Soniferous fishes in tidal freshwater Tivoli Bay of the Hudson River

Abstract

The purpose of this study was to catalogue types of underwater sounds recorded in the Tivoli Bays National Estuarine Research Reserve (NERR) located on the Hudson River. Although soniferous fishes have been studied in many different parts of the world, very few studies have been conducted in North American freshwater systems. We recorded underwater sounds with an autonomous underwater listening system consisting of a hydrophone, digital sound recorder, and weatherproof housing. In the first year of the study 46 hours of unmanned recordings were collected in mid-summer from two locations within the Tivoli Bays NERR. We identified 17 different sounds of interest. Although the specific identifications of these sounds were unknown, we categorized five sounds as most likely produced by fishes, seven as from an unknown biological source and two from a non-biological (man-made) source. Four sounds could not be identified to any of the categories and were classified as unknown. In the second year we attempted to identify the source of the observed sounds by conducting manned recording sessions and controlled sound auditing of fishes. Fishes were captured from the study sites at times when sounds were being recorded, or had been recorded in the past. These fishes were auditioned as they were caught hook and line, or in the isolation of lift nets or five gallon buckets. We recorded sounds produced by two species of catfish: brown bullhead, Ameiurus nebulosus, and channel catfish, Ictalurus punctatus. I. Punctatus was a new record increasing the total number of sounds to 18, and sounds attributed to fish to 6. Based on these recordings it was determined that A. nebulosus was the source for one of the unknown fish sounds recorded in the first year. This study reveals that unknown underwater sounds are diverse in the Tivoli Bay NERR and strongly suggests that passive acoustics can be an important new tool for the study of the bay's ecology. Future research focused on the identification of these unknown underwater sounds promise to provide scientists with new insights into the ecology of the Tivoli Bay NERR