© 2004 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Fish Behaviour in Exploited Ecosystems
Introduction
a Department of Fisheries and Oceans PO Box 5667, St John's, Newfoundland, Canada A1C 5X1
b Institute of Marine Research PO Box 1870 Nordnes, N-5817 Bergen, Norway
*Correspondence to S.J. Walsh. e-mail: walshs{at}dfo-mpo.gc.ca; aasmund.bjordal{at}imr.no.
The second ICES Symposium on fish behaviour, entitled "Fish Behaviour in Exploited Ecosystems", was held from 23 to 26 June 2003 in Bergen, Norway, and co-convened by Åsmund Bjordal (Norway) and Dr Stephen J. Walsh (Canada). The scope of the Symposium was restricted to marine finfish, and the programme was organized according to five theme sessions. The response to announcements was overwhelming, with 159 titles submitted, and of these, 56 oral presentations and 49 posters were selected for the Symposium. In addition, there were four keynote addresses. The Symposium attracted 180 participants from 31 countries. This volume contains the papers submitted, reviewed, and accepted for publication.
The first ICES Symposium on fish behaviour was entitled "Fish Behaviour in Relation to Fishing Operations" and was also held in Bergen, in 1992 (Wardle and Hollingworth, 1993). After this meeting, fish behaviour became a common topic for the joint sessions of both Working Groups of the ICES Fisheries Technology Committee. The ICES Working Group on Fisheries Acoustics Science and Technology, and the ICES–FAO Working Group on Fishing Technology and Fish Behaviour, have included in their remit that fish behaviour is widely recognized to be one of the most important sources of bias in acoustic and bottom-trawl surveys, as well as in fishing operations for marine finfish and shellfish. The Working Group on Fishing Technology and Fish Behaviour also recognized that detailed knowledge of fish behaviour was needed for developing fishing technology to meet the requirements of responsible fishing with regard to selectivity, by-catch reduction, survival of non-target species, and conservation of biodiversity in an ecosystem approach to fisheries management.
Since the 1992 Symposium, progress in the study of fish behaviour has accelerated owing to the use of emerging technologies, such as underwater video cameras, telemetry, and acoustic tags, acoustic hydrophone arrays, remotely operated and autonomous underwater vehicles, multibeam sonars, and scanning laser systems. These technologies, together with significant developments in imaging technology, storage, and archiving, as well as image-processing hardware and software, have dramatically improved the state of knowledge and understanding of the main characteristics of fish behaviour and their impact on fisheries research activities.
The 2003 Symposium was envisaged as a result of discussions of the role of incorporating fish behaviour information into stock assessment and ecosystem modelling, which took place during the meeting of the ICES Fisheries Technology Committee held at the ICES Annual Science Conference in Brugge (Bruges), Belgium, in September 2000. The time was ripe for a second Symposium.
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Overview |
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Fish live in a three-dimensional environment that is largely inaccessible to us, and their behaviour represents solutions to problems encountered in that space. We can seldom observe them directly. Yet we need to know what factors influence their growth, movements, and reproductive behaviour, and how these factors, in turn, affect fishery catches and our ability to assess and manage the fisheries. Fish behaviour research and the development of fish capture technology in the field of fisheries science received particular support from four international fishing-gear conferences, the first three of which were organized by the UN Food and Agriculture Organization (FAO) in 1963, 1967, and 1970, and the fourth by ICES as the ICES Symposium on "Fish Behaviour in Relation to Fishing Operations" in 1992. This ICES Symposium was a follow-on to the 1967 FAO Conference on "Fish Behaviour in Relation to Fishing Techniques and Tactics" (Ben Tuvia and Dickson, 1968), which was held in Bergen.
We could use knowledge of fish behaviour to alter the search strategy to develop more efficient detection devices, or to re-design extant gear to increase the probability of capture. (Dr D. L. Alverson, Chair of the 1967 FAO Conference)
The 1967 FAO Conference involved a mix of disciplines: biologists and fishing-gear specialists, theoreticians and practical workers, those who study fish in the aquarium, and those who work on them at sea, took part. Some of the most eminent scientists studying fish behaviour were there and, as in 1992 and 2003, a number of crucial issues emerged. The schooling behaviour of fish proved to be of special interest, and the differences between "schools" and "aggregations" were debated. The movements of fish were described, including the great migrations of the Norwegian spring-spawning (Atlanto-Scandian) herring. The swimming of fish and the subject of fatigue were considered. There were critical discussions of the sensory capabilities of fish: how well could they see, hear, and smell? How quickly did fish learn? Was there genetic selection for fish that could lead to avoidance of fishing gears? The operation of fishing gears was considered: did the nets simply sieve fish from the sea, or did the fish react to them? Were fish herded by the trawl wings, sweeps, and otter boards? The behaviour of fish in the mouth of trawls was modelled for the first time, from the simple movements of individual fish to the collective movements of schools. One of the key questions then, as in 1992 and 2003, concerned the contribution fish-behaviour and fishing-gear specialists could make to the wider problems of managing fisheries in a changing world.
Catch efficiency and selectivity are real-world manifestations of fish behaviour, and better understanding of natural behaviour and learning capacity is a prime topic for future research. (Steinar Olsen, Convener of the 1992 ICES Symposium)
The 1992 ICES Symposium also attracted a mix of theoreticians and experimentalists, engineers and biologists, fishing-gear and acoustic experts, those who work in labs and those who work at sea. The scope of this meeting gave priority to the effects of fish behaviour directly, and indirectly, on fishing success. The theme sessions covered topics such as fish behaviour relevant to fish capture processes and techniques of observation, and the application of fish-behaviour knowledge (Olsen, 1993). Questions fundamental to the 1967 Conference were again discussed. What are the learning capabilities of fish? Can they learn to avoid capture? Can we predict fish behaviour through mathematical modelling? New information arose, and new questions were debated. The radiated noise levels of research vessels were considered, and their effects on fish avoidance/capture and the ability to estimate population size of pelagic fish were questioned. What were the critical factors that determine the success of whether a fish is caught or not? What were the critical behavioural patterns seen in attempts by fish to escape through meshes, and can they be used to increase escapement and selectivity? Do fish survive when they escape through codends, and if so, for how long? Interesting applied applications of fish behaviour to develop better fishing gears and improve size- and species-selectivity were presented, such as herding fish into set nets by air bubble curtains, and the sorting of fish size and species by using metal grids in bottom trawls. A lot of attention was given to utilizing fish-behaviour information to improve resource-survey estimation of abundance and to fisheries management practices. It was also noted that fish-behaviour studies that led to changes in fishing-gear designs could solve management problems such as by-catch and bottom-impact reductions just as effectively as prohibiting certain methods of fishing or designating closed areas.
The 1967 FAO Conference had produced a great deal of basic fish-behaviour information and suggested that more emphasis be placed on exploring the relationship between natural behaviour and behaviour in relation to fishing gears. It was evident at the 1992 Symposium that a lot of work had been done, but not much of it was along the lines proposed in 1967, and even though there had been revolutionary changes in our understanding of animal behaviour between the two time periods, little of it had influenced the research on fishing gear and behaviour (Fernö, 1993).
Much has also changed since the 1967 and 1992 meetings. Although we are now discussing many of the same themes, their context has changed significantly. In 1967, there was strong interest in making fishing gears more effective and efficient, and it was a time when the most successful fishing techniques were being applied in more and more fisheries around the world. In 1992, there was a more conservation-oriented approach to harvesting, with emphasis on making the trawls more selective in fishing and reducing by-catch. However, there was a recognition that stocks were being overfished in many oceans, and their sustainability was being questioned in some areas. At the very time of the 1967 Conference, some of the world's largest pelagic fisheries had begun to fail: those for North Sea mackerel, Norwegian spring-spawning herring, North Sea herring, and Peruvian anchovy; and some of them were later closed. At the time of the 1992 Symposium, many of the world demersal stocks were also declining: the second largest cod stock in the Atlantic, off the coast of Newfoundland, was closed to fishing, and many other gadoid and flatfish stocks off the east coast of Canada and the United States would soon follow suit. Many of these closures are still in effect. In 1967, concern over the need to conserve fish stocks was largely abstract in nature and there was little anticipation of the impending changes to the great fisheries. In 1992, some of these great fisheries had collapsed, and others were in danger of collapsing. Yet there was a naïve hope that these events could be quickly reversed. In the ensuing decade, other fisheries have collapsed, and although some stocks have since recovered, we are all aware of just how vulnerable even the largest fisheries can be.
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Objectives and scope |
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By 2003, many marine fisheries were no longer sustainable, and the future of many stocks was in jeopardy. The recent overexploitation and collapse of several fish populations worldwide and the ensuing social consequences for many fishers demanded that key sources of uncertainty in stock assessment be identified. It was now accepted by all stakeholders in the fishery that fishery management was often based on imprecise estimation of population size, productivity, and age structure, as well as incomplete knowledge of the dynamics of populations and their fisheries. Many fishers and others have lost confidence in the ability of scientists and managers to find solutions to the problems of fisheries management. Fish abundance estimates are now questioned, and some are perceived as being based on untested assumptions about the behaviour of fish. Much of the attention during the past decade has centred on analytical modelling of single species, often ignoring the role of fish behaviour, and the way this behaviour changes as stock size is drastically reduced and/or as the size of prey stocks is reduced, or as the environment and fishing operations change.
Undeniably, fish behaviour plays a pivotal role in the understanding of variability in the results of resource and monitoring surveys, and fishing operations, and a further role in the design of selective fishing gears to reduce by-catch and lessen ecosystem effects of fishing. Yet fish-behaviour information is often qualitative, and when quantified, rarely incorporated into stock assessment and forecasts of stock size. The study of fish behaviour can play a major role in improving our understanding of exploited ecosystems and the adoption of an ecosystem approach to fisheries management.
In 2003, the second ICES Symposium on fish behaviour sought to provide a broad international forum for global synthesis of the scientific knowledge of fish behaviour in exploited ecosystems, to review and discuss the advances in technology and analytical methods used to study fish behaviour and to provide a forum for discussions on how objectives related to fish behaviour can be effectively incorporated into stock assessment and fisheries management. Although the primary focus was to be on the relationship between fish behaviour and variability in resource abundance indices, and the development of more selective and environmentally friendly fishing gears, the symposium also recognized that certain studies of natural fish behaviour such as movements, migrations and aggregations, and fish physiology such as vision and sound perception, have both direct application and influence in scientific evaluation and the behaviour of fisheries. Papers reporting ongoing fish-behaviour research in exploited stocks of demersal fish, small and large pelagics, and sharks and rays found in coastal, estuarine, semi-enclosed seas, continental shelves, and the deep sea, were invited for the following five theme sessions.
Session 1: Observation techniques and experimental designs for the study of fish behaviour, including sampling schemes, tools, and methods for observing and quantifying behaviour of fish in their natural environment, such as optical systems, passive and active acoustics, biotelemetry, and the development of new non-intrusive technologies.
Session 2: Physiological mechanisms of sensory organs and their role in fish behaviour, including the tools and methods used to measure morphological and physiological aspects of fish behaviour, the biomechanics of sensory organs, the role of hearing, olfaction, vision, and other senses in fish behaviour. Laboratory and field studies of swimming performance, location of objects in 3D space, and the use of fish senses to control fish behaviour, were also emphasized.
Session 3: Influence of social behaviour and behavioral interactions in understanding temporal and spatial dynamics and their effect on availability and catchability in resource and monitoring surveys and fishery operations, and in the design of species-selective and ecosystem-friendly fishing gears, including schooling behaviour, factors affecting clustering and aggregations, aggression, territoriality, competition for food, reproductive behaviours, impact of site fidelity, homing, migrations (long distance and vertical), and habitat selection behaviours. Papers that further our understanding of how social behaviour influences temporal and spatial patterns of distribution and quantitative estimates of stock size that are fundamental for effective fisheries management and rational exploitation of the resources were encouraged.
Session 4: Fish behaviour relevant to fish catchability, including basic behaviour determining the probability of contact with stimuli from vessels and fishing gear, motivational effects and conflicts between stimuli, ontogenetic effects, the role of learning in fish behaviour, and the effects of selection on response pattern. Resolving reaction complexity, such as coping with variation in response threshold, for example toward vessels and fishing gear, is an important issue in understanding resource-survey variability. Papers quantifying fish reactions to fishing vessels and fishing gear, avoidance behaviour, and their effect on resource surveys and monitoring, and linking the use of fish behaviour to improve species- and size-selectivity of active and passive fishing gears and in the design of ecosystem-friendly fishing-gear studies, were encouraged.
Session 5: Modelling fish behaviour, including mechanistic and descriptive approaches and individual-based and other simulation models of natural and fishing-gear-induced behaviour. Papers demonstrating a natural extension of classical behavioural ecology theory to modelling adaptive changes in fish behaviour of exploited fish stocks in response to selective fishing were encouraged. The development of numerical models that incorporate fish behaviour into the estimation of resource abundance indices and the development of statistical models to handle large volumes of behavioural data from observational devices, such as data storage tags and other acoustics instruments, were welcomed.
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The symposium |
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On Day 1, Dr Penny Allen, BBC Natural History Unit, Bristol, gave an inspiring opening lecture entitled "Bringing Oceans into Focus: The Challenges of Filming Fish Behaviour for Wildlife Documentaries", which emphasized that unexpected behavioural patterns often appear during field experiments and must be opportunistically integrated into the experiment.
On Day 2, Dr Julia K. Parrish, University of Washington, Seattle, challenged the traditional approaches of fish-behaviour research within fisheries science, with her provocative keynote address entitled "Alle, Lagrange, Darwin, and Pangloss: Individual Behaviour and School Response in Exploited Eecosystems".
On Day 3, Dr Olav Rune Godø, Institute of Marine Research, Bergen, effectively demonstrated the relevance of fish behaviour in understanding fish-catchability estimates in resource surveys and fishery operations, in his keynote address entitled "Fish Behaviour and Fish Catchability in Modern Ecosystem-Based Assessment".
On Day 4, Professor Jean-Louis Deneubourg, Université Libre de Bruxelles, Brussels, discussed in depth the behavioural rules governing the emergence of collective patterns, in his keynote address entitled "Patterns and Group-Living Organisms".
The Symposium presentations were allocated among the five theme sessions. All posters were up on the first day, and each was assigned a session number. During each session the posters were integrated into the programme by a volunteer participant through a summary PowerPoint presentation of the main highlights of each poster.
Discussion sessions
On the opening day, the Conveners challenged the participants by noting that the presentations should not be the ultimate measure of a successful meeting and that those who attended the sessions should take away from the Symposium more than they had brought to it individually. The real yardstick of success would be the participants' vigorous discussion of the importance of the symposium and what its long-term impact on future studies of fish behaviour would be. At the end of each theme session, 20–40 min were allocated for collective discussion on the current status of research, key research areas not addressed, and the future directions this research should follow. All session discussions ran close to an hour. Synopses of the discussions are presented at the end of this proceedings volume as five individual scientific summaries. A brief synthesis of the main points, borrowed freely from these discussions, is presented here as a cohesive description of the main conclusions.
Conclusions
i) Much of the emphasis at the 2003 Symposium was on sustainable fisheries, and how we can secure the safety of fish stocks through an understanding of fish behaviour and fish catchability.
ii) The studies presented at the Symposium highlighted the point that fish show a wide repertoire of responses to both natural and anthropogenic stimuli. Fish are multi-sensory and capable of receiving and processing a lot of different signals, and are capable of learning, becoming stressed, communicating, and feeling pain. When formulating hypotheses with a behavioural component, or conducting experiments to design our studies, we must never forget that the animal is complex.
iii) In commercial operations, fish can experience stress from injury, resulting in behavioural deficits that may increase mortality in discards of live fish and in fish escaping through meshes of trawls. Current experimental designs used in survival studies of fish that encounter gear need to account for the potential of behaviour deficits to increase mortality.
iv) The technology with which to "observe" behaviour has advanced considerably since the 1992 Symposium. This technology has more than ever allowed researchers to observe and measure fish behaviour in two and three dimensions. Acoustic tags and listening devices have allowed the simultaneous measurement of fish behaviour and environmental data, including, in the latter case, species identification based on specific emitted noises from the fish. Novel approaches to developing indirect indices of behaviour, such as the relationship between growth from the microstructure of otoliths and fish movements, were noted and should be pursued further.
v) Studies of fish behaviour, especially those focused on catchability, have shown that fishing gear, trawl surveys, acoustics, and behaviour research are capable of improving fish stock assessments. Fishing-gear experts working with behavioural scientists have also contributed to developing more selective fishing gears.
vi) Many of the fish-behaviour studies presented at the symposium, such as those related to observation of dynamic and spatial patterns in an ecosystem, or of factors affecting catchability of fishing gears and sampling tools, often remain underexploited because of the lack of testable hypotheses. There is a need to define testable hypotheses under a behavioural ecology framework to enhance the understanding of fish behaviour in fishery science. It was stressed that this could be achieved through future cooperation between behavioural ecologists and fisheries scientists interested in behaviour. Developing strategic agendas for joint research was viewed as a critical step in providing information on fish behaviour useful to the resolution of problems in fisheries and ecosystem management.
vii) A stronger research emphasis is required to understand the role of fish behaviour in the ecosystem, since many fish stocks are overexploited or have collapsed, with little attention given to how these severe reductions in stock size could change the behaviour of the stock. Fishing with high effort represents stress to both fish populations and the environment, and any resultant increases could introduce an additional stress on the ecosystem, limiting the potential for stock recovery.
viii) Many areas of future behavioural research on commercial catchability and selectivity would benefit from a more integrated international approach in testing hypotheses and designing experiments to solve scientific issues and specific management requests. The time may be right to consider a new way of thinking about the use of technical devices in a wider context, and focus more on selective methods rather than solely on selective gears, together with a wider array of other technical measures, such as seasonal and temporal closures and marine protected areas.
ix) Models of fish behaviour describing the interactions between species are well developed, but newer models should integrate behavioural observations with biological, ecological, environmental, and physiological state variables, together with fishery data and changes in management approaches when focusing on the influence of behaviour on catchability. More than one theme session strongly emphasized the need for integrating various applicable data sources. Generic models of fish behaviour should be a primary focus for future development, with attention to the scale of the study.
x) Symposium participants suggested that another Symposium on fish behaviour be held in 2013 in Bergen, which should focus on the progress of the lines of research on fishing gear and fish behaviour suggested here.
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Epilogue |
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There is a risk, however, of scientific specialists like us here at the Symposium pursuing work in isolation, without understanding its broader context, and without realizing the contribution that can be made to solving the broader problems of fisheries management. Current stock assessment depends on long time-series of data to create a static picture of the world's oceans. The stock assessment scientists seek to establish fixed reference points, standing for all time, to indicate whether fish stocks are in danger or not. Fishermen see things somewhat differently. They observe that fish distributions change and their migration routes alter. Fishermen, from their own activities, see the seas as dynamic and liable to alter, where fish are affected by the climate, and where changes in one species affect the abundance of another. Scientists studying the behaviour of fish are only too aware of the way it changes, and know that this may affect stock assessments. We must take greater account of these dynamic factors if we are to improve the stock assessments, and especially if we are to manage fisheries with wider regard for conservation. (Professor Anthony D. Hawkins, Symposium summary).
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Symposium awards |
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The Symposium recognized the outstanding achievements of its participants by selecting Sophie Bertrand, l'Institute de Recherche pour le Développement (IRD), France, as winner of the "Best Talk" award, and Hans Polet, Sea Fisheries Department, Belgium, as winner of the "Best Poster" award.
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References |
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Proceedings of the Conference on Fish Behaviour in Relation to Fishing Techniques and Tactics19–27 October 1967Bergen, Norway (1968) vol. 1: 47 pp.
Fernö A. (1993) Advances in understanding of basic behaviour: consequences for fish capture studies. ICES Marine Science Symposia 196: pp. 5–11.
Olsen S. (1993) Fish behaviour in relation to fishing operations/introduction. ICES Marine Science Symposia 196:1.
Wardle C. S. and Hollingworth C. E. (1993) Fish Behaviour in Relation to Fishing Operations. Selected papers from a Symposium held in Bergen11–13 June 1992 ICES Marine Science Symposia, 196. 215 pp.
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