Foreword to Acoustic Tags and Arrays Section
Matthew G. Mesa
Acoustic tags are small, sound-emitting devices that allow remote monitoring of fish in three dimensions. The tags are useful for collecting simple presence–absence data or can be used for detailed studies of fish behavior at a relatively small spatial scale. The tags, which have no trailing antenna, are effective in many environments, including lakes, streams, estuaries, and oceans. Unlike radio-tags, acoustic tags have a large detection range in water and can be used effectively in deep or marine environments. Acoustic tags, when coupled with sophisticated arrays of hydrophones and receivers or mobile tracking with only a single hydrophone, allow the simultaneous tracking of hundreds of individuals. Modern acoustic telemetry systems offer a long tag battery life (some greater than 3 years), many sizes of tags (down to 0.5 g), and the ability to collect data on fish temperature, depth, and other metrics.
Because of the many advantages acoustic tags may have over radio tags (for example, see http://www.htisonar.com/spec_sheets/ATvsRadioTags_2007.pdf), the use of acoustic telemetry in fisheries studies seems to be gaining in popularity and has perhaps surpassed radio telemetry (see Cooke et al., however, for relevant insight). This has certainly been true in the Columbia River basin, where studies of juvenile salmonid behavior are now dominated by use of the Juvenile Salmon Acoustic Telemetry System (JSATS; see McMichael et al. 2010) and radio telemetry seems to be a thing of the past. The call for papers for the acoustic tags and arrays session requested presentations on technology development, diversification of use, and innovative or unique approaches to using this technique for the study of fish behavior. Included in these proceedings are eight papers from a diverse, international set of authors that clearly achieved the goals of the session. The first paper by Michelle Heupel and Dale Webber provides an overview of trends in acoustic telemetry, including case studies showcasing the diversity of this technology and comments on its use in the future. Following this are two papers on the design and use of acoustic telemetry arrays, one describing a new method for estimating positions of tagged animals using the Synthetic Aperture Positioning System (SYNAPS) vessel-based active tracking method (Nielsen et al.) and another on the effectiveness of a large freshwater-estuarine array of acoustic receivers to describe the movements and behavior of two Australian catadromous fishes (Walsh et al.). The papers by Haugen et al. and Wood et al. present two case studies using acoustic telemetry describing the habitat use and migratory behavior of various fishes and the influence of environmental variables. The section concludes with two “methods” papers—both dealing with aspects of detection probabilities for acoustic telemetry studies (Melnychuk and Hobday and Pincock). We trust that this section will provide the reader with new insights and ideas on the use of acoustic telemetry for behavioral and movement studies of fish in a variety of aquatic environments.