Browsing by Subject "Water depth"
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Culture of Macrobrachium rosenbergii (De Man 1879) in experimental cages in a freshwater eutrophic lake at different stocking densities -
Aquaculture Research, 2007 - Blackwell PublishingMacrobrachium rosenbergii (de Man 1879) juveniles (0.4 g) were cultured in experimental cages (L × W × H: 2.5 × 1 × 1 m) in Laguna de Bay, the largest lake in the Philippines. The following stocking densities at four replicates each were used: 15, 30, 60 and 90 prawns m−2 of cage bottom. The mean sizes at harvest after 5 months of culture ranged from 14.3 g for the highest stocking density to 26.3 g for the lowest. The mean size at harvest, daily growth rate and size class distribution were significantly influenced by stocking density, with those at the lowest stocking density showing significantly better growth and overall proportion of larger prawns. Heterogeneous individual growth (HIG) was fairly evident in all treatments. The percentage of blue-clawed males was not influenced by treatment but the mean weight was significantly higher in the lower stocking densities. Both the percentage and mean weight of berried females were significantly higher in the lowest stocking density. Survival was the highest in the lower stocking densities (55.3%, 54.0%, 52.7% and 36.9% for 15, 30, 60 and 90 prawns m−2 respectively). Feed conversion ratio (FCR) improved with decreasing stocking density, ranging from 2.1 to 3. As expected, yield per cropping increased with stocking density and ranged from 450 to 1089 g m−2 yr−1 of actual cage area. Production values obtained in the cage cultured M. rosenbergii were comparable to or even higher than those reported from pond culture, given that the stocking densities used in this study were generally higher than in ponds. The results show that the farming of M. rosenbergii in cages in lakes is a viable alternative to pond culture and has the potential of improve aquaculture production in lakeshore fish farming communities.
Marine Ecology Progress Series, 1985 - Inter ResearchA population of juvenile milkfish, C. chanos (Forsskaal) was studied in a small mangrove lagoon in Naburut Island, central Philippines. Several size groups of milkfish occurred in the lagoon as a result of its periodic connection with the sea. Body-weight to fork-length relation was: log W = - 5.2991 + 3.2388 log L, similar to that of pond-cultured specimens. In Naburut lagoon, juvenile milkfish take in primarily blue-green algae, as well as mangrove and seagrass debris, diatoms and detritus. The condition factor of fish caught during the day from May to Nov. stayed constant, indicating that lagoon conditions for growth in terms of food did not change markedly during the year. The monthly size-frequency distribution shows that juvenile milkfish in the lagoon grew at a rate of 7 to 9 mm wk super(-1) in 1979. Compared with pond-cultured specimens, their growth rate was lower during the first month but higher during the second month in the nursery. The limited area and depth of Naburut lagoon probably set the limit to the size of juvenile milkfish; these can be sustained there to just 150 to 180 mm fork length.