Chromosome preparation from gill tissue of the tropical oyster (Crassostera belcheri Sowerby, 1871) collected from an oyster farm in Kantang District, Trang Province, southern Thailand was studied by conventional staining and Ag-NOR baining techniques. The result revealed that the diploid chromosome number is 2n=20 and the fundamental number (NF) is 40. The karyotype has revealed 10 large metacentric and 10 medium metacentric chromosomes. One pair of nucleolar organizer regions (NORs) was apparent on the short arm telomeric region of chromosome pair 10. Basic information on the cytogenetics of the C. belcheri may be useful for future studies on interspecific hybridization and polyploidy. The karyotype formula of C. belcheri is as follows: m m 10 10 2 (diploid) 20=L +M n

Members of the freshwater halfbeak genus Dermogenys are hard to identify to the species level, despite several previous attempts to isolate fixed meristic, morphometric and colour pattern differences. This has led to ongoing confusion in scientific literature, records of species occurrence, and entries in museum collections. Here, a DNA barcoding study was conducted on the genus to gain further understanding of its taxonomic status across the Southeast Asian region. Fish were collected from 33 localities, spanning freshwater and brackish habitats in Malaysia, Western Indonesia, Thailand and Vietnam. In total, 290 samples of Dermogenys spp. were amplified for a 651 base pair fragment of the mitochondrial cytochrome oxidase c subunit I (COI) gene. Analysis was able to successfully differentiate the three species: D. collettei, D. siamensis, D. sumatrana; reveal the presence of a new putative species, Dermogenys sp., that was sampled in sympatry with D. collettei at three locations; as well as uncovering two genetic lineages of a fifth species, D. bispina, that display non-overlapping geographical distributions in drainages of northern Borneo; Kudat and Sandakan. This study expands the barcode library for Zenarchopteridae, demonstrates the efficacy of DNA barcoding techniques for differentiating Dermogenys species, and the potential thereof in species discovery.

Oyster seed production in hatchery and nursery systems has relied on the production of microalgae, which is cost effective, but often unpredictable. The development of a satisfactory substitute diet would greatly reduce production costs of hatchery operations. Single cell detritus (SCD) production from seaweed (Porphyra haitanensis) may have great potential as a partial substitute for microalgae. In this experiment, a technique for producing SCD was developed and the product was used as a partial substitute for microalgae for the nursery culture of juvenile tropical oysters (Crassostrea belcheri) in a hatchery setting. A reverse osmosis technique was used on ground seaweed (particle size <200 lm) immersed in freshwater and placed on a shaker at 100 rpm for 2 h before being returned to seawater. This technique was shown to be highly effective for SCD production with a density of 33.7 AE 7.0 9 10 4 cell mL À1 and the percentage of SCD particle diameter <20 lm was 89.2%. A partial replacement of microalgae with SCD was found to be unsuitable for nursing oyster larvae. For juvenile oysters (shell width 1.85 AE 0.03 mm and shell length 1.78 AE 0.06 mm) substituting 75% of microalgae with SCD showed lower absolute shell growth, and lower daily yields and survival rates when compared to rates substituting 50% or lower substitution with SCD, or 100% microalgae (P < 0.05). It was found that substituting 50% of the traditional microalgae with SCD produced from seaweed (P. haitanensis) can be used as a partial microalgae substitute for the nursery culture of the juvenile tropical oyster.

Juveniles of hatchery-reared oysters (Crassostrea belcheri) were grown in a semi-closed recirculation system at water flow rates of 0.5, 1, 2, and 4 l min −1 . Growth rate increased with increasing water flow rate (P < 0.05) over four weeks. No significant differences in survival were found among water flow rates (P > 0.05). Four stocking density treatments were compared: 4, 8, 12, and 16 juveniles cm −2 . Stocking density affected the growth of animals, with higher growth rates obtained at the lower densities. Optimum stocking density based on growth rate was obtained for oysters at 12 juveniles cm −2 . Survival of oysters declined with increasing density (P < 0.05) over four weeks. Among the treatments tested, a water flow rate of 4 l min −1 and stocking density of 12 juveniles cm −2 are suitable for nursing hatchery-reared juvenile oysters (C. belcheri) in a semi-closed recirculation system.

A post-tsunami rehabilitation of cage culture along the Andaman Sea coast of Thailand was carried out in five provinces (Ranong, Phang-nga, Krabi, Trang and Satun) from September 2007 to February 2008. Based on the survey conducted, the money compensated subsequently used to buy materials for cage re-construction and cage repair accounted for 28.1% of the total, and to buy seed, feed and chemicals for culture operations, 15.8%. A surprising finding is that 56.1% of compensated money was used for other purposes. The analysis showed that the quality and quantity of equipment, seeds and feeds invested in aquaculture farms were increased in comparison with the pre-recovery period. Importantly, the farm area, growth rate, amount of product and revenue were improved during the post-tsunami rehabilitation period. Additionally, the area and quality of houses, household consumption, household infrastructures, health care and education were also improved. The satisfaction level of cage farmers in regard to the recovery programs was high (weigh average index = 3.88). The results from this study showed that the net economic profit (NEP) achieved was 41,030.49 baht/crop (33.9 baht = 1 US$) for sea bass culture, while NEP for grouper culture was 59,529.98 baht/crop. The result from the present study indicated that the economic value of cage culture farms was profitable. However, the seed shortage, high cost of trash fish, disease outbreak and marketing were among key problems and constraints encountered. In this study, we also found that the