Acoustic characteristics of Jesogammarus annandalei in Lake Biwa

Abstract

Mass mortality of Jesogammarus annandalei, an amphipod species endemic in Lake Biwa, has been recently observed. J. annandalei is useful in fisheries; therefore, analyzing its occurrence is important for conserving the species and maintaining biodiversity. The acoustic method can be used in monitoring the distribution and abundance of J. annandalei. Therefore, along with measuring total body length (TL), we measured the acoustic factor target strength (TS), density contrast g, and sound speed contrast h necessary for the application of the theoretical model (distorted-wave Born approximation model) of J. annandalei. The results indicated g = 1.0725 and h = 1.003, and the measured TS values agreed well with the estimated ones. The relationships between the average TS and TL at 38, 120, and 200 kHz were TS = 60.4logTL − 165.6; TS = 53.4logTL − 141.4; and TS = 46.5logTL − 129.0, respectively. Overall, this study advances our understanding of the acoustic properties of J. annandalei, potentially aiding in future acoustic monitoring, particularly for identifying the cause of similar mass mortality events.