Biomass estimation by hydro-acoustic methods in the Gulf of Thailand and Peninsular Malaysia

The abundance of fisheries resources and their structure in the Gulf of Thailand and East coast of Peninsular Malaysia were investigated during the SEAFDEC Collaborative Research Survey. Hydro-acoustic surveying using a scientific echo sounder model FQ-70 was conducted to estimate the fish abundance and biomass. Two survey cruises were carried out by M.V.SEAFDEC during the pre and post-northeast monsoon seasons. The scientific echo-sounder was equipped with an echo-integrator and two quasi-ideal beam transducers with operating frequencies of 50 and 200 kHz. The volume back scattering strength (SV) of the fish schools were collected from the layer of water at a depth from 10 m to the bottom along the track of survey cruise. The estimated biomass measured by high frequency shows clearly that a high concentration is observed at the upper and middle part of the Gulf of Thailand and the border area between Thailand and Malaysia waters during the pre-northeast monsoon season. Whereas, high biomass concentration shows only in the middle part of the Gulf of Thailand during the post-northeast monsoon season