Dolphins and the Tuna Industry (1992)

The tuna vessels fishing in the ETP and the governments under whose flags they fish have made significant progress in reducing dolphin mortality in the past two decades. In addition, three major tuna canneries recently announced that they would not buy or sell tuna caught in purse seines set around schools of dolphins, and other canneries may take similar steps. However, it was the clear consensus of this committee that the problem of reducing dolphin mortality from tuna fishing in the ETP is far from solved.

The effects of the voluntary ban by the canneries on actual dolphin mortality, for example, are uncertain. Enforcement of this ban may not be practical or even possible. For example, tuna fishermen may transship tuna caught on dolphins to foreign ports where it may be canned and sold to U.S. canneries as dolphin-free tuna. The ban may even increase mortality if it drives boats out of the more closely regulated nations' fisheries.

The committee's recommendations are divided into two parts. The first part recommends avenues for developing promising new techniques for reducing dolphin mortality in the existing purse-seine fishery on dolphins. The second part recommends research on and development of new methods of harvesting ETP yellowfin not in association with dolphins.

These recommendations fall into four categories: (1) vessel-captain education, certification, incentives, and monitoring; (2) modifications of purse-seine gear and methods; (3) research on behavior of tuna and dolphins; and (4)

development of new methods of harvesting yellowfin without encircling dolphins.

The committee recommends that an international meeting be convened of representatives from government and industry from all countries engaged in the ETP purse-seine fishery. The purposes of this meeting would be the following:

1. Develop an educational certification and monitoring protocol for all captains in the international fleet, which would include:

   • Establishment of program objectives.

   • Training and evaluation of captain performance.

   • Criteria for certification of captain.

   • Monitoring through 100% observer coverage.

2. Initiate research on the development of incentives to improve captain performance, as discussed in Chapter 7.

The primary objective of this program would be to reduce dolphin mortality caused by the relatively small number of captains that account for a majority of the kill (see Figure 6-4). The committee believes that improvement in captain performance is the single most important step that can be taken to reduce dolphin mortality in the ETP purse-seine fishery. For example, if in 1989 the average kill per set for all captains of the international fleet had been the same as the average for those of the U.S. fleet, the total dolphin mortality would have been reduced by 60% (see Figure 6-3 ). This prediction is being fulfilled: In 1991 to date, the average mortality per set for the whole international fleet matched the 1989 U.S. rate, and the reduction in the total mortality between 1989 and the projected level for 1991 is 75%. If in 1989 all captains had operated with the rates of the best five captains of the international fleet, the total mortality would have been reduced by 87%. This reduction could occur without making any improvement in the basic technology or auxiliary equipment of purse seining.

The committee recommends that two approaches, short term and long term, be undertaken in gear and methods research and development.

First, a number of small modifications of current methods (see Chapter 7) could be built and tested immediately on commercial fishing trips. The most promising of these are the current profiler, jet boat, double corkline, pear-shaped snap rings, and polyester net. The committee emphasizes that it is of paramount importance that an international program be developed to systematically deploy, test, and evaluate these modifications of current methods.

Second, a number of major modifications of current methods need to be researched and developed on a long-term basis. Many of these are described in Chapter 7 and include such modifications as inflatable sections or partitions in the net, lifting surfaces, modified purse cable, new netting materials, and modified net designs. The committee is recommending a long-term approach toward eliminating major causes of dolphin mortality in the purse-seine process—canopies, roll-ups, and collapses in the backdown channel—that couples an understanding of tuna and dolphin behavior with sound engineering.

Some of the minor modifications to purse seines, as discussed in Chapter 7, would offer an incremental reduction in dolphin mortality and little risk or expense to the commercial enterprise. These improvements are recommended because they look promising based on previous experimentation. These modifications may result in significant reductions in dolphin mortality, but they should not be expected to achieve a kill rate approaching zero.

On the other hand, some of the major modifications discussed may hold the potential to reduce dolphin mortality significantly, but none of them is developed sufficiently to offer a clear advantage without some associated risk. This risk can come in several forms: financial risk to the operator, continued risk to dolphins, or risk to the tuna stocks. Examples of each type of risk are the cost of a new net of unproven advantage, the adoption of a dolphin-sparing gear having unanticipated dangers for the dolphins, and the adoption of a technique that results in exploiting immature tuna not associated with dolphins and thus reducing stocks.

Research is needed for a better understanding of the behavior of both dolphins and tuna and the bond between them. Details, costs, and potential benefits of many of the concepts delineated above cannot be judged at present.

Previous research programs addressing the tuna-dolphin problem have been constrained in three significant ways: (1) inadequate support of gear development and research on behavior; (2) the use of vessels in which the production of knowledge had to be balanced against the production of tuna; and (3) concentration on perfecting the conventional purse seine and the backdown process instead of developing other technologies. From a global perspective, the only way to reduce dolphin mortality is either to develop gear and techniques that will safely and efficiently harvest the tuna found beneath dolphins or to stop setting nets on dolphins. The current approach to the problem—monitoring the dolphin mortality and prodding the backdown process toward perfection —will almost certainly not achieve zero mortality.

Fishermen need both incentives and options to make further progress in reducing dolphin mortality. The individual fisherman alone cannot be expected to develop the options that offer significant improvements if they represent major changes to the present gear because fishermen who adopt

gear that is likely to reduce dolphin mortality might incur economic losses. A program of research should be established to develop options and to demonstrate them to the industry. Such a program should include two facets:

• An experimental research program of innovative gear that would investigate performance and techniques. This program would have access to a modern commercial purse seiner as a dedicated vessel that would not be constrained by the normal pressures of tuna productivity. Because the capture of animals by fishing gear involves interactions between the animals and the gear, the research must include a program of behavioral studies focused on the reactions of both tuna and dolphins to fishing gear and other stimuli. Research techniques would include underwater video observation and acoustic sensing and tracking. Most of the research effort would be at sea.

• The information gained from the research above would then be used to develop rational purse-seine modifications and alternative harvesting methods based on the engineering requirements of the fishery. This focus would use analysis and modeling to develop, refine, and evaluate each concept to ensure a reasonable chance of success before it was attempted as a commercial prototype. After the analysis and modeling, promising prototypes would be field-tested.

The tools of this research would include remote-operated vehicles (ROVs), scanning sonar, electronic gear monitoring sensors, hydrodynamic test tanks, and computers, in addition to the dedicated vessel. To accomplish the research, experts from a variety of disciplines would be used. In addition to people with a historical involvement in the tuna fishery, experts from other fisheries and from relevant engineering and scientific disciplines would be involved. The goal of the research would be to develop techniques that can exploit yellowfin tuna in the ETP without significant dolphin mortality. The program would be of finite duration, and long-term monitoring activities would be performed by existing agencies. The program would cost at least several million dollars.

Some specific aspects of the interaction of tuna, dolphins, and fishing gear that are in particular need of study are discussed below.

As was indicated in Chapter 5, very little is known about tuna and dolphin behavior, particularly when they are inside the net and when they escape from the net. Either scanning sonar or ROVs could be used in conjunction with a chartered purse seiner to study this behavior. Several scientists have proposed using ROVs to allow videotaping and other sensing during tuna seining. These mobile data-gathering platforms can be designed to operate in the net, even into the backdown period. Their use throughout the entire course of the set

should allow the gathering of many visual and acoustical data showing the relations of tuna and dolphins to each other and to the net. It should also be possible to gather data during the seine set by deploying the ROV from a small associated vessel and then setting the net around both vessel and ROV.

ROV technology could help answer some of the following questions:

• Is the tuna-dolphin bond broken during seining? If so, when and why?

• How deep in the net do tuna go?

• Is there any useful behavioral difference between the two partners in the bond that would allow differential release of dolphins and retention of tuna?

• When might this separation occur in a set?

• What is the underwater effect of outside stimuli such as net skiffs, jet skis, and speedboats on dolphins and fish?

• What are the shape, behavior, and disposition of dolphins and tuna schools in a net at the various stages of its closing?

• What is the relation of tuna and dolphin to the net throughout a set?

• Can more be learned about entanglement, avoidance of canopies, and other problems of backdown?

• Can changes in dolphin behavior at sunset, compared with daylight, be documented?

In summary, thorough videotaping of events throughout a set should provide a great deal of new information about behavior during seining.

No specific information is available concerning the effects of the chase on the biology of dolphins. The chase is likely to result in stress. Some herds have developed strategies to avoid capture; others seem to have habituated to encirclement and seem to have developed behavioral patterns that reduce their risks once in the net. Further studies on physiological and behavioral impacts of the chase are obviously needed.

The increased mortality of seined dolphins taken near dusk makes it seem likely that visual problems are involved. Behavior of netted dolphins as seen from ROVs probably would be instructive. Measurements of the progress of light intensity in the net as dusk arrives would also be useful, as would testing of net materials that could improve the visibility of the net.

If, as is suspected, bubble trails from the seiner's propeller are crucial to the present success of encircling dolphins, it may be that bubbles made by generators could be used to maneuver animals in the net and hence to help release them. Such methods could reduce the duration of sets and hence the stress upon netted animals and aid in pre-backdown release.

If current models of dolphin-herd function are correct, as discussed in Chapter 7, then it should be possible to predict the size of openings that will be required to exploit normal escape behavior of dolphins to produce quick and complete release of dolphins from tuna seines.

Three needs must be met if this concept can be used to release dolphins during tuna seining. First, the mechanical and operational means of producing such a gate at sea without loss of tuna is essential. Second, the predicted dimensions of such an opening must be refined in actual tests. Third, proposed methods of maneuvering dolphin herds in the open net toward such a gate must be tested and refined.

If the association of tuna with dolphins is an extension of the behavior that leads them to associate with flotsam, as some researchers believe, comparative data are needed on environmental conditions where dolphins and tuna associate and where they do not associate. All observers on seiners should be trained and equipped to collect basic environmental measurements, including water color and clarity, thermal profiles, and weather, in all sets, whether on dolphins, flotsam, or school fish. Good samples of the same information should be collected from places without fish.

The most direct way to determine the durability of the tuna-dolphin bond is to tag and follow individuals of both species that are caught together. Carey and Olson (1981) tagged yellowfin tuna with ultrasonic transmitters and successfully followed individuals. They uncovered enough information about tuna behavior that was not suspected to show that the effort needs to be

extended and coupled with simultaneous radio tracking of tuna and dolphins. Recent advances in telemetry allow measurement of enough factors, such as body temperature, swimming speed, depth, and duration of dives, to construct a good profile of the environmental correlates of the bond.

Placing sonic tags on tuna caught near flotsam or FADs would provide valuable data on that association as well as data for comparison with those obtained from dolphin-associated tuna. Comparative data from large yellowfin tuna associated with flotsam are especially important.

The committee believes that IATTC's flotsam information program— aimed at finding out why tuna associate with logs and with dolphins (see Appendix 2)—should be intensified. All IATTC observers document the physical and biological characteristics of the flotsam they find. In 1987, they attached tags to the objects and sent out notices to fishermen requesting documentation of the times and places where fishermen saw a tagged log, its condition, and information about any fish associated with it (see Appendix 3 ). The objective was to understand drift patterns and learn about longevity and relative attractiveness of various kinds of flotsam. Recoveries were very few, but IATTC hopes to repeat the experiment, using satellite transmitters to track the logs. All observers on seiners should collect these data, as should oceanographic research vessels. Body-length data for the fish caught in different situations and at different locations also are important to collect.

Although tuna aggregation around floating objects differs in important ways from tuna aggregation with dolphins, the tendencies that underlie tuna aggregation around logs and dolphins probably have much in common. Studies using instrumented FAD platforms are likely to provide valuable information. A FAD can be easily designed as a data-gathering platform, and instrumented with lights and 24-hour underwater video and other monitoring devices (such as acoustic sampling). Sets made around instrumented FADs may reveal further information about the reactions of animals to seining. In addition, the use of structures much larger than current FADs might be worth consideration.

It is possible to track radio-tagged dolphins of various species for several days. Such work should illuminate the nature of the association between dolphin species—for example, spotted and spinner dolphins —taken in the

same net. The degree of permanence of the herds that have experienced netting and the timing of their different feeding strategies should be defined. Disruption of schools caused by seining may have serious social consequences on dolphins, which could be monitored. Such data may begin to define a number of unknown features of dolphin herds and their interrelations, such as range of species. Long-term tracking should give information on the coherence of dolphin herds (i.e., are they persistent or are they frequently re-found with different individuals?) and data on the frequency of seining on specific dolphin herds, as well as their behavior during approach of vessels and after release. Such questions as how rapidly netted dolphins swim before they reaggregate into feeding herds and how far they travel can be considered. Short-term tracking may allow physiological assessments of the stress of seining on dolphins. Studies of the composition of netted herds also may help answer questions about the social consequences of seining on dolphins.

The committee recommends two avenues of research. The first recommendation involves research into the night behavior of tuna and dolphins and the second involves research into new methods of purse seining large yellowfin not in association with dolphins in the ETP. If purse seining for tuna in association with dolphins is discontinued, the committee recommends that the impact on tuna populations be carefully assessed and further notes that additional restrictions may be necessary to maintain the productivity and viability of tuna stocks in the ETP. Differences exist in the size-specific fishing mortality rates imposed by dolphin sets and non-dolphin sets, the result being that sets of the latter type produce lower yield per recruit than the former. Although a relationship between stock size and recruitment has not been detected for the range of observed population levels, increased pressure on young tuna eventually may reduce adult stock size to a level at which recruitment may be reduced, which would further decrease overall production.

If large yellowfin do not associate with dolphins at night, purse seining or trawling could be done at night, which would reduce dolphin mortality significantly. To study night behavior, tuna and dolphins that are associated during the day need to be tracked at night, the tuna with acoustic tags and the dolphins with radio tags.

Even if harvest of yellowfin tuna in association with dolphins continues, the committee recommends that a major research effort be undertaken to explore new methods of harvesting yellowfin in the ETP. Three promising avenues of research identified by the committee are as follows:

• Can anything about FADs be changed—e.g., size, depth, shape, structure, composition—to make them attract larger yellowfin and change the mixture of species they attract? In the short term, existing FADs could be deployed and monitored by observer-manned commercial fishing vessels. In the long term, a chartered purse seiner could be used to investigate the performance of such new technologies as submerged FADs, which may have a greater potential than surface FADs for attracting and holding commercially harvestable schools of large yellowfin tuna. This research would be conducted in conjunction with that described in Chapter 5 on the behavior of tuna and dolphins.

• The use of satellite oceanographic techniques to locate aggregations of tuna not associated with dolphins in the ETP. Information from satellites on surface oceanography would be analyzed with catch information from tuna-vessel log books to determine whether large yellowfin aggregate in harvestable numbers without dolphins under certain environmental conditions in the ETP.

• The use of alternative techniques of locating tuna that do not depend on the sighting of dolphins. Emerging technologies such as light-induced detecting and ranging (LIDAR) and synthetic aperture radar (SAR) hold promise because of their ability to detect the presence of tuna as described in Chapter 7; sonar, despite its drawbacks, might have promise as well.

In addition to the above three items, the committee members had diverse opinions about the promise of research on the potential of non-purse-seine techniques that do not involve the encircling of dolphins. Two methods were discussed. The first would be the development of high-intensity economically viable techniques of longlining such as the use of a fleet with catcher boats and a mother vessel (which works in other fisheries) or the use of helicopters to place baited hooks in the path of tuna schools (which is more remote a possibility). The second would be development of midwater pair-trawl techniques designed to catch tuna by towing well beneath the associated dolphins.

In summary, the committee recommends that two major international efforts be undertaken to reduce the mortality of dolphins in the ETP tuna fishery. Once again, we emphasize the word “international, ” since most of the ETP dolphin mortality occurs in the non-U.S. fishery. The first recommendation is to develop an educational, monitoring, and incentives program for tuna vessel captains aimed at reducing the dolphin mortality from the relatively small number of captains that accounts for a large proportion of the kill. The committee considers this to be the single most important short-term step that can be taken to reduce dolphin mortality in the existing ETP purse-seine fishery. The second recommendation is to develop a major international program for gear and behavior research aimed at reducing dolphin mortality through the following:

• Systematic deployment of small, currently available modifications of present-day purse-seine methods that show promise (e.g., current profiler, jet boat, double corkline, pear-shaped snap rings, and polyester net).

• Development of major new modifications in purse-seine technology through a three-pronged program of engineering, modeling, and full-scale testing using a chartered purse seiner.

• Design and implementation of a major research program on the behavior of tuna and dolphins in the ETP. This program would be conducted from a chartered purse seiner and would investigate such phenomena as (1) tuna and dolphin behavior when they are inside the purse-seine net and when they are escaping from the net; (2) night behavior of tuna and dolphins; (3) the effects of chasing dolphin herds; (4) the effects of sets in dim light; and (5) techniques for maneuvering and separating tuna and dolphins inside the seine.

• Design and implementation of a major research program on new methods of harvesting yellowfin in the ETP without encircling dolphins. This program would be conducted from a chartered purse seiner and would investigate such concepts as (1) the use of surface and subsurface FADs to aggregate large yellowfin; (2) the use of satellite oceanographic techniques to locate aggregations of large yellowfin not in association with dolphins in the ETP; and (3) the use of LIDAR and SAR, and possibly sonar, to detect tuna.

The committee recommends that both programs be initiated immediately. The vessel captain educational, monitoring, and incentives program should be created through international meetings of government and industry representatives of all nations currently purse seining in the ETP. To implement and evaluate this effort, mortality reduction targets must be established. The gear and behavior research program should be developed through a collaborative international effort and should be designed to run for 5-7 years.