Thirty years of fleet dynamics modelling using discrete‐choice models: What have we learned?

Anticipating fisher behaviour is necessary for successful fisheries management. Of the different concepts that have been developed to understand individual fisher behaviour, random utility models (RUMs) have attracted considerable attention in the past three decades, and more particularly so since the 2000s. This study aimed at summarizing and analysing the information gathered from RUMs used during the last three decades around the globe. A methodology has been developed to standardize information across different studies and compare RUM results. The studies selected focused on fishing effort allocation. Six types of fisher behaviour drivers were considered: the presence of other vessels in the same fishing area, tradition, expected revenue, species targeting, costs, and risk‐taking. Analyses were performed using three separate linear modelling approaches to assess the extent to which these different drivers impacted fisher behaviour in three fleet types: fleets fishing for demersal species using active gears, fleets fishing for demersal species using passive gears and fleets fishing for pelagic species. Fishers are attracted by higher expected revenue, tradition, species targeting and presence of others, but avoid choices involving large costs. Results also suggest that fishers fishing for demersal species using active gears are generally more influenced by past seasonal (long‐term) patterns than by the most recent (short‐term) information. Finally, the comparison of expected revenue with other fisher behaviour drivers highlights that demersal fishing vessels are risk‐averse and that tradition and species targeting influence fisher decisions more than expected revenue.     

Behavioural diversity in fishing—Towards a next generation of fishery models

Despite improved knowledge and stricter regulations, numerous fish stocks remain overharvested. Previous research has shown that fisheries management may fail when the models and assessments used to inform management are based on unrealistic assumptions regarding fishers' decision‐making and responses to policies. Improving the understanding of fisher behaviour requires addressing its diversity and complexity through the integration of social science knowledge into modelling. In our paper, we review and synthesize state‐of‐the‐art research on both social science's understanding of fisher behaviour and the representation of fisher decision‐making in scientific models. We then develop and experiment with an agent‐based social–ecological fisheries model that formalizes three different fishing styles. Thereby we reflect on the implications of our incorporation of behavioural diversity and contrast it with the predominant assumption in fishery models: fishing practices being driven by rational profit maximizing. We envision a next generation of fisheries models and management that account for social scientific knowledge on individual and collective human behaviours. Through our agent‐based model, we demonstrate how such an integration is possible and propose a scientific approach for reducing uncertainty based on human behavioural diversity in fisheries. This study serves to lay the foundations for a next generation of social–ecological fishery models that account for human behavioural diversity and social and ecological complexity that are relevant for a realistic assessment and management of fishery sustainability problems.     

Fishers' targeting behaviour in Mediterranean: does vessel size matter?

Fishers have a considerable knowledge about how fish stocks behave; knowledge that is difficult to acquire in other ways. Short‐term fisher tactics employed on trip by trip basis can change significantly due to their targeting behaviour, which in turn can lead to changes in catch composition and production output. A stochastic distance function was used to examine a Mediterranean pelagic fleet's technical efficiency and fishers' ability to modulate their targeting behaviour. The purse seine fleet operated under increasing returns to scale, suggesting that the larger vessels could potentially amplify their short‐term profitability by increasing the levels of inputs and harvests. Production was mainly joint, yet the possibility for limited substitution between species existed. The observed fishers' targeting behaviour was dissimilar between fleet segments due to differences in fishing effort and vessel characteristics, with larger vessels able to modify their revenue more than smaller ones. The estimated differences between the two fleet segments could be important in designing effective management regimes aimed at reducing resource overexploitation through individual input controls.     

Exploring the ‘public goods game’ model to overcome the Tragedy of the Commons in fisheries management

In situations of declining or depleted fish stocks, exploiters seem to have fallen prey to the Tragedy of the Commons, which occurs when the maximisation of short‐term self‐interest produces outcomes leaving all participants worse off than feasible alternatives would. Standard economic theory predicts that in social dilemmas, such as fishing from a common resource, individuals are not willing to cooperate and sacrifice catches in the short term, and that, consequently, the resource is overharvested. However, over the last decades, a multitude of research has shown that humans often achieve outcomes that are ‘better than rational’ by building conditions where reciprocity, reputation, and trust help to overcome the temptations of short‐term self‐interest. The evolution of the natural human tendency to cooperate under certain conditions can be explained, and its neuro‐physiological and genetic bases are being unravelled. Nevertheless, fisheries management still often deploys top‐down regulation and economic incentives in its aim to regulate fisher behaviour, and under‐utilizes the potential for spontaneous responsible fisher behaviour through setting conditions that enhance natural cooperative tendencies. Here I introduce this body of knowledge on how to overcome the Tragedy of the Commons to the audience of fisheries scientists, hoping to open up novel ways of thinking in this field. I do this through a series of thought experiments, based on actual published experiments, exploring under what conditions responsible and cooperative fisher behaviour can be expected. Keys include reputation‐building and indirect reciprocity, face‐to‐face communication, knowledge on the state of the resource, and self‐decision on rules and sanctions.     

Assessing opportunity and relocation costs of marine protected areas using a behavioural model of longline fleet dynamics

Increasing use of spatial management tools in fisheries requires an understanding of fleet response, and in particular to where displaced fishing effort is likely to move. We develop a state‐dependent decision‐making model to address the spatial allocation of effort in an Australian tuna longline fishery. We assume that fishers have an economic objective in deciding where to fish, but that decisions in any period are also influenced by the remaining quota held at the time of the decision. Key features of the model include endogenous price dynamics, a moving stock and a competitive pool of different vessel types operating from different port locations. We utilize this model to illustrate fleet responses to marine reserves and limits on fishing effort. The results illustrate that the model framework provides advantages over statistically based models in that decisions made in response to the imposition of a reserve are not consistent with a proportional reallocation of effort. Rather, the stochastic dynamic model yielded an overall profit level of ～4% higher relative to scenarios with no reserve. Incorporating the opportunity cost of a quota into the model resulted in an optimal utilization of effort, in which effort was concentrated in time periods and locations yielding maximized profit. Under a low level of effort relative to the season length, the model indicated an overall profit level 43% greater than the highest obtained when the same level of effort was applied solely within any given quarter of the season.     

Rebuilding global fisheries: the World Summit Goal,costs and benefits

Many of the world’s fish stocks are depleted as a result of overexploitation, pollution and habitat loss. The 2002 World Summit on Sustainable Development (WSSD) sets a target for fisheries to maintain or restore stocks to levels that can produce the maximum sustainable yield (MSY) by 2015. We assessed the global stock status and found that 68% were at or above the MSY level in 2008 and that the 2015 target is unlikely to be met. We compiled data for eight indicators to evaluate the sustainability of fisheries and the gap to meet the WSSD target. These indicators show that the overall condition of global fisheries is declining, long‐term benefits are being compromised, and pressures on fisheries are increasing despite fisheries policy and management actions being taken by coastal States. We develop a bio‐economic model to estimate the costs and benefits of restoring overfished stocks. Our results show that the global fishing capacity needs to be cut by 36–43% from the 2008 level, resulting in the loss of employment of 12–15 million fishers and costing US$96–358 billion for buybacks. On the other hand, meeting the WSSD goal will increase annual fishery production by 16.5 million tonnes, annual rent by US$32 billion and improve biodiversity and functioning of marine ecosystems. However, progress towards rebuilding has been hindered by an unwillingness or inability to accept the short‐term socio‐economic consequences associated with rebuilding fisheries. Thus, there is a pressing need for integration of rebuilding plans into national political and economic decision‐making.     

Risk management for fisheries

Risk management methods provide means to address increasing complexity for successful fisheries management by systematically identifying and coping with risk. The objective of this study is to summarize risk management practices in use in fisheries and to present strategies that are not currently used but may be applicable. Available tools originate from a variety of disciplines and are as diverse as the risks they address, including algorithms to aid in making decisions with multiple stakeholders, reserves to buffer against economic or biological surprises, and insurance instruments to help fishermen cope with economic variability. Techniques are organized in a two‐stage framework. In the first stage, risks are identified and analysed. Strategies presented in this category focus on decision analysis, including multicriteria decision‐making tools, and the related concept of risk assessment. Then in the treatment stage, identified risks can be transferred, avoided, or retained using tools such as the Precautionary Approach, portfolio management, financial contracts to manage price risk and horizontal integration. Published fishery applications are reviewed, and some empirical examples of risks and risk management using US fisheries data are presented.     

The behavioural dynamics of fishers: management implications

In pursuing their livelihood, fishers develop strategies when faced with changes in regulations and other fishery conditions. Changes involve each individual in a decision‐making process governed by his/her own goals or constraints. Despite this reality, the complex dynamics of fishing has usually been ignored in designing management initiatives, which has contributed to management failures in many parts of the world. Fishers have generally been treated as fixed elements, with no consideration of individual attitudes based on their operating scales (geographical, ecological, social and economic) and personal goals. We review existing research on the social, economic and behavioural dynamics of fishing to provide insight into fisher behaviour and its implications for fisheries management. Emphasis is placed on fisher perception, and how fishers develop dynamic fishing tactics and strategies as an adaptive response to changes in resource abundance, environmental conditions and market or regulatory constraints. We conclude that knowledge of these dynamics is essential for effective management, and we discuss how such information can be collected, analysed and integrated into fisheries assessment and management. Particular emphasis is placed on small‐scale fisheries, but some examples from industrial fleets are provided to highlight similar issues in different types of fisheries.     

Integrating fishing and conservation in a risk framework: A stochastic population model to guide the proactive management of a threatened freshwater crayfish

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Marine recreational fishing and the implications of climate change

Marine recreational fishing is popular globally and benefits coastal economies and people's well‐being. For some species, it represents a large component of fish landings. Climate change is anticipated to affect recreational fishing in many ways, creating opportunities and challenges. Rising temperatures or changes in storms and waves are expected to impact the availability of fish to recreational fishers, through changes in recruitment, growth and survival. Shifts in distribution are also expected, affecting the location that target species can be caught. Climate change also threatens the safety of fishing. Opportunities may be reduced owing to rougher conditions, and costs may be incurred if gear is lost or damaged in bad weather. However, not all effects are expected to be negative. Where weather conditions change favourably, participation rates could increase, and desirable species may become available in new areas. Drawing on examples from the UK and Australia, we synthesize existing knowledge to develop a conceptual model of climate‐driven factors that could impact marine recreational fisheries, in terms of operations, participation and motivation. We uncover the complex pathways of drivers that underpin the recreational sector. Climate changes may have global implications on the behaviour of recreational fishers and on catches and local economies.     

Trawl fishing impacts on the status of seabed fauna in diverse regions of the globe

Bottom trawl fishing is a controversial activity. It yields about a quarter of the world's wild seafood, but also has impacts on the marine environment. Recent advances have quantified and improved understanding of large‐scale impacts of trawling on the seabed. However, such information needs to be coupled with distributions of benthic invertebrates (benthos) to assess whether these populations are being sustained under current trawling regimes. This study collated data from 13 diverse regions of the globe spanning four continents. Within each region, we combined trawl intensity distributions and predicted abundance distributions of benthos groups with impact and recovery parameters for taxonomic classes in a risk assessment model to estimate benthos status. The exposure of 220 predicted benthos‐group distributions to trawling intensity (as swept area ratio) ranged between 0% and 210% (mean = 37%) of abundance. However, benthos status, an indicator of the depleted abundance under chronic trawling pressure as a proportion of untrawled state, ranged between 0.86 and 1 (mean = 0.99), with 78% of benthos groups > 0.95. Mean benthos status was lowest in regions of Europe and Africa, and for taxonomic classes Bivalvia and Gastropoda. Our results demonstrate that while spatial overlap studies can help infer general patterns of potential risk, actual risks cannot be evaluated without using an assessment model that incorporates trawl impact and recovery metrics. These quantitative outputs are essential for sustainability assessments, and together with reference points and thresholds, can help managers ensure use of the marine environment is sustainable under the ecosystem approach to management.     

Predicting the spatio‐temporal distributions of pelagic sharks in the western and central North Pacific

Spatio‐temporal modeling estimates a species distribution function that represents variation in population density over space and time. Recent studies show that the approach may precisely identify spatial hotspots in species distribution, but have not addressed whether seasonal hotspots are identifiable using commonly available fishery data. In this study, we analyzed the seasonal spatio‐temporal distribution of pelagic sharks in the western and central North Pacific using fishery catch rates and a generalized linear mixed model with spatio‐temporal effects. Different spatial distribution patterns were observed between two shark species. The hotspots of shortfin mako (SFM) appeared in the vicinity of the coastal and offshore waters of Japan and the Kuroshio‐Oyashio transition zone (TZ), whereas the hotspots of blue shark (BSH) were widely distributed in the areas from the TZ to the waters of the Emperor Seamount Chain. Shortfin mako distribution changes seasonally with clear north‐south movement, which follows higher sea surface temperatures (SST). However, preferred spring and summer water temperature was still colder than those in fall and winter, but not as cold as for BSH, which did not show seasonal north‐south movement. BSH exhibits seasonal east‐west movement apparently unrelated to temperature. The spatial fishing effort by season generally follows the seasonal movement of temperature possibly making SFM more vulnerable to the fishery than BSH. These findings could be used to reduce the capture risk of bycatch sharks and to better manage the spatial distribution of fishing for targeted sharks.     

Balancing conservation and recreational fishery objectives for a threatened fish species,the Murray cod,Maccullochella peelii

Murray cod Maccullochella peelii (Mitchell) is a large, iconic Australian fish species targeted by anglers but also listed as nationally threatened. A consultative process that included conservation and fishery interests helped to develop a population model for this species and agree on management scenarios to be tested. The modelled scenarios illustrated that threats to populations (risk of decline) can be substantially reduced and catch rates increased through harvest slot length limits (HSLL) rather than minimum legal limits (MLL). A 600‐ to 1000‐mm HSLL provided lower risk of decline and greater catch rates than the existing 500‐mm MLL, but better results were achieved with a 400‐ to 600‐mm HSLL. Importantly, a range of other impacts (fish kills, stocking, thermal impacts, larval mortalities, habitat changes) were recognised and incorporated. This study provides an example of the utility of a population model to improve management decision‐making for both conservation and fishery objectives.     

Real options for precautionary fisheries management

The 1996 Food and Agriculture Organization’s (FAO) ‘Guidelines on the Precautionary Approach to Fisheries and Species Introduction’ raise important issues for fisheries managers, but fail to prescribe an approach for risk management. The distinguishing characteristics of the ‘precautionary approach’ are the inclusion of uncertainty and ‘an elaboration on the burden of proof’. The FAO precautionary approach emphasizes that managers should be risk‐averse, but does not provide tools for determining the appropriate degree of risk aversion. Consequently, application of the precautionary approach often leads to decision‐making based on ad hoc safety margins. These safety margins are seldom chosen with explicit consideration of trade‐offs. If the emphasis was shifted to choosing between competing uncertainties, then managers could manage risk. By attempting to avoid risk, managers may gain exposure to other risks and perhaps miss valuable opportunities. We place fishery management problems within the rubric of ‘real investment’ problems, and compare and contrast the consideration of risk by alternative investment frameworks. We show that traditional investment frameworks are inappropriate for fishery management, and furthermore, that traditional precautionary approaches are arbitrary and without basis in decision theory. Quantitative decision‐making techniques, such as formal decision analysis (FDA), enable integration of competing hypotheses that help alleviate burden‐of‐proof issues. These techniques help analysts consider sources of uncertainty. FDA, however, can still be subject to arbitrary safety margins because such analyses often focus on determining which strategies best achieve, or avoid, targets that have been established without complete consideration of trade‐offs. A managerial finance approach, real options analysis (ROA), is an alternative and complementary decision‐making technique that enables managers to compute precautionary adjustments that couple the size of the ‘safety margin’ with the amount of uncertainty, thereby optimizing risk exposure and avoiding the need for arbitrary safety margins. We illustrate the advantages of an approach that combines FDA and ROA, using a heuristic example about a decision to re‐introduce Atlantic salmon (Salmo salar L.) into Lake Ontario. Finally, we provide guidance on applying ROA to other fishery problems. The precautionary approach requires that managers consider risk, but considering risk is not the same as managing it. Here ROA is useful.     

Development and testing of a Bayesian population model for the bigeye thresher shark,Alopias superciliosus,in an area subset of the western North Pacific

A Bayesian population modelling tool integrating separable virtual population analysis, per‐recruit models and age‐structured demographic analysis was developed for the bigeye thresher Alopias superciliosus (Lowe) population in an area subset of the western North Pacific. The mortality rates for years 1989–2016 were estimated, various biological reference points and associated risks of decline were also estimated, and alternative harvest strategies for the stock were evaluated. Estimates of the posterior mean of fishing mortality for bigeye thresher shark suggest fishing pressure has been high in recent years (2011–2016). The estimated population growth rate (λ) (without fishing) obtained from age‐structured demographic model was relatively low (λ = 1.01 per year; 95% confidence intervals of 1.00 and 1.03 per year). Risk analyses revealed that only low levels of fishing pressure (10% of the current fishing pressure) over a wide range of ages could maintain a relatively low risk of population decline for bigeye threshers. Sensitivity testing indicated that the model is robust to prior specification. The developed framework could be used as an assessment tool to evaluate the risk of decline for other widely distributed pelagic shark species where insufficient catch and effort data are available.     

Recreational charter fishery attributes and variation in key species catches and discards: Resource management considerations

Strategic long‐term sampling programmes that deliver recreational catch, effort and species demographic data are required for the effective assessment and management of recreational fisheries and harvested organisms. This study used a spatially and temporally stratified observer programme to examine variation in the rates, quantities and lengths of retained and discarded catches of key species in a recreational charter fishery. Geographic region, but not season, significantly influenced catch rates of key demersal species, being driven by temporally persistent latitudinal clines in environmental conditions influencing species distributions. There was considerable trip‐to‐trip variation in catch rates that were attributed to localised differences in fishing operations, locations, environmental conditions and client preferences. Broad trends in retained and discarded catch rates were nevertheless, similar across different fishing effort standardisations (per‐trip, per‐hour, per‐client, per‐client/fished hour), demonstrating that the coarsest unit of effort could be used in fishery assessments. Discard rates of organisms were variable and driven by a combination of mandated legal lengths, individual client and operator preferences for particular species and sizes of organisms, and not due to attainment of catch quotas or high‐grading. This study has identified important fishery attributes that require consideration in assessing charter fisheries and stocks of recreational fish species.     

Trade‐offs in transitions between indigenous and commercial fishing sectors: the Torres Strait tropical rock lobster fishery

A bio‐economic model was developed to evaluate aspects of proposed quota‐based constraints vs the current effort control regulations for the tropical rock lobster, Panulirus ornatus, Fabricius, fishery in the Torres Strait (Australia/Papua New Guinea). The analysis integrates across biological, economic and social considerations. Model performance indicators have been chosen to reflect higher level policy objectives. The model simulation results indicate important trade‐offs. There is lower overall fleet total profit (across all the subfleets), lower fishery total value added and lower total employment if the fishery is quota‐constrained. This is due to an assumed rationalisation driven by incentives and current utilisation of capacity. The simulated re‐allocation of quota from the commercial non‐indigenous fleet allowing for greater potential indigenous fisher participation results in predicted increases in indigenous employment and would meet social objectives; however, due to limited capacity in the indigenous fleet, the simulated predicted lower catches led to lower total fishery profits and decreased total fishery value added within the supply chain. Investment in capacity could potentially offset this result.     

Marine social–ecological responses to environmental change and the impacts of globalization

Marine social–ecological systems consist of interactive ecological and human social elements so that changes in ecological systems affect fishing‐dependent societies and vice versa. This study compares the responses of marine ecological and fishing‐dependent systems to environmental change and the impacts of globalization, using four case‐studies: NE Atlantic (Barents Sea), NW Atlantic (Newfoundland), SE Atlantic (Namibia) and the equatorial Atlantic (Ghana). Marine ecological systems cope with short‐time changes by altering migration and distribution patterns, changing species composition, and changing diets and growth rates; over the longer term, adaptive changes lead to increased turn‐over rates and changes in the structure and function of the system. Fishing communities cope with short‐term change through intensification and diversification of fishing, migration and ‘riding out the storm’. Over the longer term, adaptive changes in policy and fisheries governance can interact with social–ecological change to focus on new fisheries, economic diversification, re‐training, out‐migration and community closures. Marine social–ecological systems can ultimately possess rapid adaptive capacity in their ecological components, but reduced adaptive capacity in society. Maintaining the diversity of response capabilities on short and longer time scales, among both ecological and human fishing systems, should be a key policy objective. The challenge is to develop robust governance approaches for coupled marine social–ecological systems that can respond to short‐ and long‐term consequences of global change.     

Quantifying subjective human dimensions of recreational fishing: does good health come to those who bait?

Recreational fishing is a popular sport and leisure activity in many countries worldwide. There has been growing interest by recreational fishing groups and researchers in the perceived physical and psychological health and social (or ‘biopsychosocial’) benefits of recreational fishing. However, quantifying the key subjective ‘human dimensions’ of fishing that satisfy both the needs of recreational fishing groups and fishery managers is a major obstacle. We propose the use of psychometrically valid health‐related quality of life (HRQOL) measures widely used in the medical and health sciences – namely the Short‐Form Health Survey (SF‐36) – as rapid, reliable and cost‐effective instruments for quantifying HRQOL of recreational fishers. The widespread use of SF‐36 and availability of population normative data allows comparisons of the HRQOL of recreational fishers across multiple temporal and spatial scales, with participants of other activities, and the general population. The use of such measures in periodic surveys allows the biopsychosocial status of a recreational fishery's participants to be assessed using a modified Kobe plot, a graphical format that is easily interpretable and consistent with existing reporting formats used in fisheries stock assessment. Future biopsychosocial research in recreational fisheries can further benefit from interdisciplinary collaboration to develop a suite of standardized psychometrically valid and reliable instruments for assessing specific issues that commonly affect recreational fisheries from regional to international scales, such as drivers of fisher motivation, behaviour and satisfaction.     

Impacts of fishing,river flow and connectivity loss on the conservation of a migratory fish population

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