Now showing items 1-5 of 5

    • Book

      Cage culture of the giant freshwater prawn (Macrobrachium rosenbergii) 

      ML Cuvin-Aralar, EV Aralar & AG Lazartigue - 2011 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Series: Aquaculture extension manual; No. 50
      An extension manual describing biology, site requirement, grow-out operations, health management, harvest, post harvest handling and processing, and economic analysis.
    • Article

      Effects of low nitrogen-phosphorus ratios in the phytoplankton community in Laguna de Bay, a shallow eutrophic lake in the Philippines 

      ML Cuvin-Aralar, U Focken, K Becker & EV Aralar - Aquatic Ecology, 2004 - Springer Verlag
      The effects of low nitrogen-phosphorus ratios on microalgae from a large eutrophic freshwater lake in the Philippines were investigated. Natural microalgal populations from Laguna de Bay, the largest lake in the Philippines, were cultured using three different nitrogen-phosphorus weight ratios (2N:1P; 6N:1P and 12N:1P) at two phosphorus concentrations (0.25 and 0.5 mg l–1) in each case. The growth and genera composition of the cultures under the different treatments were followed for a 12-week period. Community level responses were assessed based on species richness (s), Shannon-Wiener Index (H’), Simpson Index (λ) and Evenness (J’). Among the different microalgal groups, only the chlorophytes showed a significantly higher density in response to the 12N:1P treatment at the higher P concentration, indicating that the nutrient ratio had a significant interaction with the nutrient levels used in the experiments. The genera found in the different treatments were generally similar; however, the degree of dominance of some varied with treatment during the experiment. The succession of dominant genera also differed among the N:P treatments. The diatoms like Fragilaria, Aulacoseira (= Melosira) and Nitzschia dominated the lowest N:P. On the other hand, chlorophytes (Kirchneriella and Scenedesmus) dominated the highest N:P treatment, particularly from the second to the seventh week of the experiments with the diatoms becoming co-dominant only towards the eighth week until the end of the experimental. The 6N:1P treatment showed a mixed dominance between the diatoms and the chlorophyte genera. The various indices of diversity indicate significantly lower diversity only in the 12N:1P at 0.5 mg l–1 P and not in 12N:1P at 0.25 mg l–1 P.
    • Article

      Microcystins in natural blooms and laboratory cultured Microcystis aeruginosa from Laguna de Bay, Philippines. 

      ML Cuvin-Aralar, J Fastner, U Focken, K Becker & EV Aralar - Systematic and Applied Microbiology, 2002 - Urban & Fischer Verlag
      Laguna de Bay, the largest freshwater lake in the Philippines, experiences periodic blooms of the cyanobacteria Microcystis aeruginosa. Blooms of these cyanobacteria in 1996, 1998 and 1999 were sampled. HPLC and MALDI-TOF mass spectrometry were used to analyze for microcystins. A total of 16 structural variants of the toxin were isolated from the samples with microcystin LR (MC-LR) as the most abundant variant in the samples from 1996 and 1999 making up 77 to 85% of the total, respectively. MC-RR was the dominant variant in the 1998 bloom making up 38%. The samples from 1996 had the highest total toxin concentration (4049 µg g-1) followed by those from 1998 (1577 µg g-1) and 1999 (649 µg g-1). A strain of M. aeruginosa previously isolated from the lake was also cultured in the laboratory under different nitrogen concentrations (1, 3 and 6 mg L-1) and elevated phosphorus concentration (0.5 mg L-1) to determine the influence of these factors on toxin production. A total of 9 different structural variants of microcystin were isolated from the laboratory cultures with MC-LR consisting more than 75% of the total in all treatments. No significant differences in the total toxin concentration as well as the % distribution of the different variants among treatments were observed. However, the strain of M. aeruginosa cultured in the laboratory had from 3 to 20 times higher total microcystin than those harvested from the lake.
    • Article

      Skip feeding as an alternative strategy in the production of Nile tilapia Oreochromis niloticus (Linn.) in cages in selected lakes in the Philippines 

      ML Cuvin-Aralar, P Gibbs, A Palma, A Andayog & L Noblefranca - Philippine Agricultural Scientist, 2012 - College of Agriculture, University of the Philippines Los Baños,
      Many inland water bodies in the Philippines are currently used for fish cage culture. Inappropriate practices including feed management in aquaculture results not only in the degradation of water quality but also in economic losses for the fish farmers. The effect of two feeding management schemes on the production of cage-cultured Nile tilapia Oreochromis niloticus (Linn.) in Lakes Bato and Buhi in Camarines Sur Province and Laguna de Bay in Rizal Province were studied. Daily (DAILY) and skip-feeding (SKIP) schemes using the same daily ration based on standing biomass were used. Mean final weight and daily growth rate were 18% higher in DAILY compared with SKIP in Lake Bato. No significant differences in both parameters were observed in tilapia reared in the two feeding treatments in Lakes Buhi and Laguna de Bay. Condition factor, survival and final yield did not show any significant differences in both treatments in all three lakes. Significant differences in feed conversion ratios (FCR) were observed between the two treatments with SKIP having 36% lower feed conversion ratio (FCR) in Lake Bato and 41% lower FCR in Lake Buhi and Laguna de Bay compared with the DAILY treatment. The results suggest that skip feeding is an economically and ecologically viable alternative to the cage culture of Nile tilapia in cages.
    • Article

      Uptake and elimination of inorganic mercury and selenium by minnows Phoxinus phoxinus 

      MLA Cuvin & RW Furness - Aquatic Toxicology, 1988 - Elsevier
      Minnows were kept in aquaria containing filtered water dosed with measured amounts of mercury as mercuric chloride and selenium as sodium selenate. Fishes exposed to selenium in combination with mercury showed significantly higher survival rates than those kept in tanks containing mercury alone. A 2 to 1 selenium to mercury molar ratio proved to be most effective in reducing mercury toxicity. The presence of selenium tended to increase the uptake of mercury from the water. There was no observed difference in the rate of mercury elimination in the presence or absence of selenium. These results suggest that the observed protective effect of selenium against the toxicity of mercury does not involve reduction of mercury uptake or enhancement of mercury elimination. The presence of mercury did not significantly affect selenium uptake. However, selenium elimination was reduced in the presence of mercury, suggesting that a mercury-selenium complex is formed.