Now showing items 1-20 of 47

    • Article

      Bacterial flora of milkfish, Chanos chanos, eggs and larvae 

      RD Fernandez, EA Tendencia, EM Leaño & MN Duray - Fish Pathology, 1996 - Japanese Society of Fish Pathology
      Aerobic bacterial flora of eggs and larvae of milkfish, Chanos chanos, was investigated. Microflora in the incubating water of egg, rearing water of larvae, water source, and larval food was also analyzed.

      Aerobic bacterial flora of milkfish eggs was largely influenced by the bacterial flora in the incubating water. Both in eggs and in the incubating water Pseudomonas species were the dominant bacteria. During milkfish larval rearing, intestinal aerobic bacterial flora was examined at days 1, 3, 7, 10, 15, 18, and 21. Bacterial number in the larvae and rearing water significantly increased during the culture period up to day 18 but dropped significant at day 21. Pseudomonas species were detected from yolk-sac larvae (day 1) as the dominant bacteria, similarly to the normal flora in the rearing water. However, intestinal bacteria were predominated with Vibrio species when the yolk-sac was absorbed on day 3. Larval rearing water, water source, and larval food contained predominantly Pseudomonas species.
    • Article

      Biological evaluation of three phytoplankton species (Chlorella sp., Tetraselmis sp., Isochrysis galbana) and two zooplankton species (Crassostrea iredalei, Brachionus plicatilis) as food for the first-feeding Siganus guttatus larvae 

      MN Duray - The Philippine Scientist, 1986 - University of San Carlos
      First-feeding Siganus guttatus larvae were given different species of phytoplankton (Chlorella, Tetraselmis, Isochrysis) and zooplankton (oyster trochophores, Brachionus) or a combination of both on the first day when they can feed. None of the phytoplankton species when used as the only food source for the larvae could support life beyond four days from hatching. Brachionus of sizes less than 90 microns was the most suitable food for the first-feeding larvae. A food mixture of the three phytoplankton species and Brachionus resulted in survival rates that were significantly higher than with other treatments. Larval growth, however, did not differ significantly (p>0.05).

      Different Brachionus densities were also used during the first-feeding days. Although the range of 10 to 15 Brachionus per ml gave better survival, no significant difference existed. Growth was slightly greater but not significantly different at higher densities.
    • Book

      Biology and culture of siganids 

      MN Duray - 1998 - Aquaculture Department, Southeast Asian Fisheries Development Center
      A 53-page monograph updating AQD's 1990 publication of the same title. The book includes siganid morphology, distribution and ecology; reproduction; fisheries; diseases and parasites; genetics. It also covers larval culture; fry and fingerling production; nutrition and feeds; and problem areas in aquaculture.
    • Article

      Breeding and larval rearing of the rabbitfish, Siganus guttatus (Bloch) 

      JV Juario, MN Duray, VM Duray, JF Nacario & JME Almendras - Aquaculture, 1985 - Elsevier
      Females of Siganus guttatus reared to sexual maturity in canvas tanks were induced to spawn by using human chorionic gonadotropin (HCG, Ayerst) at 500 IU/fish or about 2 IU/g body weight. The amount of HCG used depended on the initial mean egg diameter; the smaller the diameter, the more HCG was used. Fish with oocytes characterized by germinal vesicle migration (mean egg diameter ≥ 0.47 mm) spawned without HCG injection. Fertilization and hatching rates for both treated and untreated fish were more than 90%. The larvae were reared to metamorphosis using rotifers from day 2–17, rotifers + newly hatched Artemia nauplii from day 18–20 and rotifers + newly hatched Artemia nauplii + artificial feed from day 21–35. In addition, Isochrysis galbana was introduced to the rearing tanks from day 1–10 and Chlorella sp. and/or Tetraselmis sp. from day 1–35. Survival rates of larvae tended to be lower as the broodstock became older.
    • Conference paper

      Broodstock management and seed production of the rabbitfish Siganus guttatus (Bloch) and the sea bass Lates calcarifer (Bloch) 

      MN Duray & JV Juario - In JV Juario & LV Benitez (Eds.), Seminar on Aquaculture Development in Southeast Asia, 8-12 September 1987, Iloilo City, Philippines, 1988 - Aquaculture Department, Southeast Asian Fisheries Development Center
      This paper reviews results of studies conducted on the rabbitfish, Siganus guttatus (Bloch) and the sea bass Lates calcarifer (Bloch) at the Aquaculture Department of the Southeast Asian Fisheries Development Center. Studies include broodstock development and management, induced breeding, effect of handling stress and diet on egg quality, early life history, food, feeding strategy, weaning to artificial diets, effect of stocking density and salinity on egg development, larval growth and survival, and advancement of metamorphosis in sea bass by using thyroxine.

      A seed production technique had been developed for rabbitfish with survival rates ranging from 5-35% while the seed production technique for sea bass developed in Thailand had been modified to suit local conditions. Based on results from recent morphological and physiological studies, the stocking density, water management, and feeding scheme for the production of rabbitfish and sea bass fry had been modified to reduce cannibalism and improve survival.
    • Article

      Daily amount of rotifers taken by a sea bass Lates calcarifer larvae 

      H Kohno & M Duray - Philippine Journal of Science, 1990 - Science and Technology Information Institute
      The amount of rotifers consumed by a single sea bass Lates calcarifer larva per day (R) was examined by both the direct and by the satiation-digestion methods. In the direct method, R is estimated by the number of rotifers left in the larval tanks and larval density in the tanks, while in the satiation-digestion method R is estimated by the amount of rotifers found in the digestive tract of the larvae. In both methods, the amount of rotifers consumed by the larvae increased exponentially with larval growth. The relationship between the total length (TL) and the log-log plots of the maximum amount of rotifers eaten by a larva can be expressed by the following equations; R=1.799 x TL4.398 (r=0.975) for the direct method and R= 4.861 x TL3.432 (r = 0.907) for the satiation-digestion method. The relationship between TL and body wet weight (BW) can be expressed as: BW = 2.607 x 10-4 x TL3.786 (r=0.960) for larvae smaller than 6.5 mm TL and BW = 15.053 x 10-3 x TL2.855 (r = 0.916) for those larger than 6.5 mm TL.

      The index of satiation was almost the same for day 6(0-6), D-9 and D-12 (8.3-23%), higher range was observed in D-15 larvae. The index of daily feeding amount was comparatively higher in D-12 larvae compared to D-6, D-9 or D-15 larvae.
    • Article

      Daily rates of ingestion on rotifers and Artemia nauplii by laboratory-reared grouper larvae of Epinephelus suillus. 

      MN Duray - The Philippine Scientist, 1994 - San Carlos Publications, University of San Carlos
      The amount of rotifers and Artemia nauplii consumed daily by the grouper Epinephelus suillus larvae was determined through examination of gut contents. The larvae (2.6 mm TL) were initially fed rotifers on day 2 and newly hatched Artemia nauplii on day 21 (9.1 mm TL). The amount of food consumed by the larvae increased with larval growth. Larvae also showed diurnal feeding pattern at day 7 (3.6 mm TL), day 14 (4.9 mm TL), day 21 (9.1 mm TL) and day 28 (11.1 mm TL). Feeding incidence increased in the evening and became zero at 2100-2200 h. Active feeding started earlier in the older larvae and satiation was between 0900-1100 hr.
    • Article

      Development of mouth width and larval growth in three marine fish species 

      MN Duray & H Kohno - Philippine Journal of Science, 1990 - Science and Technology Information Institute
      Hatchery-bred larvae of three marine fish species, milkfish (Chanos chanos), seabass (Lates calcarifer) and rabbitfish (Siganus guttatus) were reared on rotifers and Artemia nauplii. Development of the mouth width and larval growth were monitored in the laboratory. Growth was slow on the first six days in milkfish and rabbitfish and on the first four days in seabass. Mouth width at opening was the smallest in rabbitfish (90-110 μm), followed by seabass (170-220) μm) and milkfish (180-270 μm), and the mouth width at the time when the larvae began to eat rotifers was 219 + 7.4 μm, at 82.5 h after hatching, in rabbitfish, 224 +7.9 μm, at 71 h, in seabass, and 3306 + 38.9 μm, at 125 h, in milkfish. A positive correlation between mouth width and larval growth was shown by three species studied.
    • Article

      Economic assessment of commercial hatchery production of milkfish (Chanos chanos Forsskal) fry 

      LMB Garcia, RF Agbayani, MN Duray, GV Hilomen-Garcia, AC Emata & CL Marte - Journal of Applied Ichthyology, 1999 - John Wiley and Sons
      The economic viabilities of two types of commercial hatchery milkfish (Chanos chanos) fry operations were assessed and compared. Based on the actual cost of input, the physical facilities, and the potential production yields, four commercial hatcheries previously used for shrimp (Penaeus monodon fry production were classified as either largeor smallscale operations. Cost-return analysis revealed high profits for both types of operation. The return on investment (54-61 %) and the payback period ( approximately 1.5 years) were comparable between the two types, although a large-scale operation (476 %) had double the working capital return of a small-scale hatchery (221 %). Benefit-cost analysis over a 5-year period also revealed positive and above-baseline discounted economic indicators [net current value = 0.2-2.2 million Philippine Pesos (1 US Dollar = 25 Philippine Pesos); internal rate of return = 88-107 %]. The net benefit-cost ratio of a large-scale operation (2.0) was higher than that of a small-scale hatchery (1.4), suggesting a slight edge in the investment viability of a large-scale hatchery. Compared with a large-scale operation, a small-scale hatchery was more sensitive to changes in the acquisition price of eggs or newly-hatched larvae and in the price of selling hatchery fry. Both types of operation are viable nonetheless when the acquisition cost is P6000 per million eggs or larvae and hatchery fry are sold at P0.50 each. Together, profit and investment in milkfish hatchery fry production appear viable, making milkfish an alternative commodity for production in many abandoned shrimp hatcheries. The limited availability of spawned eggs and larvae for rearing and the quality of hatchery fry are issues requiring urgent attention.
    • Article

      The effect of background color and rotifer density on rotifer intake, growth and survival of the grouper (Epinephelus suillus) larvae 

      MN Duray, CB Estudillo & LG Alpasan - Aquaculture, 1996 - Elsevier
      Rotifer intake and early growth and survival of Epinephelus suillus larvae were determined in terms of rotifer visibility against the background color of rearing tanks and density. The larvae were stocked at 30 l−1 in 200-l fiberglass tanks with phytoplankton (green water). Larvae were fed rotifers at densities of 5, 10 and 20 ml−1. Growth and survival were comparable among larvae in both tan and black tanks with green water. Rotifer intake was significantly higher in larvae in tan tanks. In black tanks, the survival of larvae at Day 14 was enhanced by the high rotifer density of 20 ml−1. Rotifer intake and growth of larvae were similar at all densities.
    • Article

      The effect of lipid-enriched broodstock diets on spawning and on egg and larval quality of hatchery-bred rabbitfish (Siganus guttatus) 

      M Duray, H Kohno & F Pascual - The Philippine Scientist, 1994 - San Carlos Publications, University of San Carlos
      Three isocaloric and isonitrogenous diets formulated to contain 12 (diet A), 15 (B) and 18% (C) lipids were tested on hatchery-bred rabbitfish Siganus guttatus broodstock to determine their effect on spawning and quality of the eggs and larvae. The results show that fish on diet C has higher fecundity than those on diets B and A. Also, fish on diet C yielded eggs of better quality than either fish on diets B or A. This was indicated by spawns resulting in higher percentage of normal hatchlings, larger newly-hatched larvae and higher survival rates until the 14th day of rearing. Dietary lipid levels, however, have no remarkable effects on fertilization, yolk and oil globule volumes, hatching rate nor larval size at harvest.
    • Article

      The effect of tank color and rotifer density on rotifer ingestion, growth and survival of milkfish (Chanos chanos) larvae 

      MN Duray - The Philippine Scientist, 1995 - San Carlos Publications, University of San Carlos
      The effect of tank color on rotifer ingestion, early growth and survival of milkfish larvae was assessed. The larvae were stocked at 30/L in 200-L fiberglass tanks coated black or unpainted (tan). Larvae were fed rotifers at densities of 5, 10, and 15/ml. Growth and survival were higher in black tanks than in tan tanks. Rotifers ingested were also higher in larvae reared in black tanks. In black tanks, the survival of the larvae was enhanced at high rotifer density of 15/ml. Rotifer ingestion and growth of larvae improved at higher feeding levels.
    • Article

      Effects of continuous lighting on growth and survival of first-feeding larval rabbitfish, Siganus guttatus 

      M Duray & H Kohno - Aquaculture, 1988 - Elsevier
      The effects of 24-h lighting on feeding, growth and survival of first-feeding larvae of Siganus guttatus were tested. Continuous light gave a higher mean survival (31.69%) with a maximum of 40.50% compared to natural daylight (17.10%). Larval size on day 7 also showed that continuous lighting gave improved results. Although feeding incidence increased with age of the larvae, a higher incident rate was observed for larvae held in continuous light from day 3.
    • Article

      Effects of DHA-enriched live food on growth, survival and incidence of opercular deformities in milkfish (Chanos chanos) 

      RSJ Gapasin & MN Duray - Aquaculture, 2001 - Elsevier
      The use of commercial enrichers to improve the nutritional quality of live food in larviculture of milkfish was investigated. Fish were either fed rotifers cultured on Chlorella sp. and newly hatched Artemia nauplii (Control, Trt I) or rotifers and Artemia given DHA enrichment diets (DHA-treated, Trt II).

      Results showed survival was significantly better (P<0.05) in the DHA-treated fish than in the untreated fish after 25-day culture period. Although growth was not statistically different (P>0.05) between the control and DHA-treated fish during the hatchery phase, extensive rearing of the postlarvae (fry) in nursery ponds for another 60 days showed that DHA-treated fish exhibited significantly better (P<0.05) growth than the untreated fish. Opercular deformities in 85-day old milkfish juveniles were also significantly lower (P<0.05) in the DHA-treated fish than the control. Survival after nursery culture, however, was high for both treatments but not significantly different (P>0.05).

      The lack of a viable and reliable method of mass culturing copepods as live food in the hatchery makes the use of off-the-shelf commercial enrichment diets for rotifers and Artemia a practical option in the larval culture of milkfish.
    • Article

      Effects of feeding frequency and amount of feeding on the growth of the grouper, Epinephelus malabaricus 

      H Kohno, A Triño, D Gerochi & M Duray - Philippine Journal of Science, 1989 - Science and Technology Information Institute
      The effects of feeding frequency and amount of food on the growth of juvenile groupers (Epinephelus malabaricus) were investigated for 12 weeks of rearing in net-cages set in an earthen pond. The juveniles (110-130 g in body weight, BW) attained marketable size (500 g) in 12 weeks. Feeding to satiation levels once a day gave the best growth (mean BW = 509.4 ± 56.5 g) and relatively good food conversion ratio (4.78) compared to the other treatments (twice a day, once in two days and once in every three days). Concerning feeding levels, in which feed was given twice a day at 15, 10, 5 and 1% of total fish biomass per day, the best fish growth (426.6 ± 54.0 g) and a reasonable food conversion ratio (4.53) were obtained at 5% fish biomass. There was a positive correlation between the growth of fish and water temperature in both experiments.
    • Article

      Effects of salinity on egg development and hatching of Siganus guttatus 

      MN Duray, VM Duray & JME Almendras - The Philippine Scientist, 1986 - University of San Carlos
      Experiments were conducted to determine the tolerance of Siganus guttatus eggs to salinity changes. In the first run, the female was induced to spawn spontaneously by using human chorionic gonadotropin. The fertilized eggs were transferred to seawater of salinities ranging from 8 to 40‰ either at the blastomere or at the gastrula stage. In the second run, the eggs were stripped from the female and artificially fertilized following the dry method.

      Results indicated that eggs transferred at gastrula stage were more tolerant to salinity changes than those transferred at the blastomere stage. Hatching occurred at all salinities but was highest at 24‰. Percentage of viable larvae was highest at 24‰ and lowest at 8‰. The larvae that hatched at low salinities were relatively longer than those that hatched at ambient and higher salinities.
    • Conference paper

      Feeding habits of hatchery-reared grouper, Epinephelus suillus larvae 

      MN Duray - In CL Marte, GF Quinitio & AC Emata (Eds.), Proceedings of the Seminar-Workshop on Breeding and Seed Production of Cultured Finfishes in the Philippines, Tigbauan, Iloilo, Philippines, 4-5 May 1993, 1996 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The feeding habits of hatchery-reared Epinephelus suillus larvae were determined by examining their gut contents. The larvae (2.6 mm TL) were initially fed rotifers on day 2 and newly-hatched Artemia nauplii on day 21 (9.1 mm TL). The amount of rotifers initially ingested averaged 1.3 individuals/larva. The ingestion rate increased as larvae grew. Larvae immediately showed strong preference for Artemia to rotifers on the first day of introduction. E. suillus larvae showed diurnal feeding pattern at day 7 (3.6 mm TL), day 14 (4.9 mm TL), day 21 (9.1 mm TL) and day 28 (11.1 mm TL). Feeding incidence decreased in the evening and was nil at 2100-2200 h. Active feeding started earlier in older larvae and satiation was between 0900-1000 h. The results of this study will be used as a basis in developing a good feeding scheme for E. suillus larvae.
    • Conference paper

      Feeding habits of larval rabbitfish, Siganus guttatus in the laboratory 

      S Hara, H Kohno, M Duray, T Bagarinao, A Gallego & Y Taki - In JL Maclean, LB Dizon & LV Hosillos (Eds.), The First Asian Fisheries Forum. Proceedings of the First Asian Fisheries Forum, 26-31 May 1986, Manila, Philippines, 1986 - Asian Fisheries Society
      The feeding habits of Siganus guttatus larvae were determined in laboratory rearing studies at 23.8-30.3 degree C by examination of digestive tract contents of larvae given rotifers and/or brine shrimp. Larvae were initially fed on rotifers at a total length (TL) of 2.6 mm (day 2 from hatching), and on brine shrimp at 4.4 mm TL (day 12). A change in feeding habits, seen as the flexion point in the relationship between larval TL and maximum amount of prey, occurred at about 7.0-9.5 mm TL with rotifers as prey, and at 7.2 mm TL with brine shrimp. Higher preference for brine shrimp over rotifers was seen in larvae 8-9 mm TL and larger. These changes in habit coincided with the full osteological development of the feeding apparatus in larvae at 7-8 mm TL. S. guttatus larvae exhibited a diurnal feeding pattern at day 9 (mean 3.7 mm TL), day 15 (5.8 mm TL) and day 21 (7.9 mm TL).
    • Article

      The financial feasibility of small-scale grouper aquaculture in the Philippines 

      RS Pomeroy, R Agbayani, MN Duray, J Toledo & G Quinitio - Aquaculture Economics and Management, 2004 - International Association of Aquaculture Economics and Management (IAAEM)
      This paper presents the results of an economic analysis of the aquaculture of two species of grouper E. coloides (orange‐spotted grouper, green grouper, red‐spotted grouper) and E. malabaricus (malabar grouper, black‐spotted grouper) for small producers in the Philippines. The findings of the analysis indicate that, based on the assumptions, grouper culture is financially feasible. However, the capital requirements for the broodstock, hatchery/nursery, and integrated system may be beyond the financial means of many small producers. These stages of grouper culture may need to be developed as a larger project by private investors or government. The capital investment requirement for grow‐out (not including purchase of transport boxes) is within the financial means of small producers. Loans or other incentives will need to be made available for the small producer, but the cash flow indicates that these loans can be repaid in the first year of production.
    • Article

      Growth and survival of grouper Epinephelus coioides (Hamilton) larvae fed free-living nematode Panagrellus redivivus at first feeding 

      OS Reyes, MN Duray, CB Santiago & M Ricci - Aquaculture International, 2011 - European Aquaculture Society
      The free-living nematode, Panagrellus redivivus, was tested as live food for grouper Epinephelus coioides larvae during the first feeding stage. A series of experiments were conducted to determine the acceptability of the free-living nematodes in grouper larvae at first feeding, the optimum nematode density and the response of the larvae to nutritionally enriched nematode. All experiments were conducted in 200-L conical tanks filled with 150-L filtered seawater and stocked at 15 larvae L−1. Duration of feeding experiments was up to day 21 (experiment 1) and 14 days (experiment 2 and 3). Brachionus plicatilis and Artemia (experiment 1) and Brachionus plicatilis alone (experiment 2 & 3) was used as the control treatment. Observations indicated that the grouper larvae readily fed on free-living nematodes as early as 3 days posthatching, the start of exogenous feeding. Optimum feeding density for the larvae was 75 nematodes ml−1. The enrichment of cod liver oil or sunflower oil influenced the total lipids and n-3 highly unsaturated fatty acids of P. redivivus, which in turn influenced those of the grouper larvae, however, growth and survival of the larvae were not affected (P > 0.05). The results from this investigation showed that the nematode, P. redivivus, can be used as first live food for grouper larvae from the onset of exogenous feeding until they could feed on Artemia nauplii.