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May 7, 2013
Hawaii—Oceanic Institute Studies Polychaete Production
Executive Summary: Worldwide shrimp aquaculture production has increased dramatically over the last two decades with yearly production currently greater than 3.8 million metric tons a year (FAO 2010 Fisheries Statistics). The availability of domesticated and genetically improved penaeid shrimp stocks (primarily Penaeus vannamei) has been a primary driver of increased production. Shrimp aquaculture is almost exclusively based on captive reproduction. This requires the conditioning and maturation of broodstock shrimp to stimulate gonadal development and induce mating, spawning and ultimately the hatching of eggs to produce viable larvae. Broodstock diets are important in the maturation process, especially in stimulating ovarian development in female shrimp. Hatchery managers typically feed broodstock a mixed diet of raw, wet feeds. Marine polychaete worms are often a major component of broodstock diets. Because penaeid shrimp have a limited ability to synthesize the n-6 and n-3 families of fatty acids de novo or to elongate and de-saturate these into highly unsaturated fatty acids (HUFAs), high concentrations of these important HUFAs found in the ovaries of female broodstock have been attributed to the dietary intake of HUFA-rich items, such as marine polychaete worms.
It is estimated that greater than 5,000 kilograms of frozen marine polychaetes are imported into Hawaii annually to support shrimp breeding activities costing more than $200,000 a year. The primary sources for polychaetes are wild-caught Glycera dibranchiata from Maine, USA, costing around $50 a kilogram, including freight, and cultured Nereis virens from The Netherlands, costing around $33 a kilogram. Major shrimp farms in Asia and Central America typically use live wild-caught and/or cultured local polychaetes in shrimp broodstock diets. At less than $10 a kilogram, these worms are much cheaper than worms from Maine and The Netherlands, but are not a viable alternative to imported, frozen worms for Hawaii hatcheries due to biosecurity risks posed by viral pathogens. Center for Tropical and Subtropical Aquaculture funding is sought to investigate the aquaculture potential of Hawaiian polychaetes for use as a maturation feed in local and regional shrimp hatcheries.
Polychaete worms collected from local marine habitats will be assessed for their culture potential and suitability as a shrimp maturation feed. More than 250 species of polychaetes have been reported in Hawaii (Bailey-Brock 1987), but our focus will be on the larger species of free living or burrowing worms without calcareous tubes or stinging secretions (e.g. fireworms). To minimize disturbance to the native Hawaiian ecosystem, we will seek to utilize widely distributed but non-invasive polychaete species found commonly in Hawaiian waters that have the potential to produce substantial biomass in culture. Nereis and Perinereis are the two most commonly cultured genera for use as broodstock feed, so species from these genera or others in the family Nereidae will be targeted, but we will also test species from other families that we hope will match our desired criteria: large size, rapid growth, ability to grow at moderate to high density, high reproductive output not limited to a single season—and palatability.
To minimize biosecurity risks to the shrimp stocks at Oceanic Institute (OI), collected polychaetes will initially be quarantined and screened for shrimp viruses previously reported in Hawaii using quantitative PCR. Collected worms will be maintained in suitable substrate and conditions and fed shrimp or fish feed (or other materials as appropriate) and monitored for growth, survival, reproductive condition and output. If viable larvae are produced, larval development, growth and survival will be recorded. Settlement of larvae will be the next challenge, and we expect to accomplish this by providing competent larvae with settlement inducting materials from their natural habitat. Juvenile growth will be measured in terms of number of segments, total length and width and development of adult characteristics. Once worms reach a sufficient size, feeding trials will be conducted. A single species that scores well for ease of culture and palatability to shrimp will be selected for scale-up in Year 2. In Year 2, we will optimize culture conditions and test different feed regimes to maximize growth and reproduction, but also to promote high levels of desirable lipids in the adult worms.
Development of a sustainable culture system utilizing a locally collected polychaete species could dramatically improve the profit margin and stability of the marine shrimp aquaculture industry in Hawaii. Knowledge gained in this study will be disseminated through oral presentations, a factsheet brochure for local industry stakeholders and through manuscripts submitted for publication.
Information: Dustin Moss, Oceanic Institute, Center for Tropical and Subtropical Aquaculture, 41-202 Kalanianaole Highway, Waimanalo, Hawaii 96795, USA (phone 1-808-259-3168, fax 1-808-259-5971, email firstname.lastname@example.org, webpage http://www.oceanicinstitute.org).
Source: Hawaii Pacific University. Aquaculture Potential of Hawaiian Polychaetes for Use as a Shrimp Maturation Feed; Funded by the Center for Tropical and Subtropical Aquaculture. Dustin Moss, MS (Oceanic Institute) and Catherine Unabia, PhD (Hawaii Pacific University). May 2, 2013.
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