Now showing items 1-8 of 8

    • Article

      Broodstock transplantation: An approach for stock enhancement of the 'kapis' shell Placuna placenta along Panay Gulf, central Philippines 

      JA Madrones-Ladja, ET Aldon & DD Baliao - The Philippine Agricultural Scientist, 2012 - College of Agriculture, University of the Philippines Los Baños
      The Panay Gulf in central Philippines once supported a substantial ‘kapis’ Placuna placenta (Linnaeus) population that was among the six major sources for this species. However, stock depletion began in the late 1980s because of overexploitation and destructive fishing practices. To recover the declining ‘kapis’ fishery along the Gulf, a broodstock transplantation program was initiated in 1999. Results from a survey of the Gulf prior to this program confirmed reports of resource depletion. Four (4) transplantation sites (S) with natural soft-muddy substrata in adjacent coastal towns, namely, Tigbauan (S1 and S2), Guimbal (S3) and Oton (S4) were established and stocked with 3200 (1:1 male to female ratio) sexually mature ‘kapis’ broodstock collected from nearby Negros Island in March–October 1999. Transplant survival along the sites ranged 80–100%. Spontaneous spawning by ‘kapis’ transplants occurred from March 1999 (15 d after first stocking) through May 2000. Larvae (5 larvae per L) began to appear at S1 15 d after transplantation and progressively increased in density to 23 larvae per L in November 1999. During this period, local divers reported big patches of ‘kapis’ juveniles [shell length (SL), 38 ± 11 mm] at S4. Sex ratio of recruits was 3:2 (male: female). Larvae became abundant off the nearby coasts with a strong recruitment pulse at 160 larvae per L at S4 by January 2000. Likewise, transplants taken to the laboratory were induced to spawn by photochemical method, and thus validated the spawning that occurred in transplantation sites. Juvenile recruits were of variable sizes, indicating that spawning was not simultaneous. Sexually mature juvenile recruits (40% female, 90% male) were already observed in January–February 2000. The recruitment apparently resulting from these transplants was local, dispersion ranging from zero to a few kilometers distance from transplantation sites. ‘Kapis’ harvest began in 2007 for local market consumption while commercial harvest was done in 2010 with approximately 600 tons.

      The repopulation of ‘kapis’ along Panay Gulf after a decade indicated the success of the restocking program which was attributed to the suitability of the species, reproduction of transplants and the proper management of the newly established resource by the coastal fishers who are members of a local organization (FARMC) with the support of local government units (LGUs).
    • Book

      Cage nursery of high-value fishes in brackishwater ponds: seabass, grouper, snapper, pompano 

      J Madrones-Ladja, N Opiña, M Catacutan, E Vallejo & V Cercado - 2012 - Aquaculture Department, Southeast Asian Fisheries Development Center
      Series: Aquaculture extension manual; No. 54
      This extension manual describes nursery pond requirements, nursery rearing procedures, common diseases of young marine fish, and economic analysis of cage nursery as an enterprise separate from hatchery and grow-out culture.
    • Article

      The effect of micro algal diet and rearing condition on gonad maturity, fecundity and embryonic development of the window-pane shell, Placuna placenta Linnaeus. 

      JA Madrones-Ladja, MR dela Peña & NP Parami - Aquaculture, 2002 - Elsevier
      Immature Placuna placenta (Linnaeus) broodstock were given the micro algae Isochrysis galbana (T-ISO) Parke and Tetraselmis tetrahele (G.S. West) at different combinations and density levels and reared in tanks with or without mud substrate. The animals were also reared in the estuary and fed on available natural food. Monthly examination of gonad histology showed a significantly higher gonad index in broodstock reared in tanks with mud substrate than without (P < 0.05). In addition, those given a high-density algal diet (200,000 cells ml−1, 3:1 mixture of I. galbana and T. tetrahele) had a significantly faster gonad development than the low-density diet (100,000 cells ml−1, 1:1 mixture) fed broodstock reaching sexual maturity and gonad index of 330±14 after 1 month (P < 0.0001). P. placenta given the low-density algal diet attained gonad maturity after 3 months and estuary-reared animals after 2 months.

      Seawater irradiated by ultraviolet light (925–1395 mW h/l) induced spawning of all mature P. placenta. Estuary-reared animals had a higher fecundity and larger eggs and a higher percentage of fertilized eggs developed to straight-hinged larvae than those reared under other condition. Animals given a low-density algal diet released low number of small eggs which did not fertilize. Natural spawning also occurred in the estuary 2 months after stocking.
    • Conference paper

      The effect of stocking density, temperature and light on the early larval survival of the abalone Haliotis asinina Linné 

      JA Madrones-Ladja & BB Polohan - Phuket Marine Biological Center Special Publication, 2001 - Phuket Marine Biological Center
      Newly hatched trocophore larvae of the abalone haliotis asinina linne were stocked at densities of 1000, 3000 and 5000 larvae/1 at low (20-25oC) and high (ambien, 28-30oC) water temperature levels in light (transparent) and dark (black cloth-coered) lass container. Larvae were reared in UV light-irradiated sea water until pre-settement stage. Aeration was not provided during the 20-h incubation periond. A 3x2x2 factorial design with three replicates per treatment was folloed.

      A three-way analysis of variance (ANOVA) showed a significant interaction among the factors tested. Analysis at each density level showed that at stocking density of 1000 larvae/1, no significant difference between temperatures and between light or dark condition was observed. However, at densities of 3000 and5000, significantly higher survival was obtained at low, than high temperature (P<0.05), but no difference between the light and darck conditions. Analysis at each temperature showed that, at high temperature,better survival was obtained at stocking density of 1000, than higher densities (P<0.001), and at light than at darck condition (P<0.05). However, at low temperature, no significant difference between light abd darck conditions was detected. ANOVA at light or darck condition showed that at any of these conditons, larvae survival was always higher at 1000 stocking density that t other density

      (P 0.05). Survival was not significntly different between stockng density of 3000 and 5000 larvae/1 at any of those light conditions. Theredore, during incubation of newly hatched trocophore larvae of H. Asinina to pre-settlement stage, the optimum stocking density at high temperature (28-30oC) was 1000/1, in a light-penetrable rearing container. When reared at higherstocking densities of 3000 or 5000, a higher survival was obtained when temperature was lower to 20-25oC in either rearing conditions tested.
    • Conference paper

      Hatchery management for the window-pane shell, Placuna placenta Linnaeus, 1758 

      JA Madrones-Ladja & MR de la Peña - In J Hylleberg (Ed.), Proceedings of the 10th International Congress and Workshop of the Tropical Marine Mollusc Programme (TMMP), 20-30 October 1999, 2000 - Phuket Marine Biological Center
      To relieve pressure on wild stock population, a hatchery technique for the window-pane shell, Placuna placenta Linnaeus has to be developed. A study was conducted to determine the suitable algal diet for P. placenta during gonad development and larval rearing. Sexually immature P. placenta broodstock were reared in the estuary or in tanks for four months. Tank-reared animals were fed daily mixture of Isochysis galbana (T-ISO) Parke and Tetraselmis tetrahele (G.S. West) at 100,000 cells/ml, 1:1 (100-I:T), or 200,000 cells/ml, 3:1 (200-3I:T) combinations. Monthly gonad histological examination showed that sexual maturity was attained by animals fed 200-3I:T diet after four months but not in 100-I:T. Estuary-reared broodstock had the highest gonad index among treatments after the first month, but did not reach sexual maturity until the end of the conditioning period. Sexually mature P. placenta from 200-3I:T fed-group spawned when exposed to UV light-irradiated seawater. One-day old larvae were reared in UV light-irradiated seawater until metamorphosis to plantigrade. Larvae were fed daily with monoalgal diet of I. galbana, T. tetrahele, or Chaetoceros calcitrans (Takano) at densities of 10,000-30,000 cells/ml. Larval settlement was observed in all diets after 14 days. Survival rate at metamorphosis was highest (12.60%) when diet of I. galbana was used, but lowest in T. tetrahele [5.1%) (P<0.05). Average shell length increment during the 14 days rearing period were 11.0, 11.38 and 9.92 µm day-1, for Isochrysis, Tetraselmis and Chaetoceros fed larvae, respectively.
    • Article

      Netcage rearing of the Asian seabass Lates calcarifer (Bloch) in brackishwater pond: The technical and economic efficiency of using high protein diets in fingerling production 

      JA Madrones-Ladja & MR Catacutan - The Philippine Agricultural Scientist, 2012 - College of Agriculture, University of the Philippines Los Baños
      Intensification in the grow-out culture of high-value fish requires a large quantity of quality fingerlings. Fingerling production is a component of fish farming that comprises nursery and grow-out culture, and may be a commercial enterprise option for fish farmers with limited pond area. The nursery rearing of the Asian seabass Lates calcarifer (Bloch) was conducted in netcages inside a brackishwater pond. The fish were fed with two isocaloric, high-protein diets formulated at the Southeast Asian Fisheries Development Center (SEAFDEC/AQD) and a control treatment: diets A (40.40% crude protein, CP) and B (46.17% CP), and trashfish (TF) as control. Hatchery-bred seabass early juveniles of two size groups (S1, 4.0 ± 0.2 g; S2, 2.40 ± 0.03 g) were stocked at 75–100 fish per m3 and given diets A or B at 6–10% of average body weight (ABW) d-1, or TF at apparent satiation. Seabass given the formulated diets attained the desired size (≥ 20–40 g) after 45 d but not the fish fed with trashfish. Size and treatments showed significant effects on final ABW, although no significant interaction between these factors was shown to affect body weight. As expected, S1 fish attained a significantly higher ABW (30.7 ± 18 g) compared with S2 fish (20.7 ± 11 g) regardless of diet treatment. Seabass fed with trashfish exhibited significantly lower final ABW (6.6 ±1.6 g) than those fed Diet A (33.4 ± 6.5 g) or Diet B (37.1 ± 9.4 g). Fish size did not have any significant effect on specific growth rate (SGR), but diet treatments did. SGR was significantly better when either Diet A (5.2 ± 0.30) or B (5.4 ± 0.20) was used compared with the SGR of seabass fed with trashfish (1.7 ± 0.5). Although size and treatment did not show significant interaction on fish survival, the use of bigger seabass resulted in higher survival (89 ± 11%) compared with smaller seabass (80 ± 11%). Regardless of size, similar survival was attained in seabass fed Diet A (89 ± 6%) or B (95 ± 5%), significantly higher than that in seabass given trashfish (72 ± 6%). An interaction between size at stocking and diet treatment significantly affected protein efficiency ratio (PER). When S1 fish was used, diets A and B gave similar PER. However, when S2 fish was used, diet A gave significantly higher PER (2.49 ± 0.02) among the treatments (P < 0.05). Regardless of size, significant differences (P ≤ 0.05) were observed in the mean production cost, revenue and income among the three diet treatments. Moreover, post hoc analysis using Tukey’s HSD test further showed that use of diet B resulted in significantly higher revenue (PhP25,132.80) and income (PhP12,597.47) compared with the two other treatments. Trashfish treatment gave the least revenue (PhP 9,525.60) and negative income (- PhP 1,798.40). Production cost was not significantly different between diets A and B. Hence, diet B is the most economically viable and productive diet treatment. The low break-even price of fingerlings obtained for diet B showed that selling price can still be reduced to lower production cost in grow-out farming.
    • Conference paper

      Restocking of windowpane shell, Placuna placenta in a depleted bed off Tigbauan, Iloilo, the Philippines 

      JA Madrones-Ladja & WG Gallardo - In J Hylleberg (Ed.), Proceedings of the 10th International Congress and Workshop of the Tropical Marine Mollusc Programme (TMMP), 20-30 October 1999, 2000 - Phuket Marine Biological Center
      The Tigbauan coast, Iloilo, the Philippines, has been depleted of the natural population of the windowpane shell, Placuna placenta Linnaeus, 1758, since the early 1980's. To support the declining P. placenta industry of the Philippines, restocking of depleted natural beds has to be done. This work aimed at assessing the suitability of the area for restocking of this valuable bivalve species. Immature P. placenta broodstock (71.6 ± 6.2 mm) and juveniles (40 ± 10mm) were stocked in a 40 m2 muddy bottom area off Tigbauan. Growth , survival, and reproduction of the animals were monitored monthly for 3 months. All juveniles were found dead after a month covered with sand and silt. However, broodstock remained alive. Broodstock samples, taken after a month, spawned after exposure to UV-light irradiated sea water. Survival rate, shell length and body weight increment of the broodstock after 91 days were 51%, 15.0 mm and 12.6 g, respectively. P. placenta veligers were found in the plankton one month after spawning and until the end of the three-month rearing period. Net productivity of the area ranged from 0.03-0.32 ml O2/l. Phytoplankton species and macrobenthic organisms, such as Ophelina acuminata Oersted, 1843, Halophila johnstoniae Busk, 1852 and sipunculans, associated with P. placenta in the natural habitat were also collected in the area. Restocking of the depleted bed is still feasible by using adult animals to naturally repopulate the area.
    • Article

      Salinity effect on the embryonic development, larval growth and survival at metamorphosis of Placuna placenta Linnaeus (1758) 

      JA Madrones-Ladja - Aquaculture, 2002 - Elsevier
      The effects of salinity on the embryonic development, growth, and survival of D-larvae to plantigrade as well as settling in Placuna placenta were studied. Embryos were developed to D-larvae of shell length (SL) 86±12 μm (SL±S.D.) after 20 h at salinities of 22–34 ppt, but not at lower salinity levels. Percentage production of straight-hinged larvae from fertilized eggs at these salinities ranged from 51% to 63% (P≥0.05). P. placenta larvae survived and settled in salinities of 16–34 ppt. Settlement occurred first (14 days) in salinities of 22–34 ppt and later (19 days) in 16 ppt when SL≥200 μm. Larval size at metamorphosis was not significantly different among these salinities (P≥0.05). Percentage survival of plantigrades at 34 ppt (13%) was significantly higher (P≤0.05) than at 16 ppt (4.5±3%), but not greater than at 22 (6.3±3%) or 28 ppt (7±4%) salinity. The best salinity levels for embryonic development and larval survival at metamorphosis ranged from 22 to 34 ppt and larval growth from 16 to 34 ppt. The tolerance of P. placenta to lower and higher salinities progressively increased as larvae develop from embryo to the plantigrade stage.