High losses due to cannibalism immediately after metamorphosisKeeping nursery tanks shallow and a circular current moving
prevents food stratification, which eliminates the size differential that prompts the cannibalism