Measurements of Volume Reverberation Off the Coasts of Southern California and Northern Mexico

Abstract

Abstract : Measurements were conducted to investigate the geographic and frequency variability of volume reverberation off the coasts of southern California and northern Mexico during the fall. Some locations show a peak in volume reverberation around 2 kHz. This peak is most notable at night and at those locations closest to shore. Northern anchovy are the most probable cause of this peak. There is a general south to north increase in volume reverberation between 1 and 5 kHz. Volume reverberation levels above 5 kHz are higher than at lower frequencies, generally increasing rapidly with frequency between 6 and 10 kHz and then increasing less rapidly between 10 and 20 kHz. At the higher frequencies there is a general south to north decrease in volume reverberation during the day, while at night levels are highest at the more inshore locations. Mesopelagic fish, siphonophores, and possibly, deep sea shrimp are suspected to be the dominant scatterers at the higher frequencies.