The silver perch Leiopotherapon plumbeus, locally known as ayungin, is an endemic freshwater fish that is commercially valuable as it commands a high price in the local market. Due to excessive fishing and other potential causes such as predation by invasive alien species, the local L. plumbeus stocks are observed to be depleting hence there is a need for an induced breeding protocol to propagate silver perch and conserve what remains of the resource. In this study, 30 females (total length or TL: 109.4 ± 12.2 mm; total body weight or TBW: 20.3 ± 6.1 g) and 60 males (TL: 97.1 ± 11.6 mm; TBW: 13.4 ± 5.5 g) were injected once intra-muscularly with different doses of hormones. Various dosages of human chorionic gonadotropin (HCG), luteinizing hormone releasing hormone analog (LHRHa) and salmon gonadotropin releasing hormone (sGnRH) were evaluated to identify the most effective dosage and hormone that resulted to high ovulation, fertilization and hatching rate. For the hormone sGnRH, 20, 30 and 40 µg/kg body weight (BW) and 1, 2 and 3 µg/kg BW for LHRHa were the dosages used in the experiment. The dosage used for HCG is 50 IU/g BW and served as the control. The findings of the experiment determined that the use of 20 µg/kg body weight of sGnRH resulted to high ovulation, fertilization and hatching rates. The result of the experiment would provide an efficient protocol for the local fishermen so they can produce, on demand, a large supply of this high quality fish species.

Chitin is a natural biopolymer and the second most abundant after cellulose. Chitosan, a derivative of chitin which is soluble in acidic aqueous media, is used in many applications like food, cosmetics, biomedical and pharmaceutical products. It is used in agriculture for enhancing growth in crops while in aquaculture, chitosan is believed to improve the immune response of fish to stress-inducing agents, thus enhancing survival and possibly growth. This preliminary study was conducted to investigate the effects of various concentrations of irradiated chitosan on the growth performance of Nile tilapia, O. niloticus. Fish was fed with a control diet and three formulated diets containing increasing levels of irradiated chitosan (10g, 20g and 50g kg-1). Juvenile O. niloticus was fed once daily for 21 days. The ration was based on 5% of the fish biomass. Tilapia fingerlings (n=30 per tank) of uniform size were randomly distributed in four experimental groups each with three replicates following a completely randomized design. Growth and food utilization parameters were measured. Specific growth rate (SGR), mean weight gain (MWG), mean length increment (MLI) and feed conversion ratio (FCR) were computed and analyzed using ANCOVA. Results from the feeding trials showed no significant difference (P>0.05) in the different performance parameters under the different fish feed treatments. MWG, MLG, SGR and FCR varied in the stocks fed different fish feed treatments but with no significant differences. The results also showed 45-62% survival ratio. These suggest that although there is no significant difference between treatments and control, irradiated chitosan-supplemented diets do not retard the growth of O. niloticus. Chitosan should be studied further to determine how it can improve the growth performance, feed utilization and immune response of Nile tilapia.

Snapping shrimp Alpheus sp. is abundant in Calape, Bohol, particularly in coastal areas with a wide intertidal zone, mangroves and rich mud banks. Locally known as takla , it is considered as one of the major seafood delicacies in the municipality. An initial assessment of the natural population and fishery of the snapping shrimp was conducted. Using quadrat sampling, mean density was noted at 7 individuals m-2, body weight ranging from 3.87-12.86 g and total length at 4.78-7.44 cm. The largest individual was identified as male having larger claws, the size being two times larger than that found in females. Apart from actual field sampling, a total of 80 shrimp gatherers were surveyed to obtain relevant fishery information for the snapping shrimp. The snapping shrimp is sold in the local public market and traded in hotels and seafood restaurants at PhP50.00 bundle-1 (a bundle averaging 20 pieces) and PhP180.00 a kilo. The current average catch per gatherer is at 75 pieces on a daily basis which is relatively lower compared to the average catch in the 1980s and 1990s ranging from 150-300 pieces day-1. Destruction of mangrove swamps due to fishpond conversion, unabated mangrove cutting for commercial firewood production and unrestricted gathering of snapping shrimps were identified as possible causes for the decline. These baseline data are essential for the local government and the community to come up with appropriate protection and conservation measures. An intensive and comprehensive study on the snapping shrimps ecology and biology also need to be conducted to provide basis for sound and holistic management of this valuable resource.

Success in larval rearing of silver therapon can be achieved through early weaning of fish larvae from live food to artificial diet. Two experiments were carried out to investigate the effects of (a) weaning age (abrupt and gradual) and (b) larval diets (artificial and live foods) on survival and growth of silver therapon (Leiopotherapon plumbeus). In the first experiment, larvae were randomly stocked in round 4-l plastic basins at 15 larvae per basin to provide triplicates of four weaning age treatments (8, 14, 20 and 26 days after hatching or DAH, respectively). Larvae were fed thrice daily for 21 days with commercial feed (CF) and with copepods (COP) which served as the control. Larvae weaned at 26 DAH had the highest survival, body weight and total length among the treatment groups, which were comparable with that of the control. In the co-feeding protocol, larvae were fed Artemia nauplii (ART) as the control group and co-fed with either zooplankton i.e. 50% COP + 50% CF or 50% ART + 50% CF for 8 (8-15 DAH), 6 (14-19 DAH) and 4 (20-23 DAH) days, and suddenly weaned to FM until 21 days. Survival ranged from 22.2 ± 16.8 to 40.0 ± 24.0% between treatments, but was still lower than the control (88.9 ± 3.8%). Body weight and total length were significantly higher in larvae with co-feeding for 4 days (70.1 ± 2.8 mg; 18.1 ± 0.8 mm), but were still lower than that of the control (142.8 ± 7.6 mg; 22.3 ± 0.3 mm). In the second experiment, 26-day old larvae were stocked in 20-l glass aquaria at 4 larvae l-1. Larval diets ((I) commercial prawn feed (38% crude protein); (II) Artemia nauplii; (III) copepods; and (IV) free-living nematode Panagrellus redivivus) were given twice daily for 28 days. Survival was highest in larvae fed Artemia nauplii and poor in copepod fed larvae. Final total length (TL) of larvae fed prawn diet was higher than those fed copepod or nematodes. However, best growth was noted in larvae fed Artemia nauplii (TL= 24.30 ± 0.81 mm; BW = 156 ± 8 mg; specific growth rate or SGR = 5.33 ± 0.19%/d).

Shrimp aquaculture is one of the most important sources of income and livelihood in the Philippines. For the past two decades, the white spot syndrome virus (WSSV) has adversely affected the production of the Philippine shrimp industry resulting to losses in revenue. Shrimps infected by the virus experience up to 100% mortality, 3 to 10 days post-infection. One way of controlling the disease is early detection, which remains to be too complicated and inaccessible to shrimp farmers. Being a DNA virus, the first step to WSSV diagnosis is the isolation of high-quality DNA suitable for polymerase chain reaction (PCR) or loop-mediated isothermal amplification (LAMP). Using readily available and affordable reagents, a DNA extraction protocol has been especially developed for rapid WSSV-detection; DNA has been successfully extracted from the pleopods of shrimps and the results were comparable with that of commercially available kits from Promega and Zymoresearch. LAMP has been optimized for WSSV detection in the temperature range of 55°C to 68°C and was shown to be faster and ten times more sensitive than conventional PCR. This study together with a locally fabricated machine, offers a more convenient, practical and efficient way of detecting WSSV, with the advantage of using non-invasive means of obtaining shrimp tissue therefore not losing any shrimp meat in the process.

A resource assessment of sea cucumber was conducted in six out of eight coastal towns in northern Iloilo, a fisheries rich area facing the Visayan Sea in the central Philippines. A yearlong assessment was conducted in 2012. Fishery dependent survey was done with the use of survey questionnaire translated into dialect. Six trained enumerators administered the questionnaires to 114 gatherers and 18 local traders. Fishery independent survey involving Belt Transect Method (BTM) for intertidal areas and Timed-Search Method (TSM) for subtidal areas were conducted in 21 GPS (Global Positioning System)-referenced sampling stations. Sample specimens were also collected and prepared for taxonomic identification. External morphology, internal structures (dissected samples) and spicule analysis were used in the identification. Fishery dependent survey showed that gleaning (40%) is the most dominant extraction method used. Various methods were also employed including the dangerous compressor diving and the destructive karas, a method using a rake-like device to scrape the sea bed. In terms of volume, the most heavily exploited sea cucumber belongs to the Stichopus groups. The trade of sea cucumber is dominated by island-based traders. Almost half of the traders are women, signifying that trading is a woman's domain as well. Derived monthly income from sea cucumber trade ranges from PhP 2,000-3,000 for gatherers and PhP 2,000-5,000 for the traders. Fishery independent survey resulted in the identification of six sea cucumber genera (Bohadschia, Holothuria, Paracaudina, Pseudocholochirus and Stichopus). Of the 32 species found belonging to the six genera, only 16 were identified up to the species level. Samples of unidentified specimen were sent to the University of the Philippines - Marine Science Institute (UP MSI) laboratory for molecular taxonomic identification. In terms of species count, the most dominant genera is the Holothuria with nine identified and seven unidentified species. H. impatiens is also the most dominant sea cucumber found in the area. Further, the recorded catch per unit effort (CPUE) for fishery-independent survey is 3-4 pcs/diver/hr. The resource assessment showed that the trade of sea cucumber is dictated by economic value rather than by ecological abundance. While the scale and extent of sea cucumber fishery in northern Iloilo is small-scale and island based, the study highlights the need for trade regulation and stock enhancement of heavily exploited species as extraction affects the ecological distribution of sea cucumber stocks in the area.

The global population according to the United States Census Bureau has reached 7 billion as of October 2013. The continuous growth in human population will continue to put tremendous pressure on food production. The demand for fish as source of good protein is no exception. In 2011 total capture fisheries supplied 90.4 million tons of food and total aquaculture provided 63.6 million tons. While aquaculture production has increased dramatically, more than 50% of fishery production still depends on capture fisheries. Overexploitation of wild fish stocks has become one of the biggest problems in global fisheries. Stock enhancement has become a potential viable strategy for marine fisheries in danger of collapse. With the tremendous progress made in the breeding and larval rearing techniques of marine species, hatchery-based stock enhancement is now operated in many stock enhancement programs. However, many questions are raised in the use of hatchery-reared fish in stock enhancement. This paper will discuss genetic considerations in stock enhancement in developing countries.

The giant trevally, maliputo (Caranx ignobilis), a highly prized and most popular indigenous migratory fish in Taal Lake, Batangas, Philippines, was induced to spawn using various hormones (to assess hormone efficacy on spawning performance). Different feeding regimes used in the larval rearing of this species were also evaluated. Sexually mature breeders, 5 to 7 years old with at least 0.5 mm oocyte diameter and 60% of ova at GVM stage were injected intramuscularly, in two doses, with: (a) 1,000 IU/kg BW human chorionic gonadotropin (HCG); (b) 100 µg/kg BW luteinizing hormone releasing hormone analogue (LHRHa); and (c) 5 mg/kg BW carp pituitary extract (CPE), at five breeders per hormone treatment. Uninjected fish served as the control. Treated fish were released and allowed to spawn spontaneously in 40-ton (5m diameter) circular tanks. Successful spawning was achieved during the months of March to July (28-30 ppt salinity; 27.6-29.25°C). Maliputo eggs are pelagic, clear and spherical, with a single oil globule and mean diameter of 0.8 mm. Ovulation period was 24-36.5 hours after 2nd injection in HCG-treated fish and 25-52 hours for LHRHa-injected fish. Only one of the CPE-treated fish spawned after 27 hours but eggs were not fertilized. Uninjected control fish did not spawn. Eggs were hatched in 11-13 hours in HCG treatment and 11-17 hours in LHRHa. Mean number of spawned eggs (3,500-4,000 eggs•gram-1) was higher in HCG treatment (223,068 eggs•kg-1 breeder at 58.27g•kg-1 breeder) than LHRHa (176,524 eggs•kg-1 breeder at 50.44 g•kg-1 breeder). Fertilization and hatching rates were both higher in LHRHa (60.88% and 71.07%, respectively), than HCG treatment (30.53% and 43.06%). Mean number of produced larvae was higher in LHRHa treatment (56,040 larvae•kg-1 breeder) compared to HCG-treated fish (41,547 larvae•kg-1 breeder). Hatched larvae (1.6 mm mean length) reared for 30 days in 3m x 3m concrete tanks using the standard protocol for marine finfish hatchery attained a maximum survival of 4.47%. Complete metamorphosis was observed after 26-28 days (8.1 mm mean length). Successful larval rearing was attained using greenwater (Nannochloropsis sp.) technology fed with live food (Brachionus sp. and Artemia salina). Critical periods were days 1-7 and days 19-22 when heavy mortalities were observed. Being the first recorded spawning in captivity of Caranx ignobilis in the Philippines, the results of this study provides an important baseline data and is a major step towards the development of a hatchery technology for maliputo in the country as well as for seed enhancement of its natural habitat. The project has provided 400,000 maliputo larvae to private hatcheries for larval rearing trials while 100,000 larvae were seeded in Balayan Bay and 5,000 fingerlings released in Taal Lake.

Continuous intensification of aquaculture production has brought about environmental issues associated with eutrophication worldwide. Environmental deterioration such as hypoxia and sulfide production due to water and sediment eutrophication originating from aquaculture effluents have been problematic, resulting to sporadic disease outbreaks and fish kills in the Philippines. Integrated multi-trophic aquaculture (IMTA) is one of the promising methods for sustainable aquaculture as it also provides a supplementary source of income to the fish farmers. IMTA is a polyculture system that integrates culturing of fed species (e.g. finfish) the main commodity, organic extractive species (e.g. deposit and filter feeding benthos) and inorganic extractive species (e.g. seaweed). In this study, IMTA techniques were established for small-scale coastal fish farmers in the Philippines, with sea cucumber (Holothuria scabra, commonly known as sandfish), as the key species. Sandfish commands the highest price in tropical sea cucumber species. Nitrogen (N) budget of sandfish in polyculture with milkfish (Chanos chanos) and Elkhorn sea moss (Kappaphycus alvarezii), both of which are commonly cultured in the Philippines, was estimated using a simple closed box model. Information on stocking density, stocking size, mortality, growth, feed ration, feed assimilation, NH4-N production and NH4-N absorption of these species was obtained from a series of experiments and existing literature. Culture conditions were as follows: 26 g milkfish were cultured in a 5 x 5 x 4 m cage at an average stocking density of 36.7 ind/m3 (i.e. usual practice in the Philippines) with an initial feeding ration of 10% of body weight which was gradually decreased to 4% over time; 10 g sandfish were cultured in a 5 x 5 x 0.3 m cage hung under the milkfish cage to trap particulate N waste (i.e. feces and leftover feed) from milkfish culture at a stocking density of 35 ind/m2; the stocking weight of Elkhorn sea moss line culture was 10 kg. The culture period was 200 days. It was estimated that milkfish culture under the above-mentioned schemes cumulatively produced 145 kg of particulate N, and milkfish and sandfish together excreted 60 kg of NH4-N in 200 days of culture. Daily assimilation rate of the particulate N by sandfish ranged from 3.4 to 12.4%, and 6.4% of the particulate N was estimated to be removed by sandfish during the entire 200 days of culture. Daily absorption rate of NH4-N by Elkhorn sea moss increased exponentially with time and reached 100% at 125 days of culture. Cumulative NH4-N from milkfish and sandfish excretion was estimated to be depleted by 162 days of culture. For complete utilization of particulate N by sandfish by the end of milkfish culture period (i.e. zero emission), sandfish stocking density should be 805 ind/m2, which is 200 times as high as that in existing sandfish aquaculture operations in countries such as Viet Nam and New Caledonia. The purpose of sandfish culture in IMTA should be emphasized in terms of its economic advantages and not very much on environmental integrity. Cages for sandfish culture should be designed in such a way where only a small fraction of organic matter from milkfish culture (i.e. about 6% in this culture scheme) enters it to avoid sediment quality deterioration and possible death of sandfish. Elkhorn sea moss on the other hand seems very efficient in bioremediation capability.