Fish Behaviour in Exploited Ecosystems

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. 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. 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. 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, in the behavioural the of collective in his keynote address entitled and The Symposium presentations were the five theme sessions. posters were on the first and was a the posters were integrated into the programme by a through a of the main of On the opening the challenged the participants by that the presentations not be the measure of a successful meeting and that those who the sessions from the Symposium more they had to it The of success would be the of the of the symposium and what impact on future studies of fish behaviour would be. At the of theme were for collective on the of key research not and the future this research discussions to an of the discussions are at the of this volume as five individual scientific A synthesis of the main from these is as a of the main Much of the emphasis at the 2003 Symposium was on and how we can the of fish stocks through an understanding of fish behaviour and fish The studies at the Symposium the that fish a of to both natural and Fish are and of and a lot of and are of and with a behavioural or experiments to design our studies, we must that the animal is In operations, fish can from in behavioural that increase in of live fish and in fish through of trawls. experimental designs used in survival studies of fish that gear need to for the of behaviour to increase The technology with which to behaviour has since the 1992 Symposium. This technology has more to observe and measure fish behaviour in two and three tags and have the of fish behaviour and in the species based on from the fish. approaches to developing indices of behaviour, such as the relationship between from the of and fish movements, were noted and be of fish behaviour, those on catchability, have that fishing gear, trawl surveys, acoustics, and behaviour research are of improving fish stock with behavioural scientists have also to developing more selective fishing gears. Many of the fish-behaviour studies at the such as those related to of and spatial patterns in an or of factors affecting catchability of fishing gears and sampling tools, often of the of There is a need to a behavioural ecology to the understanding of fish behaviour in fishery It was that this could be through future between behavioural and fisheries scientists in behaviour. for joint research was as a critical in information on fish behaviour to the of problems in fisheries and ecosystem management. A research emphasis is to the role of fish behaviour in the since many fish stocks are or have collapsed, with little attention given to how these reductions in stock size could the behaviour of the Fishing with represents to both fish populations and the environment, and could an on the the for stock Many of future behavioural research on catchability and selectivity would from a more integrated international approach in and experiments to solve scientific issues and management The time be to a new way of about the use of in a wider and focus more on selective methods on selective gears, together with a wider of other such as and temporal closures and marine areas. of fish behaviour the interactions between species are well but models behavioural with and physiological state together with fishery data and changes in management approaches when on the influence of behaviour on one theme emphasized the need for data models of fish behaviour be a primary focus for future with attention to the of the Symposium participants suggested that Symposium on fish behaviour be held in in Bergen, which focus on the progress of the lines of research on fishing gear and fish behaviour suggested There is a of scientific specialists at the Symposium work in understanding and the contribution that can be to the problems of fisheries management. stock assessment on of data to a of the world's The stock assessment scientists to for all time, to whether fish stocks are in danger or observe that fish and their from their the as and to fish are by the and changes in one species affect the abundance of studying the behaviour of fish are aware of the way it and know that this affect stock We must of these factors if we are to improve the stock and if we are to manage fisheries with wider regard for D. 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