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  • 1
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    Japan International Cooperation Agency | Tokyo, Japan
    In:  http://aquaticcommons.org/id/eprint/26177 | 17342 | 2019-01-28 07:51:20 | 26177 | Japan International Cooperation Agency
    Publication Date: 2021-07-24
    Description: An echo-sounder is an effective method of location and evaluation of fishing grounds, although its scope of coverage is narrow and the intensity of its echogram tracing as a means of estimating the size of fish schools is still a problem. Approximately 800 hours of echo-sounder recordings made in the South China Sea and Andaman Sea during the survey cruises of R/V CHANGI from 1970 to March 1973 were analysed. The results show that there is a definite correlation between fish catch and the gradings of fishing grounds as evaluated from the echograms obtained from the same area. This is especially so in areas where the values of mean catch per hour are more than 200 kg. The presence of upwelling, current rip and boundary layer, important factors for the formation of good fishing grounds can be clearly detected by an echo-sounder. During drifting, the growing size of fish schools attracted to the vessel’s light in the hours of darkness, as appeared on the echogram, may indicate abundance of fish in that area. The different modes and types of fish schools of some large fishes are easily recognisable on the echograms.
    Keywords: Fisheries ; Fish counters ; Echo surveys ; Fishery surveys ; Schooling behaviour ; Fishery resources ; Abundance ; Population number
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 85-88
    Format: 4
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  • 2
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    Japan International Cooperation Agency | Tokyo, Japan
    In:  http://aquaticcommons.org/id/eprint/26185 | 17342 | 2019-01-25 06:02:17 | 26185 | Japan International Cooperation Agency
    Publication Date: 2021-07-24
    Description: The analysis of echo-sounding records obtained from the South China Sea showed that scattering layer is caused by a concentrated layer of zooplankton and is related to thermocline. The occurrence of scattering layer may be used to indicate either the depth where thermocline occurs or the vertical movement of zooplankton. Fish schools were recorded at the vicinity of the scattering layer and this phenomenon is probably associated with the feeding habits of the fish.
    Keywords: Fisheries ; Echosounding ; Hydrobiology ; Thermocline ; Environmental factors ; Water temperature ; Zooplankton ; Scattering layers ; Schooling behaviour ; Feeding behaviour ; Marine fish ; Biomass ; Abundance ; Plankton equivalents
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 115-117
    Format: 3
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  • 3
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    Japan International Cooperation Agency | Tokyo, Japan
    In:  http://aquaticcommons.org/id/eprint/26171 | 17342 | 2019-01-24 07:22:46 | 26171 | Japan International Cooperation Agency
    Publication Date: 2021-07-24
    Description: The shovel-nosed lobster, Thenus orientalis lund, is a widely distributed and a commercially important crustacean in the South China Sea. To study its habitat, distribution and catch the data obtained by trawl operations carried out by Thai research vessels in 1967—1968 and by R/V CHANGI in 1972 were analysed. In the South China Sea it is most abundant in the coastal waters of the Malay Peninsula, South Vietnam and Sibu Bay of Sarawak at depth of less than 50 m. and relatively good catch has been obtained from waters with sandy rather than muddy bottom. The catch at night time is higher than that in the daytime. This phenomenon may be related to the feeding behaviour of this species as observed in the case of prawn.
    Keywords: Fisheries ; Lobster fisheries ; Commercial species ; Commercial fishing ; Habitat ; Catch statistics ; Seasonal variations ; Seasonality ; Length-weight relationships ; Sex ratio ; Fishing gear ; Geographical distribution ; Thenus orientalis
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 49-52
    Format: 4
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  • 4
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    Japan International Cooperation Agency | Tokyo, Japan
    In:  http://aquaticcommons.org/id/eprint/26184 | 17342 | 2019-01-25 06:10:55 | 26184 | Japan International Cooperation Agency
    Publication Date: 2021-07-24
    Description: This paper discusses the relationship between environmental factors and the distribution of fisheries resources in the South China Sea and the Andaman Sea, based on the oceanographic and fisheries resources data collected by R/V CHANGI from November, 1969 to March, 1973. The fish catch is related more to the bottom topography than the bottom feature of the sea. Good mean catch (〉 200 kg/hr) was obtained in up welling regions at the steep continental slope in areas off the north and the east coast of the Andaman Sea, and in areas with boundary zone at the flat area along the east coast of Malay Peninsula. The distribution of fisheries resources was also related to the hydrological factors. In general, better catch (〉 116 kg/hr) was obtained from areas having depths of 45—65 m, salinity range of 32.0 — 33.5 ‰ and bottom temperatures above 23°C. However, in the coastal waters off Sarawak and North Andaman Sea (off Burma), good fishing grounds were characterized by low salinity, low temperature and high nutrient contents, suggesting the influence of freshwater discharge in the area. Abundant occurrence of coastal water fishes were found in these areas. From the present analysis, it appears that the combination and interaction of both hydrological and topographic conditions are important factors contributing towards the formation of good fishing ground in the surveyed areas.
    Keywords: Fisheries ; Fishery resources ; Environmental factors ; Geographical distribution ; Fishery data ; Oceanographic data ; Environmental conditions ; Catch statistics ; Catch-effort ; Seasonal variations ; Topography ; Abiotic factors
    Repository Name: AquaDocs
    Type: book_section
    Format: application/pdf
    Format: application/pdf
    Format: 111-115
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