Hydroacoustic Technology, Inc. Direct Observation of Predation Using Acoustic Tags

Conference: ICES Symposium on Marine Ecosystem Acoustics 25-28 May 2015, Nantes, France
Authors: John Ehrenberg, Bill Allen, Sam Johnston, Scott Hemmings, HTI
Contact: support @ HTIsonar.com
 

ABSTRACT

Presenter: John Ehrenberg, PhD, Hydroacoustic Technology, Inc., Seattle, WA
Bill Allen, HTI Hydroacoustic Technology, Inc, Seattle, WA
Sam Johnston, Hydroacoustic Technology, Inc., Seattle, WA
Scott Hemmings, Hydroacoustic Technology, Inc., Seattle, WA


The application of acoustic tags and three dimensional tracking technology has proven to be a useful technique for studying fish behavior in fresh water and marine environments.  The information collected by tracking tagged fish has been used for evaluating the effectiveness of fish bypass systems at dams and barriers designed to direct migrating fish.  However, in many of these studies, predation of the fish species of interest has a major impact on the results of the study. 

In some case, the fact that predation has occurred can be inferred from the fish 3D tracks.  However, in many cases, it is isn’t possible to infer from the tracks which tag returns are from free swimming fish and which are from predated fish.  This paper describes a new type of acoustic tag that directly detects when the tagged fish has been eaten by a predator.  When the predation event is detected, the signal transmitted by the acoustic tag is modified to indicate that predation has occurred while at the same time still providing specific tag identification and a signal suitable for three dimensional tracking.  Field results for this new predation detection tag are presented.



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