Catch Estimation Using Acoustic Data Obtained from Research Vessel's Routine Surveys in the Coastal Waters of Northern Taiwan

Abstract

In this study, we compiled data of 37 acoustic surveys (1999-2003) collected by the Ocean Researcher Ⅱ using Simrad EK500 scientific echosounder to establish a method to monitor total standing stock variation in the coastal waters of northern Taiwan. All acoustic data of different transects in each survey were aggregated into 2 nm ×2 nm grids, then average volume backscattering strengths (SV) of each grid were calculated to estimate relative density of marine organism. The SV values of the entire surveyed area from April to September were 1.5-12.6 dB higher than those from October to March, and 5.7 dB higher than the 5-year average. These differences suggested that there were strong seasonal variabilities of standing stock in the surveyed area and the SV values of the entire surveyed area were positively correlated with the total catches of coastal fisheries (r=0.8849, p＜0.01). Therefore, the post-processed acoustic data collected by the research vessel can be used as fishery independent indices when there is shortage of fisheries catch data.