Acoustic Deterrence of Harmful 

Marine Mammal-Fishery Interactions: 

Proceedings of a Workshop held in 

Seattle, Washington, 20-22 March 1996 

Randall R. Reeves 

Robert J. Hofman 

Gregory K. Silber 

Dean Wilkinson 

U.S. Department of Commerce 

National Oceanic and Atmospheric Administraf ion 

National Marine Fisheries Service 

NOAA Technical Memorandum NMFS-OI'R-10 

December 1996 
At the request of the National Marine Fisheries Service, the Marine Mammal 

Commission convened an international workshop in Seattle, Washington, to examine 

issues related to the use of accoustilc deterrent devices in fisheries. This workshop 

report was submitted by the Marine: Mammal Commission to the National Marine 

Fisheries Service in partial fulfi1lmc:nt of Purchase Order NA95AANFG0624. 

Suggested citation: 

Reeves, Randall R., Robert J. Hofman, Gregory K. Silber, and Dean Wilkinson 

1996. Acoustic deterrence of harmful marine mammal-fishery interactions: 

proceedings of a workshop held in Seattle, Washington, 20-22 March 1996. U.S. 

Dep. Commer., NOAA Tech. Memo. NMFS-OPR-10,68 p. 
Acoustic Deterrence of Harmful 

Marine Mammal-Fishery Interactions: 

Proceedings of a Workshop held in 

Seattle, Washington, 20-22 March 1996 

Edited by 

Randall R Reeves 

Okapi Wildlife Associates 

27 Chandler Lane 

Hudson, Quebec, JOP MO, Canadis 

Robert J. Hofrnan 

Gregory K. Silber 

Marine Mammal Commission 

4340 East-West Highway, Room 9105 

Bethesda, MD 20814 

Dean Wilkinson 

NMFS Office of Protected Resources 

13 15 East-West Highway 

Silver Spring, MD 20910 

NOAA Technical Memorandum 

NMFS-OPR-10 

December 1996 

U.S. Department of Commerce 

Michael Kantor, Secretary 

National Oceanic and Atmospheric: Administration 

D. James Baker, Under Secretary for Oceans and Atmosphere 

National Marine Fisheries Service 

Rolland A. Schmitten, Assistant Administrator for Fisheries 

1 TABLE OF CONTENTS 

1 1.0 Introduction ............................................. 8 

.......................... 1 2.0 Workshop Organization and Arrangements 9 

~ ............................ 3.0 Workshop Objectives and Procedures 10 

~ ............................................ 4.0 Background 14 

~ .... ............................... 5.0 Working Group Reports ; 16 

~ 5.1 Working Group 1 ...... : Guidelines and Criteria for Decision Making 16 

5.2 Working Group 2: Gulf of' Maine Harbor Porpoises and 

Gillnet Fisheries (Pingers) ............................. 18 

5.3 Working Group 3: Other Species and Other Gillnet 

(Mainly Drift Gillnet) Fishtxies (Pingers) .................... 23 

51.4 Working Group 4: Use of Acoustic Harassment Devices to 

Reduce Predation by Pinnipeds on Salmonids 

and Other Fish Species ............................... 27 

5.5 Working Group 5: Statistical Approaches for Evaluating 

the Effectiveness of Acoustic Deterrents ..................... 33 

~ ...... 5i.6 Working Group 6: Basic Etesearch. Engineering. and Education 37 

5.7 Working Group 7: Other Possible Uses of Sound for Marine 

Mammal Conservation ............................... 49 

....................... 1 6.0 Principal Workshop Findings and Conclusions 50 

~ References ............................................... 54 

Appendix 1: Glossary of Terms ................................... 56 

...................... 1 Appendix 2: Common and Scientific Species Names 58 

~ Appendix 3: Participants ....................................... 59 

~ Appendix 4: List of Background Documents Provided to Participants ............ 66 

~ Appendix 5: Agenda ......................................... 68 
EXECUTIVE SUMMARY 

A workshop was held in Seattle, Washington, 20-22 March 1996, to consider problems and 

uncertainties related to the use of acoustic deterrents in the conservation and management of 

marine mammals. Acoustic deterrent devices have been used to help solve two distinct types 

of fishery-marine mammal conflict: (1) bycatch of marine mammals in fishing gear, and (2) 

depredation by marine mammals on fish caught in fishing gear, confined in aquaculture 

enclosureis, or aggregated or constrained at "choke points" in river systems. Acoustic alarms 

(mainly small, low-intensity sound-generators called "pingers") have been developed for 

"alerting" marine mammals to the presence of fishing gear, with the goal of reducing bycatch 

rates. High-intensity acoustic "harassment"' devices (AHDs) have been used widely to reduce 

depredation on fish, especially by pinnipeds. 

The workshop's main objectives were to: (a) evaluate experimental and other evidence 

concerning the efficacy of acoustic deterrents in preventing or reducing interactions between 

marine mammals and fisheries, including aquaculture operation; @) identify critical 

uncertainties about the effectiveness of acoustic deterrent devices and their effects on marine 

mammals and other biota; (c) identify and establish priorities for relevant research; and (d) 

develop guidelines for when, how, and under what conditions acoustic deterrents should be 

incorporated into management. Workshop participants included representatives of the fishing 

industry, environmental groups, and manufacturers of acoustic deterrent devices, staff 

members from government agencies in the United States, Canada, and Australia, and 

scientists from seven countries and 21 institutions. Participants broke into working groups 

with specific terms of reference, and the reports of the working groups are included as part 

of the ovlerall workshop report. 

The resu1,ts of a controlled experiment with pingers in the Gulf of Maine sink gillnet fishery 

in 1994 were the focus of the bycatch disc~ussions. In this experiment, nets with active 

pingers caught significantly fewer harbor porpoises than control nets. It was generally 

agreed that pinger use offers a promising rneans of reducing the bycatch of harbor porpoises 

in this type of fishery. The results of another experiment off Washington and an 

experimental fishery in the Gulf of Maine in 1995 were consistent with those of the 1994 

Gulf of Maine study. There was a strong consensus that pinger use should be incorporated 

immedial.ely into the management regime fbr the Gulf of Maine sink gillnet fishery. It was 

expected that full-scale pinger deployment could achieve a sufficient reduction in the harbor 

porpoise bycatch to meet the requirements of the 1994 amendments to the Marine Mammal 

Protection Act (MMPA). However, higher than anticipated numbers of harbor porpoises 

were caught in experimental fisheries in Massachusetts Bay and on Jeffreys Ledge in spring 

1996, following the workshop. Thus, the expectation may not be valid. If pingers are not 

efficacioius, the only other apparent means of meeting the requirements would involve largescale, tinne-area fishery closures in the Gulf of Maine. 

Although pingers are already being used extensively by fishermen outside the Gulf of Maine 

on an ad' hoc basis, there is much uncertainty about their long-term efficacy and about their 

efficacy in fisheries that involve marine mammal species other than the harbor porpoise. 
Participants strongly urged against regarding the pinger as a panacea for reducing bycatch. 

They poilnted out that, in the Gulf of California (Mexico) where the critically endangered 

vaquita is threatened by fishery bycatch, the introduction of pingers as a substitute for fishery 

closures would be ill-advised (and possibly disastrous). For the present, the only situations 

where pingers can reasonably be expected to significantly reduce bycatch are fixed gillnet 

fisheries in which the harbor porpoise is the main species of concern. 

It is uncertain how long-lasting the efficacy of pingers will prove to be in a given fishery. 

Will the target animals (e.g., harbor porpoises) become less responsive to the alarm effect of 

the pingers over time? It also is uncertain how pingers may affect non-target species. While 

the potential benefits of a pinger program seem fairly clear -- reduced harbor porpoise 

mortality,, continuation of the fishery -- the environmental costs are less clear. Until the 

uncertainties are resolved, both the bycatch and the status of the affected marine mammal 

populations should be closely monitored. 

The workshop concluded that this is an appropriate time for carefully designed pinger 

experimeints in the drift gillnet fisheries for swordfish and other pelagic species off California 

and New England. These fisheries differ i~n many ways from sink gillnet fisheries and 

involve bycatch of a greater variety of marine mammal species (including some that are 

endangered or threatened). The experimental design should include: use of the currently 

standard lpinger, placed and deployed according to the particular conditions in these fisheries; 

randomization of active and dummy pingers between sets from the same vessel; power 

analysis, in advance, to determine necessary sample sizes and observer coverage; and singleblind controls, with only the on-board observers knowing whether the pingers on a given set 

are active or not. 

The workshop also concluded that pinger experiments in coastal gillnet fisheries along the . 

U.S. east coast south of the Gulf of Maine would be premature at present. Substantially 

more information is needed about fishery characteristics and bycatch before scientifically 

rigorous experiments can be designed. 

The use of acoustic devices to reduce baleen whale mortality in fishing gear (particularly 

humpback whales in Newfoundland cod traps) was not discussed in detail. Available 

information indicates that entanglement and mortality have been substantially reduced due to 

a combination of factors, including the rout.ine use of acoustic devices by fishermen. The 

workshop concluded that there were no critical uncertainties requiring priority attention in 

this regard. 

Depredation Issues 

Although the MMPA originally allowed fislhermen and fish farmers to use lethal force against 

predators to protect their catch, gear, and stock, they are no longer allowed to do so under 

the 1994 amendments to the Act. Thus, the pressure to develop non-lethal deterrent methods 

has increased. As wild fish stocks decline, and aquaculture enterprises and pinniped 

populations increase, the conflicts are bound to become more numerous and more intense. 
Since the early 1980s, AHDs have been used throughout the aquaculture industry in North 

America l;o combat depredation by otariids (California and Steller sea lions, west coast only) 

and phocids (harbor seals, both coasts; gray seals, east coast only). They have also been 

used in some fisheries to keep pinnipeds away from caught fish and from natural or artificial 

aggregations of fish. Workshop discussion centered on two aspects of the use of AHDs: (1) 

whether it achieves the desired result, and (2) the degree to which it may negatively affect 

marine mammals, including ones that are not involved in the depredation, and other biota. 

AHDs used during the 1980s and early 1990s typically had the desired effect of keeping 

pinnipeds away from the protected sites, but only for a relatively short time. After several 

weeks of effective deterrence, the pinnipeds would become less responsive to the AHDs. In 

fact, the iicoustic signal of an AHD often was interpreted as having a "dinner bell" effect, 

alerting predators to the presence of a fish pen, trap, or net. It then became necessary to 

alter the signal (which usually meant increasing the output), move the transducers, or resort 

to other means of deterrence., including shooting the animals. New, very high-intensity 

AHDs (e.g., a device now being marketed by Airmar Technology Corporation transmits a 

signal of 10 kHz at an average output of 194 dB re lpPa at 1 m) are reported to have 

remained effective for at least two years. (Reference to brand names or companies is not 

intended ito be a product endorsement.) 

Pinnipeds; are difficult to deter by acoustic means. They tend to accommodate reasonably 

quickly to loud noise, which may be explained either by threshold shifts in hearing or by 

"habituation," perhaps both. The new high-intensity AHDs have greater potential for causing 

hearing damage and for affecting non-target species. They therefore should be used 

cautiously until their effectiveness and potential side-effects are determined. 

A problem involving depredation by killer whales on longline catches of sablefish (black cod) 

in Prince William Sound and the Bering Sea was also discussed briefly. It was suggested 

that changes in fishery practices and gear modifications were more likely than the use of 

AHDs to resolve this conflict. 

General Issues 

Workshop participants concluded that there: was reasonable evidence that pingers significantly 

reduce the bycatch of harbor porpoises in gillnets and that AHDs, when properly deployed 

and of sufficient power output at appropriate frequencies, may be effective in reducing levels 

of pinniped depredation on fish. Also, it was recognized that pingers, possibly in 

combination with acoustic reflectors of some kind, may prove useful in reducing bycatch of 

other marine mammal species in other types of fisheries. Participants repeatedly emphasized, 

however, that artificial sound should be introduced into the underwater environment only 

when the costs and benefits of doing so are clearly understood and only after the potential 

ecological consequences have been carefully considered. The state of knowledge about 

marine nlammal hearing abilities and behavior in response to various types of sound is 

limited. It is therefore extremely difficult to evaluate either the long-term effectiveness or 

the side-effects of any acoustic deterrent device. Much more research and monitoring is 

required before such evaluations can be made with a high degree of confidence. A number 

of suggestions were made regarding the potential future use of acoustic deterrent devices. 
To meet the intent and provisions of the MMPA, without at the same time causing severe 

economic: distress in fishing communities, approaches to management should be both 

inclusive and adaptive. Much of the responsibility for developing and implementing 

solutions to the problems of marine mammal-fishery interactions resides with the fishing and 

aquacultu~re industries themselves. Thus, fishermen and fish farmers need to be included in 

the planning and conduct of research, the interpretation of results of field experiments, and 

the development of management measures. Moreover, management regimes need to be 

adaptive in nature. In other words, regulatory measures need to be updated routinely to 

incorpora,te new knowledge and new technologies. Long-term monitoring is an essential 

element of adaptive management. Innovation should be supported and encouraged, and 

rigorous testing should be required before new technologies are deployed as part of fishery 

and marine mammal management programs. 

INTRODUCTION 

1.0 Bycatch of marine mammals in fishing gear occurs throughout the world (Northridge 

1984; Pe~rrin et al. 1994). In some instances, bycatch of marine mammals in fisheries is 

causing or contributing to population declines and preventing the recovery of depleted stocks. 

1.1 Much public attention has focused on the bycatch of dolphins in tuna purse seines, 

humpbaclc whales in cod traps, and various species in set and drift gillnets. Many other 

kinds of fishing gear and methods also have marine mammal bycatch. 

1.2 Oftein, marine mammals may be caught purely by accident because their swimming path 

intersects a net or trap in the water. In such cases, bycatch might be avoided if the marine 

mammals could be made aware of the gear's presence. Marine mammals are also sometimes 

attracted ito fishing gear because of opportunities to remove bait or caught fish from it. They 

may have learned to associate fishing vessels or gear with food. In these cases, bycatch 

might be prevented by changing the acoustic signals produced by the gear and fishing 

operations, by fishing when marine mammals are not present in the area, or by deterring 

them, sonnehow, from approaching the gar. 

1.3 Another concern, quite apart from the effects of bycatch on marine mammal 

populations, is how to protect valued fishery and aquaculture resources from the depredations 

by marine mammals. Pinnipeds, in particular, frequently remove caught fish from nets, 

hooks, or traps and attack fish that are being raised in pens. The damage often extends to 

gear as well (e.g., torn nets and lines). Some pinnipeds converge on areas where 

anadromous fish stocks aggregate or where the movements of fish are naturally or artificially 

constrained (e.g., below falls or fish ladders). In such situations, the pinnipeds' competitive 

interactions with fishery operations and their impacts on recovery, enhancement, or 

restocking efforts are highly visible. In some areas and circumstances, odontocete cetaceans 

remove bait or catch from fishing gear. 

1.4 Because many marine mammals use solund to communicate, sense their surroundings, 

and locate: and capture prey, scientists and fishermen have sought to develop acoustic 

methods to prevent or reduce harmful marine mammal-fishery interactions. The main 
approaches have involved (a) broadcasts of killer whale vocalizations; @) alteration of the 

acoustic reflectivity of gear to make it more detectable by marine mammals; (c) attachment 

of mechanical or electronic noise-makers to gear so that marine mammals will be alerted to 

its presence; and (d) placement of high-energy sound sources on or near fishing gear and 

aquaculture facilities to cause approaching marine mammals to experience pain or discomfort 

(Jefferson and Curry 1994). Unfortunately, none of the studies to date has provided 

unequivocal evidence that a particular sound generator or reflector will both (a) prevent or 

significan,tly reduce incidental takes of marine mammals in commercial fisheries and @) have 

no associ;ated adverse effects on fish catches, the "targeted" marine mammals, or othcr biota. 

Likewise,, studies using natural sounds and high-energy sound generators have failed to 

produce llnequivocal evidence that they both (a) prevent or significantly reduce marine 

mammal depredation on caught or penned fish and @) have no associated adverse effects on 

fish catchies, penned fish, the "targeted" marine mammals, or other biota. 

1.5 In the United States, the National Marine Fisheries Service (NMFS) has lead-agency 

responsibility for assessing and, when necessary, preventing or mitigating the adverse effects 

of marine: mammal-fishery interactions. Since the early 1990s, the NMFS has received 

requests f om scientists, fishermen, and fishery groups for financial support and authorization 

to test or use acoustic deterrent devices to prevent or reduce the adverse effects of 

interactions. The NMFS has had difficulty responding to these requests, in part because of 

uncertainties about the design and results of previous studies and in part because not enough 

is known about the behavior and hearing abilities of the marine mammals. Therefore, in 

1995 the NMFS asked the Marine Mammal Commission (MMC) to organize and convene a 

workshop on acoustic deterrence. The information gathered at the workshop was to be used 

in the development of a national policy on the use of acoustic deterrents. It was also 

expected that the workshop would identify actions necessary to resolve critical uncertainties 

about the effectiveness of various devices and about their effects on target and non-target 

species. 

1.6 Although the conveners and participarlts were well aware of the geographically broad 

relevance: of the issues, the focus of the workshop was on problems in the United States. 

Thus, this report, while it will be of interest to many individuals and agencies, is aimed 

primarily at people within the NMFS who have responsibilities for implementing the Marine 

Mammal Protection Act and the Endangered Species Act. A sense of urgency has arisen 

from the 1994 amendment to the MMPA requiring that, for "strategic stocks" (see Appendix 

I), fishe~y-caused mortality be reduced to less than the calculated potential biological 

removal level (PBR level; see Appendix 1). 

1.7 The discussions at the workshop highlighted the need to define terminology as 

unambiguously as possible. A glossary of terms is provided as Appendix 1 of this report. 

Scientific: names of species mentioned in the report are given in Appendix 2. 

WORKSHOP ORGANIZATION AND ARRANGEMENTS 

2.0 The workshop was held on 20-22 March 1996 at the Battelle Conference Center in 

Seattle, Washington. It was organized and chaired by R.J. Hofman and G.K. Silber of the 
MMC anti D. Wilkinson of the NMFS's Office of Protected Resources. Participants, listed in 

Appendix 3, included representatives of the fishing industry, environmental community, and 

manufact~~rers of acoustic deterrent devices, scientists with relevant expertise from seven 

countries and 21 academic and private institutions, and staff members of governmental 

agencies in the United States, Canada, and Australia. R.R. Reeves of Okapi Wildlife 

Associaters, Hudson, Quebec, was contracted by the Commission to edit and draft portions of 

the workshop report. Funding for the workshop was provided by the NMFS. 

2.1 Background documents sent to participants before the workshop are listed in Appendix 

4. The workshop agenda is provided as Appendix 5. 

WORKSHOP OBJECTIVES AND PROCEDURES 

3.0 The objectives of the workshop were to: 

1. evaluate the design and results of (a) studies done to determine the 

efficacy of acoustic deterrents in reducing interactions between marine 

mammals and fishery or aquaculture operations; and (b) studies of how 

marine mammals respond to, and are affected by, different types and 

levels of sound; 

2. identify critical uncertainties about the effectiveness and effects of 

acoustic deterrents; 

3. describe research and monitoring programs needed to resolve the 

uncertainties, and estimate the time, funding, special equipment, and 

logistic support required; 

4. rank the identified research and monitoring programs according to the 

likelihood that they would contribute to the development of effective, 

non-harmful ways of mitigating marine mammal-fishery interactions; 

and 

5. use available knowledge to suggest when, how, and under what 

conditions acoustic deterrents should be incorporated into marine 

mammal, fishery or aquaculture management regimes. 

3.1 To help meet objectives 1 and 2, the MMC contracted with experts to prepare and 

present ba.ckground papers on particular subjects. These were: 

1. an overview of hypotheses concerning the causes of, and possible 

means for preventing or reducing, harmful marine mammal-fishery 

interactions -- Thomas A. Jefferson, Ocean Park Conservation 

Foundation, Aberdeen, Hong Kong; 
2., an overview of what is known about the hearing capabilities of small 

cetaceans and how these animals use and respond to different types of 

sound -- Whitlow W.L. Au and Paul E. Nachtigall, Hawaii Institute of 

Marine Biology, University of Hawaii; 

3, an overview of what is known about the hearing capabilities of 

pinnipeds and how these animals use and respond to different types of 

sound -- Ronald J. Schusterman, Long Marine Laboratory, University 

of California, Santa Cruz, California; 

4 ,. a review of research done to assess the possible use of sound reflectors 

and generators to prevent or reduce entanglement of large cetaceans in 

fishing gear -- Jon Lien, Whale Research Group, Memorial University 

of Newfoundland, St. John's, Newfoundland; 

5. a review of research done to assess the possible use of sound reflectors 

and generators to prevent or reduce entanglement of small cetaceans in 

fishing gear -- Stephen Dawson, University of Otago, Dunedin, New 

Zealand; 

6. a review of research done to assess the possible use of sound to prevent 

or reduce pinniped depredation on caught fish, fish returning to 

hatcheries or spawning grounds, and fish being raised in aquaculture 

facilities -- Peter D. Shaughnessy, CSIRO Division of Wildlife and 

Ecology, Canberra, Australia; 

7. a review of efforts by fishermen and researchers to use sound to 

prevent or reduce depredation by killer whales and other cetaceans on 

fish caught on longlines -- Craig 0. Matkin, North Gulf Oceanic 

Society, Homer, Alaska; and 

8. a review of available information concerning the possible effects of 

acoustic deterrents on marine mammals and other biota -- Bernd 

Wiirsig, Texas A&M University, Galveston, Texas. (Wursig was 

unable to attend the workshop. His paper was presented by William A. 

Watkins.) 

3.2 Two background papers, in addition to those prepared under contract to the MMC, were 

presented by other workshop participants. They were: 

1. an overview of marine mammals and fisheries involved in adverse 

interactions in the United States and elsewhere -- Michael Payne, 

Office of Protected Resources, National Marine Fisheries Service, 

Silver Spring, Maryland; and 

2. an overview of what is kno,wn about the hearing capabilities of large 

cetaceans and how these aniimals use and respond to different types of 
sound -- William A. Watkins, Woods Hole Oceanographic Institution, 

Woods Hole, Massachusetts. 

3.3 Spec:ific individuals had been asked, before the workshop, to comment on the 

presentations (commenters are identified in the workshop agenda -- Appendix 5). These 

experts made their comments immediately following the respective presentations during the 

first day (of the workshop. In most cases, an outline or the written text of the presentation 

had been provided, in advance, to the invited commenters. 

3.4 To help meet workshop objectives 2 and 3 (see 3 .O, above), D.P. DeMaster of the 

National Marine Mammal Laboratory led a facilitated discussion during the second morning. 

Participants initially identified a broad range of issues and uncertainties, which were then 

grouped under seven general headings. These headings were: 

1. guidelines or criteria for deciding when and under what conditions 

acoustic deterrents should be incorporated into fishery and aquaculture 

management regimes; 

2. evaluating whether the use of low-intensity sound generators (pingers) 

was likely to remain effective in reducing the bycatch of harbor 

porpoises in sink gillnet fisheries, without having unacceptable adverse 

effects on fish catches or other biota; 

3. evaluating whether pingers would be effective in reducing bycatch of 

marine mammals in other fisheries, without having unacceptable 

adverse effects on fish catches or other biota; 

4. assessing the long-term effectiveness, and possible undesirable sideeffects, of AHDs used to keep pinnipeds away from aquaculture 

facilities, hatcheries, and areas where valuable fishery resources are 

concentrated; 

5. aspects of experimental design and analysis required to produce 

statistically meaningful results from field tests of acoustic deterrent 

devices; 

6. basic research, engineering, and educational programs needed to 

resolve critical uncertainties. This was understood to include not just 

more science and technology, but also the development of ways to 

ensure that fishermen and operators of aquaculture facilities are well 

informed about and involved in seeking solutions to problems caused by 

interactions; and 

7. other marine mammal conservation problems, not directly related to 

fisheries or aquaculture, that might be addressed using acoustic 

methods. 
3.5 These seven subject areas were referred to small working groups for in-depth 

discussion. The groups were asked to (a) identify and agree on critical uncertainties, @) 

describe the kinds of research needed to resolve them, and (c) determine the general 

circumstances when acoustic devices should or should not be incorporated into management 

regimes. Each group's report was expected to include: 

1. a brief characterization of the problem, e.g., the fisheries or 

aquaculture operations involved, the nature of the interactions with 

marine mammals, and the relevant uncertainties; 

2. a statement of the objectives of the project or task; 

3. an explanation of the rationale for any engineering work, field trials, 

etc. needed to attain the objectives most cost-effectively. If relevant, 

this explanation was to include required sample sizes and methods for 

collecting and analyzing the data; 

4. estimates and justifications for the required time, costs, special 

equipment, and logistic support; 

5. an illustrative list of the fisheries or aquaculture operations that could 

benefit from, or be involved in, the work; and 

6. criteria for judging the success of a particular project or task and for 

applying the results to management programs. 

3.6 The working groups met during the afternoon and evening of the second day of the 

workshopl. The above terms of reference were followed to differing degrees by the groups. 

The working group reports were presented and discussed during the final plenary session on 

the third day. These reports constitute the principal output of the workshop and are 

provided, in edited form, in Section 5, below. 

3.7 In the two months immediately following the workshop, considerable exchange of views 

and information continued by phone, facsimile, and e-mail. Chairmen and rapporteurs of the 

working groups continued to oversee the completion of their reports. A draft of the entire 

workshop report, containing all of the edited working group reports, was circulated to 

participants in late May 1996. Their suggestions and corrections were taken into account in 

the preparation of this final version. 

3.8 No :Formal attempt was made, during or after the workshop, to establish priorities 

among the many tasks identified. Participants viewed that process as primarily an agency 

(NMFS) responsibility. 
BACKGROUND 

Bycatch Ixsues 

4.0 The lsycatch of marine mammals in fisheries is a serious conservation problem. For 

many species and populations, it far exceeds any current threat from deliberate catching or 

killing. Pilthough fishery bycatch was recognized as one of the problems facing marine 

mammals when the MMPA was enacted in 1972, it was not until the 1988 amendments to 

the Act that it became a principal focus of management efforts within the NMFS. By the 

late 1980sl, bycatch in fisheries had also come to be recognized as a major problem at the 

international level. For example, a Workshop on Mortality of Cetaceans in Passive Fishing 

Nets and 'Traps, co-sponsored by the International Whaling Commission, the NMFS, and the 

MMC, as well as a variety of other agencies, was held at the Southwest Fisheries Science 

Center in La Jolla, California, in October 1990. That workshop galvanized interest in the 

bycatch issue and resulted in compilation of fishery and bycatch data from around the world 

(Pemn et al. 1994). 

4.1 The IHMPA amendments of 1994 infused efforts to find a solution to the bycatch 

problem i~n U.S. waters with a sense of urgency. Although bycatch of several stocks is 

estimated to exceed PBR levels, the most dramatic disparity between bycatch and PBR in the 

U.S. occurs in the case of the harbor porpoise population in the Gulf of Maine (Barlow et al. 

1995: their Table 1). The annual bycatch has been on the order of 2000 while the estimated 

PBR level is about 400 (Blaylock et al. 1995). This means that the annual bycatch from this 

stock must be reduced by about 80% to achieve the take reduction required by the MMPA. 

Achievement of the MMPA's immediate take-reduction goals for some other stocks (e.g., 

bottlenose dolphins, pilot whales, and beaked whales) will also require management 

measures. Clearly, if fishery closures are to be avoided, another means of reducing bycatch 

of harbor porpoises and several other species will be necessary. 

4.2 Until 1994, the use of sound to reduce the incidental mortality of small cetaceans in 

gillnet fisheries had met with scientific skepticism; most field trials had been flawed or 

inconclusive (for a recent review, see Jefferson and Curry 1994). However, controlled 

experimenis in the Gulf of Maine sink gillnet fishery in autumn 1994 (Kraus et al. 1995) and 

the northern Washington coastal set-net fishery for chinook salmon in summer 1995 (Gearin 

et al. 1996) showed significant reductions in the bycatch of harbor porpoises in nets equipped 

with active pingers. In November-December 1995, the New Hampshire Gillnet Fishermen's 

Association, in cooperation with the NMFS, conducted an experimental fishery in which 

pinger usalge was integrated into standard commercial gillnetting operations. No bycatch of 

harbor po;rpoises was recorded. The probability of catching zero porpoises on observed trips 

(48% of tlhe total) by chance, given the level of effort and the data from previous years, was 

statistical1:y negligible (P < .01) (Potter 1996)'. These results provided a basis for workshop 

discussions concerning the effectiveness and side-effects of pingers, the desirability of 

'The results of further experimental fisheries conducted in spring 1996, following the 

workshop,, were not as encouraging. Catch rates in nets with pingers attached were similar 

to historic rates when pingers were not being used (Potter, personal communication). 
incorpora1:ing their use into gillnet fisheries in other areas, and the need for additional 

research and experimentation. 

Depredation Issues 

4.3 Fishermen have traditionally found their own ways of coping with competitors and copredators, often shooting marine mammals observed near fishing operations. The recent 

proliferation of aquaculture has coincided, at least in much of North America, with growth of 

some pinriiped populations brouglit abuut by legislative and rcgulatory changes intended to 

promote the recovery, rather than continued "control," of depleted marine mammal 

populations. Recent collapses in wild commercial fish stocks, especially salmonid runs in 

western North American rivers, have greatly intensified the conflict between marine 

mammals and fishing interests, even though the collapses were caused by overfishing or 

habitat loss rather than by marine mammal depredations. 

4.4 The MMPA Amendments of 1994 expressly prohibit the "intentional lethal take of any 

marine mammal in the course of commercial fishing operations." The amendments authorize 

fishermen and fish farmers to deter marine mammals from damaging their gear, catch, and 

cultured fish so long as the measures used do not result in the death or injury of marine 

mammals (MMPA $101(a)(4)). The amendments direct the NMFS and the Fish and Wildlife 

Service (FWS) to develop guidelines for safely deterring marine mammals and, for species 

listed as endangered or threatened under the Endangered Species Act, to recommend specific 

measures that may be used to non-lethally deter marine mammals. The Services may 

prohibit, after notice and opportunity for public comment, any forms of deterrence that have 

significant adverse effects on marine mammals2. 

4.5 No experimental data, comparable to those mentioned above regarding pinger use with 

gillnets, are available to evaluate the efficacy of AHDs in deterring pinnipeds. AHDs have 

been used in aquaculture operations since the early 1980s. Until recently, effectiveness was 

generally short-term. In most instances, the pinnipeds eventually became less responsive, 

due either to "habituation" or to changes in their hearing sensitivity, and the depredation 

resumed. In some cases, depredation may have increased because animals learned to 

associate the sound with a readily available source of food. 

4.6 Recent advances in underwater acoustic technology have led to development of AHDs 

that transmit very high-amplitude signals at frequencies thought to be well within the range 

of pinniped hearing. Manufacturers have reported good results for two to three years, with 

no signs of "habituation" or declining effectiveness. The newer-generation AHDs are 

presumed to cause pain at short ranges and appear to be effective deterrents against 

depredation by pinnipeds. 

21n May 1995 the NMFS published for comment a proposed rule setting forth guidelines 

and prohibitions regarding the use of deterrents. At the time of the workshop, the FWS had 

taken no action and the NMFS had not yet published a final rule. 
4.7 There is a need for definitive experimental evidence that they perform their intended 

deterrent function, and do not have unacceptable effects on non-target marine mammals and 

other biota. With regard to the second point, a study in British Columbia showed a possible 

avoidance response by harbor porpoises. The abundance of porpoises within a radius of 3.5 

km (1.9 nautical miles) of an AHD was significantly lower during experimental periods 

(AHD activated) than during control periods (AHD deactivated) (Olesiuk et al. 1995). Thus, 

AHDs may have a biologically significant impact on harbor porpoises and other marine 

biota, which are not intended targets. Since many, if not all, of the signals from AHDs are 

probably within the hearing sensitivity ranges of large whales, the potential impact on these 

species also needs to be investigated. Although no impacts on the behavior, hearing, or 

physiology of fish and marine birds have been demonstrated, neither have appropriate studies 

been conducted to verify that the new high-intensity AHD systems do not have such impacts. 

WORKING GROUP REPORTS 

5.0 The working group reports reflect the combined insights and opinions of a group of 

experts. The group chairmen sought to achieve consensus and to address their respective 

topics in a balanced and comprehensive manner. All reports were nearly complete by the 

end of the workshop, although in some cases substantial dialogue among members and 

redrafting of the reports took place in the weeks after the workshop. The formats of the 

reports arc: not entirely consistent, and a certain amount of redundancy was unavoidable. 

5.1 Working Group 1 : Guidelines and Criteria for Decision Making 

Bxlow, Bowles, Dawson, Hofman (Chair), Kraus, Read, Reeves, Wilkinson, 

Williamson, Young 

To help structure discussion, the chairman prepared a list of possible guidelines and 

criteria, biised on the workshop presentations and discussions. This list was presented and 

discussed briefly during the plenary session on the second day of the workshop. The 

working group then met to review and revise the list to reflect the discussion. 

Thr: working group concluded, and the plenary concurred, that the following general 

guidelines and criteria should be used to help decide when, and under what conditions, active 

acoustic devices should be tested and used for management purposes. These guidelines and 

criteria art: tailored for use in the United States (e.g., the categories of fisheries and the 

terms "environmental assessment" and "environmental impact statement" are derived from, 

and have precise meanings within, U.S. law), but they should be helpful to managers and 

administrators in other countries as well. 
1. Anthropogenic sounds should be introduced into the ocean only when such 

introduction is necessary to accomplish a beneficial or potentially beneficial 

purpose, and when it is clear that such a purpose cannot be accomplished in a 

less intrusive waf. 

2. Acoustic devices should not be used for management purposes unless there is 

good reason to believe (e.g., there are significant empirical data showing) that 

their use will contribute significantly to solving the problem of concern. Such 

use should also be contingent on reasonable evidence demonstrating that there 

will be no unacceptable side-effects -- e.g., the safety of fishermen or others 

will not be jeopardized, the target or other species will not be harmed, and a 

significant decline in the fish catch will not result. 

3. Some form of licensing or prior authorization should be required for 

operational (as opposed to experimental) use of high-output devices that 

reasonably might be expected to harm target or other species -- e.g., cause 

temporary or permanent hearing damage. 

4. The registration forms used by U.S. fishermen participating in Category I and 

Category I1 fisheries should request information on the numbers and types of 

acoustic devices (e.g., pingers) used in the preceding year and expected to be 

used in the coming year. 

5. In some instances, experimental or other data may provide good reasons for 

suspecting that a particular device or acoustic system would solve or contribute 

to solving a problem, yet substantial questions will remain concerning longterm efficacy and possible harmful side-effects. In these circumstances, use of 

the device or system for management purposes should be conditional on the 

implementation of an appropriate monitoring program. The monitoring 

program should be sufficient to verify that the device or system works as 

expected and has no unacceptable side-effects. 

6. Obtaining authorization to test an acoustic device or system that reasonably 

might be expected to ameliorate a marine mammal-fishery conflict should be 

made as simple as possible, especially if the device or system is unlikely to 

have unacceptable side-effects. 

7.. Tests should not be haphazard or unstructured. They should be designed and 

carried out to optimize the likelihood of producing meaningful results in the 

shortest possible time and at the least possible cost. 

'~urin~ discussion of this point, it was noted that a general policy on the introduction of 

sound into the marine environment from all anthropogenic sources is needed. Although all 

participants shared this view, it was recognized that the workshop was not the appropriate 

forum for developing such a policy. 
8. Whenever a proposed experiment or management program could have adverse 

environmental impacts, an environmental impact assessment should be done 

before any resources are allocated to the project. If the assessment indicates 

that significant adverse impacts are possible, an environmental impact 

statement should be done in accordance with applicable state and Federal law. 

9. Impact assessments should be done by the responsible regulatory authority. 

The organization, industry, or individual desiring to test or employ a particular 

device or system should provide, or pay the cost of obtaining, the data and 

information needed for the assessment. They also should conduct or pay the 

cost of monitoring necessary to verify that the device or system works as 

expected and has no unacceptable side-effects. 

10. Resource users, public interest groups, and industries that could be affected by 

policies and regulations regarding the use of acoustic devices and systems 

should be involved in identifying and evaluating the relative advantages and 

disadvantages of alternative actions. 

5.2 Working Group 2: Gulf of Maine Harbor Porpoises and Gillnet Fisheries (Pingers) 

Payne (Chair), Potter, Read, Reeves, Silber (Rapporteur), Swartz, Williamson 

This group focused on the most critical marine mammal bycatch problem in U.S. 

waters: mortality of harbor porpoises in the Gulf of Maine sink gillnet fishery. 

I. Description of the Problem 

The harbor porpoise bycatch in the Gulf of Maine sink gillnet fishery exceeds the 

level considered sustainable by the population. Management measures taken to date, 

including time and area closures, while reducing the bycatch, have not reduced it to the 

calculated PBR level. Moreover, they have been difficult to implement. 

Section 118 of the 1994 amendments to the MMPA requires that the bycatch be 

reduced tco below the PBR level prior to 1 April 1997. Thus, if the fishery is to continue in 

its present form, the bycatch will need to be reduced by 70-80%, i.e., from approximately 

2000 porpoises per year to approximately 400 per year by 1 April 1997. 

11. Uncertainties 

The core of any plan to reduce bycatch in the Gulf of Maine will be based, at least in 

part, on the significant results of the 1994 New Hampshire pinger experiment. This 

experiment demonstrated that the pingers could be effective in achieving the desired bycatch 

reduction in the sink gillnet fishery. Nevertheless, uncertainties remain about their continued 

effectiveness in this fishery through time, and about their potential effectiveness in fisheries 

that catch other species. The uncertainties are as follows. 
1. Although it is clear that the pingers significantly reduced the harbor porpoise 

bycatch in the experiment, it is not clear why they worked. For example, it is 

not clear whether porpoises were alerted or repelled by the sounds made by 

pingers; their prey responded by moving away from the sounds and the 

porpoises followed; or other factors were involved. In addition, it is not clear 

what characteristics of the sound were responsible for the observed results. 

Despite these uncertainties, there is no doubt that something about the pingers 

rather than, for example, a natural change in porpoise distribution or behavior, 

caused the observed reduction in bycatch. The fact that porpoises were taken 

in the control nets at the historic, or expected, rate indicates that substantial 

numbers were present in the area at the time of the experiment. 

It is not clear if, and to what extent, the results of the 1994 New Hampshire 

experiment can be extrapolated to other fisheries and bycaught species. 

Because of the many variables (e.g., how gear is fished, how the marine 

mammals of concern are distributed spatially and temporally, environmental 

factors), it would be unwise to assume that identical, or even similar, results 

can be achieved in other situations. Therefore, full-scale operational use of 

pingers should not be extended to other fisheries and bycaught species without 

prior testing. If pingers are used in other fisheries, well-designed test studies 

and monitoring programs should accompany the use so that the effects and 

efficacy of the pingers can be evaluated. In this regard, it is noteworthy that 

the experimental use of pingers resulted in a significant reduction in the harbor 

porpoise bycatch in the northern Washington coastal set-net fishery in 1995 

(Gearin et al. 1996; see footnote 1). 

3. Gillnet gear is fished differently, depending on the target species and other 

factors. Even within the "Gulf of Maine sink gillnet fishery," various gear 

types and techniques are used. Pingers may not have the same effects when 

used on all types of gillnet gear and with all techniques of gillnet deployment. 

Although baseline porpoise bycatch rates are known to vary among the 

different components of the Gulf of Maine fishery, a full analysis of this 

variability has not been done. The results of such an analysis might be 

usefully incorporated into any strategy for expanding the use of pingers in the 

Gulf of Maine fishery. The same type of uncertainty is likely in other gillnet 

fisheries as well. 

4. The catch of 25 porpoises in the control nets in the 1994 experiment suggests 

clearly that the animals were in the area and either were avoiding or for other 

reasons were not being caught in the pinger-ensonified nets. If they were 

avoiding the ensonified nets, it is possible that they will stop doing so or that 

pinger use will displace porpoises from essential foraging areas or other types 

of essential habitat. These possibilities mean that long-term monitoring of the 

bycatch and of porpoise distribution and abundance should accompany any 

widespread use of pingers on fishing gear. 
5. As noted above, the effectiveness of pingers may diminish as porpoises 

become habituated, or desensitized (e.g., due to changed hearing thresholds), 

to the stimulus. One indicahon that habituation or desensitization could be 

occumng would be an increase in the bycatch rate. An increase in the bycatch 

rate alone, however, would not be sufficient to establish that habituation or 

desensitization was the cause. A variety of other factors could be involved, 

e.g., pinger malfunction or increase in the porpoise population. Thus, a 

monitoring and research program is needed both to detect any change in the 

bycatch rate and to provide the basis for determining the cause. 

6. The effects, if any, of pingers on other biota are uncertain. Pingers, 

particularly when deployed over large areas for long periods of time, may 

cause significant distributional, physiological, and behavioral changes in large 

and small cetaceans, pinnipeds, fish, and other marine organisms. 

Uncertainty and variability in the seasonal and annual abundance, distribution, 

and bycatch of harbor porpoises will be factors in interpreting the results of 

further pinger research. Such uncertainty and variability need to be accounted 

for in a robust management plan that entails the routine use of pingers. For 

example, harbor porpoise bycatch in the Gulf of Maine sink gillnet fishery was 

higher in the fall than in any other season during 1991-94. However, the 

particular month of highest bycatch rate has varied between September and 

December throughout this period. The areas and times in which pingers are to 

be required, as well as any interpretation of their effectiveness, will depend on 

better knowledge of the within-season and inter-seasonal movements, 

distribution, and abundance of the animals. 

111. Certainties 

Several things seem reasonably certain: 

1. The legal requirements and the scale of the problem to be solved are clear. 

2. The fishermen have demonstrated a willingness and commitment to work to 

solve the bycatch problem in their fishery. 

3. The areas and season of greatest bycatch are well documented (although the 

precise time period is variable). 

4. A gross understanding exists of seasonal trends in harbor porpoise 

distribution. It is important to acknowledge, however, that much 

uncertainty surrounds the intra- and inter-seasonal movements of individual 

animals. Satellite tracking now underway (by A. Read and colleagues) should 

reduce this uncertainty. 
3. If application of pingers throughout the fishery achieves a level of bycatch 

reduction comparable to that of the 1994 experiment, the PBR goal could be 

reached. It will depend on the continued widespread support and compliance 

of the entire gillnet fleet. The potential for large-scale fishery closures, in the 

event that the take-reduction goal is not achieved, is likely to be sufficient 

motivation for the industry to ensure that pingers are used as prescribed and 

that participation in the pinger program is complete. 

4. If the PBR goal is achieved in the first year, repeat the same strategy in 

subsequent years. If it does not prove to be effective (i.e., the bycatch at the 

end of the season exceeds the PBR level), implement an alternate approach. 

Any alternative likely would need to include lengthy closures, possibly 

covering large geographic areas. The closures could be modeled on the 

existing area-closure program outlined by the New England Fishery 

Management Council, with the timing of closures following the 

recommendations of the Council's Harbor Porpoise Review Team. 

5. A survey of harbor porpoise abundance should be conducted in 1996 to 

provide an additional abundance estimate to compare with those obtained in 

1995 and previous years, and possibly obtain a trend estimate. 

6. The research and monitoring program should include: 

(a) At least 6% observer coverage on vessels fishing. 

(b) Studies of the fine-scale distribution of porpoises in areas where pingers 

are used, to look for signs of displacement or other effects. 

(c) Detailed behavioral studies of the responses of porpoises, herring (one 

of the porpoises' prey), and other species (e.g., baleen whales) to the 

sounds of pingers. 

VI. Other North American Gillnet Fisheries in which a Similar Strategy May Be Appropriate 

Several other gillnet fisheries in North America have harbor porpoise bycatch rates 

comparable to that of the Gulf of Maine sink gillnet fishery. These include the northern 

Washington set-net fishery, in which a controlled experiment with pingers in 1995 had results 

similar to those of the 1994 New Hampshire experiment (Gearin et al. 1996); a Canadian 

gillnet fish~ery in the Bay of Fundy (southeastern Canada); and various set-net fisheries in 

British Columbia and southeastern Alaska. If pingers are deployed in these fisheries to 

reduce the porpoise bycatch, such deployment should be accompanied by a monitoring 

program, iXs described above. Other gillnet fisheries off the U.S. east coast south of the Gulf 

of Maine almost certainly take harbor porpoises, but the scale of this bycatch is unknown 

(Blaylock let al. 1995). 
VII. Criteria for Successful Implementation of the Pinger Program in the Gulf of Maine Sink 

Gillnet Fishery 

:I. The MMPA-mandated reduction in porpoise bycatch is achieved on schedule. 

12. Large-scale fishery closures are avoided, and the fishery is maintained. 

3. Fishermen adopt the pinger program as their solution to the porpoise bycatch 

problem and thus ensure that it is fully and consistently implemented. 

4. Data are available to demonstrate that other biota are not adversely affected by 

the large-scale use of pingers. 

5.3 Working Group 3: Other Species and Other Gillnet (Mainly Drift Gillnet) Fisheries 

(Pingers) 

13arlow (Chair), Dawson, Gearin, Hanan, Kraus, Melvin, Northridge, Read, 

Wilkinson mapporteur) , Yi 

This group's mandate was to suggest approaches for evaluating the efficacy of pingers 

in gillnet fisheries other than those in which the harbor porpoise is the main bycaught species 

of concr:rn. The group initially focused on well-known U.S. fisheries. It was assumed that 

the principles applicable to these fisheries might also apply to other fisheries. 

I. Possil~le Target Fisheries and their Characteristics 

I,. West-coast drift gillnet fishery for swordfish and sharks 

About 150 vessels, with crews of 2-4, are involved. The fishing is done at distances 

of 5.6-370 km (3-200 nautical miles) from shore, on trips lasting 5-14 days. The nets 

are 36-61 cm (14-24 inch) mesh, 1.9 km (1 nautical mile) long, and 61-92 m (200- 

300 feet) deep. They are suspended 6-18 m (20-60 feet) below the surface. Nets are 

set at dusk and retrieved at dawn. The boats are attached to the nets overnight. The 

fishing season is from 14 August through the end of January. 

The fishery is generally regulated by the State of California (6 boats operate off 

Oregon). Its ex-vessel value is about $15 million. 

The bycatch annually includes approximately 300-400 common dolphins and smaller 

numbers of beaked whales, pilot whales, various other delphinids, Dall's porpoises, 

sperm whales, and some pinnipeds (Barlow, personal communication). The take rate 

i,s about 1 marine mammal per 10 sets. Observer coverage has been about 15 % . 
2. East-coast drift gillnet fishery for swordfish, tuna, and sharks 

This fishery is generally similar to the one on the west coast described above, but it is 

much smaller and of shorter duration. Less than 20 vessels are involved. The season 

is open only for about 10 days in summer (until the quota on swordfish is reached). 

Tht: nets are 50 cm (20 inch) mesh, 2.5 km (1.3 nautical miles) long, and 18-25 m 

(59-82 feet) deep. They are fished at the edge of the continental shelf. The total 

nurnber of sets per season is approximately 200. 

The bycatch annually includes approximately 400 common dolphins, 60 pilot whales, 

smaller numbers of other delphinids, more than 30 beaked whales, and a few northern 

right whales, humpback whales, and sperm whales (National Marine Fisheries Service 

1995). The take rate is more than 1 marine mammal per set. Observer coverage has 

been good (50-100%). 

3. Mid-Atlantic (central East Coast of U.S.) coastal gillnet fisheries 

These are small-scale fisheries that operate in state waters from New Jersey to 

Florida. Target species include weakfish, croaker, spot, shad, bluefish, and striped 

bass. More than 3000 fishermen participate in these fisheries. The gear consists of 

bottom-anchored gillnets. Regulations vary from state to state. 

Litlle information is available on fishing effort or marine mammal bycatch. Most of 

the information on takes is from stranding data. The bycatch is known to include 

harbor porpoises, bottlenose dolphins, and harbor seals. The mortality rates of harbor 

porpoises and bottlenose dolphins may be above the PBR levels (see Blaylock et al. 

19B5). 

There has been little observer coverage to date. Obstacles to implementing an 

effective observer program include the small size of many of the vessels, the large 

number of participants in the fisheries, and the presumably low bycatch rate. 

It is important to note that the State of Virginia is reported to have already purchased 

pingers for fishermen. 

11. Testing the Effectiveness of Pingers 

1. Variables applying specifically to the west-coast driftnet fishery 

(a) The depth of the nets makes them difficult to ensonify. Most 

entanglements occur in the upper two-thirds of the net, but they may occur in 

other parts of the net as well. 

(b) Because of the length of trips and the geographic extent of the fishery, 

each boat will have to be its own control and deploy both live and dummy 

pingers. 
(c) The species diversity in the bycatch makes acoustic frequency selection 

both important and somewhat complex. For some species (e.g., beaked 

whales and Kogia spp.) little is known about hearing capabilities. A pinger 

with a frequency sweep could prove useful for all species, but a "noisy" signal 

with harmonics would be easier to incorporate and might be equally effective. 

From what is known about odontocetes, all species should be able to hear in 

the frequency range of the currently standard pinger (fundamental frequency 

= 10 kHz). While there might be species differences in detection ranges, 

particularly at high frequencies, the goal -- detection of the ensonified net from 

far enough away to avoid entanglement -- should be adequately met by existing 

pingers. Thus, additional pinger development should not be necessary for an 

initial experiment in this fishery. 

2. Specifications and protocol for studies in the west- and east-coast driftnet fisheries 

(a) Salt-water switch. Use the available pingers with a salt-water switch. 

@) Pingerplacement. Pingers should be placed no more than 100 m apart. 

They should be placed on both the headrope and the leadline of nets used on 

the west coast, so that the net is totally ensonified. The placement of pingers 

should be alternated between headrope and leadline. 

In the east coast fishery, pingers should be placed on the leadline. 

(c) Randomization. Deployment of active and dummy pingers should be 

randomized between sets on the same vessel rather than between vessels to 

avoid possible geographic bias. 

(d) Power analysis. In order to generate meaningfu1 results, sample size and 

observer coverage should be determined in advance, using power analysis. 

The target bycatch level should be the PBR level for each species. However, 

for some species (e.g., beaked whales), the numbers caught are likely to be 

too small to obtain adequate sample sizes. In those cases, the study should be 

structured to detect a 50% reduction in total cetacean mortality, with particular 

attention paid to those species for which catch has exceeded PBR. 

(e) Passive devices. Simultaneous use of active and passive deterrents might 

have potential, but additional work on passive devices and combinations is 

needed. There is concern that simultaneous use could confound interpretation 

of results. 

(f) Pinger availability. Consideration should be given to pinger availability 

and supply. Substantial lead time may be required for pinger manufacture. 

Since about 500 active and an equal number of dummy -pingers are needed for 

each experiment, it might be desirable to consider transferring the pingers 

from the east to the west coast. 
(g) Blind controls. Because of difficulties created by the length of trips and 

the need to re-use pingers on consecutive sets, a double-blind experiment 

might not be possible. If so, a single-blind experiment, with the observers 

knowing whether the pingers are active, must be considered adequate. To 

keep the structure of experiments comparable on each coast, every effort 

should be made to achieve single-blind controls. 

Note: Because of similarities in the fisheries and the bycaught species, experimental 

results from one coast may have some degree of applicability to the other coast. 

3. U.S. mid-Atlantic coastal gillnet fisheries 

(a) Much more needs to be known about these fisheries before any 

investigation of the efficacy of acoustic deterrents can reasonably be initiated. 

(b) Despite the difficulties, some sort of observer program is imperative. The 

possibilities of using observers on shore or on board independent vessels 

should be explored. Also, aerial surveys could provide information on fishing 

effort and the presence of marine mammals in the fishing areas. 

(c) Habituation (decreased responsiveness; see Appendix 1) or desensitization 

(hearing threshold shifts) could be particularly important in these fisheries 

because some populations of marine mammals are probably resident rather 

than migratory. 

111. Possible Approaches to Testing Pinger Efficacy When Field Trials are not Feasible 

Two approaches might be considered in situations where, for example, uncertainty is 

caused by the inadequacy of information about the fishery (e.g., mid-Atlantic coastal gillnet 

fisheries) or catch rates are so low that observer programs would provide little data. They 

could be used in areas with resident (and preferably fairly large) cetacean populations. 

1. Deploy a pinger array as is normally done on a gillnet and monitor the 

behavior of wild dolphins or porpoises as they encounter the array. Such an 

experiment would allow an evaluation of whether animals avoided the 

ensonified area, and, if they did, at what range their behavior changed. If left 

in place for a longer period, it might be possible to evaluate the habituation 

problem by observing resident animals. 

2. Test the hypothesis that pingers elicit echolocation signals which aid cetaceans 

in detecting and avoiding nets. In an experiment, deploy a pinger in the 

vicinity of an echolocation click detectorllogger. Echolocation clicks could be 

counted over long control (silent) and experimental (pinger on) periods. 
IV. Summary 

E:xperiments with pingers in the east- and west-coast driftnet fisheries should be 

initiated as soon as possible. On the other hand, substantially more information about the 

coastal gillnet fishery (or fisheries) in the mid-Atlantic region is needed before a useful 

experiment can be designed and conducted there. 

5.4 Working Group 4: Use of Acoustic Harassment Devices to Reduce Predation by 

Pinnipeds on Salmonids and Other Fish Species 

Boutillier, Bowles, Christensen, Ford, Fraker, Gentry (Chair), Harvey, Mate, Morris 

(Rapporteur), Schusterman, Shaughnessy, Young 

Four separate kinds of interaction between pinnipeds and fisheries or aquaculture 

operations were considered by this group, namely: 

* bottlenecks or "choke points" where wild salmonids aggregate in response to 

human-made structures or natural river physiography; 

* aquaculture facilities where pen-raised salmonids attract pinnipeds; 

* the salmon drift gillnet fishery, mainly in Oregon rivers; and 

* the commercial sport-fishing industry -- party (head-boat) fishing, which targets 

salmonids and other species, and salmon trolling in California. 

AHDs have been used, at least experimentally, in each situation to keep pinnipeds away (see 

Mate anti Harvey 1986). 

The group realized that the term AHD might not always be appropriate, since a 

particular device might actually be designed to cause fright, annoyance, or pain rather than 

"harassment," per se. The term AHD has been used throughout the working group report 

(and the workshop report) to distinguish the generally high-amplitude devices used to deter 

pinnipeds, from the generally low-amplitude "pingers" used to prevent bycatch of marine 

mammals (mainly cetaceans) in fisheries. 

I. Key Observations 

1. As the 1995 Gulf of Maine Task Force on Pinniped and Aquaculture Facilities 

concluded (Task Force 1996), acoustic devices cannot be expected to provide 

100 % protection from pinniped depredation. 

2. Because sound appears not to be particularly aversive to pinnipeds except at 

very high intensities, it should not be used as the measure of first resort in 

resolving fishery conflicts. Simpler, cheaper methods having less impact on 

surrounding biota -- e.g., not locating fish farms near pinniped rookeries and 

constructing physical barriers to keep seals away from fish pens -- should be 
used first. AHDs should be used only to supplement these. AHDs should be 

used only after other non-lethal (or otherwise less intrusive) measures have 

been found to be ineffective. 

3. The possible effects of sound on non-target species should be the first concern 

when (a) using AHDs, (b) escalating efforts to drive away recalcitrant 

individual animals, and (c) choosing the site for new aquaculture pens. 

4. The problems considered here involve primarily four pinniped species: 

California and Steller (northern) sea lions, harbor seals, and gray seals. Thus, 

research intended to improve the effectiveness of AHDs in North America 

need consider only a few species. 

5. The number of recalcitrant individuals that cannot be deterred by high-intensity 

sounds is usually small. The lack of effectiveness in these cases could be due 

to impaired hearing, habituation, learned avoidance behavior, or other factors. 

Representative animals should be studied to determine why they are not 

deterred by high-intensity sounds. 

6. The question of whether lethal means should be used to remove recalcitrant 

individuals was beyond the scope of the workshop and not addressed. 

7. When AHDs fail to keep pinnipeds out of an area, mitigation should not 

necessarily be sought by increasing intensity or operating time. Most current 

AHDs already produce at or near their maximal practical levels. Increasing 

the total sound energy delivered by increasing operating times or intensity 

could cause hearing damage, which must be considered an undesirable, and 

indeed counterproductive, result. 

It should be recognized that in at least some cases, the apparent failure of 

AHDs to deter pinnipeds may be a consequence of improper maintenance and 

deployment of transducers. For example, the user may be trying to protect an 

area that is too large to be adequately ensonified or may have placed the 

AHDs where transmissions may be blocked. These possibilities should be 

considered before concluding that a particular device is ineffective. Tests 

should be done when AHDs are installed to (a) ensure that they are working 

properly, and @) measure received sound levels at the distances and in the 

areas where they are expected to deter pinnipeds. 

8. The effectiveness of AHDs is influenced by the "personalityn of pinnipeds. 

Pinnipeds are highly exploratory, persistent, and hard to frighten with most 

sounds. Growth rates of some local populations of the four pinniped species 

have been substantial (5-13% per year). In areas where pinniped populations 

are growing, increased interactions with fisheries and aquaculture operations 

can be anticipated. 
9. The nature of sound transmission is highly site-specific. Transmission loss 

depends on slope, depth, and composition of the bottom, temperature, salinity, 

and many other factors. Because of the number of variables that affect 

transmission loss, the strength and effectiveness of the signal reaching the 

animal usually cannot be predicted precisely. Nevertheless, the strength of the 

received signal, not the source level, should be the main consideration in 

assessing an AHD's effect on target animals and its likely impact on other 

biota. 

10. Research is needed on the effects of exposure to sound on the hearing abilities 

of marine mammals (temporary and permanent threshold shifts). It is also 

needed on the physiological and behavioral consequences of long-term, chronic 

exposure to sound. Studies of the effects of exposure to AHD sounds need to 

include non-target species (e.g., other marine mammals, fish, turtles, 

invertebrates) as well as the target species. The possible effects of AHDs on 

harbor porpoise and other strategic stocks are of special concern because 

changes in the distribution of harbor porpoises around experimental AHDs 

have already been observed. 

11. Means of Increasing the Effectiveness of Sound as a Deterrent 

Giiven that sound intensity cannot be increased much beyond present levels, what else 

can be done to increase the effectiveness of sound as a deterrent? The following list was 

developed by the Working Group. 

1. Use hazing by humans. 

2. Pay careful attention to pen location and construction, with the paramount goal 

of keeping animals naive to penned sources of food. Predator fences, 

correctly installed and tensioned, should be used in nearly all cases and 

perhaps be required. 

3. Protect areas that are as small as possible in settings that confine the sound. 

4. Use sounds only where large numbers of fish are being taken. 

5. Use sounds to prevent depredation on free-ranging fish only where fish 

aggregations are temporary and where predators are not aggregated for some 

purpose other than feeding (e.g., resting, nursing, breeding). 

ti. Use a mild warning tone before the aversive sound is produced to try to 

develop a conditioned response to the tone, allowing the aversive sound to be 

used only intermittently. The ability to develop a conditioned response will 

depend in part on the aversiveness (e.g., suddenness and intensity) of the 

sound. Ten or more repetitions might be necessary before the conditioned 

response is developed. The aversive sound will have to be produced 

periodically to prevent the conditioned response from being extinguished. If 
successful, conditioning animals to respond to a low-intensity warning signal 

would (a) reduce the possibility of causing hearing damage; (b) lessen the 

possibility of affecting non-target species; and (c) reduce electrical power 

requirements. The effectiveness of any conditioning technique will depend in 

part on the strategy used by the animal to find the fish that are being 

protected. Animal search strategies are still largely unknown. 

While sounds of appropriate frequency, timing, and intensity can be used to 

condition animals in the laboratory, psychologists do not consider them to be 

especially effective negative reinforcers. As a consequence, such sounds are 

used in conditioning experiments only in conjunction with aversive stimuli. It 

is possible that noise will prove to be more effective as a negative reinforcer 

for marine mammals, which depend on sound for much of the information that 

they get about their environment. This possibility, however, is only a 

speculation at present. 

7. Produce sounds only when the predator approaches the area being protected. 

Predator detection is central to the success of conditioning. The onset of the 

aversive sound should have particular properties (see point 10). 

8. Tailor the aversive sound to the predator of concern. Establish what kinds of 

sound are most aversive to a given species and simulate them with the AHD. 

Acoustic features that can be manipulated include absolute level, signal-tonoise ratio, duration, onset time, rate, bandwidth and center frequency, 

modulation rate (FM and AM), and duty cycle. The sounds can be tailored to 

features of the animal's perception, such as similarity to biologically 

significant sounds, timbre, and deviation from expectation. A good AHD will 

arouse the animal and exceed its comfort range (i.e., annoy it or cause pain). 

The possibility that AHDs deter a predator by masking sounds that it is 

listening for should be investigated (see point 10). 

9. Where possible, use directional rather than omnidirectional sounds. 

10. Prevent habituation in the first place, and thus avoid the problem of 

overcoming habituation after it has begun. More research is needed on this 

phenomenon and its role in foiling acoustic deterrence. 

For a sound to drive a hungry animal away from a food source, it must be 

aversive enough to override the feeding drive. The sound must be 

uncomfortably intense; it must stimulate reflexive movements, like the acoustic 

startle response; and/or it must effectively mask sounds on which the animal 

depends for locating the food source. Thus, the aversive sound should be as 

uncomfortable as possible for the target animal, without injuring it. 

Unfortunately, the more effective the sound, the more likely it is to have 

undesirable effects on non-target species, and the more likely that it will be 

injurious to the target animal with protracted exposure. 
The most successful AHDs currently in use produce sounds that increase from 

ambient sound level to the maximum intensity (194 dB RMS SPL re 1 pPa) 

over a period of 70 seconds to "warn" animals off. The maximum intensity 

may be near what will cause hearing impairment. Any increase in sound 

intensity could increase the risk of hearing impairment. If needed, the next 

best way to increase the aversiveness of the sound is to increase the onset rate. 

This can stimulate the acoustic startle response, a reflex that is itself aversive. 

The onset rate should be rapid, perhaps as little as 200 ms, The optimal rate 

may be on the order of 50-100 dB per second: fast enough to stimulate the 

startle response, but not so abrupt that it will immediately cause acute hearing 

damage. Intense sounds with onsets < 1 ms can cause acute hearing loss after 

a single exposure, and they are not as aversive. Obviously, such types of 

sound should never be used. This point also applies to impulses from seal 

bombs and other explosive devices detonated close to an animal. 

111. Situations in which AHDs are not effective or are contra-indicated include those where: 

1. the conditions for sound propagation are poor within the desired effective 

range; 

2, the probability of adversely affecting harbor porpoises and other non-target 

species is high; 

3, fish are not well aggregated or are not somehow constrained in their 

movements (e.g., by having to pass through a constricted area); and 

4, use would prevent or interfere with access to normal haul-out sites or other 

important habitats. 

IV. Aggregation Points for Wild Salmonids 

On the American west coast from central California through Alaska and on the east 

coast from Maine through the Canadian Maritime provinces, many runs of salmonids have 

declined for a variety of reasons, most importantly overfishing and habitat degradation. In 

some instances, pinniped predation on either out-migrating smolts or returning adults may be 

one of the factors retarding the recovery or enhancement of the salmonid populations. In 

most settings, the complexities and vagaries of the food web confound attempts to 

demonstrate that the pinnipeds have a deleterious effect on the fish stock. However, in some 

rivers natural or human-made features create "choke points" where it is easier to quantify the 

effects of pinniped predation. AHDs might be used at such sites to reduce pinniped 

predation on the fish. The success or failure of such use might be measured by monitoring 

changes in the number of fish passing the points. 

V. Culturing of Salmonids and other Finfish 

The culturing of finfish, especially salmonids, is proliferating in North America. In 

some areas, the economic value of cultured fish is similar to or greater than that of wild fish. 
Many fish farms suffer attacks by pinnipeds: mainly California sea lions and harbor seals on 

the west coast; harbor and gray seals on the east coast. Losses from attacks take several 

forms: fish are killed outright; injured fish have reduced value; injury and descaling make 

fish more s,usceptible to disease; stress affects the growth rates of fish and increases their 

susceptibility to disease; and damage to pens allows fish to escape and costs time and money 

to repair. The escape of fish causes an economic loss to the owner and poses a threat to 

indigenous stocks by potential genetic contamination. Escaped fish also may transmit 

diseases to wild stocks, compete with wild fish for food and spawning sites, and disrupt 

redds of wild fish. 

Despite some encouraging early results, AHDs used in the 1980s were not effective in 

controlling depredation by pinnipeds (Mate and Harvey 1986). Recently-developed AHDs 

(such as those being sold by AirMar Technology Corporation) are reported to have been 

effective at fish farms in Maine for two years or longer (Task Force 1996) and should be 

tested further in problem areas. The effectiveness of AHDs can be measured in economic 

terms, but the effects on non-target biota are largely unknown. As noted earlier, some data 

show detectable changes in harbor porpoise distribution in response to experimentally 

activated AHDs in western Canada (Olesiuk et al. 1995). 

The group reviewed and agreed with the main conclusions of the report of the Gulf of 

Maine Aquaculture-Pinniped Interaction Task Force regarding the use of AHDs (Task Force 

1996), that the NMFS should: 

~ 1. support research on the effects of AHDs; 

2. support, through grants or directed research, innovative work on the 

development of approaches to mitigating or eliminating unwanted side-effects 

and to reducing the costs of purchasing and operating AHDs; 

3. support the development of innovative predator control strategies, including 

pen design and new technologies, that could eliminate the need for AHDs; 

4. conduct workshops to review the latest and best information on AHDs and to 

facilitate communication between aquaculture practitioners on the one hand and 

animal behaviorists, manufacturers, and acousticians on the other; and 

5. continue to ensure that all interest groups, including proponents of salmon 

aquaculture and pinniped protection, are involved in the development of 

policies pertaining to the use of acoustic devices. 

1 VI. Salmoin Gillnet Fisheries 

Hartlor seals and California sea lions take salmon caught in gillnets along the 

northwest coast of North America. They also cause significant net damage. The fisheries 

are mainly in rivers, although some fishing is done offshore. In rivers, the nets (100-300 m 

(328-984 feet) long) are drifted downstream attached to a vessel. The fishing season is short 

(several weeks). The loss of and damage to fish is economically significant in some areas, 
and some marine mammal bycatch occurs. For example, approximately 100-200 harbor seals 

are killed in these fisheries annually. It is possible that AHDs could be developed that would 

reduce bycatch, gear damage, and the loss of and damage to caught fish. However, since the 

fishing operation is moving, contraindications 1-3 (section 111, above) may apply. There are 

some concerns that acoustic deterrence may displace other fish (e.g., non-salmonids, 

especial1:y juveniles in estuaries). 

VII. Spcort-Fishing Party Boats and Salmon Troll Fisheries 

A variety of commercial sport-fishing charter boats, targeting bottom fish species and 

salmon (trolling), operate on both the east and west coasts of North America. California sea 

lions and harbor sds take caught fish off the lines. On the west coast the problem is quite 

severe in some areas, especially southern California where 40% or more of catches can be 

lost. Cracker shells and seal bombs have been used to drive pinnipeds from the immediate 

fishing area, but these are dangerous for the operator and give only brief (5-7 min) 

protection. Electronic AHDs might be developed which could keep pinnipeds away and 

prevent or reduce predation for longer periods. However, the area to be ensonified is not 

enclosed, fish are not aggregated, and other marine biota are exposed to risk (see section 111, 

above). Furthermore, if the fishery or the use of AHDs proliferates, the concentration of 

such devices in large areas, or in sensitive habitat for long periods, could be detrimental to 

non-target marine biota. 

5.5 Working Group 5: Statistical Approaches for Evaluating the Effectiveness of Acoustic 

Deterrents 

DeMaster (Chair), Jones, Laake, Matkin, Zeh 

PI. detailed outline of statistical design features was prepared, followed by comments 

on retrospective and ad hoc studies and on various other statistical considerations. Aspects 

of this group's report having to do with bycatch studies should be read in conjunction with 

the report of Working Group 3; aspects having to do with depredation studies should be read 

in conjunction with the report of Working Group 4. The group recommended that the 

following be done or considered to produce statistically meaningful results. 

I. Devdop testable hypotheses, incorporating historical data and information from fishermen 

and othe:r sources. 

11. Design experiments to address a number of different hypotheses, e.g.: 

1. species-specific bycatch rates for marine mammals, seabirds, and fish are 

independent of treatment y; 

2. depredation rate of species x is independent of treatment y; 

3. rate of depredation by "naive" animals is equal to that by "experienced" 

animals; 
4. rate of depredation by species x is constant over time, given treatment y; 

5. rate of depredation on fish under conditions of acoustic treatment is lower than 

that under conditions of physical barriers (e.g., predator nets); 

6. distribution of species x is independent of treatment y; 

7. catch rate of target (fish) species is independent of treatment y; and 

8. hearing thresholds of target (fish) and bycaught (mammal) species are 

independent of treatment y. 

111. Factors to consider include: 

1. a double-blind protocol is preferable whenever possible; at a minimum, the 

fishermen should be unaware of which gear is treated and which is control; 

2. temporal use of treated and control gear should be randomized; 

3. alpha-level for Type 1 error should be set prior to experiment (at 0.05-0.1); 

4. power should be at least 0.7 to limit the chance of Type 2 error; and 

5. sample size should be large enough to get a reasonable likelihood of detecting 

a biologically meaningful effect. 

IV. Quantifiable parameters to estimate (or measure) in bycatch experiments and monitoring 

studies: 

1. bycatch rate, by species (mammals, seabirds, fish) -- organisms killed per unit 

effort; 

2. percent incidence of hearing damage; 

3. sound levels (ambient and anthropogenic) at measured distances and depths 

from net; 

4. amount and composition of catch of target species; 

5. rate of depredation on catch of the target species (as a way of assessing the 

"dinner-bell effect"); 

6. output of a representative, random sample of pingers (amplitude by frequency 

plots); 

7. output of pingers in the vicinity of bycaught marine mammals; and 
8. distribution of marine mammals, fish, and seabirds in relation to fishing gear. 

V. Quantifiable parameters to estimate (or measure) in depredation experiments and 

monitoril~g studies: 

1, rates of scarring or other damage on fish at ladders (or other passage 

facilities) ; 

2. rate of mortality of penned fish caused by marine mammals; 

3. sighting rates of pinnipeds and other marine mammals in the vicinity of fish 

pens, fish ladders, etc.; 

4. the number of individual animals in the vicinity of fish pens, fish ladders, etc. 

if possible; 

5. sound levels (ambient and anthropogenic) at specified and measured distances 

and depths from fish pens, fish ladders, etc.; and 

6. distribution of marine mammals, seabirds, and fish in the vicinity of fish pens, 

fish ladders, etc. 

VI. Additional information needs: 

1. percent incidence of hearing threshold shifts in marine mammals, seabirds, and 

fish, in relation to frequency, duration, amplitude, and type of sound; 

2. percent habituation or aversion responses in marine mammals, seabirds, and 

fish, again in relation to frequency, duration, amplitude, and type of sound; 

fl. characteristics of signals that are aversive to individual marine mammal 

species; 

4. development of a paradigm for studying the behavior of free-ranging pinnipeds 

in the vicinity of AHDs. 

VII. Comments on retrospective and ad hoc studies: 

13esigned experiments are more reliable than opportunistic trials and are thus 

preferred for evaluating the effectiveness of acoustic deterrents. However, retrospective and 

ad hoc studies (e.g., records of predation at aquaculture sites before and after the installation 

of AHDs) can be used to judge whether acoustic deterrents are likely to be successful in a 

comparable situation. They can also be used to identify factors that are potentially important 

in influencing the fishery-marine mammal interaction. 

'The validity of conclusions from such studies will depend on the quality of the 

records that were kept and on how the study was implemented. Such studies generally have 
focused om bycatch or depredation rates, so they are not useful for assessing indirect effects 

on the marine mammals or other biota (e.g., hearing loss, displacement from critical habitat). 

VIII. Statistical considerations: 

For trials using pingers to reduce bycatch, the primary measure of outcome will 

usually be: the proportion of nets (or strings of nets) in which marine mammals were caught. 

The unit of fishing capacity -- strings in this case -- should be standardized. Results will 

usually be summarized in 2-way tables like the following: 

No. of strings without bycatch No. of strings with bycatch 

With pingers A B 

Without :pingers C D 

where A, B, C, and D are the numbers of strings in the respective cells. Both B and D will 

often be small, so Fisher's exact test, an exact binomial test, will be needed. Although 

sophisticated analyses may consider covariates such as soak time, this is not essential in a 

randomized trial, so power calculations can be based on this simple analysis. 

Ca:sagrande et al. (1978) and Conlon and Thomas (1993) discuss algorithms for 

determinin~g sample size in the treatment (with pingers) and control (without pingers) groups, 

to provide specified power to detect a specified difference with a test at a given alpha level. 

The required sample size can also be determined by simulation. It would be useful for the 

regulatory agency (the NMFS in the United States) to have a computer program available to 

make these calculations. Such a program could be provided for use by anyone designing a 

study of this kind. 

When a power calculation shows that the required sample sizes are not feasible in a 

particular fishery, a sequence of experiments over several years may be needed. 

Alternative:ly, historical controls may be used, although they are less desirable because of the 

possibility that environmental variability and temporal changes in the fishery will confound 

results. Finally, the results of small studies of several similar fisheries might be combined to 

make an overall inference about significance. 

In some circumstances, it may not be adequate to simply detect a difference of a 

specified magnitude between treatment and control. To determine whether the acoustic 

deterrent is capable of reducing the bycatch to below the PBR level, for example, it may be 

necessary to estimate the difference with considerable precision. This may require larger 

sample sizes than suggested by a simple power calculation (see Goodman and Berlin 1994). 

Estimation of bycatch with acceptable precision must also be considered when determining 

how much observer coverage is needed for long-term monitoring once a management 

program ic~volving the acoustic deterrent has been put into place. 
Trials to test the effectiveness of acoustic devices in deterring predators will probably 

require a different design from that used for testing the effectiveness of pingers in reducing 

bycatch., Some sort of paired "on versus off" design will usually be needed. Retrospective 

studies of aquaculture operations in which AHDs have been used can provide valuable 

information on (a) expected effectiveness of a device, @) required duration of "on" and "off" 

periods for measuring effects, (c) how long a "washout period" is needed after an "on" 

period to return to control conditions, and (d) what outcome measures are most useful (e.g., 

number of fish mortalities per pen of a given size). Designed studies will require power 

calculations based on paired t-tests rather than on analysis of 2-way tables if the most 

appropriate outcome measures are best treated as continuous rather than categorical. It is not 

altogether clear in AHD studies what the appropriate experimental unit should be, whereas in 

pinger experiments it seems clear that the experimental unit is a set (or haul in the case of 

trawls) of a given piece or unit of gear. 

5.6 Working Group 6: Basic Research, Engineering, and Education 

Au, Goodson, Jefferson, Kastelein, Ketten, Lien, Nachtigall (Chair), Popper, 

Thomas, Watkins 

During plenary discussions, it was noted that there were many uncertainties 

concerning the behavior and hearing capabilities of marine mammals, the operational 

characte~istics of pingers and AHDs, and the nature and operations of commercial fisheries 

(e.g., factors that determine when, where, and how various types of gear are deployed and 

retrieved). These uncertainties contribute to the difficulty of determining, a priori, how 

different species of marine mammals may react to or be affected by different sounds. They 

also make it difficult to design and interpret the results of experimental trials. It also was 

noted that many fishermen lack understanding of the possible biological impacts of their 

bycatch, that many environmental groups lack understanding of the social and economic 

impacts of gear damage and fish loss caused by marine mammals, and that many scientists 

lack understanding of fishing gear and practices. 

After developing a long list of uncertainties, the members of this Working Group 

chose to partition their efforts according to four discrete areas of interest and expertise (1) 

social science and policy, (2) bioacoustics, (3) technology development, and (4) animal 

behavior. Each item in the list was addressed by one or more subgroups. The Working 

Group's report is, accordingly, a series of four subreports. 

Tlhe overall intention was to identify areas of needed research and to suggest ways 

that this research might best be designed. The result is, in a sense, a "shopping list," with 

no indication of priorities. 

Subgroup1 1: Human dimensions and policy aspects (Jefferson, Lien) 

This subgroup started from the premise that it is as important to understand the 

human dimensions of fishery-marine mammal conflicts as it is to understand the biological 

aspects. A greater focus on understanding and effectively dealing with the human 
dimensions should improve the chances of resolving the conflicts. Areas of needed inquiry 

or attention include: 

I. Public education 

Often, fishermen and the general public lack a clear understanding of the goals and 

objectives of marine mammal bycatch reduction measures. For example, the rationale behind 

the PBR concept, and the methods for calculating that level, are not known to many people. 

The resultant lack of understanding often impedes acceptance of measures necessary to 

achieve the PBR goal. The public, and especially people directly involved in the fishing 

industry, need to be better informed about the importance of bycatch reduction practices and 

methods, proper (and improper) use of acoustic deterrent devices, and the scientific 

rationales regarding causes and solutions. 

11. Including affected groups in decision making 

Fishery management may take the form of rules and regulations developed by 

government officials. These measures may be imposed on the fishing industry without clear 

consideration of the possible socio-economic consequences. Understandably, such top-down 

management leaves fishermen feeling alienated, resentful, and reluctant to cooperate. The 

chances of successful management (i.e., a sustainable fishery) are greatly enhanced if there is 

an open clialogue and both fishermen and other interested parties are consulted for their input 

early in the process. 

Mutually agreed management objectives are critical for achieving long-term 

conservation goals. Better methods of involving interested groups in the decision making 

process must be identified, evaluated, and implemented. 

111. Adaptive management 

Gjiven the complexity of the problems, fishery-marine mammal conflicts are best 

managed adaptively. In other words, management measures need to be subject to continual 

review and revision in the light of new knowledge, changed circumstances, and shifting 

priorities,, The costs and benefits of management practices need to be evaluated on an 

ongoing basis. This means evaluating old and new technologies, monitoring effectiveness of 

the existing management regime, and regularly examining and re-evaluating the options. 

Adaptive management does not just happen: it requires dedicated forethought and planning. 

IV. Untalpped information sources 

Extensive information on marine mammal bycatch exists, but much of it has not yet 

been used to its fullest potential. Sources include fishermen's knowledge and several large 

data sets in government files. Examples of the latter are the 1978-87 data from the observer 

program of the North Pacific Japanese salmon driftnet fishery, and the 1989-91 data from the 

North Pacific squid driftnet fishery. Analyses of factors related to bycatch from these data 

could iml~rove understanding of what influences incidental catch rates and, perhaps, provide 

guidance about how to modify fishing practices in order to reduce bycatch. Many obstacles 
may need to be overcome to obtain such data, but the potential for insight makes it worth the 

effort. 

V. Additional topics that need to be addressed 

1. The purpose (objectives and goals) of the use of acoustic deterrent devices 

needs to be clear and should, if at all possible, be accepted by affected groups. 

:2. All aspects of noise pollution and its effects, not just on marine mammals but 

on entire ecosystems, need to be addressed. 

3. Non-acoustic methods of bycatch reduction and predator control should be 

considered before acoustic methods are used. Changes in fishing techniques or 

aquaculture structures (e.g., better siting decisions) might resolve some 

conflicts better, or more nearly permanently, than acoustic fixes. Some 

problems have no technical solution and thus require other approaches. 

4. Better communication among fishermen, conservation groups, scientists, and 

resource managers is needed. Open forums that foster a free exchange of 

ideas and information should be encouraged. Most graduates of fishery 

science and biology programs are ill-equipped to deal with the human 

dimensions of issues, and this needs to change. 

4- I. Some acoustic methods may work at first but become less effective over time. 

Monitoring of a method's effectiveness needs to be accompanied by 

contingency planning -- i.e., what is to be done if a system fails to work as 

expected? 

Subgroup 2: Bioacoustics (Au, Ketten, Nachtigall, Popper) 

This subgroup considered the following critical data insufficiencies and what is needed 

to overcome them: 

I. Insufficient information on the hearing capabilities of bycaught marine mammal species 

(e.g., harbor porpoises); intra- and inter-species differences in normal hearing ranges; 

incidence of hearing loss from disease or damage in wild populations. 

Statemerzt of Problem: 

Effective design of acoustic deterrent devices requires, among other things, 

knowledge about the sounds that the animals can most readily detect. Very limited data are 

currently available on the hearing ability of the harbor porpoise. Thus, basic information is 

still needed about what this species can hear. 

Only limited understanding exists about the hearing abilities of pinnipeds and most 

odontocetes. In many instances, what is known is based on data from a single specimen. 

While such data are certainly useful, they are not adequate. Virtually all mammalian species 
show individual variation in hearing ability, depending on an animal's age, acoustic history 

(e.g., whether it has been exposed to intense sounds), and, in a few cases, sex. Clearly, the 

signal of an acoustic deterrent needs to be within a frequency range that is detectable to the 

widest possible span of individuals in the target population. Not only is it necessary to know 

what sourlds are detectable by the largest number of animals of a particular species, but also 

whether there is a common signal that is likely to be effective for several different species. 

Experiments are needed on multiple species and individuals and on individuals of different 

ages and sexes. 

Suggested' Approach: 

1. Conduct basic behavioral and evoked-response experiments, and anatomical 

studies to develop an understanding of hearing in the relevant species (i.e., 

those most involved in and affected by fishery interactions). 

2. Design and conduct behavioral studies to measure hearing capabilities 

(audiograms), critical ratios, and directional hearing. 

3. Use evoked potentials and anatomical methods to analyze variations in the 

auditory systems, particularly of those species whose hearing cannot be studied 

through behavioral experiments. 

In each case, multiple animals should be studied to determine the intra-species 

variation iin hearing capabilities, especially as it relates to age, sex, and disease or 

impairment. 

11. Insufficient information on the hearing capabilities and behavioral responses of nonmammal bycaught species (turtles, birds, fish) and of fish species targeted by fisheries. 

Statement of Problem: 

Nan-mammalian species, including birds and turtles, are often bycaught in fisheries. 

Acoustic methods are of potential use in scaring these animals away, or in warning them of a 

net's presence (though none of these species is known to be able to detect nets by 

echolocation). As with marine mammals, it is not possible to determine a priori what stimuli 

are likely to be effective unless something is known about the hearing capabilities of these 

animals. Data on hearing capabilities are, to our knowledge, insufficient for all species of 

marine birds and turtles. 

Many species of fish, both those that are the targets of fisheries and those that are 

found in regions where fishing occurs, may be attracted by the sounds used to deter 

mammals. They also may be repelled or affected physically by these sounds. The sounds 

could pote:ntially repel targeted fish if they were capable of detecting the sounds. (Note: 

Recent dalh indicate that cod and herring may be able to detect ultrasound.) 
Better information is needed about the detection capabilities of fish so that either (a) 

sound sources can be designed that will not alter fish behavior, or (b) sounds can be designed 

that are: not detectable by the fish. 

Suggesl'ed Approach: 

1. Determine hearing capabilities of non-mammalian species that are caught 

incidentally in fisheries and that might be affected adversely by acoustic 

dcterrcnts. 

:2. Use study techniques appropriate to each species, but use behavioral paradigms 

whenever possible. 

:3. Use evoked potentials when behavioral studies are not possible. 

4. Include measurements of hearing sensitivities (audiograms) and critical ratios. 

5. Study anatomy to help understand the mechanisms of sound detection. 

111. The: echolocation capabilities of bycaught odontocete species, and how those capabilities 

might be used to avoid artificial barriers such as nets, are largely unknown. 

Statement of Problem: 

Odontocete cetaceans can use echolocation to sense their environment , potentially 

including the presence or absence of fishing gear. Without a comprehensive understanding 

of the echolocation capabilities of the bycaught species, it is difficult to design gear that is 

readily detectable, and thus decrease the chances of animals being bycaught. 

Suggested Approach: 

1. Determine whether a particular odontocete species caught commonly in fishing 

gear has an echolocation capability. 

2. Assuming that it does, investigate that species' ability to detect nets of 

different mesh size and composition -- e.g., obtain basic information about the 

species' echolocation system, such as frequencies, beam widths, functions in 

noise, etc. 

IV. Little information is available on how wild odontocetes use echolocation. 

Statement of Problem: 

Although echolocation has been demonstrated for several odontocete species in a 

laboratoly setting, there have been few demonstrations of the use of echolocation by wild 

animals. In fact, the limited data on wild odontocetes suggest that most of the time they are 

not echolocating. Very little is known about when, why, and how these animals use 
echolocation in nature, and this raises important questions. For example, were bycaught 

animals caught because they were not searching for targets at the time of capture or because 

they were unable to detect the net or failed to recognize it as potentially life-threatening? 

Depending on the animal's "normal" behavior, it might be possible to find a signal that tells 

an odontocete to "turn on" its echolocation system. 

Suggested Approach: 

1. A methud n~ds to be develupd tu d~rcrrninc wllt;tllr;r fuuraging iuiii~lals 

animals near nets are using echolocation. This will be difficult since 

echolocation signals are highly directional. Receiving hydrophones will have 

to be within the beam width to detect the signal. 

2. Because animals often forage in large groups, a method needs to be developed 

to differentiate the echolocation signals from different individuals. Only in 

this way will it be possible to determine whether all animals in a group are 

echolocating, or, alternatively, whether just a few animals are echolocating for 

the group. 

V. For most marine species, very little is known about damage to hearing caused by 

underwater sound. 

Statemen~t of Problem: 

It is well known that sound can damage vertebrate ears. However, virtually nothing 

is known about the combined effects of frequency, duration, and amplitude on the auditory 

system of aquatic vertebrates. 

Suggested Approach: 

1. Conduct experiments with mammals and non-mammals to determine what 

types of sound cause temporary and permanent threshold shifts. 

2. Examine bycaught animals to evaluate whether the condition of their auditory 

system could have been a factor in making them vulnerable to entanglement or 

entrapment. It has been suggested that many bycaught animals may be 

individuals with impaired hearing. If true, this would have serious 

implications for the use of acoustic deterrents. 

3. Any dead or captive animal suspected of having been exposed to highamplitude devices should be evaluated for evidence of damage to its auditory 

system. Such evaluation can be done by studying the animal's behavior, 

evoked potentials, and/or, in the case of a dead specimen, its ear anatomy. In 

this regard, it was noted that California sea lions captured or killed to prevent 

predation on steelhead trout migrating through Ballard Locks would be good 

candidates for such studies. 
4. For species that are not endangered, a complete series of experiments should 

be done to establish the acoustic parameters of sounds that produce 

characteristic stages of ear damage (i.e., temporary versus permanent threshold 

shifts). This means a connected series of behavioral, evoked potential, and 

full anatomical analyses. 

VI. Alnnost nothing is known about the hearing of mysticete cetaceans. 

Statement of Problem: 

Although mysticetes certainly use sound for communication, their hearing capabilities 

in relation to behavior are completely unknown. The hearing ranges of several species can 

be inferred from their sound production and from their inner ear anatomy. However, these 

provide only indirect suggestions as to bandwidth and sensitivity, parameters critical to the 

design of signals to alert mysticetes to the presence of fishing gear. 

Suggested Approach: 

C:ontrolled experiments to study mysticete behavior relative to different sounds are 

unlikely to be possible in the foreseeable future. It may nevertheless be possible to measure 

auditory brainstem responses of live-stranded whales, and this could provide some idea of 

these animals' hearing bandwidths and sensitivities. Considering the importance of 

information on hearing to the development of bycatch mitigation measures, a major effort 

should be made to obtain relevant data from live-stranded or gear-entrapped animals 

whenever possible. 

Subgroup 3: Technology development (Goodson, Watkins) 

This subgroup identified a series of concerns and considerations, presented below in 

the form of an annotated outline. 

I. Acou!stic characteristics of devices -- Before a device is approved for general use, the 

manufact.urer should supply polar plots of directivity and data on waveform, repetition rate, 

mark/spa.ce ratio (see Appendix I), sound spectrum, source level, and tolerances that are to 

be maintained during manufacture, and expected performance change during the device's 

normal operating life. Changes in specifications or simple spreads in performance due to 

component tolerances could affect a device's acoustic characteristics and, in turn, its 

effectiveness. Example: The presence or absence of harmonics elicited radically different 

behavior by a captive harbor porpoise during a pinger experiment. 

11. '~oise pollution -- An assessment should be made of the shape and extent of the 

ensonified area surrounding any acoustic device. This area would be defined by the distance 

at which detection above ambient noise is possible. Such a threshold plot would be useful 

for planning placement of fish pens and fishing gear and establishing "quiet" (below ambient 

noise) safe passage zones between them. It is suggested that the sea state zero noise floor (at 
the frequency of the sound generated) be used to define this threshold until more is known 

about the minimal sound pressure levels which actually induce responses in the behavior of 

the mammal species at risk. 

111. Detection of targets (subjects) -- For optimal functioning of a device, a method of 

automatically detecting and activating the device when marine mammals are near the fishing 

or aquaculture equipment ("smart" technology) needs to be developed. Examples: 

1. acoustic detection of vocalizing animals (e.g., ones that are making social calls 

or echolocating); and 

2. video imaging to extract visual cues (e.g., of animals approaching a static net 

at a fish farm). 

The benefits of a target (subject)-activated or on-demand system include: less potential 

for habituation by the target species; less acoustic pollution of the local environment; and 

extended life of battery-powered systems. De-activation may be desirable for "out of 

season" conditions (better economics; makes de-rigging of alarms unnecessary). 

IV. Signal suitability -- Transmitted signals should correspond to the sensitive part of the 

target ar~imal's hearing. 

1. Audiograms are needed for most marine mammal species. (Characteristics of 

the hearing ability of relevant fish species also need to be determined so that 

negative effects on them can be avoided.) 

2:. Determine signal waveforms best suited to (i) gaining the animal's attention, 

and (ii) creating an aversive response (if desired). 

3;. Optimize marklspace ratio -- unnecessary exposure may induce habituation and 

increase risk of hearing loss. 

V. Oceanic conditions affect acoustic propagation from devices. 

1.. High sea states and rain increase background noise levels and induce aeration 

effects, which mask and severely attenuate acoustic signals underwater. 

2. Possible trade-offs among alarm frequency, waveforms, and detection range 

need to be examined. 

fl. In situ recordings are essential for such examinations. 

VI. Optimize the target strength and resonant characteristics of passive reflectors. Passive 

devices, intended for use in conjunction with active alarms, may be designed at specific 

frequencies keyed to species. These could augment the effectiveness of the active alarms. 
1. Determine maximal prey size for each odontocete species. Use it to peg the 

minimal acoustic target strength of the reflector, which should exceed the 

acoustic characteristics of the largest typical prey. 

2. Such size information can be obtained by examining stomach contents of 

bycaught animals. 

3. Targeting behavior of odontocete sonar suggests that during fish interception, 

echo returns from beyond the target range are not being processed. 

4,. Inter-element (reflector) spacing needs to be optimized for each odontocete 

species. 

5,. Passive reflectors can incorporate resonant characteristics that can be 

stimulated by pingers. 

VII. Malfunctioning equipment may produce "gaps" in the perceived acoustic obstruction, 

thus enhancing the probability of bycatches at such points. Device failures need to be 

detected as they occur. 

1. In order to monitor deployment, alarm signals should be used which contain 

fundamental (or harmonic) components that can be detected using a standard 

(50 kHz) fish echo-sounder. Chirp transmissions are detectable on a wide 

range of echo-sounding equipment. 

2. Golno-go testers should be supplied by device manufacturers to allow easy 

detection of devices that are not functioning properly. 

3. Devices should be deployed with spacing that provides acoustic overlap and 

allows one defective device to be tolerated. 

VIII. Alternative technologies 

1. In the context of aquaculture, adaptive sonar beam-forming techniques could 

provide high-intensity deterrent sounds targeted directly at the predator. They 

could similarly provide quiet zones with "nulls" in the projected sound pattern 

allowing unimpeded movement around pens. 

2. Devices triggered by the presence of a predator (or a potential bycatch victim) 

are technically possible and might be mass produced economically. 
1 Subgroup 4: Behavior (Kastelein, Thomas) 

Xaowledge of the behavior of marine mammals will facilitate the development of 

effective bycatch deterrence strategies4. This subgroup attempted, systematically, to develop 

a list of statements about behavior relevant to deterrence. Suggested approaches to research 

were appended to each statement. The idea was that this outline should be consulted 

problem-by-problem, and thus used as a guide to research on behavior that could be of 

relevance. Priorities would depend on the nature of the problem and on the availability of 

resources. 

~ I. Influences of natural history on susceptibility to bycatch 

Statement: Each species of marine mammal has its specific natural history, and this will 

influence that species' bycatch probability. 

Approach: Analysis of a species' natural history might provide insights that could facilitate 

mitigation. The research objectives should be related to a specific bycatch problem. 

1. Age may influence susceptibility to bycatch. In some species, individuals are 

probably most vulnerable during the transition from suckling to solid food, when they 

begin investigating their environment independently. Older animals, with impaired 

s,ensory abilities, might also be especially susceptible to bycatch. Acoustic devices 

are probably less effective at detemng these individuals. 

Z!. Sex may be a factor. In some species, the sexes are spatially segregated, at least 

cluring part of the year, and the two sexes may use different foraging strategies, areas, 

2nd prey species. 

3. Social system may play a role. For example, males may behave differently, in 

relation to fishing operations, than females, particularly those with calves. Social 

interactions, such as mating, could distract the animals so that they fail to notice nets. 

The size and composition of a group could affect the probability of entanglement. 

4. Individuality may be important. Strong individual differences are typical of at 

least some marine mammal species. An animal's previous experience in general, and 

])articularly around fishing operations, may influence the way it responds to acoustic 

deterrents. 

11. Implications of behavior in relation to bycatch 

Statement: An animal's behavior is likely to affect its bycatch probability and, in turn, to 

help determine which form of mitigation will be effective. 

4Kn~owledge of behavior as described by this subgroup also would facilitate development 

of techniques for preventing marine mammal depredation on both cultured and wild fish. 
Approach: Careful monitoring of wild animals around fishing operations can improve 

understanding of the factors that affect bycatch. Information is needed about the following. 

1. Manner or context of entanglements -- Do the animals blunder into nets? Do they 

patrol along them? Do they investigate fish in the net? Do they sometimes escape 

after being entangled? 

2. Behavior around barriers -- Do the animals reduce their swim speed? Do they try 

to go underneath, around, over, or through nets? How far are they willing to travel 

to get past a barrier safely? Through what size opening in a barrier are they willing 

to venture? 

3. Use of echolocation in the wild -- Which individuals echolocate? How often? 

Under what circumstances? How far do they swim before producing another 

echolocation signal? Are there circadian or seasonal differences? At what distances 

cim the animals detect gear acoustically and visually, and under what circumstances? 

4. Eflects of varying oceanic conditions -- How do factors such as wind speed and 

direction, sea state, depth of the surface layer, salinity, and water temperature affect 

thke behavior of the animals and the effectiveness of any deterrent device? (At least 

some of these factors may be integrated as "ambient noise. ") 

5. Reasons that marine mammals are nearjishing gear -- Are they feeding on the 

target species of the fishery? Do they follow depth contours in pursuit of prey, a 

strategy matching that of fishermen that leads, inevitably, to geographic overlap? If 

marine mammals are feeding near fishing gear, they could be interested in species 

other than those targeted by the fishery. Are marine mammals present in the fishing 

areas when no fishing gear is present? 

111. Beh;ivioral responses to various acoustic devices 

Statemencc: Characteristics of sounds can vary in many respects, such as frequency, duration, 

amplitude, duty cycle, psychoacoustic character (see Appendix I), and onset time. 

Approach!: Careful examination of how various sounds affect the behavior of particular 

species may help identify the optimal characteristics of an acoustic deterrent. Many possible 

effects can be investigated using captive animals. 

1. Characteristics of the most aversive signals 

(a) Psychoacoustic character 

(b) Duty cycle 

(c) Amplitude relative to response threshold 
2. Immediate effect of acoustic device 

(a) Deters the animal 

(b) Makes the animal attentive to its surroundings 

3. Effect of acoustic device over time 

(a) Accommodation 

(b) Habituation 

(c) Remains effective 

IV. Behavior of fish that are targeted by the fishery 

Statement: Acoustic devices used to reduce marine mammal bycatch could have negative 

effects on the fishery. 

Approach: Catches of target fish species should be carefully monitored so that catches in sets 

with acoustic devices (treatment) can be compared with catches in sets without devices 

(control). The following can then be investigated: 

1. rate of harvest; 

2. avoidance or attraction effects of the device; 

3. physiological and anatomical effects, such as stress, hearing impairment, and 

changes in growth or reproduction. 

Points (2) and (3) might best be addressed in the laboratory. 

V. Belnavior of animals (other than mammals) not targeted by the fishery 

Statemtlnt: Acoustic devices can have negative effects on non-target species in addition to 

marine mammals (e.g., turtles, diving birds, fish, crustaceans). 

Approach: The behavior of such non-target species near fishing gear should be carefully 

monitored. Data should be collected so that behavior near ensonified gear can be compared 

with that near control gear. Catch data should be handled in the same way as indicated in 

point I'V (above). 
5.7 Working Group 7: Other Possible Uses of Sound for Marine Mammal Conservation 

Ford (Chair), Kraus (Rapporteur), Watkins 

Sound might be used to address problems in marine mammal conservation and 

management in addition to those involving interactions with fisheries and aquaculture 

operations. They were not discussed in detail at the workshop, but this small working group 

met briefly and provided a list of possibilities. 

I. Reduction of the frequency or severity of vessel collisions with whales. This problem is 

most acute in the case of northern right whales along parts of the eastern North American 

seaboard. Nearly 30% of the documented mortality in this critically endangered population 

is due to1 ship strikes. The magnitude of the vessel-collision problem is still being defined 

for other cetacean species and populations. 

The vulnerability of whales to collisions with ships may involve: 

1. localization problems (the animal hears the vessel but cannot judge 

where it is); 

2. confusion problems; 

3. lack of awareness (on the part of both the whale and the vessel 

operator); and 

4. a poor learning curve since mechanized, high-speed ships are a 

relatively new feature in the ocean. 

A,mong the types of data needed to address this problem are data on: 

1. acoustic characteristics of ships; 

2. kinds of sounds that would alert the animals; and 

3. kinds of sounds that would "scare" the animals away from the vessel's 

path (investigate through, for example, playback experiments and a 

literature review). 

11. Reduction in the frequency that Florida manatees are struck by vessels and crushed in 

flood-coi~trol structures. Factors similar to those mentioned above for right whales would 

apply. 

111. Temporary displacement of marine mammals from sites where underwater construction, 

demolition, or military exercises are planned. An acoustic stimulus possibly could keep or 

drive the: animals away, or alternatively attract them to a safer area. 
IV. Temporary displacement of marine mammals from the location or path of an oil or toxic 

chemical spill or from the site of a planned, loud acoustic event (e.g., a ship shock trial). 

Same comment as in point 111. 

V. Assistance in extricating marine mammals from particular types of entrapment (e.g., 

killer whales from Barnes Lake, southeastern Alaska; "Humphrey" the humpback whale from 

the Sacramento River; narwhals from an inlet in Repulse Bay, Canada). 

PRINCIPAL WORKSHOP FINDINGS AND CONCLUSIONS 

6.0 Many uncertainties surround all aspects of acoustic deterrence applied to marine 

mammals,. This means that much more research and monitoring is essential if the problems 

of marine mammal interactions with fisheries and aquaculture operations are to be addressed 

responsiblly and in a manner consistent with the MMPA. Of particular concern is the paucity 

of informtation about marine mammal hearing thresholds and how the animals use and 

respond to sound. There is an immediate need for research on how marine mammals behave 

around fishing gear, on how and when they use echolocation, and on their hearing thresholds 

(audiogra~ms). 

6.1 A basic principle that must underlie all use of acoustic deterrent devices to resolve 

marine m,ammal conflicts with fisheries and aquaculture operations is that any introduction of 

artificial sound into the underwater environment is potentially harmful to marine mammals 

and other biota. The physical, psychological, and ecological disbenefits will usually be less 

obvious and less easily measured than the economic benefits. This is particularly true in 

view of the potential for cumulative and synergistic impacts of each new acoustic device or 

system. 

6.2 Other management strategies, not involving the introduction of artificial sound into the 

underwate:r environment, should always be sought, even after an acoustic solution appears to 

have been found. Also, it should be kept in mind that solutions which work in an 

industrialized country may be impractical in less developed countries where low-cost, lowmaintenance solutions are the only kind that have any hope of being used. 

6.3 The iresponsibility for resolving conflicts between marine mammals and fisheries or 

aquacu1tu1:e operations needs to be shared among resource users (fishermen and fish 

farmers), resource managers (governmental officials), and resource consumers (including the 

general public). Management strategies need to be inclusive and adaptive, as outlined in the 

report of 'Working Group 6, Subgroup 1. 

6.4 It is unrealistic to expect statistically meaningful experiments to be conducted for all 

potential target species and for all fishery or aquaculture contexts in which the use of 

acoustic deterrent devices may be contemplated or tried. The results of experiments done 

with partilcular species in particular contexts should be used to make inferences about 

applicabiliity to other species and contexts. Such inferences should be made cautiously, and 

m~nitorin~g programs should be conducted to determine efficacy and side-effects. 
6.5 In view of the promising results from the 1994 New Hampshire and 1995 Washington 

experiments, pingers might be used experimentally in situations for which their effectiveness 

in reducing bycatch is untested. This includes different types of fisheries as well as similar 

fisheries that involve bycatch of species other than the harbor porpoise. All participants 

agreed that it would be inappropriate for either fishermen or managers to act on the 

assumption that pingers will be effective universally. The importance of obtaining direct 

evidence: for each type of fishery, and each bycaught species of concern, must not be 

ignored. For example, in the case of the critically endangered vaquita, an endemic species 

of the upper Gulf of California, Mcxico, it must not be assumed, without direct supportive 

evidence, that the use of pingers in the gillnet fisheries in this region would reduce the 

bycatch of vaquitas. If it is assumed, based on experience with other fisheries and species, 

that pingers will solve the vaquita bycatch problem, and the assumption is wrong, the 

resumption of fishing with pinger-equipped nets could lead to extinction of the vaquita. 

6.6 It is; appropriate to proceed with the full-scale integration of pingers into the 

management regime for the New England sink gillnet fishery provided that the regime 

includes observer and monitoring programs adequate to verify that the bycatch remains 

acceptably low and that no non-target species is affected adverselys. 

6.7 The use of pingers is appropriate in other similar gillnet fisheries in which the harbor 

porpoise is a major bycaught species of concern (see footnote 5). However, such use should 

always be conditioned on a monitoring program to validate expectations. 

6.8 Experiments should be conducted as soon as possible to determine if pingers could 

prevent or substantially reduce marine mammal bycatch in the driftnet fisheries off the U.S. 

east and west coasts. It is important that these experiments be designed according to the 

specifications laid out in the reports of Working Groups 3 and 5, using blind controls and a 

priori assessment of statistical power. 

6.9 Before any but experimental use of pingers is begun in the many gillnet fisheries along 

the eastein U.S. seaboard south of the Gulf of Maine, an observer program should be 

conducted to determine the operational characteristics of the fisheries and obtain data needed 

to assess the species and numbers of marine mammals and other non-target species being 

caught incidentally. 

6.10 A major, continuing concern related to those acoustic deterrent devices that seem to be 

effective, including both pingers in reducing the bycatch of harbor porpoises and AHDs in 

reducing the depredation of fish by pinnipeds, is that the actual mechanisms involved in 

making them effective are unknown. Effectiveness probably varies not only by species, but 

also with respect to an individual animal's experience, age, social status, and sex, and 

possibly location, weather conditions, and time of year. Uncertainty about the details of 

cause andl effect means, among other things, that reliable predictions cannot be made of how 

 his conclusion might have been different had the workshop been held after the 

experimei~tal fishery in the spring of 1996 in which significant numbers of harbor porpoises 

were caught in nets with pingers attached. 
long a device will continue to have the desired effect. Attempts to extrapolate the results 

from studies of one species or fishery to another are confounded by this same uncertainty. 

Moreover, it adds to the difficulty of assessing the likely nature and magnitude of side-effects 

on both target and non-target species. 

6.11 Another major concern is that the side-effects of acoustic deterrent devices on nontarget organisms are unknown. conclusive studies have not been done to investigate these. 

An experimental study of the effects of AHDs showed that harbor porpoises were displaced 

by at least a few kilometers when the AHDs wcrc activated (Olcsiuk et al. 1995) (possible 

effects on other non-target species were not assessed). Studies on the effects of the latest 

generation of high-amplitude AHDs on marine mammals, fish, and other organisms are badly 

needed. It is important to recognize that the powerful signals produced by AHDs are 

probably well within the hearing ranges of most (possibly all) species of marine mammals, 

including endangered baleen whales. 

6.12 Studies to date in commercial fisheries provide no evidence that the addition of sound 

reflective materials to nets will, by itself, cause a reduction in bycatch. Some participants 

urged that. discrete passive sonar reflectors might be usefully deployed in combination with 

pingers, but this possibility requires testing before large-scale, non-experimental application 

of reflectors is considered. 

6.13 The ad hoc development and proliferation of AHDs over the last 15 years have been 

accompanied by little controlled experimentation and effects monitoring. Opportunities for 

empirical investigation of changing responsiveness on the part of pinnipeds have therefore 

been lost. Also, in many areas, side-effects on non-target organisms may already have 

occurred without documentation. It is important that this situation be reversed and that 

rigorous e:xperimental studies be conducted, taking account of the methodological 

considerations in the reports of Working Groups 4 and 5. 

6.14 Experiments should be done to determine if animals can be conditioned, using 

occasional aversive stimuli, to stay away from aquaculture facilities and fishing gear. When 

trying to generate a conditioned response on the part of offending pinnipeds, there is a risk 

that comrrlitment to one particular approach will preclude future options. This means that 

any measure taken should be preceded by careful design and testing. 

6.15 In all investigations of acoustic deterrents, propagation characteristics need to be 

considered. Actual measurements of sound fields are necessary to evaluate the distances at 

which the sounds are likely to be perceived by target and non-target animals. Optimal 

deployment of acoustic devices depends on site-specific propagation conditions, which are 

themselves influenced by factors such as weather, vessel traffic, and biological background 

noise. 

6.16 It is important to recognize that single solutions are unlikely to be universally 

applicable. Also, it should not be assumed that any given approach will remain effective 

indefinitely. Thus, it is incumbent on both the private and public sectors to maintain an 

ongoing commitment to support innovative research and development in the pursuit of ways 

to achieve. bycatch reduction and the safe control of depredation. 
6.17 Incidental mortality in fishing gear can be a serious problem for baleen whale 

populations, particularly northern right whales and humpback whales. Low-frequency 

"clangers" have helped reduce the incidence of humpback collisions with cod traps in 

Newfoundland and should be considered in other areas where whales are caught in fishing 

gear. 

6.18 All.hough marine mammals are caught incidentally in trawl fisheries, the scale of this 

bycatch is generally lower than that in gillnet fisheries. Thus, the workshop did not address 

trawl fisheries as a priority. 
REFERENCES 

Barlow, J., S.L. Swartz, T.C. Eagle, and P.R. Wade. 1995. U.S. marine mammal stock 

assiessments: guidelines for preparation, background, and a summary of the 1995 

assessments. U.S. Department of Commerce, National Oceanic and Atmospheric 

Ad,ministration, National Marine Fisheries Service, NOAA Technical Memorandum 

NMFS-OPR-6, September. 73 pp. 

Blaylock, R.A., J.W. Hain, L.J. Hansen, D.L. Palka, and G.T. Waring. 1995. U.S. 

Atllantic and Gulf of Mexico marine mammal stock assessments. U.S. Department of 

Colmmerce, National Oceanic and Atmospheric Administration, National Marine 

Fisheries Service, NOAA Technical Memorandum NMFS-SEFSC-363, July. 21 1 pp. 

Casagrandle, J.T., M.C. Pike, and P.G. Smith. 1978. An improved approximate formula 

for calculating sample sizes for comparing two binomial distributions. Biometries 

34::483-486. 

Conlon, h4. and R.G. Thomas. 1993. The power function for Fisher's Exact Test. 

Applied Statistics 42:258-260. 

Gearin, P.J., M.E. Gosho, L. Cooke, R. DeLong, J. Laake, and D. Greene. 1996. 

Acoustic alarm experiment in the 1995 northern Washington marine setnet fishery. 

Report prepared by U.S. Department of Commerce, National Oceanic and 

Atmospheric Administration, National Marine Fisheries Service, National Marine 

Mammal Laboratory, Seattle, and Makah Tribal Fisheries Management Division, 

Neah Bay. 16 pp. 

Goodman, S.N. and J. A. Berlin. 1994. The use of predicted confidence intervals when 

planning experiments and the misuse of power when interpreting results. Annals of 

Internal Medicine. 12 1 :200-206. 

Jefferson, T. A. and B.E. Curry. 1994. Review and evaluation of potential acoustic 

methods of reducing or eliminating marine mammal-fishery interactions. Report to 

the: U.S. Marine Mammal Commission, Contract No. T10155628. NTIS PB95- 

100384. 59 pp. 

Kraus, S., A. Read, E. Anderson, K. Baldwin, A. Solow, T. Spradlin, and J. Williamson. 

19'95. A field test of the use of acoustic alarms to reduce incidental mortality of 

harbor porpoises in gillnets. Unpublished report to the U.S. Fish and Wildlife 

Foundation, Washington, DC. 29 pp. 

Mate, B.R. and J.T. Harvey (eds). 1986. Acoustical deterrents in marine mammal conflicts 

with fisheries. Oregon Sea Grant report. ORESU-W-86-001. 116 pp. 
National Marine Fisheries Service. 1995. Environmental assessment of proposed regulations 

to govern interactions between marine mammals and commercial fishing operations, 

under Section 118 of the Marine Mammal Protection Act. Department of Commerce, 

National Oceanic and Atmospheric Administration, National Marine Fisheries Service, 

Office of Protected Resources, June. 138 pp plus appendices. 

Northridge, S.P. 1984. World review of interactions between marine mammals and 

fisheries. Food and Agriculture Organization Fisheries Report. 251: 1-190. 

Olesiuk, P.F., L.M. Nichol, P.J. Sowden, and J.K.B. Ford. 1995. Effect of sounds 

generated by an acoustic deterrent device on the abundance and distribution of 

harbour porpoise (Phocoena phocoena) in Retreat Passage, British Columbia. 

Unpublished manuscript. Department of Fisheries and Oceans, Pacific Biological 

Station, Nanaimo, British Columbia, Canada. 47 pp. 

Perrin, W.F., G.P. Donovan, and J. Barlow (eds.). 1994. Gillnets and cetaceans, 

incorporating the proceedings of the Symposium and Workshop on the Mortality of 

Cetaceans in Passive Fishing Nets and Traps. Report of the International Whaling 

C~ommission, Special Issue 15, Cambridge, UK. 629 pp. 

Potter, Dl. 1996. Experimental fishery operational pinger feasibility Z-band area of the 

mid-coast closure November-December 1995. Report prepared for the workshop by 

Protected Species Branch, National Marine Fisheries Service, Woods Hole 

Laboratory, Woods Hole, MA. 8 pp. 

Task Force. 1996. Report of the Gulf of Maine Aquaculture-Pinniped Interaction Task 

Force. U.S. Department of Commerce, National Oceanic and Atmospheric 

Administration, National Marine Fisheries Service, Office of Protected Resources, 

Silver Spring, Maryland, February. 69 pp. 
GLOSSARY OF TERMS 

Acoustic deterrent device - A sound-producing or sound-reflecting device used to make 

marine mammals aware of, or to repel them from, an area or structure (e.g., a net, pen, or 

trap). Both passive reflectors and sound generators are included within the definition. 

Acoustic harassment device (AHD) - A sound-generating device which, because of some 

combination of intensity, frequency, or other characteristic(s), is aversive to marine 

mammals and keeps or drives them away from an area or structure. 

Category IJishery - Under a classification scheme established by the NMFS regulations 

implementing the 1994 Amendments to the Marine Mammal Protection Act (Section 118), a 

U.S. fishery which is responsible by itself for the annual mortality or serious injury of 50% 

or more of a marine mammal stock's PBR level (see below for a definition of PBR level). 

Category IZJishery - A U.S. fishery which is responsible by itself for an annual take of 1 to 

50% of the PBR level for a marine mammal stock, and when that stock's total annual 

mortality imd serious injury caused by commercial fisheries exceeds 10% of its PBR level. 

Depredation - In the present context, understood to mean something akin to "facilitated 

predation," in which an animal "attacks" or "raids" (plunders) something already caught or 

otherwise claimed by people. 

Habituation - A gradual waning in responsiveness to repeated or continuous stimuli that are 

not reinforced by negative consequences, or at least by consequences that are intolerable. 

Habituation might be said to represent increased tolerance toward an aversive stimulus. 

Markhpace ratio - The ratio between the duration of an acoustic pulse and the time between 

pulses. It indicates the rate at which acoustic power is being delivered into the environment. 

Changes to the marklspace ratio directly affect the battery life of battery-operated systems. 

A 300 ms signal repeating every 4 seconds has a marklspace ratio of 1: 13. 

Pinger - I:n general, a small, low-intensity sound-generating device intended to function as 

an "active acoustic alarm." The current standard pinger, as used in the landmark experiment 

in New Hampshire in 1994 (Kraus et al. 1995), emits a fundamental signal at 10 kHz with 

harmonics to at least 60 kHz, with a source level at 132 dB re 1 pPa at 1 m. The signal 

lasts for about 300 ms and repeats every 4 seconds. This pinger was designed specifically to 

deter harbor porpoises from becoming entangled in gillnets. 

Psychoacoustic - This term refers to the psychological effect of a sound. For example, the 

high amplitude and frequency modulation of an ambulance siren stimulates a flight/alarm 

response in humans. A sound of equal amplitude, but without frequency modulation, would 

not necess;arily stimulate this response. 
Potential biological removal (PBR) level - Defined in the Marine Mammal Protection Act 

Amendments of 1994 as "the maximum number of animals, not including natural mortalities, 

that may be removed from a marine mammal stock while allowing that stock to reach or 

maintain its optimum sustainable population." For details of how PBR is calculated, see 

Barlow et al. (1995). 

Reflector - A passive sonar reflector, analogous to "cat's eyes" built into a road to reflect car 

headlights back to the driver. It works on the same principle as devices on boats that reflect 

radar and thus make the boats "more visible" to radar. Reflectors fastened to nets are 

intended to make nets more detectable to echoranging animals, i.e., increase the "target 

strength" of the nets. 

Strategic stock - A marine mammal population that is either (a) listed as endangered or 

threatened under the U.S. Endangered Species Act, or is declining and likely to be listed in 

the foresexable future; (b) designated as depleted under the Marine Mammal Protection Act; 

or (c) sut~jecto human-caused mortality greater than the estimated PBR level. 
APPENDIX 2. 

COIUMON AND SCIENTIFIC NAMES OF SPECIES MENTIONED IN THIS REPORT 

Beaked whales, whales in the family Ziphiidae 

Bluefish, Pomatomus saltatrix 

Bottlenose dolphin, Tursiops truncatus 

Cod, Gadus spp. 

California sea lion, Zalophus californianus 

Chinook salmon, Onchorhynchus tshawytscha 

Common dolphins, Delphinus spp. 

Croaker, ,Micropogonias undulatus 

Florida manatee, Trichechus manatus latirostris 

Gray seal, Halichoem grypus 

Harbor porpoise, Phocoena phocoena 

Harbor seal, Phoca vitulina 

Herring, (Clupea spp. 

Humpback whale, Megaptera novaeangliae 

Killer whide, Orcinus orca 

Mesoplodonts, cetacean species in the genus Mesoplodon 

Narwhal, Monodon monoceros 

Northern right whale, Eubalaena glacialis 

Pilot whalies, Globicephala spp. 

Sablefish (black cod), Anoplopoma cfimbria 

Shad, Alosa sapidissima 

Sperm whale, Physeter catodon 

Spot, Leioxtomus xanthurus 

S teelhead trout, Oncorhynchus mykiss 

S teller (Northern) sea lion, Eumetopias jubatus 

Striped bass, Morone saxatilis 

Swordfish, Xiphias gladius 

Vaquita, Phocoena sinus 

Weakfish, Cynoscion regalis 
Appendix 3. 

PARTICIPANTS 

Whitlow W.L. Au 

P.O. Box 1106 

Kailua, HI 96734 

Jay Barlolw 

Southwe~~t Fisheries Science Center 

National Marine Fisheries Service 

8604 La Jolla Shores Drive 

P.O. Box. 271 

La Jolla, CA 92038-0271 

James Boutillier 

Department of Fisheries and Oceans 

Pacific Biological Station 

Nanaimo, British Columbia V9R 5K6 CANADA 

Ann E. Bowles 

Hubbs-Sea World Research Inst. 

2595 Ingraham Street 

San Diego, CA 92109 

Steven G. Christensen 

Product Manager 

Sea Mammal Protection/Control 

AIRMAR Technology Corporation 

69 Meadowbrook Drive 

Milford, 1TH 03055-4618 

Stephen Dlawson 

Lecturer in Marine Science 

University of Otago 

Department of Marine Science 

P.O. Box 56 

304 Castle: Street 

Dunedin, NEW ZEALAND 
Douglas I). DeMaster 

National Marine Mammal Laboratory 

National Marine Fisheries Service 

7600 Sand Point Way, NE, Bldg. 4 

Seattle, WA 98 1 15-0070 

John K.B. Ford 

Vancouvea Aquarium 

P.O. Box 3232 

Vancouve:r, British Columbia V6B 3x8 CANADA 

Mark A. Fraker 

86 17 Lochside Drive 

Sidney, Blritish Columbia V8L 1M8 CANADA 

Patrick Gearin 

National Marine Mammal Laboratory 

National Marine Fisheries Service 

7600 Sand Point Way, NE, Bldg. 4 

Seattle, WA 981 15-0070 

Roger L. Gentry 

National Marine Mammal Laboratory 

National :Marine Fisheries Service 

7600 San~d Point Way, NE, Bldg. 4 

Seattle, VVA 981 15-0070 

A. David Goodson 

Sonar & Signal Processing Research Group 

Electronic & Electrical Engineering Department 

Loughborough University 

Loughborough, Leicestershire LEI 1 3TU UNITED KINGDOM 

Doyle Halnan 

Senior Marine Biologist 

California Department of Fish & Game 

c/o National Marine Fisheries Service 

P.O. Box. 271 

La Jolla, CA 92038 
James T. Harvey 

Moss Landing Marine Laboratories 

P.O. Box. 450 

Moss Landing, CA 95039 

Robert J. Hofman 

Marine Mammal Commission 

4340 East-West Highway, Room 905 

Bethesda, MD 20814 

Thomas A. Jefferson 

Ocean Park Conservation Foundation 

Ocean Park Corporation 

Aberdeen, HONG KONG 

Linda L. Jones 

Deputy Director 

Northwest Fisheries Science Center 

National Marine Fisheries Service 

2725 Morltlake Blvd. East 

Seattle, WA 98 1 12-2097 

Ronald A. Kastelein 

Harderwijk Marine Mammal Park 

S trandboulevard-oost 1 

3841 AB Harderwijk THE NETHERLANDS 

Darlene Kletten 

Department of Otolaryngology 

Harvard Medical School MEEl 

243 Charles Street 

Boston, MIA 021 14 

Scott D. Eaus 

Associate Scientist 

New England Aquarium 

Central Wharf 

Boston, M:A 021 10-3399 
Jeffrey L. Laake 

National Marine Mammal Laboratory 

National Marine Fisheries Service 

7600 Sand Point Way, NE, Bldg. 4 

Seattle, UrA 98 115-0070 

Jon Lien 

Ocean Sciences and Psychology 

Whale Research Group 

Memorial University of Newfoundland 

230 Mt. Scio Road 

St. John's Newfoundland A1C 5S7 CANADA 

Bruce R. Mate 

Professor of Oceanography 

Hatfield Marine Science Center 

Oregon State University 

2030 S. Marine Science Drive 

Newport, OR 97365-5296 

Craig 0. Matkin 

Marine Mammal Biologist 

North Gulf Oceanic Society 

P.O. Box 15244 

Homer, AK 99603 

Edward F. Melvin 

Marine Fisheries Specialist 

Washington Sea Grant Program 

University of Washington 

3716 Brooklyn Ave., N.E. 

Seattle, W'A 98105-6716 

Daniel Morris 

Northeast Regional Office 

National Marine Fisheries Service 

One Blackburn Drive 

Gloucester, MA 01930 
Paul E. Nachtigall 

Marine Mammal Research Program 

Hawaii Institute of Marine Biology 

University of Hawaii 

P.O. Box 1106 

Kailua, EII 96734 

Simon P. Northridge 

Sea Mammal Research Unit 

Standing stones Farm 

Maryculter 

Aberdeen AB1 OBN SCOTLAND 

Michael Payne 

Office of Protected Resources 

National :Marine Fisheries Service 

13 15 East-West Highway, Room 8258 

Silver Spring, MD 20910 

Arthur Popper 

Departme.nt of Zoology 

University of Maryland 

College Park, MD 20742 

David C. Potter 

Northeast Fisheries Science Center 

National ]Marine Fisheries Service 

166 Water Street 

Woods Hole, MA 02543 

Andrew J. Read 

Duke University Marine Laboratory 

School of the Environment 

11 1 Pivers Island Rd. 

Beaufort, NC 285 16-9721 

Randall R. Reeves 

Okapi Wildlife Associates 

27 Chandler Lane 

Hudson, Quebec JOP 1HO CANADA 
Ronald J. Schusterman 

Long Marine Laboratory 

100 S haffer Road 

Santa Crun, CA 95060 

Peter D. Shaughnessy 

CSIRO Division of Wildlife and Ecology 

P.O. Box 84 

Lyneham .ACT 2602 AUSTRALIA 

Gregory K. Silber 

Marine Mammal Commission 

4340 East--West Highway, Room 905 

Bethesda, MD 20814 

Steven L. Swartz 

Office of Senior Scientist for Fisheries 

National Marine Fisheries Service 

13 15 East-West Highway 

Silver Spring, MD 20910 

Jeanette A. Thomas 

Western Illinois UniversityIRIRUC 

6502-34th Avenue 

Moline, 11, 61265 

William A.. Watkins 

Woods Hole Oceanographic Institution 

Shiverick House, MS36 

Woods Hale, MA 02543 

Dean Wilkinson 

Office of ]Protected Resources 

National Marine Fisheries Service 

1315 East--West Highway 

Silver Spring, MD 20910 
John Williamson 

New Hanipshire Commercial Fishermen's Association 

201 Wells Road 

Kennebun~k, ME 04043 

Wesley Yi 

Dukane C:orporation 

Seacom Division 

2900 Dukane Drive 

St. Charles, IL 60174 

Sharon Young 

Humane Society of the US 

22 Washburn Street 

Bourne, MA 02532 

Judith E. Zeh 

University of Washington 

Departmeint of Statistics 

Box 3543:22 

Seattle, NrA 98195-4322 
Appendix 4. 

LIST OF BACKGROUND DOCUMENTS PROVIDED TO 

WORKSHOP PARTICIPANTS 

Anon. 1994. Report of the scientific review panel to assess the effectiveness of acoustic 

devices in reducing harbor porpoise bycatch in the New England sink-gillnet fishery. 

Workshop Report (D. Wilkinson, convener). 9-10 June 1994, Seattle, Washington. 

Au, W.W,.L. and L. Jones. 1991. Acoustic reflectivity of nets: implications concerning 

incidental take of dolphins. Marine Mammal Science 7:258-273. 

Barlow, J., R.W. Baird, J.E. Heyning, K. Wynne, A.M. Manville, L.F. Lowry, D. Hanan, 

J. Sease, and V.N. Burkanov. 1994. A review of cetacean and pinniped mortality in 

coastal fisheries along the west coast of the USA and Canada and the east coast of the 

Russian Federation. Pages 405-426. In W.F. Perrin, G.P. Donovan, and J. Barlow 

(eds.). 1994. Gillnets and cetaceans, incorporating the proceedings of the 

Syinposium and Workshop on the Mortality of Cetaceans in Passive Fishing Nets and 

Traps. Report of the International Whaling Commission, Special Issue 15, 

Cambridge, UK. 629 pp. 

Dawson, S.M. 1991. Modifying gillnets to reduce entanglement of cetaceans. Marine 

Mammal Science 7:274-282. 

Dawson, !Z.M. 1994. The potential for reducing entanglement of dolphins and porpoises with 

acoustic modifications to gillnets. Pages 573-578. In W.F. Perrin, G. P. Donovan, and 

J. Barlow (eds.). 1994. Gillnets and cetaceans, incorporating the proceedings of the 

Symposium and Workshop on the Mortality of Cetaceans in Passive Fishing Nets and 

Traps. Report of the International Whaling Commission, Special Issue 15, 

Cambridge, UK. 629 pp. 

Goodson, A.D. and R.H. Mayo. 1995. Interactions between free-ranging dolphins (Tursiops 

truncatus) and passive acoustic gill-net deterrent devices. Pages 365-379. In R.A. 

Kastelein, J.A. Thomas, and P.E. Nachtigall (eds). Sensory Systems of Aquatic 

Mammals. De Spil Publishers, Woerden, The Netherlands. 

Hatakeyarna, Y., K. Ishii, and T. Akamatsu. 1994. A review of studies on attempts to 

recluce the entanglement of the Dall's porpoise, Phocoenoides dalli, in the Japanese 

salmon gillnet fishery. Pages 549-563. In W.F. Perrin, G.P. Donovan, and J. Barlow 

(ecls.). 1994. Gillnets and cetaceans,incorporating the proceedings of the Symposium 

and Workshop on the Mortality of Cetaceans in Passive Fishing Nets and Traps. 

Report of the International Whaling Commission, Special Issue 15, Cambridge, UK. 

6219 pp. 

Jefferson, T.A., B. Wiirsig, and D. Fertl. 1992. Cetacean detection and responses to fishing 

gear. Pages 663-684. In J.A. Thomas, R.A. Kastelein, and P.E. Nachtigall (eds). 

Marine Mammal Sensory Systems. Plenum Press, New York. 
Jefferson, T.A. and B.E. Curry. 1994. Review and evaluation of potential acoustic methods 

of reducing or eliminating marine mammal-fishery interactions. Report to the Marine 

Mammal Commission, Contract No. T10155628. NTIS PB95-100384. 59 pp. 

Kastelein, R.A., D. de Haan, C. Staal, S.H. Nieuwstraten, and W.C. Verboom. 1995. 

En~tanglement of harbour porpoises (Phocoena phocoena) in fishing nets. Pages 91- 

156. In P.E. Nachtigall, J. Lien, W.W.L. Au, and A.J. Read (eds). Harbour 

porpoises - Laboratory Studies to Reduce Bycatch. De Spil Publishers, Woerden, The 

Netherlands. 

Kraus, S., A. Read, E. Anderson, K. Baldwin, A. Solow, T. Spradlin, and J. Williamson. 

1995. A field test of the use of acoustic alarms to reduce incidental mortality of 

harbor porpoises in gillnets. Unpublished report to the U.S. Fish and Wildlife 

Foundation, Washington, DC. 29 pp. 

Lien, J., W. Barney, S. Todd, R. Seton, and J. Guzzwell. 1992. Effects of adding sounds to 

cod traps on the probability of collisions by humpback whales. Pages 701-708. In 

J.A. Thomas, R.A. Kastelein, A.Y. Supin (eds). Marine Mammal Sensory Systems. 

Plenum Press, New York. 

Mate, B.F!. and J.T. Harvey (eds). 1986. Acoustical deterrents in marine mammal conflicts 

with fisheries. Oregon Sea Grant report. ORESU-W-86-001. 116 pp. 

Olesiuk, P.F., L.M. Nichol, P.J. Sowden, and J.K.B. Ford. 1995. Effect of sounds 

generated by an acoustic deterrent device on the abundance and distribution of 

harbour porpoise (Phocoena phocoena) in Retreat Passage, British Columbia. 

Un~published manuscript. Department of Fisheries and Oceans, Pacific Biological 

Station, Nanaimo, British Columbia, Canada. 47 pp. (Abstract only provided). 

Silber, G.K., K.A. Waples, and P.A. Nelson. 1994. Response of free-ranging harbour 

poipoises to potenta gillnet modifications. Pages 579-584. In W.F. Perrin, G.P. 

Donovan, and J. Barlow (eds.). 1994. Gillnets and cetaceans, incorporating the 

proceedings of the Symposium and Workshop on the Mortality of Cetaceans in 

Passive Fishing Nets and Traps. Report of the International Whaling Commission, 

Special Issue 15, Cambridge, UK. 629 pp. 

Task Force. 1996. Report of the Gulf of Maine Aquaculture-Pinniped Interaction Task 

Force. U.S. Department of Commerce, National Oceanic and Atmospheric 

Administration, National Marine Fisheries Service, Office of Protected Resources, 

Silver Spring, Maryland, February. 69 pp. 
Appendix 5. 

WORKSHOP TO ASSESS THE EFFECTIVENESS AND EFFECTS OF 

ACOUSTIC DEVICES FOR PREVENTING OR REDUCING THE 

ADVERSE EFFECTS OF MARINE MAMMALFISHERY INTERACTIONS 

Battelle Conference Center 

4000 N.E. 41st Street 

Seattle, Washington 

20 - 22 March 1996 

AGENDA 

20 March 1996 

0900 Welcome and introductions; review of meeting objectives and arrangements 

(Convener) 

0930 General overview of marine mammals and fisheries in the U.S. and elsewhere 

affected adversely by interactions (presented paper -- Michael Payne) 

1000 General overview of hypotheses concerning the causes of, and possible means 

for preventing or reducing, problems caused by marine mammal-fishery 

interactions (presented paper -- Thomas Jefferson) 

Coffee Break 

General overview of what is known about the hearing capabilities of marine 

mammals, how and for what purposes marine mammals produce and use 

sound, how marine mammals respond to and are affected by different sounds, 

and why marine mammals fail in some situations to detect and respond to 

potentially hazardous fishing gear -- presented papers (15 min. each) 

-- Large cetaceans (William Watkins) 

-- Small cetaceans (Whitlow Au and 

Paul Nachtigall) 

-- Pinnipeds (Ronald Schusterman) 

Panel discussion/commentary regarding marine mammal hearing and 

production of, and response to, sound 

(Panel: John Ford, Darlene Ketten, and Jeanette Thomas) 
1200 General discussion 

1215 Lunch 

1330 to Identification and evaluation of research done to date 

1730 -- Presented papers (30 min.); invited commentary (10 min.); general 

discussion (5 min.) 

(1330) Using sound reflectors and generators to prevent or reduce 

entanglement of large cetaceans in fishing gear (presented paper 

-- Jon Lienlcommenter -- David Goodson) 

(1415) Use of sound reflectors and generators to prevent or reduce 

entanglement of small cetaceans in fishing gear (presented paper 

-- Stephen Dawsonlcommenter -- Andrew Read) 

Coffee Break 

(1515) Using sound to prevent or reduce pinniped depredation of caught 

fish, fish returning to hatcheries or spawning grounds, and 

mariculture operations (presented paper -- Peter 

Shaughnessy/commenter -- Bruce Mate) 

(1 600) Using sound to prevent or reduce depredation of caught fish by 

killer whales and other cetaceans (presented paper -- Craig 

Matkinlcommenter -- Ann Bowles) 

(1 645) Possible effects of acoustic deterrents on marine mammals and 

other biota (Paper prepared by -- Bernd Wiirsiglpresented by -- 

William Watkins) 

Panel discussion/commentary regarding possible effects of acoustic deterrents 

on marine mammals and other biota (Panel -- Roger Gentry, Ronald Kastelein, 

Scott Kraus, William Watkins) 

General discussion 

Adjourn 
21 March 1996 

0900 Facilitated discussion to try to reach agreement on -- 

critical uncertainties and variables 

priority species and fisheries 

research needs and priorities 

when acoustic deterrence might usefully be 

incorporated into fishery management regimes 

(Douglas DeMaster -- facilitator) 

1230 Lunch 

1345 Constitute small drafting groups to prepare descriptions of key research tasks 

and to estimate the time, funding, special equipment, and logistic support that 

would be required to complete the described tasks 

1415 Small drafting group meetings 

1700 Progress reports by chairpersons of drafting groups 

1730 Break for dinner 

Evening free for continuation of small group discussions and drafting of research task 

descriptions 

22 March 1996 

Distribution of draft task descriptions 

Review and, as possible, agree upon descriptions of key 

research/monitoring/management tasks 

(Douglas DeMaster -- facilitator) 

Outline, and agree upon a procedure for completing and reviewing, the 

meeting report 

Adjourn 

70 * U.S. GOVERNMENT PRINTING OFFICE: 1997 - 590-503 1 62010 REGION NO. 10