Evaluation of an acoustical-optical platform for measuring species specific abundance in a weir trap

Abstract

Data recorded by a bottom mounted survey platform deployed within the opening of a fishing weir were used to calculate absolute abundance estimates for comparison to the weir catch. Species specific abundance estimates were calculated from a combination of sonar and video information recorded by the acoustical-optical platform (AOP). Individual targets were detected in the sonar images using an echo counting technique. Video images were used to provide species identification of acoustic targets within an approximate 10 m range. The number and identification of acoustic targets detected during each deployment was positively correlated with the total catch weights and dominant species in each deployment. The algorithm used to calculate AOP abundance estimates tended to underestimate abundance when more than 50 individuals of the same species were caught and overestimate abundance when less than 50 individuals were caught. Target strength, bearing, and range distributions for individual targets are presented in addition to the species specific percent difference between the AOP estimates and absolute abundances of the weir catch. The agreement between the species specific AOP estimates and absolute abundances of each species indicate that the AOP has the potential to provide data for accurate estimates of multispecies abundance. [Work supported by NOAA.]