Now showing items 1-9 of 9

    • Article

      Anti-luminous Vibrio factors associated with the ‘green water’ grow-out culture of the tiger shrimp Penaeus monodon 

      The ability of the “green water” grow-out culture of the tiger shrimp Penaeus monodon to prevent outbreaks of Luminous Vibriosis was investigated by screening associated isolates of bacteria, fungi, phytoplankton and fish skin mucus for anti-luminous Vibrio metabolites. Among the 85 bacterial isolates tested, 63 (74%) caused +∼+++ inhibition of the Vibrio harveyi pathogen after 24–48 h co-cultivation. The variation in growth inhibition rates of +, ++, and +++ were demonstrated by 15 (18%), 13 (15%), and 28 (33%) isolates, respectively, 24 h after treatment. Eight bacterial isolates showed consistently sustained maximum inhibition of luminous Vibrio after 24 to 48 h exposure. The majority of these luminous Vibrio inhibiting bacterial isolates were obtained from tilapia mucus and gut. In tests with fungi, 4 of 20 (20%) yeast isolates showed intracellular metabolites inhibitory to luminous Vibrio. Among filamentous fungi, 5 of 45 (11%) isolates yielded intracellular metabolites while 3 of 41 (7%) isolates had extracellular metabolites inhibitory to luminous Vibrio. These fungal isolates were identified as Rhodotorula sp., Saccharomyces sp., Candida sp., Penicillium sp., mycelia sterilia, and two unidentified species. The microalgae, Chaetoceros calcitrans and Nitzchia sp., consistently demonstrated complete inhibition of luminous Vibrio from 24 h and 48 h post exposure, respectively, and during the 7-day experiment. Leptolyngbia sp. caused a 94–100% reduction of the luminous Vibrio population from 104 to 101 cfu/ml 24 h post exposure which was sustained throughout the 10-day observation period. In contrast, the inhibitory effects of Skeletonema costatum on luminous Vibrio was bacteriostatic throughout the 7-day exposure while Nannochlorum sp. did not significantly inhibit luminous Vibrio. The skin mucus of jewel tilapia, Tilapia hornorum, had no resident luminous bacteria and inhibited this bacterial pathogen in 6–48 h, which was proportionate to the 103 and 105 cfu/ml test concentrations of luminous Vibrio. This study provides a scientific explanation that the effectiveness of the “green water” culture of tiger shrimp (P. monodon) in preventing outbreaks of luminous Vibriosis among P. monodon juveniles in grow-out ponds can be attributed to the presence of anti-luminous Vibrio factors in the bacterial, fungal, phytoplankton microbiota and the skin mucus of tilapia associated with this novel technique of shrimp culture.
    • Article

      Assessment of stocks of a natural Gracilaria population on Panay Island, Philippines 

      TR de Castro, NG Guanzon Jr. & MR Luhan - Botanica Marina, 1991 - Walter de Gruyter
      Two peaks in biomass were recorded from natural beds of Gracilaria sp. at Leganes, Iloilo and Batan, Aklan study sites. The major peak occurred in February 1989 for both areas. The minor peak occurred in September 1988 at Batan and October 1988 at Leganes. Highest biomass at Ivisan, Capiz occurred in May 1988. Lowest biomass was recorded in June at Batan and December 1988 at Leganes. At Ivisan, no biomass was recorded from November 1988 to February 1989. Correlation analysis showed no relationship between biomass and temperature or pH at all study sites. However, salinity was negatively correlated with biomass at Leganes and Batan. Rainfall was inversely correlated with biomass. Based on salinity data gathered from the three study sites, Gracilaria sp. is euryhaline and can tolerate a wide range of salinity. The results show a marked seasonality in the biomass of Gracilaria sp.
    • Article

      The effects of different stocking densities and some abiotic factors on cage culture of Gracilaria sp. (Rhodophyta, Gigartinales) 

      NG Guanzon Jr. & TR de Castro - Botanica Marina, 1992 - Walter de Gruyter
      Specific growth rates (% day-1) and production rates (g m-2 day-1) of Gracilaria sp. reared in net cages on a bamboo floating raft from March 1989 to February 1990 were determined at different stocking densities (200, 250, 300 and 350 g 0.5 m-2/net cage). Mean specific growth rates for the whole culture period were highest at stocking densities of 200 and 250 g 0.5 m-2 (P < 0.05). Highest mean net production rate was obtained at a stocking of 250 g 0.5 m-2, but was not significantly different from stocking densities of 300 and 350 g 0.5 m2 (P < 0.05). Highest monthly mean specific growth rates and monthly mean net production rates for all treatments were obtained during March and November 1989 and February 1990. There were no significant differences (P > 0.05) in monthly mean specific growth rates and mean net production rates between the three peak months, although they were significantly different from the rest of the months (P < 0.05). Production was higher during the dry season. Correlation analysis showed that total rainfall was negatively correlated with specific growth rate and production rate. Salinity, temperature and pH were not correlated with specific growth rate and production rate.
    • Article

      Gathering of economically important seaweeds in Western Visayas, Philippines 

      AQ Hurtado-Ponce, MRJ Luhan & NG Guanzon Jr. - The Philippine Scientist, 1992 - San Carlos Publications
      A survey was conducted in 12 coastal municipalities of Western Visayas, Philippines from March to July 1990 to determine the seaweed gathering practices of fishermen. There were 83 gatherers involved in this small-scale industry, who live below the poverty line and who consider it as the number one minor source of income. Only seaweeds of commercial value are gathered in big volume. There were approximately 114 T year-1 of seaweeds harvested from natural stock with a market value of P414, 950.00 ($14,819.64). The harvest is broken down into 3 main groups: (1) agarophytes, 99.5 T (Gelidiella, Gracilaria and Gracilariopsis), (2) carrageenophytes, 10 T (Eucheuma and Kappaphycus) and (3) table vegetable, 10 T (Caulerpa). An average maximum income of P5,600.00 or $200 gatherer-1 season-1 is derived from seaweed gathering.
    • Article

      Gracilaria (Rhodophyta) farming in Panay, Western Visayas, Philippines 

      AQ Hurtado-Ponce, GPB Samonte, MRJ Luhan & NG Guanzon Jr. - Aquaculture, 1992 - Elsevier
      Interviews were conducted among eight Gracilaria growers in Panay, Western Visayas, Philippines from March to July (1990) using a structured questionnaire. The "rice planting" method was employed by farmers growing seaweeds in natural drainage canals and ponds. Initial harvests are made 15–60 days after planting. Higher production [ 7–14 t (dry) ha−1 year−1] are obtained from cultures in canals than in ponds [3–4 t (dry) ha−1 year−1]. The net income derived from culture in ponds is estimated at P698/crop or P6313/year (US$234/year). A higher net income of P4936/crop or P41766/year (US$1547/year) was generated from Gracilaria farming in canals. Returns on investment (ROI) from farming in ponds and canals are 39% and 908%, respectively. Payback period is 2 months in canal farming and 1.8 years in pond farming.
    • Article

      Growth and photosynthesis inhibition by agricultural pesticides in three freshwater microalgae. 

      NG Guanzon Jr. & H Nakahara - Fisheries Science, 2002 - Wiley-Blackwell
      Growth rate and photosynthesis of Microcystis aeruginosa, Scenedesmus quadricauda and Aulacoseira granulata exposed to different concentrations of the agricultural pesticides CNP (p-nitrophenyl 2,4,6-trichlorophenyl ether), MEP [O,O-dimethyl O-(3-methyl-4-nitrophenyl) thiophosphate], ISP [isoprothiolane (C12H18O4S2)], and TBT (tri-n-butyltin chloride) were determined. The effective concentration (EC50) for growth and photosynthesis in each species of microalga was then calculated. Inhibition of growth and photosynthesis in the three microalgae was greatest when exposed to CNP and TBT. Microcystis aeruginosa and A. granulata showed a higher tolerance, whereas S. quadricauda showed a higher sensitivity. Except for MEP, the EC50 values for growth obtained in the three microalgae were higher than those for photosynthesis. The growth–photosynthesis response relationship showed that, for CNP and TBT, growth of the three organisms tested were less inhibited than their photosynthesis at a lower exposure (0.001–0.05 μg/L). At a higher exposure (0.10–1.0 μg/L), the response between relative growth rates and relative photosynthesis was proportional. For MEP and ISP, a proportional response existed between relative growth rates and relative photosynthesis in all test organisms. These results suggest that the inhibition of growth and photosynthesis by agricultural pesticides differs for the three microalgae. The differences can be explained in terms of the physico-chemical properties of the four pesticides and the physiological and morphological properties of the three microalgae.
    • Article

      Production of Penaeus monodon (Fabricius) using four natural food types in an extensive system 

      I Bombeo-Tuburan, NG Guanzon Jr. & GL Schroeder - Aquaculture, 1993 - Elsevier
      Growth, survival, and production of P. monodon feeding on four types of natural food, i.e., lablab (benthic mat of cyanobacteria, diatoms, and associated fauna), Ruppia maritima, lumut (filamentous green algae and attached organisms entangled in the water column and on the bottom), and plankton, were evaluated in ponds in Iloilo, Philippines. The gut content of shrimp was analyzed and the flow of the food web was traced using stable carbon isotope (δC) analysis. Twelve 500-m2 ponds were stocked with juvenile shrimp (average weight 0.8 g) and grown for 3 months at the rate of 4000 ha−1. In Ruppia and plankton ponds, the shrimp attained 91–92% survival, and in lumut and lablab ponds, 76–80%. Total shrimp production in Ruppia and plankton ponds was 114 and 129 kg ha−1 crop−1, while lumut and lablab ponds yielded only 59 and 85 kg ha−1 crop−1, respectively. The δC analysis of all treatments was not significantly different, indicating that a common food (detritus), as shown by the gut content analysis, appears to be the most significant food resource of shrimp in this study. Shrimp foreguts from all the treatments consisted of detritus (non-living particulate matter), copepod/animal remains, diatoms, cyanobacteria, and green algae. Detritus ranked highest in frequency of occurrence, followed by copepod/animal remains.
    • Book

      Seaweeds of Panay 

      AQ Hurtado, MRJ Luhan & NG Guanzon Jr. - 2006 - Aquaculture Department, Southeast Asian Fisheries Development Center
      This practical book on the seaweeds of Panay, Philippines, acquaints and provides information to members of the academe and research institutions, policy makers, fishermen and businessmen regarding the taxonomy, distribution, ecology and economic importance of these resources. It consists of 4 major parts: (1) Introduction, which reviews the literature, habitat, distribution, morphological structure and reproduction; 2) Classification, which describes the classes to which the seaweeds generally belong; 3) Collection and preservation, which explains the procedure used in treatment of specimens; and, 4) Taxonomic list. A glossary is included, covering technical terms used. All species listed and described in this book are macrobenthic and were collected in Panay and Guimaras Islands.
    • Book

      Seaweeds of Panay 

      AQ Hurtado-Ponce, MR Luhan & NG Guanzon Jr. - 1992 - Aquaculture Department, Southeast Asian Fisheries Development Center
      This practical book on the seaweeds of Panay, Philippines, acquaints and provides information to members of the academe and research institutions, policy makers, fishermen and businessmen regarding the taxonomy, distribution, ecology and economic importance of these resources. It consists of 4 major parts: (1) Introduction, which reviews the literature, habitat, distribution, morphological structure and reproduction; 2) Classification, which describes the classes to which the seaweeds generally belong; 3) Collection and preservation, which explains the procedure used in treatment of specimens; and, 4) Taxonomic list. A glossary is included, covering technical terms used. All species listed and described in this book are macrobenthic and were collected in Panay and Guimaras Islands.