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April 2, 2015
Hawaii—Aquaculture Potential of Hawaiian Polychaetes
Because penaeid shrimp have a limited ability to synthesize the n-6 and n-3 families of fatty acids or to elongate and de-saturate them into highly unsaturated fatty acids (HUFAs), managers of shrimp broodstock facilities typically feed broodstock polychaete worms that are loaded with HUFAs.
Hawaii is a world leader in the supply of specific pathogen free, selectively bred Penaeus vannamei broodstock. It is estimated that more than 5,000 kilograms of frozen marine polychaetes are imported into Hawaii annually to support shrimp breeding activities at a cost of more than $200,000 per year. The primary sources of polychaetes are wild-caught Glycera dibranchiata from Maine, USA, which cost around $50 a kilogram (including freight) and cultured Nereis virens from the Netherlands, which cost around $33 a kilogram. Shrimp broodstock facilities in Asia and Central America typically use live, wild-caught and farmed polychaetes because they are cheaper, less than $10 a kilogram, than frozen worms and female shrimp broodstock perform better (e.g. more nauplii per spawn, stronger nauplii) when fed live worms. Importing live worms from Asia (or elsewhere) is not a viable alternative to imported, frozen worms for Hawaii broodstock facilities because of biosecurity risks and transportation costs. Thus, having a local source of live polychaete worms could potentially reduce worm costs, reduce/eliminate worm imports and improve production efficiency at Hawaii broodstock facilities.
With funding from Center for Tropical and Subtropical Aquaculture, the Oceanic Institute of Hawaii Pacific University has begun accessing the aquaculture potential of several species of locally available polychaetes. To date, several species have been collected from various locations around the island of Oahu. Five species were found to be of acceptable size (adults ≥5 cm in length) and in high abundance: Marphysa sanguinea, Lumbrineris japonica, Sabellastarte spectabilis, Malacoceros indicus, and Chaetopterus variopedatus.
Collected worms were screened for the presence of whitespot, Taura and IHHN viruses and for the bacterium that causes early mortality syndrome. To date, all polychaete and shrimp samples have tested negative for the four shrimp pathogens.
All candidate species have been successfully cultured for more than 30 days, with a population of M. sanguinea being cultured for more than 200 days. This population currently includes more than 100 adults and 400 juveniles. Worms are housed in small baskets lined with mesh bags to retain sediment and the worms. Culture baskets are placed in a tank receiving flow-through seawater and aerated with airstones to maintain water quality. Worms are fed small quantities of shrimp feed (crumbles).
M. sanguinea larvae and juveniles have been collected from the culture system. These collections were made more than three weeks after the last introduction of worms to the culture system, which provides strong evidence that the worms are spawning in culture. Larvae and juveniles (post-settlement) of three size classes have been collected, suggesting that there have been multiple spawning events and that larval settlement for this species will not be a major impediment to captive reproduction. A simple larvae/juvenile collection system has been setup, so that reproductive output and spawning trends of this species can be determined.
Due to its large size, high abundance in near-shore environments, high survival in culture and the apparent ease of captive reproduction, M. sanguinea has been selected as the primary candidate for culture. In addition, preliminary palatability screening revealed that shrimp responded most favorably to M. sanguinea with both a rapid attack time and complete consumption of the worm.
Additional studies will be performed to compare palatability of wild-caught M. sanguinea, cultured M. sanguinea and frozen, wild-caught polychaetes from Maine. Nutrient and lipid concentrations will also be compared. Efforts will continue to further characterize reproductive output, larval development/settlement and growth of M. sanguinea.
Source: Center for Tropical and Subtropical Aquaculture. Regional E-Notes. CTSA Project Update: Aquaculture Potential of Hawaiian Polychaetes. Dustin Moss and Cassandra Turner. Volume 7, Issue 3, March 2015.
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