Shrimps like all invertebrates are believed to lack true adaptive immunity but recent evidence indicate that they can be protected against pathogenic organisms by priming their immune system with immunostimulatory substances. Here, we describe results of investigation aimed to strengthen shrimp immunity as a preventive strategy against white spot syndrome virus (WSSV) infection. Oligodeoxynucleotides (ODNs) with and without Cytosine-Guanine (CpG) motifs, and Vibrio harveyi genomic DNA (VHD) were administered by intramuscular injection and shrimp responses were assessed by ex vivo assays and experimental infection trials. Results showed that CpG ODN significantly increased ex-vivo immunity indices such as total hemocyte count (THC), plasma agglutination titer (PAT) and hemocyte lysate agglutination titer (HLAT). VHD significantly increased immune indices such as THC, plasma total protein (PTP) and HLAT. Reverse (GpC) motifs increased THC only. At a lower viral challenge dose, both CpG and GpC motifs, and VHD, were able to reduce shrimp mortality significantly but only CpG and VHD did so at a higher challenge dose. Strengthening shrimp immunity by the use of immunostimulatory nucleotides and bacterial genomic DNA could be a feasible preventive approach in the management of WSSV infections in shrimp.

The fish assemblage of a small, open access mangrove creek highly influenced by aquaculture farms, was studied for the first time in the Philippines as a baseline of such system as well as examining the degree of ecological disturbance among fish habitats, as basis for the necessity to rehabilitate mangrove resources aiming to balance human activities and mangrove functioning. In total, 475 fishes (total weight = 3875 g) were captured and 50 species representing 32 families were identified. Thirty two species were represented by small numbers (< 5 individuals). Commercial species was considerably high (~23 species) but majority were low grade commercial species. Total species, species diversity and fish abundance consistently showed a decreasing pattern from outside creek to inner creek. Fish habitats exhibited substantial differences following a distinct spatial segregation of fish communities, a dominance of non-shared species and a minimal species overlapping inside the creek, which is attributable to the existing mangrove fragmentation associated with aquaculture ponds in the area. Increasing levels of disturbances were observed within the creek indicating ‘stress’ as a result of overutilization of mangroves by aquaculture farms. Our results confirmed the need to rehabilitate mangrove resources in this area. The development of mangrove resources through reforestation, coupled by strict regulation of fishing activities and aquaculture ponds will reduce ecological stress in the area and regain gradually a robust mangrove functioning that will improve fish diversity, fisheries and productivity of adjacent coastal systems by creating a suitable fish nursery, feeding ground and refuge habitat.

Unwarranted accumulation of halogenated compounds in the rivers and streams has in recent years emerged due to the widespread use agricultural pesticides. The presence of these halogenated compounds in the water does not only suppress the immune system of fish but adversely induce serious morbidity and mortality among cultured stocks. Importantly, gradual accumulation of these compounds in the system of cultured and wild freshwater fish species cultured in ponds and floating net-cages in dams and rivers, respectively, poses some risks to humans, the end users. In this study, we attempted to isolate bacteria from the gut of pond-reared rohu (Labeo rohita) in Myanmar, screened the isolated bacteria for dehalogenase gene using molecular technique and tested the ability of these bacteria to degrade halogenated compounds in vitro. The eight bacterial strains studied were identified as Enterobacter mori strain MK-121001, Enterobacter cloacae strains MK121003, MK-121004, MK121010, Ralstonia solanacearum strain 121002, Acinetobacter baumannii strain MK121007, Chromobacterium violaceum strain MK121009 and Pantoea vagans strain 121011. Only three bacterial strains (MK121002, MK121007 and MK121009) were capable of degrading 2,2-dichloropropionic acid (2,2-DCP) as the sole carbon source up to a final substrate concentration of 20 mM. Their mean growth doubling time ranging from 6 - 23 hours with the maximum of chloride ion released of 85%. PCR amplification with oligonucleotide primers designed from group I dehalogenase revealed the presence of dehalogenase genes in all isolates suggesting dehalogenase gene in strains 121001, 121003, 121004, 121010 and 121011 were silenced. In contrast, group II dehalogenase primers did not show any PCR amplification. These results suggest that MK121002, MK121007 and MK121009 only encode a group I dehalogenase and its non-stereoselectivity is in agreement with previoulsly described group I haloacid dehalogenase. The partial gene sequences were blasted but no significant sequence identity was observed. Therefore, it suggests the 2-haloacid dehalogenase of MK121002, MK12-1007 and MK- 121009 might be a novel group I 2-haloacid dehalogenase. The results indicated a broad distribution of dehalogenation genes in many microbial genomes that harbor dehalogenase(s) due to the exposure of the microorganisms to the naturally occurring or man-made halogenated compounds in the environmental systems. So far, microorganisms capable of producing dehalogenases were mainly isolated from soil and scarcely from aquatic animals and their environments. To the authors’ knowledge, this is the first report on the isolation of dehalogenase-producing bacteria from the gut of pond-reared freshwater fish, Labeo rohita, in Myanmar.

The SS-type rotifer Brachionus rotundiformis is a common initial food for rearing fish larvae with a small mouth. However, there are commercially important fish species whose mouth sizes are too small to feed on SS-type rotifers. In 2004, we isolated a small (body length = 82.7 ± 10.9 μm; body width 40.5 ± 6.4 μm), flexible, and iloricate rotifer, Proales similis from an estuary in Okinawa, Japan. Under laboratory conditions (25 °C, 2–25 ppt) P. similis produced its first offspring on 2.5 to 2.8 days after hatching, and produced 4.3 to 7.8 offspring within 4.0 to 4.7 days life span. Batch cultured P. similis fed Nannochloropsis oculata suspension at 28.8 μg dry weight ml^{− 1} and cultured at 25 °C, 25 ppt filtered seawater, increased exponentially from 25 to 2400 ind ml^{− 1} after 11 days of culture with an overall intrinsic rate of natural increase (r) of 0.42 day^{− 1}. The growth rate of P. similis was not significantly different when fed fresh N. oculata and super fresh Chlorella vulgaris-V12®. Total lipid per wet weight of P. similis fed by N. oculata and C. vulgaris were 2.4 and 2.6%, respectively. The compositions of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA) of P. similis fed N. oculata were 23.2, 0.0 and 5.3%, respectively, while these were 11.0, 17.5 and 0.5% respectively, when fed C. vulgaris. The use of P. similis to feed small mouth fish including seven-band grouper Epinephelus septemfasciatus, rusty angelfish Centropyge ferrugata, and humphead wrasse Cheilinus undulatus showed that it is an excellent starter food for these species because of their high selectivity index and improved survival. In addition, P. similis was ingested by Japanese eel Anguilla japonica larvae with a complicated digestive system. The use of P. similis as starter feed for small mouth fish larvae is highly recommended.

In coastal ecosystems, variations in food quantity may have significant effects on the clearance and ingestion rates of suspension-feeding bivalves. In this study, clearance rates and ingestion efficiencies were determined for Japanese scallop (Patinopecten yessoensis) juveniles (60.6±4.5 mm in shell height) under laboratory conditions. Scallops were kept individually in glass beakers at 15°C and fed with different cell numbers of Pavlova sp. (0.8 to 57.60×10⁶ cells) to provide a wide range of food quantity as particulate organic carbon (POC). Clearance rates (CR) and ingestion efficiencies (IE) were estimated by monitoring POC concentration over a two-day period, and from 2 to 14 days of feeding, respectively. Both CR and IE were significantly influenced by POC concentration. CR ranged from 15.8 to 38.5 mL ind^-1 h^-1 (or 8.9 to 49.6 mg Ch^-1 g dry weight^-1) with maximum values at high POC concentrations. IE varied from 40 to 71% and differed significantly between the lowest (2,900 μg C L^-1) and highest (8,000 μg C L^-1) food rations. The feeding response of juvenile scallops to different POC concentrations was fitted to a power curve equation: \(\mathsf{IE}\,(\%)=0.9272 \times \mathsf{POC}^{0.5105}, r=0.98\). Extrapolated field-based estimates of IE ranged from 7.8 to 12.7% in response to seasonal changes in POC concentration (64.5 to 168.6 μg C L^-1). It is concluded that particle filtration rates by juvenile scallops are related to food quantity, as suggested by both field and laboratory-derived feeding rates.

Over the years, commercial production of mudcrab, Scylla spp, has been undertaken only in bamboo or net-fenced brackishwater ponds. Its feasibility was proven through series of verification trials conducted in commercial ponds by SEAFDEC/AQD researchers and is now being practiced elsewhere in the country. Of late, the introduction of using net enclosure to grow mudcrabs in mangroves or tidal zones offers a bright prospect in aquasilviculture. Using mangroves as natural resource, paves the natural way of creating livelihood among fisherfolk in the coastal areas. While this method is by far not very popular in the Philippines, the same has been carried out for quite some time in Indonesia, Malaysia, Viet Nam and China. The advantages of this method include low investment cost, ease of construction, environment-friendly and this project can be operated quickly.

The potential for stock enhancement by release of hatchery-reared juveniles continues to be a topic of interest to researchers and fisheries managers. While, in many studies, the focus has tended to be on the technology for production of juveniles, the need for a more multidisciplinary approach is now becoming accepted. Ideally, this includes studies of population dynamics and recruitment-limitation of wild stocks, environment–stock interactions, habitat availability, genetic studies of wild and released stocks and integration with appropriate fisheries management. While it may be relatively straightforward to culture large numbers of seed animals, the quality of hatchery-reared juveniles may limit the effectiveness of any release programme. The quality of juveniles may be defined either by their ability to attain the age and size to recruit to a commercial fishery or their fitness to survive to contribute to the spawning stock. Many factors will inevitably influence batch–batch variability in the viability of hatchery-reared juveniles and their ability to recruit and compete in the wild. Some effects of nutrition and environment in the hatchery are well-known or at least recognised and their manipulation offers the potential for improvement of survivorship of juveniles post-release. The choice and utilisation of broodstock also represent a crucial stage in enhancement programmes, and considerations of bottleneck effects arising from reduced effective population size due to skewed parental and family contributions must be given careful consideration. A broodstock design that encompasses sufficient numbers of animals that reflect the genetic, and preferably ecological, identity of the stocks to be enhanced should be adopted. In addition, environmental conditions and husbandry practices within the hatchery as well as broodstock and larval nutrition can all influence the quality of offspring. Further conditioning and/or selection during nursery culture may also be critical in maximising the physiological and behavioural fitness of hatchery juveniles post-release. Although evaluation of long-term performance of individual batches of juveniles requires considerable effort or may be impossible in some cases, this type of quantification is likely to be an important component in the determination of the effectiveness of release programmes. This paper reviews the effects of hatchery and nursery practice on larval and juvenile fitness for stock enhancement and presents examples of comparisons of the quality of wild and hatchery-reared juveniles and the effect of pre-release conditioning on subsequent survival and growth.

This report consists of two parts, the first deals on the cage culture of grouper, and the second on cage culture of tilapia. The culture of groupers is done in netcages set in marine waters, while tilapia is raised in netcages set in freshwater ponds, reservoirs or in lakes.

Reports of the economically-important agarophytic seaweed genus Gracilariopsis Dawson from Philippine waters are verified for the first time. Cystocarpic, spermatangial and tetrasporic materials collected from various localities in eastern Panay and northwestern Negros islands conform to the circumscription of this recently reinstated genus. Materials are referred to Gracilariopsis heteroclada Zhang & Xia after morphological comparisons with type materials from southern China. In addition, a discussion of the complicated nomenclatural history of this species is included. Another putative Gracilariopsis species is reported from Zamboanga City based on cystocarpic materials alone. This species differs from G. heteroclada with its smaller gonimoblast cells and larger height:width ratio of the gonimoblast mass. Vegetatively, the thallus is smooth, devoid of fine, determinate branchlets observed in G. heteroclada.

This paper describes the first screening in the Philippines of slipper-cupped oysters (Crassostrea iredalei) for the presence of parasites. Slipper-cupped oysters were sampled at 2 sites in Ivisan, Capiz, from September to December 2007. Macroscopical and histological analyses were carried out in oyster tissues. Histological examination showed gregarine protozoan Nematopsis sp. as the most prevalent parasite (71.33% and 65.0%) at 2 sites with a moderate intensity of infection. Tylocephalum sp. cestode was found in the connective tissue around the digestive gland, with a prevalence of 60% and 52.3% in 2 sites, with a moderate intensity of infection. Digenean trematodes had a 37.80% prevalence at site 1 and a 22.45% prevalence at site 2. Ciliates were also observed with a prevalence of 18.75% (site 1) and 13% (site 2). The observed infection of oysters had no apparent effect on oyster production at these sites maybe due to low infestation levels or to the fact that the parasites have no pathological effect.