Skill assessment of models relevant for the implementation of ecosystem-based fisheries management

The advance of ecosystem-based fisheries management worldwide has made scientific advice on fisheries related questions more complex. However, despite the need to take interactions between fish stocks, and between stocks and their environment into account, multispecies and ecosystem models are still hardly used as a basis for fishery advice. Although reasons are numerous, the lack of high-level guidance for target-oriented skill assessments of such models contributes to the mistrust to use such models for advice. In this study, we propose a framework of guiding questions for a pragmatic and target-oriented skill assessment. The framework is relevant for all models irrespective of their complexity and approach. It starts with general questions on the advice purpose itself, the type of model(s) and data available for performance testing. After this, the credibility of the hindcasts are evaluated. A special emphasis is finally put on testing predictive skills. The skill assessment framework proposed provides a tool to evaluate a model's suitability for the purpose of providing specific advice and aims to avoid the bad practice of incomplete skill assessments. In the case of multiple models available, it can facilitate the evaluation or choosing of the best model(s) for a given advice product and intends to ensure a level playing field between models of different complexities. The suite of questions proposed is an important step to improve the quality of advice products for a successful implementation of ecosystem-based fisheries management

Fishery-Based indicators of Management Impact: Assessing Relevance and Robustness Using A Bio-Economic Simulation Model

Indicators are widely used in fisheries management decision process as measures for monitoring ecosystem status or management performance. In the current context, the shift to an ecosystem-based approach to fisheries management requires to complete usual population or community indicators with indicators reflecting state and dynamics of fishing activity as well as economic viability. However, it is difficult for decision makers to select relevant indicators among the numerous existing ones. In addition, the complexity of the mechanisms involved makes the unequivocal interpretation of indicator variations seldom possible using only statistical models. We propose to resort to the ISIS-Fish fishery dynamics model to select robust and relevant fishery indicators. ISIS-Fish population submodel was set up to reproduce major processes of anchovy population dynamics in space and time and surplus production models were used for the other target species of the fishery. To take fishermen behavior into account while modeling fleet dynamics, we considered a discrete choice model using economical interest in the different possible métiers, fishers habits and management constraints within a random utility modeling framework. Applying sensitivity analysis methods, simulation designs were built crossing a variety of management scenarios and uncertainty hypotheses. Consequently, a list of resulting candidate metrics referring both to population and fishing activities were computed and statistically analyzed. Metrics that were the most sensitive to management and the most robust to uncertainties were considered to be relevant and selected for assessing management impact on the fishery

Research for PECH Committee - Discard ban, landing obligation and MSY in the Western Mediterranean Sea - the Spanish case

The demersal fisheries in the Mediterranean Sea are heavily overfished but the landing obligation will not help to reach MSY because it will not decrease fishing mortality. The new proposal of the Commission introduces total allowable effort as a new way to regulate Western Mediterranean demersal fisheries by significantly reducing fishing time. However, this new management measure must be complemented with increased gear selectivity, implementation of closed areas and local co-management plans. Different approaches to reduce fishing mortality may have different socio-economic impact

Research for PECH Committee - Discard ban, landing obligation and MSY in the Western Mediterranean Sea - the Spanish case

The demersal fisheries in the Mediterranean Sea are heavily overfished but the landing obligation will not help to reach MSY because it will not decrease fishing mortality. The new proposal of the Commission introduces total allowable effort as a new way to regulate Western Mediterranean demersal fisheries by significantly reducing fishing time. However, this new management measure must be complemented with increased gear selectivity, implementation of closed areas and local co-management plans. Different approaches to reduce fishing mortality may have different socio-economic impact

Working group on ecosystem assessment of Western European shelf seas (WGEAWESS)

The ICES Working Group on Ecosystem Assessment of Western European Shelf Seas (WGEA-WESS) aims to provide high quality science in support to holistic, adaptive, evidence-based man-agement in the Celtic seas, Bay of Biscay and Iberian coast regions. The group works towards developing integrated ecosystem assessments for both the (i) Celtic Seas and (ii) Bay of Biscay and Iberian Coast which are summarized in the Ecosystem Overviews (EOs) advice products that were recently updated. Integrated Trend Analysis (ITA) were performed for multiple sub-ecoregions and used to develop an understanding of ecosystem responses to pressures at varying spatial scales. Ecosystem models (primarily Ecopath with Ecosim; EwE) were developed and identified for fisheries and spatial management advice. The updated Celtic Seas EO represents a large step forward for EOs, with the inclusion of novel sections on climate change, foodweb and productivity, the first application of the new guidelines for building the conceptual diagram, inclusion of socio-economic indicators, and progress made toward complying with the Transparent Assessment Framework (TAF). We highlight ongoing issues relevant to the development and communication of EO conceptual diagrams. A common methodology using dynamic factor analysis (DFA) was used to perform ITA in a comparable way for seven subregions. This was supported by the design and compilation of the first standardized cross-regional dataset. A comparison of the main trends evidenced among subregions over the period 1993–2020 was conducted and will be published soon. A list of available and developing EWE models for the region was also generated. Here, we re-port on the advances in temporal and spatial ecosystem modelling, such as their capacity to model the impacts of sector activities (e.g. renewables and fisheries) and quantify foodweb indi-cators. We also reflect on model quality assessment with the key run of the Irish sea EwE model. The group highlighted the hurdles and gaps in current models in support of EBM, such as the choice of a relevant functional, spatial, and temporal scales and the impacts of model structure on our capacity to draw comparisons from models of different regions. The group aims to ad-dress these issues in coming years and identify routes for ecosystem model derived information into ICES advice.info:eu-repo/semantics/publishedVersio

Contrasting impacts of the landing obligation at fleet scale: impact assessment of mitigation scenarios in the Eastern English Channel

How the implementation of the European Commission's landing obligation (LO) would affect French vessels of the mixed demersal fishery in the Eastern English Channel was hardly foreseen because of the diversity of vessel characteristics and strategies in the area. Assessing whether the vessels would be able to mitigate the bio-economic impacts of LO and avoid choke situations through exemptions, by changing their fishing patterns or by avoiding areas, required fine scale spatio-temporal modelling of fish and fleet dynamics and of resulting technical interactions. We conducted a bio-economic impact assessment for seven scenarios of mitigation focussing on the differences across fleets and the impact of fleet spatial behavioural flexibility. We found that netters rapidly benefited from the LO as opposed to trawlers and that exemptions helped mitigate the economic loss with limited biomass loss. The avoidance strategies proved to be efficient in reducing unwanted catch of whiting and enabled unexpected protection of juvenile sole. Sensitivity analysis on the drivers of fishing behaviour indicated that the ability and efficiency of adapting fishing patterns depended on main gear and vessel size. Results evidenced the difficult trade-offs LO implies among stocks, fish stages, fleets, and even sub-regions, beyond the usual biological vs. economic contrasts

Including dynamic fishermen behaviour in a fisheries simulation model to assess the impact of environmental changes

Poster online : http://www.ifremer.fr/isis-fish/publications/Poster_Vermard_et_al.pd

Impact des mesures de gestion sur la dynamique de la pêcherie pélagique du golfe de Gascogne (Quelles certitudes ? Quels descripteurs )

Des évaluations quantitatives de l impact de mesures de gestion sur les ressources et la viabilité des flottilles sont nécessaires pour établir des diagnostics et pour fournir des éléments d orientation pour la gestion des pêcheries. Les pêcheries sont des systèmes complexes mettant en œuvre de nombreuses dynamiques à des échelles de temps et d espace très variables et interagissant très fortement entre elles. Cette complexité et la difficulté d observer les systèmes marins, conduit à une grande incertitude sur leur fonctionnement qui rend difficile la détermination des mesures de gestion adaptées. La reconnaissance de ces incertitudes, plaide de plus en plus en faveur d une gestion robuste plutôt qu optimale. Déterminer la robustesse des mesures de gestion nécessite le développement de modèles de description et de prédiction capable d intégrer la complexité et l incertitude du système, ainsi que d outils de description synthétiques (indicateurs) de l état et de la dynamique de la pêcherie à partir d observations. L objectif de ce travail est de proposer des méthodes génériques pour le développement de tels outils. Ces développements méthodologiques sont appliqués à la pêcherie pélagique du golfe de Gascogne. Cette pêcherie ciblant principalement l anchois a été fortement perturbée par la fermeture de la pêche à cette espèce en 2005. Le déterminisme environnemental et le rôle de la pêche dans le déclin de la population d anchois sont mal compris ce qui rend difficile la prise de décision dans un contexte économique et écologique critique. La gestion traditionnelle par TAC pourrait s avérer insuffisante pour permettre l exploitation durable et des mesures spatialisées sont envisagées en complément.Quantitative evaluations of management measure impact on resource and fleet viability are required to provide diagnostics and feed decision process. Fisheries are complex systems where numerous dynamics interact at various spatial and temporal scales. This complexity and the difficulty to observe marine systems are responsible for the high uncertainty surrounding fishery functioning that makes it hard to identify adequate management measures. The increasing consideration of uncertainties in diagnostics argues in favor of robust management measures rather than optimal management measures. Identifying robust management measures requires the development of models that account for complexity and uncertainty in the description and prediction of management impact as well as the identification of synthetic descriptors (indicators) of the state and dynamic of the system. The aim of this work is to propose generic methodologies for developing such tools. The methodological developments are applied to the pelagic fishery of the bay of Biscay. This fishery mainly focused on anchovy and was highly impacted by fishing ban on this species since 2005. Causes for anchovy drop in biomass either environmental or due to fishing are poorly understood, making management decision much harder in a critical environmental and economic context. The adequacy of traditional management using TAC is questioned and additional spatial management measures are proposed.RENNES-Agrocampus-CRD (352382323) / SudocSudocFranceF

Are maximum yields sustainable? Effect of intra-annual time-scales on MSY, stability and resilience

The concept of Maximum Sustainable Yield (MSY) have been lying at the core of the theory of sustainable harvesting a fishery for decades and have become a key reference point for many fishing administrations, including the European Union. However, the existence of a MSY relies on the stability of a population equilibrium. This hypothesis, though always true in the original Schaeffer model, is still challenging in more realistic and recent population models. However, recent advances shows that fish population can exhibit complex dynamics that are ill described by the classical theory. In particular, processes occurring at intra-annual time scales can affect the stability of a population equilibrium even in a strictly single species case. Associated to stability, the resilience of the equilibrium (defined as an inverse return-time following a perturbation) also matters in a management purpose. Here, we introduce an analytical single population model in discrete time with a monthly time-step allowing temporal distinction between maturation and recruitment with density-dependent mortality and fishing exploitation. We show that, thanks to an appropriate population structure, we can easily derive inter-annual population equilibrium, and study their resilience and stability properties. Then, we show that under classical hypothesis concerning density-dependence, equilibrium stability is not guaranteed and that MSY can, in theory, be associated to unstable or low resilient states. However such destabilisation seems unlikely with realistic sets of parameters. Finally, a numerical illustration for sole (Solea solea) of the Bay of Biscay suggests that the value of MSY was sensitive to maturation period whereas viability, stability and resilience was more sensitive to timing of recruitment. The value of appeared robust to uncertainty concerning maturation and recruitment. We conclude by saying that even if the risk of destabilisation is low for real populations, the risk of decreased resilience near the border of extinction should be cared of