Acoustic discrimination between juvenile walleye pollock and pointhead flounder

摘要

When using acoustic methods to investigate fish biomass, it is important to distinguish the target species from other organisms. Previous limitations to acoustic information in surveys meant it was not possible to discriminate juvenile walleye pollock from their predator, pointhead flounder, in Funka Bay, Japan, possibly leading to overestimates in population size. Thus, here, an acoustic method was developed to distinguish the two species based on relative frequency response. This method was used to survey juvenile walleye pollock to evaluate capture potential around Funka Bay, Japan, where pointhead flounder is reportedly its most abundant predator. Volume backscattering strength of pointhead flounder was highest at 200 kHz, while that of juvenile walleye pollock was highest at 38 kHz. Therefore, the relative frequency response at 38 kHz and 200 kHz was successfully used to distinguish between the two species. This method could be more extensively applied to other species in other aquatic environments globally.