Pelagic stock assessment by hydroacoustic method in the South China Sea, Area IV: Vietnamese waters

Abstract

A collaborative acoustic survey between the Research Institute of Marine Products (RIMP), Vietnam and the Marine Fishery Resources Development and Management Department (MFRDMD) of SEAFDEC, was carried out in Vietnam waters from April, 29 to May, 29 1999. Survey was conducted by using the scientific echo sounder, FQ70 installed on board of MV SEAFDEC. Survey transects were designed perpendicular to the coastline with standard length of 60 nautical miles. The vessel was cruised at 10 knot and stopped at each station for oceanographical sampling. During cruising, the back scattering strength, SV were collected and saved in multiple storage media. SV values were verified during data analyses by removing any noise and scattering layers. The back scattering values by area (SA) is calculated and the fish density by transects are produced. Using those parameters, the biomass of pelagic is estimated based on representative species from the sampling program and national fisheries statistics. Pelagic biomass in Vietnamese waters was estimated at 9.26 x 10⁶ tonnes with the average density of 15.93 tonnes/km². This estimation is based on dominance species of Decapterus maruadsi.