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Cuvin-Aralar M.L.A.,Southeast Asian Fisheries Development Center
Lakes and Reservoirs: Research and Management | Year: 2016

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. © 2016 John Wiley & Sons Australia, Ltd. Source

Bautista-Teruel M.N.,Southeast Asian Fisheries Development Center | Koshio S.S.,Kagoshima University | Ishikawa M.,Kagoshima University
Aquaculture | Year: 2011

Experiments on diet development and evaluation for juvenile abalone, Haliotis asinina focusing on lipid and essential fatty acid (EFA) levels were conducted. Six isonitrogenous diets were formulated in Experiment 1 (E1) to contain 27% protein with lipid levels at 0, 2, 4, 6, 8, and 10%. Experiment 2 (E2) (EFA levels), used the optimum lipid level (3.59%) in E1 with EFA supplementation of 0.0, 0.2, 0.4, 0.8, and 1.6%. Abalone juveniles [mean initial weight and shell length of 0.60 ± 0.07. g and 14.70 ± 0.12. mm (E1)], [0.60 ± 0.16. g and 15.30 ± 0.73. mm (E2)] respectively, were fed these diets at 2-5% body weight in 3 replicates. Feeding trials in 90. days/experiment evaluated growth, survival, feed conversion ratio (FCR) and fatty acid composition in abalone tissues. Results showed significantly higher growth rates (ANOVA P < 0.05) with abalone fed diets with lipid levels of 2.2%, 3.6%, and 6.1% compared with those containing lipid levels of 7.6% and 9.8%. Abalone fed the lipid-free diet showed significantly the lowest growth rate among treatments. Break point analysis as a function of growth, showed optimum lipid requirement at 3.59%. Survival was high at 95-99% in both experiments. FCR values for D3 and D4 were significantly better compared to D2, D5 and D6 (E1) while no significant differences were found for D2-D6 for E2. Abalone body lipid increased with corresponding increase in dietary lipid. Addition of 18:2n-6, 18:3n-3, and n-3 HUFA showed significant improvement in weight gains up to 1.6% supplementation. Fatty acid composition of the lipid samples reflected those of the diets. Total lipid of abalone fed the lipid-free diet showed higher monoenes. Addition of EFA resulted in an increase in both n-3 and n-6 fatty acids. Lipid incorporation at 3.6% using a 1:1 ratio of CLO and SBO with EFA supplementation (1.6%) is best in juvenile abalone diet formulation. © 2010 Elsevier B.V. Source

Erazo-Pagador G.,Southeast Asian Fisheries Development Center
Journal of Shellfish Research | Year: 2010

This paper describes the first screening in the Philippines of slipper-cupped oysters (Crassostrea iredalei) for the presence of parasites. Slipper-cupped oysters were sampled at 2 sites in Ivisan, Capiz, from September to December 2007. Macroscopical and histological analyses were carried out in oyster tissues. Histological examination showed gregarine protozoan Nematopsis sp. as the most prevalent parasite (71.33% and 65.0%) at 2 sites with a moderate intensity of infection. Tylocephalum sp. cestode was found in the connective tissue around the digestive gland, with a prevalence of 60% and 52.3% in 2 sites, with a moderate intensity of infection. Digenean trematodes had a 37.80% prevalence at site 1 and a 22.45% prevalence at site 2. Ciliates were also observed with a prevalence of 18.75% (site 1) and 13% (site 2). The observed infection of oysters had no apparent effect on oyster production at these sites maybe due to low infestation levels or to the fact that the parasites have no pathological effect. Source

Cuvin-Aralar M.L.A.,Southeast Asian Fisheries Development Center
Invertebrate Reproduction and Development | Year: 2014

The freshwater knob-tooth prawn Macrobrachium mammillodactylus is a commercially exploited species in the Philippines. To study the biology of this species, broodstock from the wild was collected, transported to the laboratory and kept in pairs in indoor polyethylene tanks for breeding. Eggs from berried females were sampled to follow the stages of embryonic development until hatching to zoea larva. It took 18.0 ± 2.1 days for the eggs to hatch at ambient water temperature between 25 and 28 °C. The morphological landmarks of development at the different stages (pre-cleavage, cleavage, blastula, pre-nauplius, post-nauplius and pre-hatching) of the live embryos are described. Incremental percentage staging was adopted from 0% at fertilization to 100% at hatching and were matched with corresponding morphological development. Egg volume increased significantly toward the mid-to-later stages of development. The eye index also showed a significant increase as the egg developed. The colour of the egg mass changed from light olive green to grey as the eggs progressed in development. The general pattern of development was comparable to other members of the genus Macrobrachium. © 2014 Taylor and Francis. Source

Quinitio E.T.,Southeast Asian Fisheries Development Center | Estepa F.D.P.,Southeast Asian Fisheries Development Center
Aquaculture | Year: 2011

The effects of removing or trimming the chelipeds at various molt stages on regeneration, molt interval (MI) and specific growth rate (SGR) were determined in mud crab Scylla serrata. These strategies in combination with provision of shelters and food were tested in relation to survival and growth.Hatchery-reared S. serrata juveniles (1.3-2.2. g body weight) in the postmolt, intermolt, and premolt stages were subjected to autotomy of two chelipeds, and trimming of dactylus and pollex. Intact crabs served as the control group. Interval from stocking to first molt was significantly longer in crabs autotomized at intermolt or premolt than in trimmed or intact crabs, but was similar to intact crabs when autotomy was done at postmolt. However, MI from first to second molts was longer compared to intact crabs when chelipeds were removed or trimmed at premolt.After the first molt, autotomy and not trimming caused significant decrease in SGR. The SGRs at the end of the test were similar to intact crabs (postmolt: 7.90 ± 0.39, intermolt: 5.64 ± 0.50) when trimming of chelipeds was done at postmolt (8.01 ± 0.75) or intermolt (4.38 ± 0.40). However, SGR was lower when premolt crabs were subjected to autotomy (4.11 ± 0.67) and trimming (5.29 ± 1.40) than when chelipeds were intact (9.45 ± 0.47).A two-factor experiment was conducted in the second phase where intermolt crabs with autotomized or trimmed chelipeds (factor A) were either fed or starved but provided with shelters or fed but without shelters (factor B). After 10. days, higher survival was obtained in crabs with autotomized (95.55 ± 2.94%) or trimmed chelipeds (93.33 ± 3.33%) than in intact crabs (73.33 ± 6.67%). Survival was not affected by factor B, but higher final mean body weights were attained in fed crabs with (0.78 ± 0.04. g) or without shelters (0.74 ± 0.04. g) than unfed ones (0.48 ± 0.04. g). A third experiment was conducted to verify these results. Crabs with trimmed or intact chelipeds were either fed or unfed. No shelters were provided. Crabs with trimmed chelipeds (88.57 ± 0%) had higher survival than intact crabs (59.76 ± 7.56%) regardless of whether they were fed or starved; and fed crabs (0.82 ± 0.04. g) had higher mean body weight than unfed crabs (0.61 ± 0.07. g) regardless of whether chelipeds were intact or trimmed. These results indicate that trimming or total removal of chelipeds are effective strategies in reducing cannibalism. © 2011 Elsevier B.V. Source

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