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  • cage aquaculture  (1)
  • oligotrophic and eutrophic rivers  (1)
  • 1
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    Growth performance and cost efficiency of tilapia (Oreochromis niloticus) and milkfish (Chanos chanos) fed extruded floating and non-floating feeds reared in net cages in Taal Lake (2021)
    In:  http://aquaticcommons.org/id/eprint/26761 | 25026 | 2021-02-27 20:59:44 | 26761 | National Fisheries Research and Development Institute, Philippines
    Details
    Publication Date: 2021-07-24
    Description: This study evaluated the growth and cost efficiency of tilapia (Oreochromis niloticus) and milkfish (Chanos chanos) fed three feed types used in cage farming in Taal Lake, Batangas, Philippines to serve as baseline information for cage aquaculture regulations. O. niloticus and C. chanos were reared in net cages fed three feed treatments: extruded floating feed (EFF), slow-sinking feed (SSF), and sinking feed (SF). Growth performance, feed conversion ratio (FCR), yield, and cost efficiency were compared at harvest. Results of the study showed that EFF had significantly higher mean weight gain, absolute growth and specific growth rate, biomass harvest, percentage good size fish, and FCR than SF in both O. niloticus and C. chanos (P〈0.05), but had no significant difference with SSF in terms of growth parameters (P〉0.05). FCR and biomass harvest were significantly higher in EFF than SF in O. niloticus (P〈0.05) but were not statistically different in C. chanos (P〉0.05). Survival rate was not significantly different among feed types (P〉0.05) in both species. Net profit was significantly higher in EFF than the other feed types (P〈0.05). At the same volume of fish production in the lake, the use of extruded floating feeds in cages lessened the feed cost by 17.91-29.44% for higher net returns and decreased feeds use by 19.64-30.0%, which could minimize negative impacts on the lake water environment. The results of the study revealed the comparative advantage of floating feeds over slow-sinking feeds and sinking feeds and is therefore recommended as the ideal feed type for cage farming in the lake.
    Keywords: Aquaculture ; Fisheries ; extruded floating feeds ; slow sinking feeds ; sinking feeds ; growth performance ; cage aquaculture
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 41-56
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    PAPER (OA)
  • 2
    Electronic Resource
    Electronic Resource
    The distribution of dissolved DNA in an oligotrophic and a eutrophic river of Southwest Florida (1991)
    Springer
    Hydrobiologia 218 (1991), S. 53-63 
    Details
    ISSN: 1573-5117
    Keywords: dissolved DNA ; oligotrophic and eutrophic rivers ; dissolved organic carbon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution of dissolved DNA concentrations and some microbial variables were compared in an oligo-mesotrophic river (the Crystal River) and a phosphate-rich eutrophic river (the Alafia River) in Southwest Florida over a 15 month period. Concentrations of phosphate and nitrate in the Alafia River averaged 135 and 18.2 times the respective phosphate and nitrate concentrations of the oligo-mesotrophic Crystal River. The seasonal average dissolved DNA concentration for the Alafia River exceeded that of the Crystal River by a factor of 1.8 (8.2 μg 1−1 compared to 4.6 μg 1−1, respectively). The greatest concentrations of dissolved DNA in the Alafia River were found in areas that contained the largest populations of phytoplankton and bacteria (a reservoir formed from an abandoned phosphate mining pit and two downstream stations near the mouth of the river). Differences in dissolved DNA concentrations between these environments and more pristine environments (i.e. all Crystal River Stations and upstream Alafia River stations) were of the same order of magnitude (1.8 to 2.2-fold) as the differences in bacterial abundance and activity, but considerably less than differences in phytoplankton abundance and activity between such environments. Seasonal variations in dissolved DNA concentrations in the Crystal River corresponded to seasonal variations in microbial populations, with minimal values in January and greater values in July. In the Alafia River, lowest concentrations for dissolved DNA occurred in July during the wet season, when seasonal flooding of area of leaf litter yielded high levels of dissolved organic carbon (DOC) which were low in dissolved DNA. These results suggest that: 1) in situ planktonic activity is a greater source of dissolved DNA than allochthonous or terrestrial sources of DOC; 2) factors that control the magnitude of heterotrophic bacterial populations are more likely to control dissolved DNA levels than factors regulating autotrophic population activity and abundance; 3) differences in dissolved DNA between eutrophic and oligo-mesotrophic environments are often much smaller than the differences in nutrient concentration between such environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00006418
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    Paper (German National Licenses)
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