Now showing items 1-5 of 5

    • Article

      Cage culture of the Pacific white shrimp Litopenaeus vannamei (Boone, 1931) at different stocking densities in a shallow eutrophic lake 

      MLA Cuvin-Aralar, AG Lazartigue & EV Aralar - Aquaculture Research, 2009 - Blackwell Publishing
      Postlarvae of Litopenaeus vannamei were acclimated and stocked in lake-based cages at the following stocking densities: 10, 20, 30 and 40 shrimp m−2. Another set of shrimp was stocked in concrete tanks as reference samples at 30 shrimp m−2. Significant differences were observed among stocking densities throughout the 95-day culture. The final weight at harvest decreased with increasing stocking density: mean weights of 23.3, 15.8, 13.0, 10.9 and 14.6 g for the 10, 20, 30, 40 shrimp m−2 and reference tanks were observed respectively. There were no significant differences in survival throughout the culture period, ranging between 69% and 77%. Daily growth rates (range: 0.11–0.24 g day−1) and specific growth rates (range: 3.54–4.34%) also differed significantly among stocking densities, both increasing with decreasing stocking density. The feed conversion ratio in the cages did not differ among the stocking densities, ranging from 1.53 to 1.65. The relationship between stocking density and mean individual weight at harvest followed the equation y=81.06x−0.54 (R2=0.938) and that of stocking density and production (in g m−2) is y=58.01x−0.46 (R2=0.834).
    • Article

      The current state of aquaculture in Laguna de Bay 

      DC Israel - 2007 - Philippine Institute for Development Studies
      Series: PIDS Discussion Paper Series; No. 2007-20
      This paper presents some of the preliminary results and findings of an ongoing study, jointly conducted by the Southeast Asian Fisheries Development Center (SEAFDEC AQD) and Philippine Institute for Development Studies (PIDS), which assesses the current state of aquaculture in Laguna de Bay.

      The study uses primary and secondary data. The primary data were gathered through interviews with key informants and a cross-section survey of fishpen and fishcage operators and their operations in Laguna de Bay conducted in 2007. The secondary data were gathered from the published statistical indices of institutional sources and other relevant literature.

      The results of the study indicate that aquaculture in Laguna de Bay is a vibrant industry that includes not only fishpen and fishcage operators but also various participants in its input and product markets. Furthermore, they show that aquaculture contributes significantly to fish production in the lake as well as to national aquaculture and fisheries production.

      The results of the study also indicate that while aquaculture in Laguna de Bay has been an important economic contributor locally and nationally, it has been facing numerous problems over time that constrain its development. Of these, environment-related problems, lack of access to cheap capital, obstruction of navigational lanes by fishpens, existence of illegal fishpens, poaching and overall limited support from the government were considered very serious by aquaculture operators. These problems, therefore, may be the ones needing the most attention.
    • Conference paper

      Fish biodiversity and incidence of invasive fish species in an aquaculture and non-aquaculture site in Laguna de Bay, Philippines 

      MLA Cuvin-Aralar - In C Biscarini, A Pierleoni & L Naselli-Flores (Eds.), Lakes: The Mirrors of the Earth. Balancing Ecosystem and Human Wellbeing, 2014 - Science4Press
      Laguna de Bay is the Philippines' largest inland water with 900 km2 surface area. The lake has been assessed as hypereutrophic (Rohani and Roblo, 1984) to dystrophic (Barril and Tumlos, 2002). To make use of the lake's natural productivity a pilot aquaculture project started in 1971 (del Mendo and Gedney, 1979). The aquaculture industry in the lake rapidly developed, mainly using species not native to the lake. Since then, the lake has become a major source of fish in Metro Manila and the adjacent provinces.

      An assessment of the impact of aquaculture in the lake showed increased total finfish biomass in the lake; ecotrophic efficiency of phytoplankton increased; and the calculated total net primary production decreased by a factor of two compared to the pre-aquaculture period (de los Reyes, 1993). The dominant species cultured in Laguna de Bay are introduced species. After more than 40 years the lake is now populated with non-native species including species that are considered invasive and nuisance. Many of these species were deliberately introduced for aquaculture and there are those that were considered accidental introductions like ornamental fish cultured in ponds within the lake's watershed.

      To assess the impact of aquaculture in localized areas in the lake, a study was conducted to monitor diversity in the fisheries resources of the lake at two adjacent, but distinctly different sites: the West Cove (WC), an open fishery area, with no aquaculture and the East Cove (EC) which is an aquaculture site with cages for Nile tilapia, bighead carp, giant freshwater prawn.
    • Article

      Microcystin production during algal bloom occurrence in Laguna de Bay, the Philippines 

      SF Baldia, MCG Conaco, T Nishijima, S Imanishi & KI Harada - Fisheries Science, 2003 - Japanese Society of Fisheries Science
      The amount of microcystin in Microcystis aeruginosa bloom was investigated during the rainy season of 1999 in Laguna de Bay, the Philippines. Bloom samples taken from the West Bay and East Cove stations of the lake were studied in relation to the characteristics of environmental conditions. Four types of microcystins, microcystin-LR (MC-LR), microcystin-RR (MC-RR), 6(Z)-Adda-microcystin-RR, and 3-desmethylmicrocystin-LR were identified from the natural bloom samples among which MC-LR was the most dominant type of microcystin. Production of microcystin (88.6 µg/100 mg dried cells) was highest during the first sampling week that coincided with high water transparency and high conductivity. The occurrence of a strong typhoon during the second sampling week had changed the environment drastically, which was characterized by low water transparency, high turbidity, low water temperature, and with trace amounts of MC-LR detected at the East Cove station. Thus, toxin production over time as well as the relationship between Microcystis production and toxin concentration could not be fully evaluated.
    • Conference paper

      Potential of cowpea (Vigna unguiculata L.) meal as an alternative protein source in diets for giant freshwater prawn (Macrobrachium rosenbergii, de Man 1879) 

      FA Aya, ML Cuvin-Aralar & RM Coloso - 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
      Growth trials were conducted to evaluate cowpea Vigna unguiculata (L.) meal as a potential protein source in diets for giant freshwater prawn, Macrobrachium rosenbergii (de Man 1879), reared in tank and lake-based cages. Five isonitrogenous (approximately 37% crude protein) and isocaloric diets were formulated where fish meal (FM) protein was replaced with 0%, 15%, 30%, 45% and 60% cowpea meal protein (or CP0, CP15, CP30, CP45, and CP60, respectively). Results of an 8-week tank trial showed that the final body weight (FBW), percent weight gain, specific growth rate (SGR) and survival of prawns were not significantly influenced by dietary treatments (P > 0.05), although the highest values, except for survival, were observed with CP45. In a lakebased cage trial that lasted for 16 weeks, prawns fed CP30 and CP45 had significantly higher FBW (13.1 and 14.4 g, respectively) compared to other treatment groups (P < 0.05). SGR (4.52 5.00%/ day), survival rates (53-77%), yield (98.5-116.5 g m-2) and feed conversion ratio (FCR; 2.0-2.7) were not affected by increasing levels of cowpea meal in the diets. Based on these results, cowpea meal can be considered as an alternative protein source in diets for M. rosenbergii.