Standardizing catch and effort data: a review of recent approaches

Conservation conflicts are increasing and need to be managed to minimise negative impacts on biodiversity, human livelihoods, and human well-being. Here, we explore strategies and case studies that highlight the long-term, dynamic nature of conflicts and the challenges to their management. Conflict management requires parties to recognise problems as shared ones, and engage with clear goals, a transparent evidence base, and an awareness of trade-offs. We hypothesise that conservation outcomes will be less durable when conservationists assert their interests to the detriment of others. Effective conflict management and long-term conservation benefit will be enhanced by better integration of the underpinning social context with the material impacts and evaluation of the efficacy of alternative conflict management approaches.

Understanding and managing conservation conflicts

There is broad consensus that the main problem facing fisheries globally is too many boats chasing too few fish Unfortunately it is also possible to argue that there are too many proposed solutions and not enough practical answers to improving fisheries management There is a deepening divide between those who propose alternative regulatory controls on fishers, including establishing large areas permanently closed to fishing, and those who argue for better alignment of incentives combined with broad participation of resource users in fishery management decisions (in simple terms, between top down and bottom up systems of governance) However despite the choice of policy instruments used, a consistent outcome is that resource users behave in a manner that is often unintended by the designers of the management system Hence whilst uncertainty is broadly recognized as a pervasive feature of fisheries management, to date most of the attention has focussed on only part of that uncertainty - scientific uncertainty about the status of exploited resources The effect of uncertainty generated on the human side of fisheries science and management has received much less attention However, the uncertainty generated by unexpected resource user behaviour is critical as it has unplanned consequences and leads to unintended management outcomes Using empirical evidence of unexpected resource user behaviour and reviewing current responses to unexpected management outcomes, we identify different approaches that both improve prediction of human behaviour in fisheries systems and identify management measures that are more robust to these sources of uncertainty However, unless the micro scale drivers of human behaviour that contribute to macro scale implementation uncertainty are communicated effectively to managers and considered more regularly and in greater depth, unanticipated responses to management actions will continue to undermine management systems and threaten the sustainability of fisheries

Human behaviour: the key source of uncertainty in fisheries management

Models are key tools for integrating a wide range of system information in a common framework. Attempts to model exploited marine ecosystems can increase understanding of system dynamics; identify major processes, drivers and responses; highlight major gaps in knowledge; and provide a mechanism to ‘road test’ management strategies before implementing them in reality. The Atlantis modelling framework has been used in these roles for a decade and is regularly being modified and applied to new questions (e.g. it is being coupled to climate, biophysical and economic models to help consider climate change impacts, monitoring schemes and multiple use management). This study describes some common lessons learned from its implementation, particularly in regard to when these tools are most effective and the likely form of best practices for ecosystem-based management (EBM). Most importantly, it highlighted that no single management lever is sufficient to address the many trade-offs associated with EBM and that the mix of measures needed to successfully implement EBM will differ between systems and will change through time. Although it is doubtful that any single management action will be based solely on Atlantis, this modelling approach continues to provide important insights for managers when making natural resource management decisions.

Lessons in modelling and management of marine ecosystems: the Atlantis experience

Ecological risk assessment for the effects of fishing

Standardization of catch and effort data in a spatially-structured shark fishery

Experience in implementing harvest strategies in Australia's south-eastern fisheries

The school shark (Galeorhinus galeus) resource off southern Australia is assessed by use of an assessment approach that takes account of the spatial structure of the population. The population dynamics model underlying the assessment considers the spatial as well as the age-specific characteristics of school shark. It allows for a series of fisheries (each based on a different gear type), explicitly models the pupping/recruitment process, and allows for multiple stocks. The values for the parameters of this model are determined by fitting it to catch-rate data and information from tagging studies. The point estimates of the pup production at the start of 1997 range from 12% to 18% of the pre-exploitation equilibrium size, depending on the specifications of the assessment. Allowing for spatial structure and incorporating tag release–recapture data lead to reduced uncertainty compared with earlier assessments. The status of the resource, as reflected by the ratio of present to virgin pup production and total (1+) biomass, is sensitive to the assumed level of movement between the stocks in New Zealand and those in Australia, with lower values corresponding to higher levels of movement.

Stock assessment of school shark, Galeorhinus galeus, based on a spatially explicit population dynamics model

The Management Strategy Evaluation (MSE) approach is used to assess the benefits of alternative harvest strategies to set annual Total Allowable Catches (TACs) for school shark (Galeorhinus galeus) and gummy shark (Mustelus antarcticus). The harvest strategies are based on a stock assessment method that includes consideration of the gear-types employed in the fishery and the nature of the shark pupping process. The harvest strategies are compared in terms of performance measures that relate to average catches, catch variability and resource conservation. The uncertainties that impact performance to the greatest extent are the technical interaction between fishing for school shark and for gummy shark, the productivity of the overexploited school shark resource, and the extent to which tagged animals lose tags (or die) immediately after tagging.

Population modelling and harvest strategy evaluation for school and gummy shark

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Fred Pribac

Papers

Standardization of catch and effort data in a spatially-structured shark fishery

Experience in implementing harvest strategies in Australia's south-eastern fisheries

Stock assessment of school shark, Galeorhinus galeus, based on a spatially explicit population dynamics model

Population modelling and harvest strategy evaluation for school and gummy shark

Harvest Strategy Evaluation for School and Gummy Shark