Seasonal reproduction of the climbing perch Anabas testudineus in the Candaba wetland, Philippines, is described. Monthly specimens were collected, gonads and viscera excised, and the gonads histologically examined. Low mean female gonadosomatic index [GSI (%)] from September to February (0.3–2.1 %) increased in March (8.7 %), peaked in May (10.9 %), and declined in June (3.3 %), but increased again in July and August (8.3–5.5 %). Male GSIs (at least 1 %) were low from September until May, increased in June (2.5 %), and then declined thereafter. All the six oocyte and four spermatogenic cell development stages were observed in the gonads throughout the annual cycle. The ovary was dominated by primary growth oocytes (chromatin nucleolus, perinucleolus) from August to February (77–90 %), but yolky oocytes (previtellogenic, vitellogenic) comprised 15 % to 28 % of the ovary from March to July. Mature oocytes were present for most of the year, comprising 40 % of the total oocytes in March-April, peaking in May (50 %), but declining to 30 % in June–July. Spermatozoa consistently dominated the testis throughout the annual cycle, particularly in November and March (58 %). Food intake in both sexes was generally low during the dry season (December–April) when gonad activity was also low, but started to increase at the onset of the wet season (May–November) when gonad activity began to peak. These results demonstrate that the climbing perch gonads exhibit asynchronous development, allowing a protracted breeding season with intense gonad activity timed at the onset of the wet season, concurrent with increasing food intake through the rest of the season.

Because of high mortality recorded in pond-reared shrimps due to luminescent vibriosis infection, a study was conducted to determine if postlarvae (PLs) could be major sources of luminescent bacteria (LB). Batches of hatchery-reared (PL12 to 18) and wild-caught Penaeus monodon PLs were examined to determine their bacterial load. Results show that although all PLs have associated Vibrio spp., not all of them harbored detectable levels of LB. Fifty eight percent of wild-caught postlarval batches did not have associated LB compared with only 23-44% of hatchery-reared postlarvae. A significant difference in quantitative LB load was noted between hatchery reared and wild-caught PLs with the former harboring up to 3.0 x 10⁵ cfu LB/postlarva. Wildcaught PLs had only up to 3.5 x 10² cfu LB/postlarva. Antimicrobial sensitivity tests using disc diffusion method show significant resistance to Chloramphenicol and Oxytetracycline among isolates from hatchery-reared PLs (33 and 44%) compared with bacteria from wild-caught PLs (3 and 6%) and near shore seawater (0 and 12%). The differences between the quantitative and qualitative bacterial flora of hatchery-reared and wild-caught PLs may have contributed to the occurrence of luminescent vibriosis in grow-out ponds, which generally make use of hatchery-reared postlarvae.

This case study presents the successful practice of sustainable intensification of milkfish aquaculture in marine fish cages under semi-intensive grow-out conditions in the Panabo City Mariculture Park (PCMP) in Davao del Norte, Philippines. Established in 2006, PCMP became operational through the promulgation of a City Ordinance declaring 1 075 hectares of municipal waters in Panabo City as a Mariculture Development Zone/Park. The operations of PCMP were so successful that in just five years it became the third largest among the 63 operational MPs in the Philippines during 2011, with 86 private investors-locators operating a total of 322 units of cages. At present, a total of 372 units of fish cages are operating in the mariculture park (MP). A combination of factors contributed to the successful operation of PCMP, but the success is usually attributed to the effective partnership between the government (both local and national) and the private sector. The Comprehensive MP City Ordinance that governs the PCMP is strictly implemented and includes, among others, the tenurial rights and access to locators. Regulations on distances between cages are strictly enforced and security measures in the total area are jointly undertaken by the government and the locators. The national government, through the Bureau of Fisheries and Aquatic Resources-National Mariculture Center (BFAR-NMC), provides technical support in all aspects from stocking to harvest during the production cycle. BFAR-NMC staff conduct regular periodic sampling of the stocks and compute feeding rates for the stocks which are implemented by the technicians/caretakers. Likewise, BFAR-NMC staff regularly monitor the water quality of the MP and the health status of the stocks. Since it became operational in 2006, the PCMP did not report a single incident of mass fish kill, which indicates that the technical guidelines of MP operations are strictly followed. Workers are trained and organized into groups by BFAR-NMC such as caretakers, cage framers, netters, harvesters, fish processors, and others, and actively participate in discussions related to MP operations to ensure protocols are properly followed. Harvests of stocks are done by skilled workers trained by BFAR-NMC, all done in the “Bagsakan Center” or fish landing area and are well-coordinated. The support facilities in the fish landing area are provided by both the local and national government and the PCMP Producers Association. The operators provide complete data for their operations to BFAR-NMC for record keeping. The strong partnership between the national government through BFAR-NMC, the local government unit, the investors, as well as the acceptance and support from the community for the PCMP is the hallmark of its success.

The oxygen consumption rate (OCR) and ammonium excretion rate (AER) of a tropical sea cucumber, Holothuria scabra, were determined in laboratory experiments. OCR and AER exhibited a significant negative correlation to body weight (BW), expressed as a power function of \(\mathrm{BW:}\; \mathit{OCR} = 0.09 \times BW^{-0.58}(\mathrm{mgO_{2}/g/h, r^{2}=0.89, n=15})\) and \(AER = 0.38 \times BW^{-0.19}\) \((\mathrm{\mu\text{molN/g/h}}, \mathrm{r^{2}=0.54}, n=15)\). These values were comparable to those in previous studies on other sea cucumber species. The OCR of shrimp tank sediment was reduced to less than half \((4.5 \pm 0.3 \mathrm{\;to\;} 1.0 \pm 0.1\;\mathrm{mgO_{2}/gdry/h)}\) by the ingestion and excretion process of H. scabra. Acid volatile sulfide (AVS-S) concentration was also decreased to less than half (0.67 to 0.31 mgS/mgdry); despite the low reduction rates of organic carbon and nitrogen contents (0.19 to 0.14 mgC/mgdry and 0.022 to 0.019 mgN/mgdry, respectively). These results suggest that components in the sediment with high oxygen consumption potential were removed by H. scabra. These findings also provide fundamental information with which to evaluate the quantitative role of H. scabra in polyculture with shrimp.

The growth of the juvenile sea cucumber, Holothuria scabra, was studied under captivity to elucidate the growth variation pattern and determine the best-fit growth model to estimate age- and size-specific growth rates. Individual growth was extremely variable, with some individuals below the mean initial weight and some expanding their original body length (L) and weight (W) by up to 6.4 and 156 times, respectively; during 84 days of culture starting at 127 days of age. Some of the smallest individuals showed a higher condition factor than larger individuals in the presence of ample food, indicating that lack of food may not be the only impediment to growth. Among the three growth models compared (von Bertalanffy, Gompertz and logistic), the Gompertz model was considered optimal to express H. scabra growth; both in L and W. The age- and size-specific daily growth rate for L and W up to 365 days of age, as estimated by the Gompertz model, had a range of two and nine orders of magnitude in L (0.035 – 0.96 mm/day) and W (3.4 × 10^-7 – 3.5 g/day), respectively. Use of the Gompertz model over the linear model, which tends to overestimate growth rates, is encouraged to estimate the growth of H. scabra more accurately.

This study was conducted to investigate low-cost substrate alternative and the optimum culture conditions in mass producing the local marine thraustochytrid, Schizochytrium sp. LEY7 isolated from the mangrove leaves of Baybay, Southern Leyte Philippines. Results showed that Schizochytrium sp. LEY7 is able to utilize commercial grade glucose and yeast extract from NaCl-treated baker's yeast as source of carbon and micronutrients respectively. Cost of mass producing the thraustochytrid isolate using the alternative production substrates was substantially reduced. Incubation temperature and salinity levels were the two growth factors significantly affecting the biomass production of the isolate. The short duration of lag phase shown by the isolate suggests a growth advantage in that cells are readily able to adapt to their new environment. Total lipids averaged to 19.4%. Principal fatty acids were palmitic acid (C16:0) with 33.52% and docosahexanoic acid (DHA, C22:6n-3) with 39.92% proportion to total fatty acid. Eicosapentaenoic (C20:5n-3, 1.01%) and arachidonic (C20:4n-3, 0.90%) are present but in relatively lower amount. Our findings showed the potential of low-cost substrate in mass producing the local thraustochytrid isolate, Schizochytrium sp. LEY7 as lipid and polyunsaturated fatty acid source in aquaculture. Biomass production was enhanced by optimizing the culture conditions.

Research in the application of fundamental concepts of fish behaviour to aquaculture has intensified recently and this chapter further elucidates fish sensory systems and functions and their involvement in the success or failure of hatchery and farm operations. Most marine fishes hatch with rudimentary sense organs that are elaborated by the time of first feeding and further improved with growth; thus, hatcheries must have the appropriate food, light and water currents for proper larval development. In grow-out farms, the ambient conditions must be at optimum or tolerable levels for the fish stock and the diets must have the right sensory characteristics to stimulate efficient feeding. Stressors for fish sensory systems include crowding, turbidity, underwater noise, chemotherapeutants, extreme pH, gas supersaturation and infection. High-density farms are stressful because the fish can sense, but cannot escape from, unfavourable conditions. Monitoring fish behaviour provides early warning of stress and disease and helps avert mortality and financial losses in aquaculture.

This study demonstrates the potential of low-cost production substrates in mass producing the Schizochytrium sp. LEY7 for maximum DHA production. High biomass yield was achieved by optimizing the culture conditions particularly the incubation temperature and salinity levels. Preliminary data on feeding trials have shown promising results and therefore confirmatory experiments need to be conducted to verify the results obtained.

This study was conducted to develop compounded feeds having a low content of fish meal for juvenile grouper and as an alternative to trash fish feeding. Epinephelus coioides juveniles were stocked in 36 units of 250-litre tanks at 25 fish/tank. Eight dietary treatments representing increasing (0, 10, 20, 30, 40, 60, 80 and 100%) percentage replacements of fish meal protein with 4:1 combination of meat meal and blood meal were tested in quadruplicate groups of fish arranged in a completely randomized design. Weight gain and specific growth rate (SGR), survival, food conversion rate (FCR) and body composition of fish were determined. Up to 80% of fish meal protein could be replaced by processed meat meal and blood meal, with no adverse effects on growth, survival and feed conversion efficiency of E. coioides juveniles. Use of animal byproduct meals as protein source substantially lowered the level of fish meal required in the juvenile grouper diet. The diet could be effectively used as a substitute for trash fish feeding, thereby reducing the requirements for fishery resource. From an economic standpoint, replacement of fish meal with cheaper animal byproduct meals in a practical diet for grouper could alleviate the problem of low fish meal availability and high cost.

This study was conducted to determine the quality of selected feed ingredients as protein sources in grouper diets, based on their nutrient composition and apparent digestibility coefficients for dry matter (ADMD) and crude protein (APD). A total of 56 juveniles were used for the 1st batch of test ingredients (Chilean fish meal, white fish meal, shrimp meal, defatted soyabean oilmeal, white cowpea meal and ipil-ipil leaf meal). 54, 72 and 48 juveniles were used for the 2nd, 3rd and 4th batches of test ingredients (squid meal, local meat and bone meal, meat solubles, soya protein concentrates and rice bran; tuna fish meal, imported meat and bone meal, blood meal, maize gluten meal and wheat flour; and poultry feather meal, lupin seed meal and maize germ meal, respectively). Apparent digestibility coefficients were measured in vivo. The apparent digestibility coefficients for ADMD ranged from 37-99%. Squid meal and meat solubles had the highest coefficients, whereas blood meal had the lowest. The APD of all feed ingredients tested were relatively high (79-99%), except for rice bran (43%) and blood meal (15%). ADMD values varied with the levels of fibre and other carbohydrate substances in the feed ingredients. Groupers could utilize dietary protein efficiently regardless of whether it was of animal or plant origin. High APD values were generally obtained in feed ingredients with high protein content. Low digestibility coefficients for feed ingredients could also be attributed to the processing methods used in their preparation.