Now showing items 1529-1548 of 3262

    • magazineArticle

      Illegal fishing methods 

      Southeast Asian Fisheries Development Center, Aquaculture Department - Aqua Farm News, 1993 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Conference paper

      Illuminated-cage nursery of the Asian sea bass, Lates calcarifer Bloch, (Centropomidae): effects of initial body size and stocking density 

      AC Fermin - In IC Liao & CK Lin (Eds.), Cage Aquaculture in Asia: Proceedings of the First International Symposium on Cage Aquaculture in Asia, 2-6 November 1999, Tungkang Marine Laboratory, Taiwan Fisheries Research Institute, Tungkang, Taiwan, 2000 - Asian Fisheries Society; World Aquaculture Society - Southeast Asian Chapter
      This study was conducted to determine the appropriate initial body size and the corresponding stocking density of sea bass, Lates calcarifer, during nursery rearing in illuminated cages. Hatchery-produced sea bass fry of different initial sizes of 7.2 (day 15), 13.2 (day 22), and 15.2 mm (day 29) were stocked at densities between 300 and 1,500 m-3 in decreasing order with fish size. Nylon net cages (1x1x1 m) set in a protected sea cove area were individually lit at 300 lux using incandescent bulb placed at 1 m above water surface. Artificial lights attract wild zooplankton that served as prey to young sea bass. After 42 days of culture 22-day old sea bass fry with 13.2 mm TL initial size and stocked at 400 m-3 showed the highest growth (35.3 mm TL, 535.7 mg BW) and survival rates (64.4%). At a stocking density of 800 m-3, the survival rate was the second highest at 43%. Although day 15-fry at 7.2 mm TL initial size showed higher specific growth rates (11 % day-1) and size at harvest (29-31 mm TL, 346.2-374.4 mg BW), survival rates (11-15 %) were lower than the day 22- and 29-fry (30-64%). Calanoid copepods of the genus Calanus, Paracalanus and Acartia dominated the diet (81-90%) of sea bass at different size groups. Percentage number of shooters ranged from 0.5-1.4% of total stocks and were not significantly different among treatments. The present results indicate that sea bass should spend 21 days in the hatchery prior to nursery rearing in illuminated sea cages. Sea cages are inexpensive and more cost-effective than ordinary cage or earthen pond for sea bass fingerling production.
    • Article

      Illuminating the need for ecological knowledge in economic valuation of mangroves under different management regimes - a critique 

      P Rönnbäck & JH Primavera - Ecological Economics, 2000 - Elsevier
      This is a commentary on a paper by Gilbert and Janssen (Gilbert, A.J., Janssen, R., 1998. Ecol. Econ. 25, 323–346) that deals with valuation of management alternatives for the Pagbilao mangroves, Philippines. Our main critique focuses on the undervaluation of fisheries as well as the inability to quantify the value of ecological services and internalize aquaculture's environmental costs. In addition, the sustainability criteria set up for the aquaculture management alternatives is open to debate. These weaknesses affect the result of Gilbert and Janssen's analysis so that the value of the unexploited mangrove forest is underestimated, and the value and sustainability of converting the forest into aquaculture ponds are overestimated. If applied to decision-making, the erroneous results from this partial cost–benefit analysis may have dire consequences for the mangroves and coastal communities of Pagbilao.
    • magazineArticle

      Imbao, the mangrove clam 

      RIY Adan - SEAFDEC Asian Aquaculture, 2000 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Article

      Immune responses of Asian sea bass, Lates calcarifer Bloch, against an inactivated betanodavirus vaccine 

      RV Pakingking Jr., R Seron, LD de la Peña, K Mori, H Yamashita & T Nakai - Journal of Fish Diseases, 2009 - Blackwell Publishing
      Asian sea bass, Lates calcarifer (Bloch), exhibited strong immune responses against a single injection of the formalin-inactivated red-spotted grouper nervous necrosis virus (RGNNV), a betanodavirus originally isolated in Japan. Fish produced neutralizing antibodies at high titre levels from days 10 (mean titre 1:480) to 116 (1:1280), with the highest titre at day 60 post-vaccination (1:4480). When fish were challenged with the homologous RGNNV at day 54 post-vaccination, there were no mortalities in both the vaccinated and unvaccinated control fish. However, a rapid clearance of the virus was observed in the brains and kidneys of vaccinated fish, followed by a significant increase in neutralizing-antibody titres. Furthermore, the vaccine-induced antibodies potently neutralized Philippine betanodavirus isolates (RGNNV) in a cross-neutralization assay. The present results indicate the potential of the formalin-inactivated RGNNV vaccine against viral nervous necrosis (VNN) of Asian seabass.
    • Book chapter

      Immunity and biological methods of disease prevention and control 

      EC Amar & JME Almendras - In GD Lio-Po & Y Inui (Eds.), Health Management in Aquaculture, 2010 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The chapter deals with the barriers that prevent microbial entry and the various internal defense mechanisms that are part of the host's arsenal in combating in combating invading microbes. It also discusses some of the biological methods of disease prevention and control.
    • Book chapter

      Immunity and biological methods of disease prevention and control 

      JME Almendras - In GD Lio-Po, CR Lavilla & ER Cruz-Lacierda (Eds.), Health Management in Aquaculture, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The chapter deals with the barriers that prevent microbial entry and the various internal defense mechanisms that are part of the host's arsenal in combating in combating invading microbes. It also discusses some of the biological methods of disease prevention and control.
    • Article

      Immunization regimen in Asian sea bass (Lates calcarifer) broodfish: A practical strategy to control vertical transmission of nervous necrosis virus during seed production 

      R Pakingking Jr., EG de Jesus-Ayson, O Reyes & NB Bautista - Vaccine, 2018 - Elsevier
      Outbreaks of viral nervous necrosis (VNN) in Asian sea bass (Lates calcarifer) at the larval stages via vertical transmission of nervous necrosis virus (NNV) from asymptomatic broodfish remain as a major deterrent during seed production. A five-year study was conducted to produce NNV-specific-free sea bass broodfish reared in land-based tanks through an annual immunization regimen with the formalin-inactivated NNV. We primarily immunized (intraperitoneal injection) sea bass juveniles (5 g) and monitored the neutralizing antibody (Nab) titers in the sera of these fish at scheduled intervals post-immunization. Nab titers in the sera of immunized fish peaked at Month 2 (titer: 1:4480 ± 1185) but thereafter gradually declined and significantly dropped (1:260 ± 83) at Month 12 post-primary immunization. Booster immunization of these fish at Month 12 post-immunization led to abrupt increases in Nab titers in booster immunized (B-Im) fish at Month 1 (1:12800 ± 6704) but thereafter declined and dropped at Month 12 (1:480 ± 165) post-booster immunization. The annual booster injections with the inactivated vaccine or L-15 (Unimmunized [U-Im]) were consecutively conducted for 4 years until the fish became sexually mature. Mature fish from both groups were successively induced to spawn twice (1-month interval) via intramuscular injection with luteinizing hormone-releasing hormone analogue (LHRH-a; 100 µg/kg BW). NNV was not detected by RT-PCR in oocytes and milts, and spawned eggs of B-Im fish. In contrast, oocytes and milts, and spawned eggs of U-Im fish were NNV positive. Spawned eggs of B-Im broodfish exhibited Nab titers ranging from 1:192 ± 34 to 1:240 while such was not detected (<1:40) in eggs of U-Im fish. Taken together, current data clearly demonstrate that annual immunization regimen with inactivated NNV vaccine is a pragmatic approach for sustaining immunocompetent sea bass broodfish reared in land-based tanks and circumvent the risk of vertical transmission of NNV from asymptomatic broodfish to their offspring under stress of repetitive spawning.
    • Article

      Immuno-response in tilapia Sarotherodon niloticus vaccinated with Edwardsiella tarda by hyperosmotic infiltration method 

      G Lio-Po & H Wakabayashi - Veterinary Immunology and Immunopathology, 1986 - Elsevier
      Sarotherodon niloticus with average weight of 28.42 ± 1.87g were immunized with formalin-killed Edwardsiella tarda using the hyperosmotic infiltration method. Test fish maintained in 30 l aquaria were grouped into four treatments. Group 1 and 2 were exposed to a single hyperosmotic treatment on day 0. Group 1 was bled on day 14 and group 2 was bled on day 28. Group 3 was given hyperosmotic treatments twice: on day 0 and day 14 and bled on day 28. Group 4 was an untreated control bled on day 28. All sera were analyzed for agglutinating antibody titer against E. tarda flagellar and somatic antigens. Results showed that flagellar and somatic agglutinin titers in all treatments were not statistically significant. Likewise, infection experiments where test fish were challenged with intraperitoneal injection of the test bacterium showed that the vaccination experiment did not effectively protect the test fish from infection by Edwardsiella tarda.
    • Article

      Immunolocalisation of nervous necrosis virus indicates vertical transmission in hatchery produced Asian sea bass (Lates calcarifer Bloch)—A case study 

      IS Azad, KP Jithendran, MS Shekhar, AR Thirunavukkarasu & LD de la Pena - Aquaculture, 2006 - Elsevier
      A probable vertical mode of piscine nodavirus transmission is reported in the present investigation based on a case of nodavirus associated larval mortalities in hatchery produced Asian sea bass. Polyclonal rabbit anti-SJNNV antibodies (SGWak97) detected the viral antigens in the tissue sections from the eggs and the larvae at different time intervals from − 1 to 42 days post hatch (dph). Immunopositive ovarian connective tissue associated with the oocytes along with the progressive localization of the viral antigens in the brain, spinal cord, liver, stomach and dermal musculature during the larval development indicates a probable vertical transmission of nodavirus in the Asian sea bass. The surviving larger larvae, from the batch suffering mass mortalities, produced very intense immunofluorescent positivity in the liver, stomach and dermal musculature. Results of this investigation demonstrating a possibility of vertical transmission of the nodavirus emphasize the need for screening of eggs and larvae for evolving suitable preventive and prophylactic health management strategies.
    • Book chapter

      Immunological and molecular biology techniques in disease diagnosis 

      LD de la Peña - In GD Lio-Po, CR Lavilla & ER Cruz-Lacierda (Eds.), Health Management in Aquaculture, 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The improvement of existing immunoassay techniques, development of monoclonal antibody technology and the development of new immunoassay approaches are all working together to provide new tools for the detection of disease-causing organisms in fish and crustaceans. Following the introduction of nucleic acid hybridization technique and PCR, it was recognized that the methods offered a sensitive approach to the detection and identification of specific microorganisms as in the case of a bacterial or viral infection in a variety of sample types. Potentially, a characteristic DNA sequence from a single virus particle or cell of a particular organism can be amplified to detectable levels within a short period of time. Conventional diagnostic methods that involve the culture of microorganisms can take days or weeks to complete or very tedious to perform. PCR offers a rapid, very sensitive, very specific and simple alternative. Further developments in immunodiagnostics and emerging technologies such as DNA-based tests will revolutionize the detection and identification of infectious disease agents.
    • Conference paper

      Impact assessment of cage culture in Lake Taal, Philippines. 

      MM Alcañices, RC Pagulayan & AC Mamaril - 2001 - Aquaculture Department, Southeast Asian Fisheries Development Center; Philippine Council for Aquatic and Marine Research and Development; Bureau of Fisheries and Aquatic Resources
      The environmental impact of cage culture on water quality of Lake Taal was assessed from March 1996 through February 1997. Three stations were considered namely: Balas, which serves as station 1 (non-cage area) and Sampaloc and Laurel, stations 2 and 3 (cage areas), respectively. Monthly water samples with two replicates were collected using a van Dorn sampler at 0, 5, 10 and 15-m depths in all stations. Below surface water from the inside of the cages was also collected. Water temperature, water transparency, pH, and conductivity were determined in situ. Dissolved oxygen, chloride, NO3, NH3, PO4, and total P were analyzed in the laboratory. Phytoplankton density and algal biomass (through cholorophyll a) and primary productivity indices were determined with the light-and-dark bottle method.

      Of the water quality parameters, conductivity and DO had significant differences between non-cage and cage areas. Conductivity gave significant difference (P<0.01) between control and cage area during the wet season. Highest conductivity value (2100 µ S/cm) was observed in station 3. Mean values of DO gave significant differences (P<0.05) in the different stations throughout the study period. A decrease of DO to 2.5 mg/1 was observed below 10-m depth around the cage areas. Analysis indicates that cage culture leads to oxygen depletion in the water column. The presence of cage structures decreased the flow rate resulting to weak circulation. The reduced water circulation in effect decreased the supply of oxygen and removal of toxic waste metabolites from the vicinity of the fish farm, and reduced the supply of plankton. These results suggest that the impact of cage culture in Lake Taal is minor but can alter the lake ecosystem if not properly managed. Zoning and continuous water quality monitoring are needed.
    • Article

      Impact of AMPEP on the growth and occurrence of epiphytic Neosiphonia infestation on two varieties of commercially cultivated Kappaphycus alvarezii grown at different depths in the Philippines 

      IAG Borlongan, KR Tibubos, DAT Yunque, AQ Hurtado & AT Critchley - Journal of Applied Phycology, 2011 - Springer
      Two varieties of the carrageenophyte Kappaphycus alvarezii (Tungawan, TUNG; and Giant tambalang, GTAM) from Zamboanga Sibugay, Philippines were used to test the efficacy of Acadian Marine Plant Extract Powder (AMPEP) as source of nutrients for growth, and to determine if applications had any effect on the percent occurrence of an epiphytic infestation of the red alga Neosiphonia sp. at four different depths in the sea. Results showed that the use of AMPEP significantly (P < 0.05) increased the growth rate of both Kappaphycus varieties tested but decreased the percent occurrence of Neosiphonia sp. The percent occurrence of Neosiphonia sp. infection (6–50% at all depths) of both Kappaphycus varieties with AMPEP treatment was significantly lower than the controls (i.e., 10–75% at all depths). Both the growth rate of the cultivated seaweed and the percent occurrence of the epiphytes decreased as the cultivation depth increased. Plants dipped in AMPEP and suspended at the surface had the highest growth rates (i.e., 4.1%, TUNG; 3.1%, GTAM) after 45 days; those without AMPEP dipping had the highest percent occurrence of Neosiphonia infection (viz. 70–75%). The occurrence of Neosiphonia infestation was found to be correlated with changes in irradiance and salinity at the depths observed. The results suggested that both varieties of K. alvarezii used in this study have the fastest growth rate when grown immediately at the water surface. However, in order to minimize damage caused by the occurrence of epiphytic Neosiphonia, K. alvarezii should be grown within a depth range of 50–100 cm. These observations are important for the improved management of Kappaphycus for commercial farming. Furthermore, the use of AMPEP treatments for enhancement of growth and reduction deleterious Neosiphonia sp. infections is encouraging.
    • Book chapter

      Impact of fishpond management on the mangrove ecosystem in the Philippines 

      AS Camacho & TU Bagarinao - In Mangroves of Asia and the Pacific: Status and management, 1986 - Natural Resources Management Center and National Mangrove Committee, Ministry of Natural Resources
      Fishpond development in the Philippines is discussed, examining resulting impacts on the mangrove ecosystems. Socio-economical implications and management measures are also considered.
    • Conference paper

      Impact of nickel poisoning on the histology of the ovaries of Oreochromis mossambicus 

      C Sioson & A Herrera - 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
      Ovaries of Oreochromis mossambicus exposed to sublethal concentrations of nickel sulphate (0.5 mg/1 and 1.0 mg/1) were histologically analyzed. Changes following exposure to 0.5 mg/1 nickel sulphate include irregularities in the shape of egg follicles, subcellular oocyte damage, lifting off of the theca layer and proliferation of connective tissues. In the ovaries exposed to 1.0 mg/1 nickel sulphate, degenerative changes are worse. Invasion by connective tissues is extensive, oocytes have bizarre shapes, yolk granules are scattered in the interfollicular spaces, abnormal growths are evident and previttelogenic oocytes abound.

      Nickel is a toxicant in Oreochromis mossambicus ovaries.
    • magazineArticle

      Impact of seafarming: Fish farms vs. mussel farms 

      Southeast Asian Fisheries Development Center, Aquaculture Department - Aqua Farm News, 1994 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The article presents comparative impacts of fish and mussel seafarms. Specifically, it tackles about the impacts of the two farms on the following: solid waste production, water flow and sedimentation, effect on native bottom fauna, effect on wild fish populations, the spread of toxic chemicals and drugs, and to the multi-use conflict that they brought.
    • magazineArticle

      The impact of shrimp pond construction along the mangrove coastal accretion at southwest Ca Mau Cape, Viet Nam 

      PN Hong - SEAFDEC Asian Aquaculture, 1996 - Aquaculture Department, Southeast Asian Fisheries Development Center
    • Article

      Impacts of aquaculture on fish biodiversity in the freshwater lake Laguna de Bay, Philippines 

      MLA Cuvin-Aralar - Lakes and Reservoirs: Research & Management, 2016 - Wiley
      Laguna de Bay is the largest inland water body in the Philippines, being used predominantly for aquaculture and open water fisheries. Aquaculture in the lake began decades ago, with many changes in the lake ecosystem having occurred since that time. Most dominant species for fish culture are introduced species. Other invasive species were also introduced to the lake as escapees from land-based aquaculture facilities. This study was conducted to monitor fish diversity in two adjacent, but distinctly different, sites in the lake, namely an open fishery area (OFS), with no adjacent aquaculture structures, and an aquaculture site (AQS), with cages for the culture of various commodities. Fish traps were installed at both sites, with the traps being sampled at least every 2 weeks from April 2013 to February 2015. The results of pairwise t-tests indicated significantly higher Shannon–Wiener diversity index (H′), evenness (J′), Simpson's similarity index (D) and species richness (s) in OFS than in AQS. In terms of total catch per day, significantly greater fish biomass were obtained from AQS than from OFS. Introduced aquaculture species had a mean dominance of 83% and 47% in AQS and OFS, respectively. However, invasive species introduced from the ornamental fish trade exhibited a mean relative dominance of 10.3% in AQS and 13.5% in OFS. The relative dominance of native species was also significantly higher in OFS (41%) than in AQS (6.5%). The results of this study demonstrated the adverse impacts of aquaculture in regard to the species diversity of fish in localized areas in Laguna de Bay. The dependency of aquaculture on introduced fish species adversely impacted the natural fish population in the lake. Focusing on the culture of commercially important local species for aquaculture, rather than introduced species, will improve fish production of inland waters without accompanying adverse impacts on biodiversity.
    • Conference paper

      Impacts of brackishwater pond culture on the mangrove ecosystem 

      JH Primavera - In Technologies in Mangrove-Friendly Aquaculture : final report of and papers presented to the On-Site Training on Mangrove-Friendly Aquaculture Hai Phong City, Socialist Republic of Vietnam 19-30 April 1999, 2000 - Southeast Asian Fisheries Development Center, Aquaculture Department
      This paper aims to describe Southeast Asian mangroves, the impacts of brackishwater pond culture on these ecosystems, and lessons from the region for the development of aquaculture in Malaysia.
    • magazineArticle

      Impacts of mangrove conversion 

      Southeast Asian Fisheries Development Center, Aquaculture Department - Aqua Farm News, 1995 - Aquaculture Department, Southeast Asian Fisheries Development Center
      The article presents the impact of mangrove conversion on fisheries and on coastal areas. The mangrove areas which serve as nursery grounds for important species of fish and crustaceans are also rich feeding ground for many species from various trophic levels. Thus, the destruction of mangroves could affect the availability of fry and broodstock and, consequently, aquaculture production and fisheries. While in coastal areas, the destruction of mangroves increased the risk of coastal erosion from storm surges and winds, accelerates the erosion of riverbanks, exposes acid sulfate soils, leading to poor production and mass mortality of stocks, and affects the freshwater supply through salt intrusion upstream among others.