Now showing items 1-9 of 9

    • Article

      Comparing profits from shrimp aquaculture with and without green-water technology in the Philippines 

      RH Bosma & EA Tendencia - Journal of Applied Aquaculture, 2014 - Taylor & Francis
      To reduce disease impact, Philippine farmers developed the green-water (GW) system, which has been spreading rapidly since 2008. In the most applied GW-system, the shrimp pond receives water from a reservoir stocked with tilapia. We collected financial data on GW and non-GW systems from farms having similar management and environmental context. All farms had more than one pond; the average pond area was < 1 ha, and total pond areas per farm ranged from 1.4 to 139 ha. The total variable and fixed costs per ha of shrimp pond were not different for GW and non-GW farms, but on GW farms the cost per kg of shrimp produced was lower. The latter was higher than the 2009 market price of 30 g shrimp for non-GW farms mainly. In GW farms the cost of seed was lower, and survival rates and individual shrimp weights at harvest were higher for an equally long culture period.
    • Article

      Effect of different mangrove-to-pond area ratios on influent water quality and WSSV occurrence in Penaeus monodon semi-intensive farms using the greenwater culture technique 

      EA Tendencia, RH Bosma, JH Primavera & JAJ Verreth - Aquaculture, 2012 - Elsevier
      White spot syndrome virus (WSSV) has been affecting the shrimp industry worldwide for two decades now. It continues to bring economic losses to affected farms. Despite the many studies on its epidemiology, there is no proven treatment or control measure. Diseases, like the WSSV, results from the interaction of three factors: host, pathogen and environment. The environment plays an important role in disease development and determines the health or the immune capacity of the shrimp. High mangrove-to-pond area ratio (MPR) is reported as a protective factor against WSSV. This study investigates if mangroves affect the physicochemical properties of the water and soil as well as the prevalence of infectious agents like the WSSV by monitoring farms with different MPR (0:1, 1:1, 4:1).

      Results showed that quality of influent water was not significantly better in farms with high MPR. Significantly higher available sulfur was observed in MPR-4; significantly higher percentage green vibrios in the soil in MPR-0. WSSV was detected in farms with MPR-1 and MPR-4 but did not result in an outbreak, suggesting that the presence of mangroves could prevent WSSV outbreak.
    • Article

      Effect of three innovative culture systems on water quality and whitespot syndrome virus (WSSV) viral load in WSSV-fed Penaeus monodon cultured in indoor tanks 

      EA Tendencia, RH Bosma & LR Sorio - Aquaculture, 2012 - Elsevier
      White spot syndrome virus is the most important among the shrimp diseases. It has been devastating the shrimp industry for more than 3 decades. Previous studies reported that greater percentage of yellow colonies on thiosulfate citrate bile salt sucrose agar (yellow vibrios) in the rearing water, abundant supply of natural food such as Chlorella, and the use of the greenwater technology (GW) are some ecological ways of preventing WSSV outbreak. The aim of this study was to investigate the efficiency of the 3 systems against WSSV.

      Shrimp, experimentally infected with WSSV by feeding with WSSV positive shrimp carcass, was cultured in tanks using three treatments: with tilapia to simulate the GW, seeded with Chlorella, and with molasses added to enhance growth of yellow vibrios. Shrimp cultured in seawater served as the control. Survival was recorded and shrimp were analyzed for WSSV quantification using qPCR upon termination.

      Analysis showed no significant differences in shrimp survival at 120 h post infection in all treatments and the control. However, from the original viral load of 1.40 × 101 WSSV/mg sample, WSSV decreased and was significantly lowest in shrimp cultured using GW (7.0 × 100), compared to the control (4.82 × 105) and the other treatments (3.66 × 105 for molasses added and 4.64 × 105 for Chlorella seeded) in which viral load increased 4–5 times. Shrimp survival was highest in Chlorella seeded treatment and lowest in GW. Nitrogenous waste concentrations were lowest in molasses added water and highest in GW.

      Results suggest that the GW culture technology provides protection against WSSV while addition of molasses lowers nitrogenous waste concentration. The use of GW in combination with the addition of molasses for shrimp culture is suggested.
    • Article

      Financial feasibility of green-water shrimp farming associated with mangrove compared to extensive shrimp culture in the Mahakam Delta, Indonesia 

      RH Bosma, EA Tendencia & SW Bunting - Asian Fisheries Science, 2012 - Asian Fisheries Society
      This paper presents a post-hoc assessment of the introduction of intensive shrimp farming strategies, with and without green-water (GW) technology, in the Mahakam Delta where extensive systems (ES) dominate. The study also assesses the potential of integrated mangrove GW shrimp production (MGW). The method section describes the systems considered, the cost-benefit analysis applied and the assumptions for different scenarios. The data for the GW and non-GW systems were based on a survey in the Philippines. Assessing cultured shrimp yields from the total farm area showed that production from non-GW was 10% higher than from GW farms. Compared to these two systems, the MGW system produces about 20% of the total shrimp, but provides complementary livelihood options and ecosystem services. Per unit area covered, MGW system produces 20 times more shrimp than ES, while income for farmers doubles and opportunities for livelihoods enhancement associated with the mangrove area increase. Low operating costs make the ES interesting for resource poor farmers, but risks to producers and societal cost are underrated. Transferring from ES to MGW system will increase the contribution to the national economy whilst maintaining ecosystem services, that would otherwise be lost, were intensive culture systems to predominate.
    • Article

      The potential effect of greenwater technology on water quality in the pond culture of Penaeus monodon Fabricius 

      EA Tendencia, RH Bosma, MCJ Verdegem & JAJ Verreth - Aquaculture Research, 2015 - Wiley
      Whitespot syndrome virus (WSSV) has caused severe production drops in the shrimp industry. Numerous scientific manuscripts deal with WSSV epidemiology, but reports on minimizing disease outbreaks through ecological means are rare. Industry stakeholders resorted to various innovative techniques to recover from heavy economic losses. Some shrimp farmers in the Philippines claimed that ‘greenwater’ (GW) technology could prevent disease outbreaks due to WSSV. The efficiency of the GW technology was evaluated by comparing three ponds using the GW culture technique with three ponds not using it. WSSV was detected only in one of the GW ponds and not in the non-GW ponds. No WSSV disease outbreak occurred, and no conclusion could be reached. In GW ponds, available soil sulphur content was lower; and in water, the observed counts of luminous bacteria were lower and counts of Chlorophyceae were higher. Chlorophyceae, i.e. algae, enhanced nutrient uptake in effluent streams resulting in improved water quality in Penaeus monodon Fabricius culture ponds. This suggests that the use of the GW technique to culture P. monodon improved water quality.
    • magazineArticle

      Searching for ecological ways to reduce WSSV impact 

      R Bosma, E Tendencia, M Verdegem & J Verreth - Aquaculture Asia, 2014 - Network of Aquaculture Centres in Asia-Pacific
      White spot syndrome virus (WSSV) has brought financial losses to all shrimp farming systems, and lately the “Early Mortality Syndrome” (EMS) or more accurately termed Acute Hepatopancreatic Necrosis Disease (AHPND) have added to the threats to shrimp farming in South Asia. Most studies on WSSV have been done in tanks with species other than Penaeus monodon. Several studies of RESCOPAR aimed to study WSSV epidemiology in on-farm situations and find ecological means of disease prevention or control. To achieve these goals experimental, cross-sectional, longitudinal and case studies were carried out by PhDs in Indonesia, the Philippines (Tendencia, 2012) and Vietnam.
    • Article

      White spot syndrome virus (WSSV) risk factors associated with shrimp farming practices in polyculture and monoculture farms in the Philippines 

      EA Tendencia, RH Bosma & JAJ Verreth - Aquaculture, 2011 - Elsevier
      White spot sydrome virus (WSSV) is one of the most important viral disease of shrimp. Several studies to control the disease have been done. Tank experiments identified WSSV risk factors related to the physico chemical properties of the water. A few studies reported pond level WSSV risk factors. This study identifies the risk factors associated with essentially two different farming systems: polyculture and semi-intensive monoculture of Penaeus monodon. Data were gathered from a total of 174 shrimp farmers in eight provinces of the Philippines using a structured questionnaire. Forty-seven variables related to pond history and site description, period of culture, pond preparation techniques, water management, culture methods, feed and other inputs, and biosecurity measures were investigated. In the analysis for combined monoculture and polyculture farms, feeding live molluscs was identified as important WSSV risk factors. In addition to feeding live molluscs, sharing of water source with other farms, having the same receiving and water source, larger pond size, and higher stocking density were identified as important WSSV risk factors in monoculture farms. Climate, i.e. stocking during the cold months and sludge removal and its deposition on the dikes were identified as WSSV risk factors in polyculture farms. Protective factors, listed in decreasing significance, were feeding with planktons and high mangrove to pond area ratio, both observed in the dataset with both monoculture and polyculture farms, while only the latter was observed in the dataset for monoculture farms only. No protective factor was observed in the dataset for polyculture farms.

      This study confirmed the negative effect of sharing water source with other farms and identified several new factors influencing WSSV infection such as feeding live molluscs increases the risk, while feeding with planktons and high mangrove to pond area ratio reduce the risk.
    • WSSV risk factors related to water physico-chemical properties and microflora in semi-intensive Penaeus monodon culture ponds in the Philippines 

      EA Tendencia, RH Bosma & JAJ Verreth - Aquaculture, 2010 - Elsevier
      Whitespot syndrome virus, WSSV, is the most important among the shrimp diseases. One of the suggested WSSV risk factors is the occurrence of stress since stressors could compromise the shrimp defence system thus increasing the risk of WSSV infection. Stressors are usually related to the physico-chemical properties of both water and pond bottom. This paper investigates the effect of some biotic and abiotic components of the pond ecosystem on WSSV infection and outbreak. Water physico-chemical properties and microflora of 91 production cycles of 8 semi-intensive shrimp farms were analyzed to determine WSSV risk factors, using factor analysis and logistic regression. Fluctuations of temperature and pH are important risk factors that will result to an infection but not necessarily to an outbreak. Exposure to high salinity and high temperature are important factors for an infection to result to an outbreak. The risk of an infection is reduced when the water temperature is high, salinity fluctuations are small, and percentage of yellow Vibrio colonies is greater than the green ones. Further studies are needed to clarify the effects of water depth, water transparency, and various bacterial counts; these factors could be individual or interactive.