Listening to Fish: Proceedings of the International Workshop on the Applications of Passive Acoustics to Fisheries
By Rodney Rountree1, Cliff Goudey2, and Tony Hawkins3
1School for Marine Science and Technology, UMASS Dartmouth, 706 South Rodney French Blvd, New Bedford, MA 02744
2 Center for Fisheries Engineering Research, MIT Sea Grant College Program, MIT Bldg. NE20-376, 3 Cambridge Center, Cambridge, MA 02139
3 Kincraig, Blairs, Aberdeen, Scotland AB12 5YT
On April 8-10, 2002, MIT Sea Grant hosted an international workshop on the application of passive acoustics in fisheries in Dedham, Massachusetts. The 'hands-on' workshop drew over 40 European and North American experts from fisheries, fish biology, acoustics, signal processing, underwater technology and other related fields. The workshop was divided into 4 sessions and 2 working groups with a total of 29 presentations delivered. The first session entitled: "Passive Listening for fishes what has been done?" reviewed past and current research activities, while the second session "Future developments and applications" examined recommendations for future research and examples where existing programs could be enhanced by passive acoustic technology. The third session "Acoustic technology" reviewed the state of the art and future developments for underwater acoustic and related technologies. A special session included demonstrations of hardware and software. The workshop was capped off by a working group on the biological and ecological aspects of passive acoustic research, moderated by Joe Luczkovich of East Carolina University, and a working group on technology and software issues moderated by David Mann of the University of Southern Florida in St. Petersburg. A web page was constructed to document the findings of the workshop (http://web.mit.edu/seagrant/acoustics/index.html).
The workshop was a great success at bringing together an outstanding group of international researchers to exchange research results, knowledge and ideas related to the application of passive acoustics to fisheries, census of marine life and related issues. The workshop demonstrated the high potential of passive acoustics as a research tool for fisheries and related fields through the presentation of the results of a number of successful research projects. One of the important outcomes of the workshop was the exchange of information about ongoing and past research projects that have successfully used passive acoustics. Previously, many of these scientists had been working in isolation with little interaction with their colleagues working across North America and overseas. The fisheries biologists participating in the workshop also gained valuable insight from exchange of information with scientists with well-established backgrounds in the use of passive acoustics to study marine cetaceans (see Clark, Jarvis and Moretti, herein). Another important result was the exchange of hardware and software technologies among the participants. The workshop has already fostered renewed enthusiasm among the participants for this field of research and has resulted in new domestic and international collaborations. In addition, the workshop brought researchers together with administrators, staff and scientists from several funding agencies and with the media (e.g., NURP, National Geographic, etc.). Finally, extensive discussion of the future research priorities for passive acoustics, and development of both domestic and international collaborations, are expected to go a long way towards promoting the application of passive acoustic technology to fisheries and related fields. Some of the most important research initiatives identified by the workshop participants were: 1) the importance of developing a national database of historic underwater sound archives (see Bradbury and Bloomgarden, herein), 2) the importance of establishing a National/International Reference Library of fish sounds, which would be guided by an international panel of scientists drawn in part from the workshop participants, 3) the importance of establishing an international research and training center for passive acoustics applications to fisheries and marine census (potentially at Grant Gilmores Laboratory at the Kennedy Space Center), and 4) the importance of active promotion of the technology through publications of the workshop proceedings and related articles. Many more specific research needs in biology and technology were addressed and are presented throughout these proceedings.
Fish are difficult to see and study in the ocean. SCUBA techniques can help in shallow waters and a range of active acoustic and optical techniques can assist in deep water, but we are still largely ignorant of the distribution and behavior of the great majority of marine fish. Possibly one of the greatest challenges to researchers attempting to study the behavioral ecology of fishes is that of finding the fish in the first place. Often a scientist must go to great lengths conducting expensive and time consuming biological surveys simply to determine the locations or habitats where a fish can be found, before any attempt to study its biotic and abiotic interactions can be made. After all, you can't study something you can't find. Any tool that can help scientists to locate fish is therefore valuable. Fish too face the problem of assessing their environment, navigating through it, and communicating with others of their kind. A surprisingly large number use sound to overcome the problem of living in a visually opaque medium.
Over 800 species of fishes from 109 families worldwide are known to be vocal, though this is likely to be a great underestimate. Of these, over 150 species are found in the northwest Atlantic (Fish and Mowbray 1970). Amongst the vocal fishes are some of the most abundant and important commercial fish species, including cod, haddock and the drum fishes (sciaenidae).
Passive acoustics offers a unique tool to study these fishes, which often live in dark and turbid waters and are difficult to observe by other means. Passive acoustic techniques can be used to locate concentrations of particular species, especially during their vulnerable spawning stage. This in turn allows spawning habitat to be identified, mapped, and protected. It can allow the numbers of fish to be assessed. And it can be used to gain a better understanding of fish behaviour, including fish migrations. Passive acoustics can also be used to simultaneously monitor sources of noise pollution, and to study the impact of mans activities on marine communities. Anthropogenic sources include noise generated by boating activity, seismic surveys, sonars, fish-finders, depth finders, drilling for oil and gas, and military activities. These all have an unknown but potential important impact on marine fauna. We believe that passive acoustic technologies hold special promise and will become important tools in the coming years. However, it has been largely ignored in the northwest Atlantic in the study of fishes important in the marine food chain. It is also a technique that is amenable to cooperative research with commercial fishermen, who can bring their own knowledge to such studies.
Applications to Fisheries
Sounds travel much farther in water than light and underwater sounds, including fish calls, can often be heard over much greater distances than fish can be seen. Listening to fish can contribute a great deal to our knowledge of their abundance, distribution and behavior. Passive acoustics studies using relatively simple techniques have been successful in locating concentrations of important fish species, opening the way for further, more detailed studies of their behavior, distribution and habitat use. As reflected in the various research programs described within this proceedings, already significant strides have been taken in the application of passive acoustics to fisheries:
Studies described at the workshop have pushed technology to new levels that will allow researchers to expand the frontiers of fisheries science and ocean exploration:
The Future of Passive Acoustics
Although studies described during the workshop reflect the rapid growth of research on passive acoustics applications to fisheries and marine census, there are many areas where technical developments are needed to promote future research:
-back-yard science: Perhaps of equal importance to passive acoustics systems for use in the open ocean is the development of technology to aid in small scale, low budget studies of marine fishes in estuarine and inshore habitats. We feel that passive acoustics have a great potential as a tool to provide basic information on essential fish habitat use patterns, as it becomes more widely used in classrooms and State and Federal sampling programs. Several studies presented at the workshop demonstrate the usefulness of this type of research to fisheries. A good example of this is the discovery, using passive acoustics, that striped cusk-eels are abundant in Massachusetts estuaries, where despite a long history of conventional sampling in the region, the species was thought to be a very rare straggler. Technologies to aid this type of research include:
-application of passive acoustics in a wider range of habitats where fish may aggregate to spawn. For example:
The Benefits of Passive Acoustics
Research presented at this workshop underscores the great strides that have been made in the application of passive acoustics to fisheries and related issues in the last two decades. It is clear from this body of work, that although passive acoustics is currently largely overlooked as a research tool, it is a rapidly "up-and-coming" field of research that holds great promise for the future. It is our hope that publication of this proceeding will stimulate the growth of this field, and will encourage funding agencies to support passive acoustics research.
This workshop and the publication of the proceedings benefited by contributions from many individuals. Grace Lee set up the web page and did much of the text and graphics layout for the proceedings. The staff of the Endicott House and Brooks Center provided outstanding conference facilities and support for the workshop. The workshop and publication of the workshop proceedings received major funding from MIT Sea Grant, the Office of Naval Research, and from the Northeast-Great Lakes Center of the National Undersea Research Program. Travel for some workshop participants was funded in-whole, or in-part by: Connecticut Sea Grant, Florida Sea Grant, Hawaii Sea Grant, Louisiana Sea Grant, North Carolina Sea Grant, the South Carolina Sea Grant Consortium, Texas Sea Grant, and the Woods Hole Sea Grant Programs.