Now showing items 1-20 of 29

    • Book chapter

      Adaptation of integrated fish-duck-pig farming system in Leyte 

      G Alcober - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Adaptation of a fish-duck-pig integrated farming system was conducted at the Busay Freshwater Experimental Farm in Babatngon, Leyte. Genetically improved farmed tilapia (GIFT) and common carp (at a ratio of 4:1) were stocked at densities of 3/m2 and 6/m2 in four earthen ponds; they were not given any commercial feed. Animal houses were built over the ponds and stocked with mallard ducks at a density of 375/ha, and piglets at 30/ha; they were given commercial feeds daily. After 154 days, the farming system produced a net yield of 1,685 kg fish/ha at a stocking density of 3/m2 and 2,808 kg/ha at 6/m2. Since water quality was not adversely affected, the higher stocking density of 6/m2 is a viable option. This farming system can be further improved and refined for better production and higher incomes.
    • Article

      Agar yield and gel strength of Gracilaria heteroclada collected from Iloilo, Central Philippines 

      MRJ Luhan - Botanica Marina, 1992 - Walter de Gruyter
      Seasonality of yield and gel strength of agar from Gracilaria heteroclada was determined. Gel strength was high (510-794 gm cm-2) during early dry season (October-March) and low (43-101 gm cm-2) during the wet season (May-August). A negative correlation exist (P ≤ 0.05) between agar yield and gel-strength.
    • Article

      Biomass yield of Isochrysis galbana (Parke; clone T-ISO) and growth of Brachionus rotundiformis (Tschugunoff) using continuous cultivation method 

      MR de la Peña - Philippine Agricultural Scientist, 2014 - College of Agriculture, University of the Philippines Los Baños
      Batch culture of Isochrysis galbana clone T-ISO is difficult due to its unstable biomass production; hence, the effect of continuous cultivation at different dilution rates was investigated to compare its productivity with that of batch culture. Significantly higher total algal cell yield was attained in continuous cultures (1.70 × 108 and 1.03 × 108 cells L-1 at 0.60 d-1 and 0.30 d-1 dilution rates, respectively) compared with batch culture (0.16 × 108 cells L-1); the batch culture did not receive any inflow of nutrients. The amount of protein per cell was similar in both batch and continuous cultures at 0.60 d-1 dilution rate after 24 h and 5 d in both culture systems. Chlorophyll a yield was not affected by dilution rate but decreased as the culture aged. The dry weight yield was also similar in both batch and continuous cultures. The higher nitrate concentration supplemented in the batch culture resulted in higher cell density and elevated protein content of the alga. Rotifer (Brahionus rotundiformis) cultures that received inflow of nutrients from the algal tanks had significantly higher (P<0.05) peak population count (28 and 33 individuals mL-1 at 0.30 and 0.60 d-1 dilution rates, respectively) compared with rotifer cultures that did not receive an inflow of food (18.22 individuals mL-1). The higher biomass yield of T-ISO using continuous cultivation method can increase the population growth of rotifer under tropical conditions.
    • Conference paper

      Country status on sustainable aquaculture in Lao PDR 

      T Khonglaliane - In MRR Romana-Eguia, FD Parado-Estepa, ND Salayo & MJH Lebata-Ramos (Eds.), Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia: Challenges in Responsible Production … International Workshop on Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia 2014 (RESA), 2015 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Capture fisheries and aquaculture in Lao PDR are based on water resource ecosystems which consist mainly of rivers and streams, hydropower and irrigation reservoirs, diversion weirs, small water bodies, flood plains and wet-season rice-fields. The total area of water resources for capture fisheries is believed to be more than 1.2 million ha. The estimated consumption of inland fish in Lao PDR is approximately 167,922 tonnes per year while consumption of other aquatic animals is estimated at 40,581 tonnes per year. Most of the consumption is from internal production (i.e. imports are of minor importance), so these figures represent approximate catches or yield from fisheries. These estimated yields are conservatively valued at almost US$150 million per year.

      The people of Lao PDR, especially in the rural communities that account for more than 75 per cent of the population, still depend upon the country's fish and other aquatic animals as their most reliable sources of animal protein. The estimate of actual fish consumption per capita (kg/capita/ year) of inland fish is 24.5 kg, while other aquatic animals account for about 4.1 kg and marine products around 0.4 kg, to make a total of 29 kg of fish and aquatic products consumed per capita per year.

      As aquaculture in Lao PDR expands, many forms of production systems are being developed, for example pond culture, communal ponds, rice-cum-fish culture and cage culture. Most fish culture systems in Lao PDR are small-scale. Such forms of production systems are divided into sub-categories depending on the nature and main activity of the producers. According to the Department of Livestock and Fisheries, aquaculture production in 2007 accounted for 54,750 tonnes in an area of more than 42,000 ha, including cage culture in the Mekong and some tributaries.

      There has been a significant increase in intensive tilapia production in recent years in Lao PDR (MRC Technical Paper No. 5 April 2002) based on tilapia cage culture in the Mekong river and irrigation reservoirs. In last two years, an enterprising farmer has established about 360 cages.

      Constraints in the large-scale development of tilapia cage culture are the lack of technical support (e.g. extension services) to the farmers and insufficient supply of advanced fingerlings. Morever, tilapia cage culture in the Mekong river system is perceived to be difficult to sustain because of environmental factors such as river flooding and strong currents during the rainy season and the lack of water during the dry season.
    • Article

      Culture and economics of wild grouper (Epinephelus coioides) using three feed types in ponds 

      I Bombeo-Tuburan, EB Coniza, EM Rodriguez & RF Agbayani - Aquaculture, 2001 - Elsevier
      The performance of wild Epinephelus coioides juveniles was compared by feeding with live tilapia juveniles, fish by-catch, and formulated diet for 5 months in grow-out ponds. To minimize cannibalism, the groupers were graded into small (BW=24.9±7.3 g), medium (45.8±5.7 g), and large (84.1±30.0 g) size groups as block in a Randomized Complete Block Design (RCBD) and reared in nine 350-m2 ponds. To supply the tilapia juveniles, adult tilapia were grown 2 months prior to stocking of grouper at a rate of 15 tilapia/grouper. Grouper fed by-catch were significantly higher (P<0.01) than the other treatments in terms of final length and total production. The quality of by-catch could be gleaned by its efficient feed conversion ratio (FCR) of 1.0 (dry basis), significantly better (P<0.01) than the formulated diet that had an FCR of 2.8. Using by-catch, 47% of the harvest weighed >400 g and only 14% was classified <200 g. The cost of juvenile grouper and feeds represented 88–89% of the total investment in all treatments. Economic sensitivity analysis showed that a combination of improvement in factors such as price of grouper juveniles, feeds, yield, survival, and FCR would result in higher return-on-investment (ROI). When cost and returns were considered, feeding juveniles with by-catch was more profitable because it resulted in net income of Php 361,623/ha/year, an ROI of 155%, and a payback period of 0.4 year. The results clearly show that these economic indicators appear to be attractive, thus making grouper pond culture using by-catch a viable industry. More research efforts should, however, be directed towards developing a cost-effective formulated diet for the grow-out culture of E. coioides.
    • Article

      The effect of stunting on growth, survival, and net production of milkfish (Chanos chanos Forsskal) 

      I Bombeo-Tuburan - Aquaculture, 1988 - Elsevier
      The seasonal abundance of milkfish fry in the Philippines has led to the practice of buying a sufficient supply during the peak season to compensate for the shortage during slack periods. Fry that are not immediately grown out are crowded and stunted in transition ponds until they are transferred to rearing ponds. Milkfish farmers believe that stunted fingerlings grow faster than newly grown ones and therefore yield extra croppings. To assess the efficiency of production schemes, stunted and non-stunted milkfish fingerlings were cultured in twelve 144-m2 ponds for a 3-month period. The treatments employed were: Treatment I, 2-month-old fingerlings; Treatment II, 3-month-old fingerlings; and Treatment III, 6-month-old fingerlings, with the initial weights of 3.3 g, 7.8 g, and 43.1 g, respectively. Survival, netproduction, cumulative and monthly weight gains did not differ significantly (P > 0.05) among the three treatments. The results indicate that stunting did not illicit a significant increase, nor did it adversely affect the growth, survival, and netproduction of milkfish in a straight culture system. Stunting can therefore be practised by farmers to provide an adequate supply of fingerlings for year-round operation.
    • Article

      Evaluation of agar from three species of Gracilaria from Panay and Guimaras islands 

      TR de Castro - The Philippine Scientist, 1993 - San Carlos Publications, University of San Carlos
      Agar from three species of Gracilaria, G. changii G. coronopifolia, and Gracilariopsis heteroclada, collected form Panay and Guimaras islands was evaluated. Each species was pretreated with NaOH solution before extraction. Highest agar yields were obtained following alkaline pretreatment at the lowest concentration (1% NaOH) for all species. Highest gel strengths were obtained at different alkaline pretreatment conditions: 644 ± 3.4 g cm-2 at 3 % NaOH for 60 min for G. changii, 641 ± 11.9 g cm-2 at 5 % NaOH for 30 min for G. heteroclada, and 170 g cm-2 at 5 % NaOH for 30 min G. coronopifolia. Agar gelling temperatures ranged from 38.5-40ºC and agar melting temperature ranged from 80.5-85 ºC. Specific viscosity was highest for agar from G. changii at 18 cps. Moisture and ash contents ranged from 8.04-15.20 % and 4.32-4.98%, respectively. Based on the result for this study, G. heteroclada and G. changii are two species which merit further studies for their prospective commercial value to the different industries using agar.
    • Book chapter

      Evaluation of fertilizer use and milkfish yields in Palawan 

      EB Dumada-ug & R Sevilleja - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      Milkfish yields in Palawan in 1993–94 were low, only 595 kg/ha-yr on average and ranged 100–700 kg/ha-yr in 35 of 50 farms surveyed. Only seven farms had yields between 1,000 and 1,800 kg/ha-yr. Yields were higher in deeper ponds, and shallowness of ponds was a major constraint to high yields. Farm -gate prices of milkfish ranged from P25 to P55 and averaged P42. The prices of milkfish were on average 43x greater than the price of organic fertilizers (chicken manure) and 6x more than the price of inorganic fertilizers. The income from milkfish made up 10-95% and averaged 53% of the total income of the farmers. One crop cycle a year was the practice in 28 of the 50 farms; 20 farms had two crops, and two farms went for 3–4 crops a year. A crop cycle was 3–4 months long in 14 farms, 5–6 months in 29 farms, and 7–9 months in 7 farms. Crop cycles started with draining and drying the ponds and applying fertilizers to grow natural food. Most of the farms were supplied by tidal water and water exchange in the ponds was done every spring tide in 33 farms. The other farms changed water once a month, once or twice in a crop cycle, or once a year. Application rates of organic fertilizers were mostly less than 1 ton/ha-yr and averaged 515 kg/hayr, but three farms used as much as 1,250 kg/ha-yr, and one farm used 3,000 kg/ha-yr. Half as much inorganic fertilizers were used; the average for the 50 farms was only 211 kg/ha-yr, but one farm used as much as 1,350 kg/ha-yr. The fertilizers encouraged natural food to grow in the ponds. Two of the farms grew mostly plankton, 15 grew the benthic mat lablab, and 33 grew the green filamentous algae lumut. None of the farms used commercial feeds. Stocking rates varied widely among the farms, ranged from 1,000 to 60,000 fry or fingerlings per hectare per year and averaged 8,000/ ha-yr. Two-thirds of the farms stocked less than 7,000/ha-yr, but eight farms stocked fry or fingerlings at much higher rates of 13,000–60,000/ ha-yr. An input use variation model showed that milkfish yield was a function of the ratios of prices of milkfish to prices of organic and inorganic fertilizers; pond water depth and salinity; milkfish income as percent of total income; family size; membership in aquaculture association; and contacts with government‘s extension services and information dissemination system. The surveyed farms ranged from 3 to 40 years old, with 92% under 20 years; they had been in operation 1–23 years, 76% of them for less than eight years. Of the 50 farms in the survey, only nine were private (titled) lands, 34 were covered by fishpond lease agreements (FLA issued by the Bureau of Fisheries and Aquatic Resources), and the others had only survey documents or no papers at all. Farm sizes ranged 0.8–50 ha (average 12.5 ha), and 52% of them were smaller than 6 ha. The private farms were small, only 1–7 ha except one that was 25 ha. The FLA farms were much larger, and 23 of them were 5–50 ha. Large parts of the large farms were not operational, and 90% of the farms used effective areas of less than 7 ha. The low lease fees for FLAs evidently did not encourage farm development to increase yields. The farms had mostly shallow ponds 25–100 cm deep (average 68 cm).
    • Article

      Evaluation of plant proteins as partial replacement for animal proteins in diets for Penaeus indicus and P. merguiensis juveniles 

      VD Peñaflorida - The Israeli Journal of Aquaculture-Bamidgeh, 2002 - Society of Israeli Aquaculture and Marine Biotechnology
      The growth rate and survival of two white shrimps, Penaeus indicus and P. merguiensis, fed diets in which fishmeal was partially replaced with plant protein sources were investigated in three trials. In trial 1 with P. indicus, soybean, yeast and leaf meals of kangkong, papaya and Cassia tora L. were screened as partial substitutes for fishmeal. The total biomass of shrimp fed 20% yeast (20yeast) was highest but not significantly different than that of shrimp fed 10yeast and 10papaya. Survival was highest with 20yeast, 10papaya and 10yeast. Shrimp fed Cassia tora L. had the highest weight gain and SGR but their survival was similar to those fed poor performing diets. In trial 2 with P. merguiensis, the ingredients were modified by decreasing fishmeal and increasing the yeast and soybean substitution. The biomass of the shrimp fed 10 yeast was similar to that of the shrimp fed 20yeast and 26 soybean, the weight gain and SGR were similar to shrimp fed 20yeast while survival was highest but not different from 20yeast and 26 soybean. In trial 3 with P. indicus, weight gain and SGR were best with 20yeast and 34soybean. However, biomass and survival did not differ among replacement levels.

      The performance of the white shrimp varied with different levels of yeast and soybean meal incorporation. The response of P. indicus was best with 20yeast (15% by weight) or 34soybean meal (34% by weight) while that of P. merguiensis was with 10yeast (7% by weight), 20yeast (15% by weight) or 26soybean meal (26% by weight). Partial replacement of fishmeal with yeast or soybean meal would result in lower feed costs but the use of these feeds needs further refinement since survival was low in all treatments. Rearing techniques, such as increasing the feeding frequency, simulating deep pond conditions or using adequate substrates, should be refined.
    • Article

      Genotype environment interaction in the response of three strains of Nile tilapia to poor nutrition 

      MRR Romana-Eguia & RW Doyle - Aquaculture, 1992 - Elsevier
      Experiments were conducted to determine the effects of poor nutrition on the growth of three Oreochromis niloticus strains fed protein-deficient diets. Four-week-old fry from the three "test" strains were paired with a fourth "reference" strain of tilapia (red) of the same size and stocked in 60-1 aquaria. The treatment lasted 6 weeks, with fish being fed commercial fish feed crumbles for the first and last 2-week periods and rice bran during weeks 3 and 4. Control fish were fed commercial diet throughout. Both control and treatment fish were fed at 20% of fish biomass per day. Lengths and weights were measured every 2 weeks.

      Significant strain effects were noted when the growth of test fish over the whole experimental period was analysed by analysis of covariance using the reference fish growth as a concomitant variable. The relative growth of the three test strains differed at each feeding phase. The NIFI strain grew best during the commercial feed phases, the Israel strain performed best during the rice bran phase while the CLSU strain, regardless of the type of nutritional environment, usually ranked last. Different performance rankings at each feeding phase represent strong genotype X environment interaction among these commercially important lines. This was statistically confirmed by analysis of covariance of the growth of the Israel and NIFI strains during the different feeding phases using the reference strain as a covariate.
    • Article

      Growth and survival of Penaeus monodon juveniles fed a diet lacking vitamin supplements in a modified extensive culture system 

      AT Triño, VD Peñaflorida & EC Bolivar - Aquaculture, 1992 - Elsevier
      Penaeus monodon juveniles with mean initial weight from 0.11 to 0.17 g were fed diets with and without vitamin supplement. The diets contained 34% protein and 8% fat. The animals were stocked at 5/m2 in 320-m2 earthen ponds and reared for 135 days. Growth, survival, net production, and net cost of production per kg of P. monodon were not significantly affected even if supplemental vitamins were eliminated from the diet. The absence of extra vitamins from the diet may have been compensated either by the basal diet used or by ingestion of natural food existing in the ponds. In either case, the possible influence of vitamins from these sources is manifested in the overall effects on growth, survival and net production of prawns when no vitamin supplement is added to the diet. Results obtained showed that the difference between diets in cost of production was statistically not significant (P > 0.05). However, the favorable cost difference of P 18.02 per kg of prawns produced would make it more profitable to use the diet without vitamin supplement in a modified extensive culture system.
    • magazineArticle

      Growth and yield of Asian catfish Clarias macrocephalus (Gunther) fed different grow-out diets 

      EB Coniza, MR Catacutan & JD Tan-Fermin - SEAFDEC Asian Aquaculture, 2003 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Article

      Growth and yield of Asian catfish Clarias macrocephalus (Gunther) fed different grow-out diets 

      EB Coniza, MR Catacutan & JD Tan-Fermin - The Israeli Journal of Aquaculture-Bamidgeh, 2003 - The Society of Israeli Aquaculture and Marine Biotechnology (SIAMB)
      Juveniles of the Asian catfish Clarias macrocephalus (3.6±0.17 g; 78.0±0.09 mm) were fed one of four diets: a laboratory-formulated diet of 18.9% (Diet 1) or 34.2% (Diet 2) protein, a com- mercial feed pellet of 28.9% protein (Diet 3) or a diet of 80% blanched chicken entrails and 20% rice bran (31.7% protein; Diet 4). After 120 days of culture, catfish fed Diet 2 grew significantly better (p<0.05) than the other groups, reaching 108.9 g and 232.8 mm (daily weight gain 0.88 g; specific growth rate 2.9%), with a condition factor of 0.86 and production of 18.2 kg per 25 m2 pen. Feed conversion with Diets 2 and 3 (2.5 and 2.3, respectively) was better than with Diets 1 and 4 (3.4 and 5.0). Survival (68-81%) did not differ significantly among treatments (p>0.05). Catfish fed Diet 2 had the highest apparent lipid retention (131.7%). The protein efficiency ratio was lowest (1.3) in Diet 2, but did not differ significantly from Diets 1 and 3. Catfish fed Diet 4 were fatty and had a lower crude protein content. Results suggest that C. macrocephalus fed 34.2% crude protein have a significantly higher weight and total yield. Further, a taste test showed that odor, flavor and appearance did not differ amongst the diets.
    • Book chapter

      Growth and yield of the grouper Epinephelus coioides fed 'trash fish' at different rates and frequencies in floating net cages 

      GV Galzote & EC Abrera - In T Bagarinao (Ed.), Research Output of the Fisheries Sector Program, 2007 - Bureau of Agricultural Research, Department of Agriculture
      The effects of various feeding rates and frequencies on the growth and survival of orangespotted grouper Epinephelus coides were determined in floating net cages in Tiniguiban Cove, Puerto Princesa, Palawan. Juveniles (average weight 60 g) were stocked in 2 m x 2 m x 1.5 m cages at a density of 10/m3. The experiment tested six treatments: 10% of body weight (BW) daily; 5% BW daily; ad libitum daily; 10% BW every other day; 5% BW every other day; and ad libitum every other day. After five months, the fish fed at 10% daily had 100% survival and the highest weight gain (520 g), growth rate (3.5 g/d), net production (31.44 kg), and gross income (P5,463). However, returns were negative in all treatments because of either too high feed consumption and poor conversion or low net production.
    • Article

      Growth rate, yield and economics of Gracilariopsis bailinae (Gracilariales, Rhodophyta) using fixed bottom long-line method 

      AQ Hurtado-Ponce, RF Agbayani & GP Samonte-Tan - Philippine Journal of Science, 1997 - Science and Technology Information Institute
      Vegetative thalli of Gracilariopsis bailinae weighing 10 g each were tied to a 5-m monofilament line with plastic strips and laid horizontally on the substrate and were observed to grow at 30 d interval for 9 months. The monthly growth rate and yield were determined and a cost and return analysis of the culture system was made. The monthly growth rate of the seaweed was significantly different (P=0.05) over culture month. The highest average growth rate was 6.7 percent/day while the lowest was 1.7 percent. The lowest and highest average yield (dry wt) was 72 g and 660 g m-2 mo-1, respectively.

      A capital asset of P1,680, working capital of P2,980, and annual production cost of P5,860 were calculated from the culture system. An annual net returns of P31,292 was computed based on a 1,000 m2 area. Return on investment is 671.50 percent while payback period is 1.7 months.
    • Article

      Hatchery production of Oreochromis niloticus L. at different sex ratios and stocking densities 

      AM Bautista, MH Carlos & AI San Antonio - Aquaculture, 1988 - Elsevier
      The influence of various sex ratios and stocking densities on hatchery production of Nile tilapia, Oreochromis niloticus L., was studied in land-based (concrete tanks) and lake-based (hapa nets) systems. In both hatchery systems, egg and fry production was maximum at a sex ratio of 4:1 females to males and a density of 4 females per m2.

      Seed production varied significantly among treatments at different periods of the year. In concrete tanks, significantly high seed production of 12.98 and 11.77 eggs and fry per spawner per day was obtained in March and August, respectively. In hapa nets, irrespective of sex ratios, 10.18 seeds per spawner were collected daily in March.

      In relation to the broodstock density in concrete tanks, significantly bigger daily harvests of 13.41 and 13.00 eggs and fry per spawner were produced in late February and March, respectively. In hapa nets, daily harvests of 8.95 and 7.74 eggs and fry per spawner were the highest seed production levels which occurred in April and March, respectively.

      Seed production was significantly higher in concrete tanks than in hapa nets while insignificant differences (P>0.05) were found among sex ratio and broodstock density treatments.
    • Article

      Influence of stocking density and fertilization regime on growth, survival and gross production of Penaeus monodon Fabricius in brackishwater ponds 

      PF Subosa & MN Bautista - The Israeli Journal of Aquaculture-Bamidgeh, 1991 - Society of Israeli Aquaculture and Marine Biotechnology
      Twelve 0.1 ha earthen ponds were stocked at 3,500 or 7,000/ha with 1-month old nursery reared Penaeus monodon Fabricius (1.73 g). Fertilizer treatments were 125 kg chicken manure plus 4.1 kg diammonium phosphate (18-46-0) and 6.56 kg urea (45-0-0) per application for treatments U3500 and U7000 and 125 kg chicken manure plus 8.15 kg diammonium phosphate and 0.89 kg urea per application for treatments P3500 and P7000. Fertilizers were broadcast 10 days after pest eradication and every two weeks thereafter. Water was exchanged (20%) one day before fertilization throughout the 86-day culture period. Shrimp yields at harvest were: P7000, 193.6 kg/ha; P3500, 119.4 kg/ha; U3500, 97.5 kg/ha; and U7000, 82.4 kg/ha. Mean survival for each treatment was 96.2%, 97%, 89.3% and 75%, respectively. There were significant differences in shrimp yields at harvest among treatments (p < 0.05).
    • Article

      The interactive effect of some environmental factors on the growth, agar yield and quality of Gracilariopsis bailinae (Zhang et Xia) cultured in tanks 

      AQ Hurtado-Ponce & HB Pondevida - Botanica Marina, 1997 - Walter de Gruyter
      The single and interactive effects of light and temperature, salinity, and urea enrichment on the growth and agar yield and quality of Gracilariopsis bailinae were determined under indoor and outdoor tank conditions. Culture period was 6 weeks. Growth rate reached its peak on the second week in all culture conditions and gradually decreased towards the end of the culture period. Higher growth rates were obtained in seaweed cultured in outdoor (0.27-1.12% day-1) than in indoor (0.21-0.72% day-1) tanks; with urea enrichment and lower salinity levels (15-25ppt). A significant interactive effect was demonstrated between and among the environmental parameters on the growth of the seaweed. Highest gel strength (870 g cm-1) and lowest sulfate content (3.1 µg mg-1) were obtained at 25ppt, without urea enrichment and in indoor tanks. A significant interactive effect of light intensity and temperature-urea enrichment was ascertained on agar yield; also of light intensity and temperature-salinity on gel strength and sulfate content. Positive and negative correlation was likewise established between agar properties.
    • Article

      Low or partial discharge and closed-recirculating systems for the culture of shrimp [Penaeus monodon (Fabricius)] at several demonstration sites in the Philippines 

      DD Baliao & MA de los Santos - The Philippine Agricultural Scientist, 2011 - College of Agriculture, University of the Philippines Los Baños
      A series of verification runs on the farming of shrimp [Penaeus monodon (Fabricius)] using environment-friendly techniques was conducted in different pilot demonstration sites including privately owned farms in the Philippines from 2001 to 2005. Encouraging results were achieved using the low or partial discharge and closed-recirculating systems following the advanced environment-friendly protocols. In the low or partial discharge system, 11 grow-out ponds were stocked with P. monodon post larvae (PL) at densities between 15 and 25 m-2 while in the closedrecirculating system, eight grow-out ponds were stocked with PLs at densities between 30 and 60 m-2. Both systems incorporated the use of head and tail reservoirs, crop rotation, filter box, salinity reduction, long-arm paddlewheel aerators, biomanipulators, biofilters, sludge collectors and quality feeds.

      In the low or partial discharge system, an average total yield of 5.3 ± 0.8 tons ha-1, a feed conversion ratio (FCR) of 1.4 ± 0.3 and a survival rate of 86 ± 12 % were achieved after 109–159 d of culture (DOC). In a closed recirculating system, however, an average total yield of 8.3 ± 4.0 tons ha-1, FCR of 1.9 ± 0.2 and survival rate of 76 ± 15 % were achieved after 126–150 DOC.

      Analyses of effluents from grow-out ponds revealed that treatment using the tail reservoir with installed baffles and oysters (Crossostrea sp.) and seaweed (Gracilaria sp.) used as biofilters effectively reduced the dissolved organic nutrient concentration to optimum levels before the water was recycled or released to the surrounding body of water. Shrimps were observed to be growing and feeding normally, with no signs of bioluminescence at night, and no sluggish swimming behavior.
    • Article

      Nitrogen and phosphorus utilization in the cyanobacterium Microcystis aeruginosa isolated from Laguna de Bay, Philippines 

      SF Baldia, AD Evangelista, EV Aralar & AE Santiago - Journal of Applied Phycology, 2007 - Springer Verlag
      Phytoplankton supports fisheries and aquaculture production. Its vital role as food for aquatic animals, like mollusks, shrimp, and fish cannot be overemphasized. Because of its contribution as a food source for fish, the growth kinetics of Microcystis aeruginosa, a dominant cyanobacterium in the lake, was studied. The regular occurrence of M. aeruginosa is experienced during the months of May to July or from September to November in Laguna de Bay, the largest freshwater lake in the Philippines. M. aeruginosa was collected from Laguna de Bay, isolated, and established in axenic conditions. Data on the growth kinetic parameters for nitrate-nitrogen and phosphate-phosphorus utilization by M. aeruginosa gave the following values: half-saturation constant (Ks), 0.530 mg N. L−1 and 0.024 mg P. L−1 respectively; maximum growth rate (μmax), 0.671. d−1 and 0.668. d−1 respectively; maximum cell yield, 6.5 and 6.54 log, cells. ml−1 respectively; nutrient level for saturated growth yield, 8.71 mg N. L−1 and 0.22 mg P. L−1 respectively; and minimum cell quota (Q0), 2.82 pg N. cell−1 and 0.064 pg P. cell−1 respectively. The low Ks value and high maximum growth rate (μmax) for phosphorus by M. aeruginosa would suggest a high efficiency of phosphorus utilization. On the other hand, the high Ks value for nitrogen indicated a low rate of uptake for this nutrient.