Assessing Fish Behavior Using Acoustic Telemetry Methods

Acoustic telemetry technologies are routinely used to obtain information about fish presence and absence.  This detection information is typically combined into a chronology of time-stamped tag detections to measure fish survival, passage timing and other attributes.  If tag transmissions are uniformly spaced with a high level of precision, these detection time series can also be used to evaluate fish behavior.

Fish behaviors vary from simple to complex and can be interpreted from acoustic tag detection time series.  From single receivers, movement toward or away from the hydrophone can determine fish directionality, observed cessation of tag movement can indicate holding behavior and stationary tags observed for extended periods may be interpreted as mortality or tag defecation following predation.   Arrays of multiple hydrophones can provide precise measures of individual tagged fish movement in two- or three-dimensional space, allowing fine-scale resolution of individual fish behavior relative to environmental attributes and other tagged fish.  This information has been used to infer predation of tagged fish via comparisons of swimming behavior characteristics over time. 

As more and larger fish populations are studied using acoustic telemetry methods, increased information is available to relate species-specific tagged fish behavior to attributes such as predator avoidance, schooling/shoaling, predation, and tag defecation.   Fish behavioral interpretations can be improved when multiple tag detection histories are observed and analyzed in relation to each other.  In this presentation, we document the behaviors of acoustically-tagged fish and discuss methods for classifying and interpreting this information.