Biology and status of aquaculture for giant clams (Tridacnidae) in the Ryukyu Islands, southern Japan
IwaiK2006.pdf (1.614Mb)Abstract
The Ryukyu Islands consist of many islands located between Kyushu in mainland Japan and Taiwan. The islands in the south-western area of the Ryukyu Islands belong to the Okinawa Prefecture. The Ryukyu Islands are strongly affected by the Kuroshio Current and are renowned for their coral reefs with high diversity of tropical and subtropical species. Giant clams traditionally have been utilized as fisheries resources for a long time in this area. According to fisheries statistics, catches of Tridacna crocea in Okinawa have decreased drastically during the last 30 years and currently are less than one tenth of previous catches. Fishing can easily deplete stocks of giant clams because the clams inhabit shallow waters and take at least three years to attain sexual maturity. Techniques for the mass seed production and aquaculture of three species (T. crocea, T. squamosa, and T. derasa) were established in Okinawa. Four hundred thousand seeds of giant clams of 8 mm shell length (SL) are supplied to fishermen for use in aquaculture or stock enhancement every year. This paper will review the (1) biology of giant clams, (2) present status of aquaculture of giant clams in Okinawa, and (3) other studies on giant clams in southern Japan.
Citation
Iwai, K., Kiso, K., & Kubo, H. (2006). Biology and status of aquaculture for giant clams (Tridacnidae) in the Ryukyu Islands, southern Japan. In J. H. Primavera, E. T. Quinitio, & M. R. R. Eguia (Eds.), Proceedings of the Regional Technical Consultation on Stock Enhancement for Threatened Species of International Concern, Iloilo City, Philippines, 13-15 July 2005 (pp. 27-38). Tigbauan, Iloilo, Philippines: Aquaculture Department, Southeast Asian Fisheries Development Center. http://hdl.handle.net/10862/2931
Publisher
Aquaculture Department, Southeast Asian Fisheries Development CenterSubject
Clam culture; Bivalve culture; Clam fisheries; Spat; Marine aquaculture; Seed (aquaculture); Seed production; Stocking (organisms); Transplantation; Biology; Functional morphology; Classification; Taxonomy; Habitat; Life cycle; Molluscan larvae; Japan; Tridacna derasa; Tridacna crocea; Tridacna squamosa; Tridacna maxima; Hippopus hippopus
Type
Conference paperISBN
9789718511794Related items
Showing items related by title, author, creator and subject.
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Book
Giant clam hatchery, ocean nursery and stock enhancement
- 2007 - Aquaculture Department, Southeast Asian Fisheries Development Center
Series: Aquaculture extension manual; No. 37This manual is meant to serve as a guide to the culture of giant clams (Bivalvia, Subfamily Tridacninae). The first part focuses on hatchery methods. The second part is about the ocean nursery. The first two sections refer to selection and setting the ocean nursery site. Clam transport is introduced next although this is further tackled in the last part of this manual. Finally, the third and last part discusses the purposes of stock enhancement, survey methods for stock assessment, transport, monitoring and record keeping. -
Article
Growth and survival of hatchery-bred giant clams (Tridacna gigas) in an ocean nursery in Sagay Marine Reserve, Philippines
-Aquaculture International , 2010 - European Aquaculture SocietyTo restore the diminishing population of the giant clam Tridacna gigas in Sagay Marine Reserve (SMR), Negros Occidental, central Philippines, two size classes [8- and 10-cm shell length (SL)] of hatchery-bred T. gigas were reared in an adjacent ocean nursery for restocking to Carbin Reef later upon reaching grow-out size of ≥20 cm SL. Growth rates did not significantly differ for both sizes and were on average 0.67 cm month−1. However, survival after 382 days of rearing T. gigas was significantly higher in the 10-cm SL clams than the 8-cm SL clams (96 and 83%, respectively). For future restocking projects, the use of 8-cm SL clams is recommended because the lower survival of this size class is compensated by its cheaper price. While rearing the clams to attain grow-out size, the population of wild clams (Family Tridacnidae) in Carbin Reef was assessed using ten 50 × 2-m belt transects. Four species of tridacnid clams have been recorded: Hippopus hippopus, Tridacna crocea, T. maxima>, and T. squamosa. T. crocea comprised 12.5–93.9% of all the clams observed in all ten transects. There was a significant difference in clam density between species (ANOVA, F = 6.94, P < 0.001), with T. crocea having the highest density. Living T. gigas were absent, but presence of dead shells was indicative of its presence in the reef in the past. It can be expected that the release of hatchery-bred T. gigas juveniles in Carbin Reef could provide future breeders that will repopulate this reef and the adjacent reef communities. -
Conference paper
Coral culture and transplantation and restocking of giant clams in the Philippines
- In JH Primavera, ET Quinitio & MR Eguia (Eds.), Proceedings of the Regional Technical Consultation on Stock Enhancement for Threatened Species of International Concern, Iloilo City, Philippines, 13-15 July 2005, 2006 - Aquaculture Department, Southeast Asian Fisheries Development CenterRecently, the Pew Project (2001 to 2005) of the senior author entitled ‘Coral reef habitat and productivity enhancement through coral transplantation and giant clam restocking’ was implemented with the aim to improve the biodiversity and productivity of stressed coral reef habitats in 10 selected demonstration sites in the Philippines. These were meant to serve as models for other communities. Transplantation of corals and reseeding of giant clams were the approaches. Nubbins or small fragments from nearby large coral colonies and abundant solitary forms were transplanted to the target sites. Care was exercised to avoid or reduce any negative impacts on the natural source communities. Only cultured giant clams were used, specifically the threatened Tridacna gigas at sizes that would ensure their chances of survival in the wild (approximately 20-30 cm shell length). Following deployment, monitoring activities were undertaken, focusing on macro-invertebrates and fish, as well as the assessment of the survival and growth of experimental animals. Liaison work was done with local communities to raise their environmental awareness and to ensure their cooperation. This manuscript draws principally from results of the Pew Project. At present, two other restoration projects supported by the European Union and the Global Environment Facility Coral Reef Targeted Research Project are being implemented at the Bolinao Marine Laboratory of the University of the Philippines Marine Science Institute (UP-MSI) in Pangasinan. These projects are testing the efficiency of floating and standing coral nurseries in growing coral nubbins in addition to transplanting fragments or branches of corals to restore degraded coral reefs.
