Noisy Fish and even Louder Divers: Recording Fish Sounds Underwater, with some Problems and Solutions using Hydrophones, Sonobuoys, Divers, Underwater Video and ROVs.

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Noisy Fish and even Louder Divers: Recording Fish Sounds Underwater, with some Problems and Solutions using Hydrophones, Sonobuoys, Divers, Underwater Video and ROVs.

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Title: Noisy Fish and even Louder Divers: Recording Fish Sounds Underwater, with some Problems and Solutions using Hydrophones, Sonobuoys, Divers, Underwater Video and ROVs.
Author: Luczkovich, JJ; Sprague, MW
Abstract: The sea is a noisy place. Over 400 species of fishes produce species-specific sounds in response to disturbance, during agonistic encounters in defense of territories, and in spawning events. It is desirable to use the sounds produced by fishes in the study of their behavior and ecology and fisheries management; this is called the passive acoustic approach. The first step in the use of passive acoustics is to identify which species of fish makes a particular sound, and under which conditions such sounds are made. In the past, fishes have been recorded in captivity to obtain the "sound-truth" data; this provides an unequivocal and inexpensive result, but it has some problems -e.g., tank echoes, behavioral inhibition in artificial environments, and inability to study large fishes (e.g., marlins that may make sound). An obvious alternative is to use SCUBA diving or ROVS to approach and record fishes in natural environments. But divers and underwater vehicles create their own sound environments that mask or interfere with fish acoustic recording. In addition, determining the location of sound sources in acoustically complex ocean environments can present its own set of problems. We will discuss these problems and how they can be overcome. We will present technologies and approaches that have been used by our Fish Acoustics Research Team to record fishes in situ -hydrophones suspended from vessels, autonomous sonobuoys, underwater video recorded along with sounds using calibrated hydrophones, either diver-deployed or on an ROV. Using these methods, we have been able to identify and record fishes in the drum family (Sciaenidae), cusk-eel family (Ophiididae), and toadfish family (Batrachichoididae) in North Carolina and damselfish (Pomacentridae) and squirrelfish family (Holocentridae) on coral reefs in Belize, among many others. A sonobuoy that recorded on a timer 90 s every hour for 24 h was used successfully to study sound production in multiple locations over time. Sound production in the many of these fishes was greatest after sunset, due to increased activity of these fish and nocturnal matins behavior. Behavioral acoustic avoidance interaction of silver perch (Bairdiella chrysoura) occurred when bottlenose dolphin whistles were recorded in the area or played back experimentally. Misidentifications have occurred in the past and unknown sounds of biological origin have been detected on recordings that do not match any of the captive species recorded, so further work underwater will be required to positively identify such soniferous species. A fish sound catalogue from captive and in situ individuals is being collected for use in the identification of unknown sounds and to monitor the condition of reefs and ocean spawning areas remotely. Rebreather technology can provide an alternative to SCUBA for making in situ recordings.
Description: American Academy of Underwater Sciences (http://www.aaus.org/)
URI: http://archive.rubicon-foundation.org/4751
Date: 2003

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