Article

Shifting baselines in European fisheries: The case of the Celtic Sea and Bay of Biscay

December 2012
Ocean & Coastal Management 70:10-21

DOI:10.1016/j.ocecoaman.2012.06.010

Authors:

EcOceans, St. Andrews, NB, Canada

Ph.D. thesis Integrating taxon-based, trait-based and trophic-network approaches to study community dynamics in an exploited ecosystem, the Celtic Sea

Thesis

Full-text available

Nov 2020

Laurène Merillet

These Merillet final

Thesis

Full-text available

Nov 2020

Laurène Merillet

Marine ecosystems face many pressures, the main ones being fishing and climate change. These pressures do not have the same consequences on the different facets of biodiversity, e.g. on taxa, traits and networks, and their study is necessary for the implementation of an ecosystem approach to fisheries. The Celtic Sea is a very important fishing area for European fisheries, with a specific richness greater than adjacent areas. Based on a time series from 2000 to 2016, I have studied the spatio-temporal dynamics of 101 species of the ecosystem. Over this period, taxonomic biodiversity was stable, and the importance of fishing as a structuring variable for communities decreased after 2009, and was lower than the environment (depth, chlorophyll a concentration and temperature). Following a local decrease in fishing pressure, the biomass of species with life history strategies characterised by a low renewal rate and present in the central Celtic Sea, increased. In particular, the increase in the biomass of six species of elasmobranchs has been linked to the creation of a seasonal fishing closure in the area. This vision of fishing sensitivity was enriched with data from the exploitation of underwater videos. This made it possible to highlight the presence of sensitive areas in the western Celtic Sea, along the continental slope. In addition, the study of interaction networks linking species, and in particular trophic networks, allowed considering the dynamics of the entire ecosystem based on its components. In the Celtic Sea, the sensitivity of species to fishing does not imply the sensitivity of the network to this pressure. On the other hand, the trophic network is not very robust to the loss of the 7% of the most exploited species and basal species.

Environment outweighs the effects of fishing in regulating demersal community structure in an exploited marine ecosystem

Article

Dec 2019

Global climate change has already caused bottom temperatures of coastal marine ecosystems to increase worldwide. These ecosystems face many pressures, of which fishing is one of the most important. While consequences of global warming on commercial species are studied extensively, the importance of the increase in bottom temperature and of variation in fishing effort is more rarely considered together in these exploited ecosystems. Using a 17‐year time series from an international bottom‐trawl survey, we investigated co‐variations of an entire demersal ecosystem (101 taxa) with the environment in the Celtic Sea. Our results showed that over the past two decades, biotic communities in the Celtic Sea were likely controlled more by environmental variables than fisheries, probably due to its long history of exploitation. At the scale of the entire zone, relations between taxa and the environment remained stable over the years, but at a local scale, in the center of the Celtic Sea, dynamics were driven by inter‐annual variation in temperature. Fishing was an important factor structuring species assemblages at the beginning of the time series (2000) but decreased in importance after 2009. This was most likely caused by a change in spatial distribution of fishing effort, following a change in targeted taxa from nephrops to deeper water anglerfish that did not co‐vary with fishing effort. Increasing bottom temperatures could induce additional changes in the coming years, notably in the cold‐water commercial species cod, hake, nephrops and American plaice. We showed that analyzing co‐variation is an effective way to screen a large number of taxa and highlight those that may be most susceptible to future simultaneous increases in temperature and changes in exploitation pattern by fisheries. This information can be particularly relevant for ecosystem assessments.

Catch reconstruction for the French Atlantic coast, 1950-2010

Technical Report

Full-text available

Jan 2016

Trophic models: What do we learn about Celtic Sea and Bay of Biscay ecosystems?

Article

Mar 2017

Trophic models are key tools to go beyond the single-species approaches used in stock assessments to adopt a more holistic view and implement the Ecosystem Approach to Fisheries Management (EAFM). This study aims to: (i) analyse the trophic functioning of the Celtic Sea and the Bay of Biscay, (ii) investigate ecosystem changes over the 1980–2013 period and, (iii) explore the response to management measures at the food web scale. Ecopath models were built for each ecosystem for years 1980 and 2013, and Ecosim models were fitted to time series data of biomass and catches. EcoTroph diagnosis showed that in both ecosystems, fishing pressure focuses on high trophic levels (TLs) and, to a lesser extent, on intermediate TLs. However, the interplay between local environmental conditions, species composition and ecosystem functioning could explain the different responses to fisheries management observed between these two contiguous ecosystems. Indeed, over the study period, the ecosystem's exploitation status has improved in the Bay of Biscay but not in the Celtic Sea. This improvement does not seem to be sufficient to achieve the objectives of an EAFM, as high trophic levels were still overexploited in 2013 and simulations conducted with Ecosim in the Bay of Biscay indicate that at current fishing effort the biomass will not be rebuilt by 2030. The ecosystem's response to a reduction in fishing mortality depends on which trophic levels receive protection. Reducing fishing mortality on pelagic fish, instead of on demersal fish, appears more efficient at maximising catch and total biomass and at conserving both top-predator and intermediate TLs. Such advice-oriented trophic models should be used on a regular basis to monitor the health status of marine food webs and analyse the trade-offs between multiple objectives in an ecosystem-based fisheries management context.

Trait‐Based Indicators of Marine Communities' Sensitivity to Climate Change and Fishing

Article

Full-text available

Dec 2024
DIVERS DISTRIB

Aim Overexploitation of wildlife and anthropogenic climate change are key drivers of global biodiversity loss. Investigating how these stressors interact and affect ecosystems is critical for conservation efforts. Following trait‐based vulnerability assessments, we propose two community‐level sensitivity indicators: climate change (SCC) and fishing pressure (SFP). Location Cantabrian and Spanish Mediterranean Sea. Methods Both indicators were calculated for 246 fish and megabenthos species, sampled during 1994–2019 in two areas with contrasting levels of warming and fishing pressure. Indicator calculation was based on traits that, according to existing evidence, can be linked to (1) sensitivity to climate change (scored as SCC) and (2) sensitivity to fishing pressure (SFP). Using each species' sensitivity scores, and abundance data from the surveys, we explored whether these areas' community‐level sensitivity has changed spatiotemporally in line with the expected functional responses to these predominant pressures. Results Although both regions have warmed, the Spanish Mediterranean is far more so. Its community‐level SCC has decreased, reflecting a shift in composition from warm‐sensitive to warm‐affinity species. In contrast, sensitivity dynamics in the Cantabrian Sea varied, with warm‐sensitive species increasing in deeper areas and decreasing towards the inner Bay of Biscay. Decreasing fishing pressure in both regions paralleled an increase in sensitivity in the Cantabrian Sea, particularly among slow‐reproducing, longer‐lived species. The Spanish Mediterranean, however, showed a relative loss of fishing‐sensitive, long‐lived species and both cases showed spatial heterogeneity. Main Conclusions Associations are revealed between SCC and SFP, and climate change and fishing, respectively. We conclude that SCC and SFP are valuable indicators of the community‐level sensitivities to these two pressures, and we discuss the limitations and assumptions that underly this and other trait‐based approaches. We recommend wider usage of this kind of indicators, which could be applied globally to understand risks of marine communities to climate change and fishing.

Trends in the abundance of Celtic Sea demersal fish: Identifying the relative importance of fishing and environmental drivers

Article

Full-text available

Sep 2022

The Celtic Sea is a productive fishing ground, therefore identifying the relative importance of fishing and environmental factors on fish stock dynamics is crucial for developing our understanding of sustainable yields and to operationalize Ecosystem Based Fisheries Management (EBFM). We investigated the effect of environmental variables and fishing on the relative abundance inferred from catch-per-unit-effort (CPUE), of twelve demersal stocks (i.e., cod, haddock, whiting, anglerfish, hake, megrim, plaice, sole, lesser-spotted dogfish, spurdog, Trisopterus spp., skates and rays) in the Celtic Sea from 1997 to 2019 (23 years). Annualized time series (1997-2019) of net primary production, bottom temperature, copepod abundance (Calanus finmarchicus and Calanus helgolandicus) and North Atlantic Oscillation index were used to characterize key environmental variables. Fishing exploitation rates (F/FMSY) were used to represent fishing pressure and CPUE trends derived from an International Bottom Trawl Survey (IBTS) were used to infer abundance. We used redundancy analysis to identify key explanatory variables and then dynamic factor analysis to assess their relationships with the CPUE series and identify underlying patterns in the unexplained temporal variation. Our results show that for the majority of demersal fish species, the CPUE trends were strongly influenced by fishing exploitation rates. The gradual reduction in exploitation rates observed throughout the study period most likely led to the partial recovery of cod, spurdog, hake, megrim, plaice, whiting, Trisopterus spp., and the skates and rays. In addition, exploitation patterns on one stock influenced CPUE trends of other demersal stocks (e.g., hake, megrim, plaice, lesser-spotted dogfish, sole). We also observed that the CPUE of whiting, hake and plaice increased when C. finmarchicus were abundant in the plankton. We infer from our findings in the investigated time series that the recovery of cod, spurdog, hake, megrim, plaice, whiting, Trisopterus spp., and the skates and rays in the Celtic Sea remains dependent on controlling fishing mortality, and this would not, at least for now, be confounded by the environmental conditions.

Effects of life-history traits and network topological characteristics on the robustness of marine food web

Article

Full-text available

Feb 2022

Management targets for biodiversity preservation are shifting from individual species to an ecosystem-wide focus. Indeed, the perturbation analysis of interaction networks, such as food webs, better captures the response of biodiversity to environmental pressures than single-species considerations. Here we propose a framework that examines food web robustness to a given perturbation based on life history traits and the topology of the food web, at different scales: local (species), intermediate (species directly linked together by a trophic interaction), and global (food web). Applying this framework to the Celtic Sea, a historically exploited fishing ground, we showed that the species sensitive to fishing were not the most central (i.e. with many interaction links, estimated based on eigenvector centrality) and that there is no both highly sensitive and exposed species to fishing. We then investigated how the loss of central, sensitive and exposed species to fishing could impact the robustness of the food web. We showed that the food web was the least robust to the simulated loss of species with many predators (i.e. forage species) and most exposed to fishing pressure, indicating that conservation priority could be focused on these species. Estimating species’ sensitivity to fishing was insufficient to predict food web robustness since the simulated removal of the most sensitive species led to a robustness level similar to that of a random removal sequence. Unlike what is often documented, the network appeared relatively robust to the simulated loss of the most central species, due notably to their implication in redundant trophic interactions and the fact that their disappearance increases modularity. This suggests that species-level metrics such as centrality should be completed by analysis at the scale of the whole food web to prioritize species conservation.

Biomass of slow life history species increases as local bottom trawl effort decreases in the Celtic sea

Article

Apr 2021
J ENVIRON MANAGE

Due to its selective removal, fishing pressure has long influenced the dynamics of species based on their life history traits. Sensitivity to fishing increases along a "fast-to-slow" gradient of life history strategies, and the "slow" species (large, long-lived, late-maturing, giving birth to few large offspring) require the most time to recover from fishing. In the North East Atlantic, after having reached extreme levels, fishing pressure has decreased since the 1980's due to management measures such as total allowable catch (TAC) or area closure. An effect on the distribution of species as well as a potential recovery could be expected. However, temporal patterns of life history strategies are rarely linked to management measures. In addition, a larger emphasis is often put on exploited or emblematic sensitive species but rarely on assembly processes at the ecosystem scale (both commercial and non-commercial species). Based on a 17-year time series of 101 taxa (fishes, elasmobranchs, bivalves, cephalopods and crustaceans), we observed a negative relationship between the biomass of taxa sensitive to fishing and bottom trawling pressure, as well as an increase in their total biomass in the Celtic Sea. Over the whole area, stochasticity appeared as the dominant assembly process. Deterministic assembly processes were at play in the centre of the area where significant overdispersion (caused by the presence of both slow and fast taxa) were observed. The absence of sensitive taxa from the rest of the Celtic Sea appeared to be caused mainly by a historical effect of environmental filtering when fishing was high. At the local scale, we related the decrease in fishing pressure to the increase in biomass of five of the most sensitive taxa. This local decrease in fishing pressure, resulting from the implementation of an area closure, highlights the positive effect of such management measures in less than two decades.

Using biological traits to get insights into the bentho-demersal community sensitivity to trawling in the Celtic Sea

Article

Feb 2021

Coastal marine ecosystems are under many pressures, including bottom trawling, which is the most widespread human activity that directly affects seabed habitats. Therefore, it is of great importance to characterize the impacts of bottom trawling on bentho-demersal communities, which can be done through the study of indicators sensitive to trawling pressure. Using a functional indicator applied to 54 underwater video transects, we mapped the sensitivity to trawling of epibenthic invertebrates and fish communities in the Celtic Sea. We determined the relative influence of environmental and fishing variables on sensitivity and traits distribution. Our results suggest that community sensitivity to trawling is mainly driven by a spatial gradient of depth and primary productivity that separates the area into two main regions: a shallow, productive area, with low sensitivity and a higher abundance of swimming and crawling organisms, and a deeper, less productive area, with higher sensitivity due to a higher abundance of fixed, filter-feeding organisms. Fishing intensity also drives the sensitivity of communities confirming that they have already been shaped by a long history of mixed fisheries. The methodology used here provides a valuable monitoring tool and could be used to predict communities’ response to changes in fishing intensity and climate change.

Species's traits and network topology drive the robustness of a marine food web to species removal

Preprint

Jan 2021

The analysis of the dynamics of interaction networks (i.e. trophic webs) better capture the state of ecosystem facing a perturbation than individual species dynamics could. We propose a framework that examines network robustness to a given perturbation at the local (species), mesoscale (species directly linked together) and global (network) level, based on traits and the topology of the network. Using the Celtic Sea as an example, we showed that the network was the least robust to the simulated loss of forage taxa and the most exposed taxa to fishing pressure, indicating conservation priority could be focused on these taxa. However estimating the sensitivity to fishing at the taxa ‘level was insufficient to predict the robustness of the network. The network appeared relatively robust to the simulated loss of the most central taxa, suggesting that mesoscale metrics such as centrality, although widely used, are not always adapted to prioritize species conservation.

Exploring the impacts of fishing and environment on the Celtic Sea ecosystem since 1950

Article

Full-text available

May 2020
FISH RES

Analyzing the long-term changes in ecosystems and disentangling the influence of overfishing and environment require historical data integration. Fisheries-independent data are available only since the mid-1980s in the Celtic Sea and thus provide a short-term and truncated vision of fishing impacts. We conducted a catch-based study over the 1950–2015 period. We successively (i) reconstituted catch time-series, including unreported catch estimates, and studied them through a trophic-spectrum approach and ecosystem indicators based on trophic level, size and species diversity; (ii) estimated biomass trends of the main Celtic Sea target species from catch and effort time-series, using production models that detect potential shifts in productivity; and (iii) explored linkages between species productivity potential and both fishing and environment using long-term time-series of large-scale climatic indices, locally observed hydroclimatic variables and plankton data from the Continuous Plankton Recorder. Our results highlight that fishing has caused a drastic depletion of the main exploited species in the Celtic Sea since World War II. The biomass reduction of larger demersal species may reach more than 80 %; additionally, this depletion occurred earlier than previously thought and may have initiated a trophic cascade in the ecosystem. North Atlantic hydroclimatic variability affected species productivity, worsening the early stock depletion while potentially mitigating fishing impact in the 1990s. The common pattern in productivity changes among analyzed species highlights an abrupt transition whose timing matches that of the ecosystem shifts identified in several Atlantic ecosystems. Finally, we show that the recent fishing pressure reduction led by the European Common Fisheries Policy initiated a partial recovery of stocks and ecosystem status over the last decade.

A review of the ecological role of forage fish and management strategies

Technical Report

Full-text available

Jan 2014

The report reviews the ecological role of forage fish globally and in Canada, and the policy directed at their management, with a focus on the consumption requirements of predators. The report is intended for policy makers, managers and biologists who are engaged in providing advice or making decisions concerning the management of forage species.

How will the cumulative effects of fishing and climate change affect the health and resilience of the Celtic Sea ecosystem?

Article

Full-text available

Feb 2025

Gap Analysis on the Biology of Marine Fishes Across European Seas

Article

Jan 2025

This review evaluates the current knowledge of essential biological traits (diet, fecundity, maturity, length-weight relationships, spawning, growth, lifespan, and natural mortality) of marine fishes across European and adjacent waters. These traits are crucial for ecosystem modeling and stock assessments. Using data from FishBase, the largest and most comprehensive database on fishes, a gap analysis was performed to identify areas of research focus and the corresponding gaps that require further study. Biological data coverage is strong in the Baltic and North Seas but moderate in the Adriatic, Aegean, Biscay, Celtic, Levantine, and western Mediterranean Seas. Well-documented species include the European conger (Conger conger), thornback ray (Raja clavata), and transparent goby (Aphia minuta) which are reported from all areas. The narrowest knowledge gaps concern length-weight relationships, followed by spawning and growth, while natural mortality and fecundity are the least studied biological characteristics. Regional variations exist, particularly for protected species. Future research should focus on filling gaps by addressing overlooked species (bycatch and discarded species) and traits such as natural mortality and fecundity, with special attention to vulnerable groups like sharks and rays. Expanding biological data coverage will reduce uncertainties in stock assessments and improve ecosystem models, two widely used tools for sustainable fisheries management and marine conservation.

Ecological Sensitivity Analysis of the Celtic Sea to inform future designation of Marine Protected Areas (MPAs) A report by the Marine Protected Area Advisory Group for the Department of Housing, Local Government and Heritage

Technical Report

Full-text available

Jun 2024

Following on from the ecological sensitivity analysis of the western Irish Sea completed in June 2023, the Minister for Housing, Local Government and Heritage requested the Marine Protected Area Advisory Group to carry out a further ecological sensitivity analysis of the Celtic Sea. This report is a significant milestone as we look to manage the southern Celtic Sea in a coherent and sustainable way, enabling and supporting the future designation of Marine Protected areas, and integrating MPAs with the maritime sectors of shipping and fishing and Renewable Offshore Energy. Further work under the forthcoming MPA legislation will enable potential MPA network solutions to be refined on the basis of national policy, analyses involving additional evidence and the participation and input of stakeholders.

Scientific knowledge gaps on the biology of non-fish marine species across European Seas

Article

Full-text available

Oct 2023

Available information and potential data gaps for non-fish marine organisms (cnidarians, crustaceans, echinoderms, molluscs, sponges, mammals, reptiles, and seabirds) covered by the global database SeaLifeBase were reviewed for eight marine ecosystems (Adriatic Sea, Aegean Sea, Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea, western Mediterranean Sea, Levantine Sea) across European Seas. The review of the SeaLifeBase dataset, which is based on published literature, analyzed information coverage for eight biological characteristics (diet, fecundity, maturity, length-weight relationships, spawning, growth, lifespan, and natural mortality). These characteristics are required for the development of ecosystem and ecological models to evaluate the status of marine resources and related fisheries. Our analyses revealed that information regarding these biological characteristics in the literature was far from complete across all studied areas. The level of available information was nonetheless reasonably good for sea turtles and moderate for marine mammals in some areas (Baltic Sea, Bay of Biscay/Celtic Sea/Iberian Coast, Black Sea, North Sea and western Mediterranean Sea). Further, seven of the areas have well-studied species in terms of information coverage for biological characteristics of some commercial species whereas threatened species are generally not well studied. Across areas, the most well-studied species are the cephalopod common cuttlefish (Sepia officinalis) and the crustacean Norway lobster (Nephrops norvegicus). Overall, the information gap is narrowest for length-weight relationships followed by growth and maturity, and widest for fecundity and natural mortality. Based on these insights, we provide recommendations to prioritize species with insufficient or missing biological data that are common across the studied marine ecosystems and to address data deficiencies.

Environmental DNA complements scientific trawling in surveys of marine fish biodiversity

Article

Full-text available

Sep 2023

Environmental DNA (eDNA) metabarcoding is a method to detect taxa from environmental samples. It is increasingly used for marine biodiversity surveys. As it only requires water collection, eDNA metabarcoding is less invasive than scientific trawling and might be more cost effective. Here, we analysed data from both sampling methods applied in the same scientific survey targeting Northeast Atlantic fish in the Bay of Biscay. We compared the methods regarding the distribution of taxonomic, phylogenetic, and functional diversity. We found that eDNA captured more taxonomic and phylogenetic richness than bottom trawling and more functional richness at the local scale. eDNA was less selective than trawling and detected species in local communities spanning larger phylogenetic and functional breadths, especially as it detected large pelagic species that escaped the trawl, even though trawling detected more flat fish. eDNA indicated differences in fish community composition that were comparable to those based on trawling. However, consistency between abundance estimates provided by eDNA metabarcoding and trawl catches was low, even after accounting for allometric scaling in eDNA production. We conclude that eDNA metabarcoding is a promising method that can complement scientific trawling for multi-component biodiversity monitoring based on presence/absence, but not yet for abundance.

The cross-national association between institutional imbalance, national culture, and illegal fishing

Article

May 2023
MAR POLICY

Objectives Extant research has examined various factors as driving illegal fishing at the country level. Prior research, however, lacked a cohesive theoretical framework to explain the prevalence of this practice at the macro level. The current study borrows concepts and measures from Institutional Anomie Theory (IAT), namely national culture and the relative strength of economic and non-economic social institutions (i.e., institutional imbalance), to test if this framework can account for illegal fishing. Methods We used data from 72 countries between 1995 and 2016 and fixed effects regression models to estimate the longitudinal association between institutional imbalance towards economic institutions and illegal fishing. We then estimated how different configurations of national culture (i.e., individualistic, or collectivistic; cooperative, or competitive) moderate that association. Results About 36.67% of all fishing in countries and years in our data is illegal. Institutional imbalance has a strong positive average association with the prevalence of illegal fishing. However, while that association is particularly strong in collectivistic countries, it is week to nonexistent in individualistic countries. Conclusions Most findings are consistent with the predictions of IAT, particularly regarding the institutional components of the theory, as countries which place an excessive emphasis on economic institutions tend to have more illegal fishing. It contradicts the theory, however, that individualism is protective against the deleterious influence of institutional imbalance. We explore this inconsistency in light of the particularities of fishing and discuss possible implications.

Etats de référence temporels : trouver un point de bascule dans le passé

Chapter

Jan 2023

Conservation de la biodiversité et état de référence: La nostalgie de la nature à l’ère de l’Anthropocène

Book

Jan 2023

L’ère de l’Anthropocène est marquée par une pression humaine si forte qu’elle a conduit à la sixième extinction de masse. La notion d’état de référence appliquée au domaine de la conservation de la biodiversité permet d’appréhender la domination des humains sur Terre comme un processus de modification de nos paysages qui n’est ni linéaire ni homogène.Conservation de la biodiversité et état de référence s’articule autour de trois points clés. Il définit d’abord où et quand tout a « mal tourné », réfléchit ensuite à l’utilisation des états de référence pour élaborer des stratégies de conservation et propose enfin des exemples d’application concrète de la notion d’état de référence sur le littoral, la forêt et les paysages agropastoraux.La conservation de la biodiversité est aujourd’hui confrontée à des choix nécessaires : revenir à des états moins modifiés par les humains qu’aujourd’hui, mais dans un monde qui a beaucoup changé ; laisser la nature de demain s’exprimer là où elle le peut encore, mais sans aucune feuille de route ; ou encore construire des alternatives basées sur des projets territoriaux.

La notion de référence : un chemin étroit entre fausses pistes et vraies impasses

Chapter

Jan 2023

L'état de référence : une construction sociale

Book

Jan 2023

L’état de référence : une construction sociale

Chapter

Dec 2022

Considérer l’état de référence comme une construction sociale appelle à explorer au moins trois pistes de réflexion que nous développons dans ce chapitre. Premièrement, l’état de référence n’est pas stabilisé, mais évolue dans le temps : c’était la théorie du glissement de référence de Daniel Pauly, que de nombreux travaux sont venus confirmer, mais aussi critiquer. Deuxièmement, différents éléments, non seulement écologiques, mais également sociaux, culturels, économiques, voire politiques, entrent en compte dans la construction de l’état de référence, d’où le fait que l’état de référence peut varier en fonction des groupes sociaux ou des individus, et des contextes. Enfin, puisque le choix de l’état de référence a de fortes implications en matière de gestion et qu’il n’y a pas forcément de consensus, il est nécessaire de le mettre en débat. Pour développer ces trois axes de réflexion, nous nous appuierons sur une revue de la littérature et nous étayerons notre propos par des exemples tirés d’une étude de terrain menée dans le parc national des Cévennes.

Temporal synchrony among juvenile marine fishes and potential climate and environmental drivers in the Bay of Biscay

Article

Feb 2023
PROG OCEANOGR

The existence of synchronous fluctuations among sympatric species is an important property of a community, potentially reducing temporal stability of ecosystem services. Yet, community synchrony and its potential drivers have rarely been studied in marine ecosystems. Here, we analyzed a 14-year time-series (2007-2020) of fish abundance data collected by a scientific beam trawl survey in the Bay of Biscay, a temperate marine ecosystem located in the North-east Atlantic. We used dynamic factor analysis to reveal common trends in abundance among juvenile demersal marine fishes, and to identify potential environmental drivers. Our results revealed synchronous changes in juvenile fish abundance among the 12 marine species examined in the study. This strong temporal coherence was likely related to the influence of climate and environmental factors, notably sea bottom temperature and the East Atlantic Pattern. We also found some support for alternative drivers of early-life fish dynamics, namely the North Atlantic Oscillation and sea surface chlorophyll-a concentration, the later suggesting bottom-up trophic control. In the context of ongoing environmental changes, our findings raise questions about the future stability of the demersal marine fish community in the Bay of Biscay.

Vers une approche socio-écologique d'évaluation de la perfomance de projets d'aménagements côtiers avec des récifs artificiels : étude de cas sur trois régions biogéographiques maritimes en France métropolitaine

Thesis

Mar 2022

Jessica Salaün

Les récifs artificiels sont des outils d’aménagement des zones côtières, volontairement immergées par l’homme dans le but de protéger, produire (augmenter, régénérer) ou concentrer les ressources marines. Ils sont employés à travers le monde dans le cadre de politiques publiques de soutien à la pêche (production et protection), de restauration des écosystèmes (éco-fonctionnel) ou pour développer des activités économiques de loisirs (récréatif).En France, depuis 50 ans, les récifs artificiels (RA) sont utilisés comme réponse à la diminution des stocks halieutiques et immergés sur l'ensemble des façades maritimes avec une prépondérance en Méditerranée. Toutefois, l’évaluation de leurs performances est rare ou partielle, ce qui n’est d’ailleurs pas une spécificité française mais un constat à l’échelle mondiale. Les études réalisées présentent des lacunes car elles ciblent principalement l'évolution d’indicateurs d'abondance et de richesse spécifique de la faune et la flore aux abords des récifs, se focalisent sur un compartiment spécifique ou des espèces cibles et le plus souvent sur le court terme. Ces études, bien qu’elles aient montré l’effet direct des récifs sur l’augmentation de la production secondaire locale, n'apportent qu'une réponse partielle à la problématique d’évaluation de la contribution des RA au sein d’un socio-écosystème car la dimension socio-économique est oubliée. Ce constat peut s’expliquer par des ruptures dans les étapes de l’évaluation et notamment l’absence de déclinaison de l’objectif général en objectifs spécifiques et critères de succès. En effet, un point clé de l’évaluation est la comparaison des critères de succès avec les indicateurs de résultats. Sans la définition de ces critères de succès, aucune comparaison, et de fait aucune évaluation, n’est possible.En s’appuyant sur le cadre d’analyse des socio-écosystèmes et en utilisant des méthodologies issues des sciences humaines et de l’écologie, nous proposons une approche socio-écologique d’évaluation de la performance des RA en réponse aux lacunes identifiées. La théorie de la traduction a permis d’identifier les objectifs spécifiques des RA afin de proposer des critères de succès socio-écologiques. Cette méthodologie d’évaluation a été appliquée sur dix cas sites de RA répartis sur les trois façades maritimes de France métropolitaine. Ainsi, une analyse comparative des réseaux d’acteurs et trophiques avant implantation de RA avec l’état actuel de ces réseaux a été réalisée. La définition d’indicateurs de résultats a été réinvestie pour décrire l’évolution des socio-écosystèmes, permettant de critiquer l’adéquation du système socio-écologique avec les objectifs d’immersions des sites de RA. Enfin, la performance des RA en réponse à une gestion durable des ressources et de la biodiversité à l’échelle des territoires a été évaluée, afin de fournir un tableau de bord opérationnel pour les décideurs des politiques publiques d’aménagement et les gestionnaires des fonds marins côtiers.

The Baseline Concept in Biodiversity Conservation

Book

Sep 2022

The Anthropocene era has been marked by such significant human pressure that it has led to the sixth mass extinction. The Baseline Concept in Biodiversity Conservation interprets human domination of the Earth as the process of gradual landscape change, the execution of which is neither linear nor homogeneous. This book is structured around three key questions: Where and when did everything go wrong? How do we define baseline states for biodiversity conservation strategies? How are reference states mobilized in a concrete way through case studies? Today, biodiversity conservation faces a dilemma that this book sheds light on: return to states less modified by humans than today but in a world that has changed significantly; or, let the nature of tomorrow express itself where it still can but without a road map.

Brexit, common fisheries policy and discard ban: A financial analysis of the Spanish fleet in the Grand Sole

Article

May 2022
FISH RES

In the last decades, the Spanish Grand Sole fleet has shown a negative evolution both in the number of vessels and in the turnover of its activity. This trend is mainly due to the institutional framework that determines the governance of the Spanish fleet in Community waters. The distribution of quotas, determined by the Relative Stability System, combined with successive European fishing policies, have caused a reduction in the capacity of the fishing fleet. In addition, more recently, these factors have been compounded by the progressive implementation a of the discard ban, which has been extended to all European species and fishing areas since 2019, and Brexit, which has led to the transfer of 25% of the average value of shared stocks quotas to the United Kingdom from 2021 to 2026. The objective of this article is to analyze whether the Spanish shipowning companies whose vessels operate in Gran Sol, will continue to be profitable or will have to cease their activity. For this purpose, an analysis has been carried out using the Real Options Approach and incorporating an abandonment option. The results show that the value of the abandonment option (49.3%) is high.

EcoDiet: A hierarchical Bayesian model to combine stomach, biotracer, and literature data into diet matrix estimation

Article

Full-text available

Feb 2022
ECOL APPL

Although quantifying trophic interactions is a critical path to understanding and forecasting ecosystem functioning, fitting trophic models to field data remains challenging. It requires flexible statistical tools to combine different sources of information from the literature and fieldwork samples. We present EcoDiet, a hierarchical Bayesian modeling framework to simultaneously estimate food‐web topology and diet composition of all consumers in the food web, by combining (1) a priori knowledge from the literature on both food‐web topology and diet proportions; (2) stomach content analyses, with frequencies of prey occurrence used as the primary source of data to update the prior knowledge on the topological food‐web structure; (3) and biotracers data through a mixing model (MM). Inferences are derived in a Bayesian probabilistic rationale that provides a formal way to incorporate prior information and quantifies uncertainty around both the topological structure of the food web and the dietary proportions. EcoDiet was implemented as an open‐source R package, providing a user‐friendly interface to execute the model, as well as examples and guidelines to familiarize with its use. We used simulated data to demonstrate the benefits of EcoDiet and how the framework can improve inferences on diet matrix by comparison with classical network MM. We applied EcoDiet to the Celtic Sea ecosystem, and showed how combining multiple data types within an integrated approach provides a more robust and holistic picture of the food‐web topology and diet matrices than the literature or classical MM approach alone. EcoDiet has the potential to become a reference method for building diet matrices as a preliminary step of ecosystem modeling and to improve our understanding of prey–predator interactions.

Structure and functioning of the Bay of Biscay ecosystem: A trophic modelling approach

Article

Nov 2021
ESTUAR COAST SHELF S

Characterizing the structure and functioning of marine ecosystems requires a deep understanding of the dynamics of its populations and the biotic interactions among them. To this end, we developed a mass-balanced food-web model of a regional sea in the Northeast Atlantic, the Bay of Biscay (BoB), considering one of the most important anthropogenic disturbance in the area, the fishing pressure. The food-web model was performed for the whole BoB region for the first time. The model represents the ecosystems in the early 2000s, encompassing 120433 km² between 0 and 1000 m depth. The model was composed of 52 functional groups, ranging from primary producers to top predators, and considering both Spanish and French fishing fleets. Input data included biomass obtained locally from bottom trawl and acoustic surveys, data from stock assessment, official fishery statistics, published and unpublished data on stomach content analyses and the use of empirical equations to estimate consumption and production rates. Our results highlight the importance of the pelagic domain, since the main trophic flows are determined by the interaction between phytoplankton, zooplankton and forage fishes. The role of the detritivore pathway was also relevant due to the relatively high abundance of detritivores organisms and the large percentage of primary production flowing to the detritus. Forage fish have resulted to be a key compartment fostering the connectivity between the benthic and pelagic domains. Pelagic sharks, dolphins, anglerfish, large hake and large demersal fishes were identified as potential keystone functional groups in the BoB model. The results also showed an intense exploitation by fisheries in early 2000s. Different strategies between Spanish and French fleets were also found. French fleets were mainly focussed on low trophic level forage fish (e.g., sardine and anchovy) and had larger impacts on higher trophic levels, while Spanish fleets mostly focussed on higher trophic level forage fishes (e.g., mackerel, horse mackerel and blue whiting) but also targeting sardine and anchovy; and displayed lower impacts on higher trophic levels. Overall, our model demonstrates the importance of combining data sources from different countries to regionally address the sought-after implementation of the ecosystem-based management approach.

Shifting Baselines to Thresholds: Reframing Exploitation in the Marine Environment

Article

Full-text available

Nov 2021

Current research on anthropogenic impacts on marine ecosystems often relies on the concept of a “baseline,” which aims to describe ecosystems prior to human contact. Recent research is increasingly showing that humans have been involved in marine ecosystems for much longer than previously understood. We propose a theoretical framework oriented around a system of “thresholds” referring to system-wide changes in human culture, ecosystem dynamics, and molecular evolution. The concept of the threshold allows conceptual space to account for the fluid nature of ecosystems throughout time while providing a critical framework for understanding drivers of ecosystem change. We highlight practical research approaches for exploring thresholds in the past and provide key insights for future adaptation to a changing world. To ensure ecological and societal goals for the future are met, it is critical that research efforts are contextualized into a framework that incorporates human society as integral to ecology and evolution.

Decadal changes in exploited fish communities and their relationship with temperature, fisheries exploitation, and ecological traits in New Zealand waters

Article

Full-text available

Oct 2021

Composition and length-frequency are important attributes considered in the management of fish communities and can be affected by both exploitation and environmental forces. Vulnerability to these effects varies among species depending on environmental tolerance, ecological traits, and life-history strategies. In the present study, data from scientific bottom trawl surveys conducted between 1991 and 2018 were analysed to identify long-term changes in community structure and length frequency of demersal fish species of the east coast of the South Island, New Zealand. Analysis of variance, hierarchical clustering analysis and multidimensional scaling relationships demonstrated that community composition has changed significantly over the last three decades, with a tendency towards greater spatial overlap among species in the most recent periods. Changes in depth distribution were identified but were mainly correlated with shifts in relative biomass. Total catch rate (kg km−2) of the whole community has increased significantly over time, while the average trophic level decreased, primarily explained by an increase in relative biomass of intermediate trophic level species. Fishing activity was significantly related to the variation in length frequency of species at intermediate trophic levels, confirming that the impacts of fisheries are heterogeneous throughout the community, providing vital information to support multi-species management of fishery resources.

Shining Light on Data-Poor Coastal Fisheries

Article

Full-text available

Jan 2021

Coastal fisheries provide livelihoods and sustenance for millions of people globally but are often poorly documented. Data scarcity, particularly relating to spatio-temporal trends in catch and effort, compounds wider issues of governance capacity. This can hinder the implementation and effectiveness of spatial tools for fisheries management or conservation. This issue is acute in developing and low-income regions with many small-scale inshore fisheries and high marine biodiversity, such as Southeast Asia. As a result, fleets often operate unmonitored with implications for target and non-target species populations and the wider marine ecosystem. Novel and cost-effective approaches to obtain fisheries data are required to monitor these activities and help inform sustainable fishery and marine ecosystem management. One such example is the detection and numeration of fishing vessels that use artificial light to attract catch with nighttime satellite imagery. Here we test the efficiency and application value of nighttime satellite imagery, in combination with landings data and GPS tracked vessels, to estimate the footprint and biomass removal of an inshore purse seine fishery operating within a region of high biodiversity in Myanmar. By quantifying the number of remotely sensed vessel detections per month, adjusted for error by the GPS tracked vessels, we can extrapolate data from fisher logbooks to provide fine-scale spatiotemporal estimates of the fishery's effort, value and biomass removal. Estimates reveal local landings of nearly 9,000 mt worth close to $4 million USD annually. This approach details how remote sensed and in situ collected data can be applied to other fleets using artificial light to attract catch, notably inshore fisheries of Southeast Asia, whilst also providing a much-needed baseline understanding of a data-poor fishery's spatiotemporal activity, biomass removal, catch composition and landing of vulnerable species.

The Celtic Sea Through Time and Space: Ecosystem Modeling to Unravel Fishing and Climate Change Impacts on Food-Web Structure and Dynamics

Article

Full-text available

Dec 2020

Both trophic structure and biomass flow within marine food webs are influenced by the abiotic environment and anthropogenic stressors such as fishing. The abiotic environment has a large effect on species spatial distribution patterns and productivity and, consequently, spatial co-occurrence between predators and prey, while fishing alters species abundances and food-web structure. In order to disentangle the impacts of the abiotic environment and fishing in the Celtic Sea ecosystem, we developed a spatio-temporal trophic model, specifically an Ecopath with Ecosim with Ecospace model, for the period 1985–2016. In this model, particular attention was paid to the parameterization of the responses of all trophic levels to abiotic environmental changes. Satellite remote sensing data were employed to determine the spatial distribution and annual fluctuations of primary production (PP). Spatial and temporal changes in the habitat favorable for zooplankton were predicted with a novel ecological-niche approach using daily detection of productivity fronts from satellite ocean color. Finally, functional responses characterizing the effect of several abiotic environmental variables (including, among others, temperature, salinity and dissolved oxygen concentration, both at the surface and at the bottom) on fish species groups’ habitat suitability were produced from the predictions of statistical habitat models fitted to presence-absence data collected by multiple fisheries-independent surveys. The dynamic component of our model (Ecosim) was driven by time-series of fishing effort, PP, zooplankton habitat suitability and abiotic environmental variables, and was fitted to abundance and fisheries catch data. The spatial component of our model (Ecospace) was constructed, for specific years of the period 1985–2016 with contrasted abiotic environmental conditions, to predict the variable distribution of the biomass of all functional groups. We found that fishing was the main driver of observed ecosystem changes in the Celtic Sea over the period 1985–2016. However, the integration of the environmental variability into the model and the subsequent improvement of the fit of the dynamic Ecosim component highlighted (i) the control of the overall pelagic production by PP and (ii) the influence of temperature on the productivity of several trophic levels in the Celtic Sea, especially on trophic groups with warm and cold water affinities. In addition, Ecospace predictions indicated that the spatial distributions of commercial fish species may have substantially changed over the studied period. These spatial changes mainly appeared to be driven by temperature and may, therefore, largely impact future fisheries given the continuity of climatic changes.

Identifying assessment scales for food web criteria in the NE Atlantic: implications for the Marine Strategy Framework Directive

Article

Dec 2020

The implementation of food web criteria in the Marine Strategy Framework Directive context faces several difficulties, namely the lack of data for relevant taxa, the absence of operational indicators, and spatially and temporally limited datasets. This work aims to identify ecologically relevant scales in the Celtic Seas (CS) and the Bay of Biscay and Iberian Coast (BBIC). Four food web criteria—mean trophic level (MTL), mean trophic level with cut-offs (MTL_3.25 and MTL_4), large fish indicator (LFI) and mean abundance across trophic guild (MATG)—were assessed using groundfish data and tested using generalized additive models, for six spatial scales and four temporal scales. In both subregions, MTL required yearly and locally defined assessment scales. As for MTL_3.25, it improved significantly when downsizing spatial scales but was temporally consistent. In the CS, locally defined scales and yearly data explained MTL_4 and LFI. While in BBIC, MTL_4 and LFI patterns were defined spatially by region and depth and temporally by year. MATG variability was unaffected by scales. Using the scales identified, food web criteria were assessed for the Portuguese continental waters. Criteria failed to achieve Good Environmental Status in areas of the Southwest and South of Portugal. Although downsizing scales revealed that criteria were below the threshold at local/regional level, differences in classification are expected to be limited if spatial assessments are aggregated.

Toward Ecosystem-Based Assessment and Management of Small-Scale and Multi-Gear Fisheries: Insights From the Tropical Eastern PacificData_Sheet_1.PDFImage_1.pdfImage_2.pdfImage_3.pdfTable_1.pdfTable_2.pdfTable_3.pdf

Article

Full-text available

Mar 2019

Small-scale fisheries (SSF) remain a largely under-assessed and overlooked sector by governments and researchers, despite contributing approximately 50% to global fish landings and providing food and income for millions of people. The multi-species, multi-gear and data-poor nature of SSF makes implementation of traditional single-species management approaches – like catch-quotas or size limits – particularly challenging and insufficient. A more holistic approach is thus required, which demands assessment of ecological impacts. Here we carried out an estimation of selected ecological indicators of the impact of fisheries (mean length, maximum body size, mean trophic level, trophic and spatial guilds, threatened species and landed by-catch) based on the nominal catch of different gears in three representative SSF along the Colombian Pacific using landings data collected in multiple years (2011–2017). Results showed that taxonomic, size-based, functional and conservation features of the nominal catch vary greatly with geographical location and gear type used. Overall, handlines and longlines tend to select larger sizes and higher trophic levels than nets, but they also catch a higher proportion of intrinsically vulnerable species and species of conservation concern. This challenges the idea that more selective gears have overall lower ecological impacts. In contrast, nets target a wider size range – although focusing on small or medium sized fish – and include a higher diversity of trophic and spatial guilds, which could arguably be considered a more “balanced harvest” type of fishing that retains ecosystem structure and functionality. Bottom trawls, though, exhibited a relatively high percentage of landed by-catch, an undesirable feature for any fisheries in terms of sustainability. We propose that the assessment of a suite of ecological indicators, like those implemented here, should be included as part of periodic evaluations of multi-gear and multi-species SSF in tropical coastal areas, as a practical step toward ecosystem-based fisheries management.

The building of a management system for marine recreational fisheries in Galicia (NW Spain)

Article

Full-text available

Dec 2018
OCEAN COAST MANAGE

Over the past decades, the nature of the management of marine fisheries in Galicia (NW Spain) has changed substantially. In addition to a powerful commercial fleet and high fisheries dependence of coastal communities, Galicia has a long and strong tradition in marine recreational fisheries, with 60 000 fishers and 4 000 boats engaged in this activity in coastal waters. This paper analyses, for the first time, key changes in the management framework of marine recreational fisheries in Galicia by investigating past and current regulations and research initiatives developed so far. Three periods in the management of marine recreational fisheries (1963-1982; 1983-2000; and 2001-present) have been identified. The results show that the management of marine recreational fishing (MRF) moved in the 80's of last century from a poorly regulated and de facto open access system under the rule of the Spanish administration to a current highly regulated fishery under regional, national and European Union (EU) governments. EU regulations are being fundamental to promote the ecological and socioeconomic sustainability of MRF. However, the lack of scientific data, with only eight papers about MRF in Galicia published in international referred journals, the absence of experts in the field working in the fisheries administration and in research centers, and the lack of strong fishers’ organizations are jeopardizing the sustainability of this complex socioecological system in the long term. The development of a strategic plan for MRF in Galicia is needed, including a diagnosis of its current status in relation to other sectors sharing coastal ecosystems, like commercial fisheries, and tourism. Co-management initiatives and adaptive policies favoring both the development of commercial fisheries and the promotion of MRF-based economies to offer new opportunities to local communities are encouraged.

The effects of bottom trawling and primary production on the biological traits composition of benthic assemblages

Article

Aug 2018

Although many studies have investigated the effects of disturbance and environmental drivers on marine ecosystems, comparatively few have studied their interactions. Using fuzzy coded biological traits, we compared the functional composition, diversity and evenness of benthic communities in the English Channel and in the Celtic and Irish Seas across interacting gradients of bottom trawling and primary production. Fuzzy correspondence analysis indicated greater similarity in trait composition at sites of high trawling pressure than at those of low trawling. In contrast, the analysis revealed no relationship between trait composition and primary production. Trawling and primary production had no effect on the traits ‘longevity’, ‘sediment position’, or ‘feeding mode’. However, trawling had negative effects on all modalities within the trait ‘living habit’, and these effects were strongest for attached and epifaunal organisms but weakest for burrow- and tube-dwelling species. Trawling also negatively affected most modalities within the trait ‘maximum weight’, with strongest effects for organisms weighing between <0.1 g and up to 1 kg. Conversely, trawling positively affected organisms weighing >10 kg. For the trait ‘bioturbation’, upward conveyors were positively related with primary production, whilst other modalities exhibited no clear pattern. Because trawling affected some traits more than others, community biomass was less evenly distributed across traits in highly trawled areas, which resulted in lower levels of functional diversity and evenness. Overall, the effects of bottom trawling were greater in areas of high primary production.

Underwater video offers new insights into community structure in the Grande Vasière (Bay of Biscay)

Article

May 2018
J SEA RES

Based on towed underwater videos, diversity patterns and their main environmental and anthropogenic drivers were assessed in the “Grande Vasière” (northeast Bay of Biscay), one of the main French fishing grounds. The density of bentho-demersal megafauna was recorded along 152 transects in this area in 2014. The highest number of taxa and densities were observed on the external margin of the Grande Vasière, in deep areas with low fishing intensity. The highest levels of taxa evenness were located on the central and coastal parts that are shallower and exposed to medium to high trawling intensity. Multivariate analysis identified four different communities driven by fishing intensity, depth, sediment type and bottom current speed. We distinguished three communities in the centre of the Grande Vasière covered by medium to highly trawled soft sediments and characterized by Hydrozoa, Crustacea such as Munida rugosa, Nephrops norvegicus and Goneplax rhomboides and Actinopterygii unidentified. A fourth community was identified on the external margin, deeper, undergoing lower trawling intensity than the other communities and dominated by sessile filter feeders. The fragile taxa observed in this study had almost always been unobserved by from previous studies using scientific trawl sampling. Underwater video thus allowed collecting unprecedented data by direct visualization of the seabed and the observation of fragile taxa that cannot be effectively sampled by traditional scientific sampling methods used in previous studies.

The spring mesozooplankton variability and its relationship with hydrobiological structure over year-to-year changes (2003–2013) in the southern Bay of Biscay (Northeast Atlantic)

Article

Apr 2018
PROG OCEANOGR

Mesozooplankton can be considered the most important secondary producers in marine food webs because they hold an intermediate position between the phytoplankton assemblage and the upper trophic levels. They also are a robust indicator of climatic and hydrological conditions. We conducted an analysis of the interannual variability of the spring mesozooplankton assemblage, as sampled by the PELGAS fisheries survey in the southern part of the Bay of Biscay (Northeast Atlantic Ocean) between 2003 and 2013. We examined hydrology and trophic drivers to explain the variability. Our results revealed that the subsurface temperature, the subsurface salinity, the biomasses of subsurface pico-, nano-, and microphytoplankton, and the copepod assemblage exhibited a recurrent spatial pattern that was driven mainly by freshwater and nutrient inputs from the main rivers. The mesozooplankton assemblage was dominated by copepods (82%), composed of coastal, neritic, and oceanic copepod genera that paralleled the various hydrological fronts converging in the southern Bay of Biscay. The copepod community displayed high temporal-variability; there were three periods of abundant adult copepods throughout the southern Bay of Biscay. The copepod community was structured primarily around the drive for resource control, especially by the microphytoplankton biomass (24.3% of the total variability), and to a lesser extent by hydrological features (13.7% of the total variability).

Spatiotemporal variation in the structure of reef fish and macroalgal assemblages in a north-east Atlantic kelp forest ecosystem: implications for the management of temperate rocky reefs

Article

Full-text available

Jan 2018

Temperate rocky reefs and kelp forest ecosystems have been severely affected by overfishing, pollution and habitat destruction, and climate change is a major driver of kelp decline in many regions. Although necessary for management, ecological interactions between kelp and fish remain largely unknown in the north-east Atlantic. In the present study, underwater visual censuses (UVC) and univariate and multivariate multiple regression models were used to analyse the spatiotemporal variations in the abundance and habitat use of the rocky reef fish and macroalgae assemblages of Galicia (north-west Spain). The underwater seascape was dominated by large rocks and kelp forests of Laminaria hyperborea, L. ochroleuca and Saccorhiza polyschides. Fish assemblages were ruled by gadids, labrids and sparids. The most frequent fish species were Labrus bergylta (counted in 90% of UVC) and Pollachius pollachius (in 100% of UVC), whereas the most abundant were Boops boops (mean ± s.d., 556.4 ± 39.7 individuals ha–1) and L. bergylta (432.10 ± 440.05 individuals ha–1). Fish and macroalgal assemblages showed different spatial preferences and responded strongly to seasonality, wave exposure and depth. To a lesser degree, fish and macroalgal assemblages showed preferences for habitat structure. Moreover, because the findings of the present study indicate that L. bergylta is a good indicator species of the health of rocky reef and kelp forests ecosystems, monitoring of this fish can be helpful for management and conservation actions.

Variability of energy density among mesozooplankton community: New insights in functional diversity to forage fish

Article

Oct 2017
PROG OCEANOGR

To explore some aspects of mesozooplankton functional diversity, this study quantified energy density during the springtime in the Bay of Biscay both between different species and between different size-classes. Energy densities of copepod species (Centropages typicus, Anomalocera patersoni, Calanus helgolandicus, and Labidocera wollastoni), as well as anchovy eggs (Engraulis encrasicolus) ranged from 0.5 to 6.7 kJ/g wet weight (ww). Considering size-classes, energy densities varied from 0.74 to 1.26 kJ/g ww. Energy density of C. helgolandicus exhibited a spatial pattern with the highest values in the plume of the Gironde estuary. In contrast, no spatial pattern of energy density has been detected considering size-classes. Our results showed that the mesozooplankton cannot be considered as a homogeneous resource in terms of quality. During spring, some species and some geographical areas seem thus to be more profitable to predators than others. We argued that the energy density is a key functional trait of mesozooplankton species. Finally, we discussed how interspecific and spatial variability of energy density among the mesozooplankton community can have important implications on fish population dynamics.

Prey consumption by cetaceans reveals the importance of energy-rich food webs in the Bay of Biscay

Article

Sep 2017
PROG OCEANOGR

Ecosystem-based management requires a clear understanding of marine ecosystem functioning, particularly the transfer of energy (consumption) to higher trophic levels. However, robust estimates of consumption are generally hampered by a dearth of data for predators (diet and abundance), and by methodological weaknesses. We undertook a comprehensive assessment of energy requirements and prey consumption for the 10 most abundant cetacean species in the Bay of Biscay (northeastern Atlantic Ocean, France) by combining recent data on their abundances from aerial surveys, and diets from stomach content analyses. We also incorporated functional considerations to group prey and address interspecific differences in the cost of living of cetaceans that are independent of body size. Species considered included harbour porpoise, common dolphins, striped dolphins, bottlenose dolphins, long-finned pilot whales, Risso's dolphins, sperm whales, Cuvier's beaked whales, minke whales and fin whales. We used Monte Carlo resampling methods to estimate annual and seasonal (winter and summer) consumption over the continental shelf and slope-and found that small toothed whale populations (which were much more abundant than other cetacean groups) required about twice as much resources as baleen whales and deep-diving toothed whales combined. Our results show that small energy-rich schooling fish are the key prey group sustaining a large part of the cetacean community in the Bay of Biscay. The biomass removal of small energy-rich schooling fish by cetaceans is 6 times higher than removals of all other prey groups. High quality nutritional resources appear to be crucial to sustaining cetaceans and maintaining ecosystem functions and services in the Bay of Biscay, and should be carefully monitored.

Research and management priorities for Atlantic marine recreational fisheries in Southern Europe

Article

Sep 2017
MAR POLICY

Long-term changes in the French fisheries for crustaceans in the Eastern English Channel: 1901 to 2020

Article

Nov 2024
CRUSTACEANA

Small-scale crustacean fisheries in the English Channel have existed for centuries but have never been formally assessed; hence, concerns about their ecological and socio-economic sustainability could be raised. This study explores trends in this fishery’s landings from 1901 to 2021, based on historical and recent landings data in two of the main administrative fishing divisions of the area, Cherbourg and Boulogne-sur-Mer quartiers. Crustacean fisheries were reported for both divisions from the beginning to the end of the time period considered, demonstrating that a dedicated crustacean fishery existed in the area since at least the 20 th century. The species composition of the crustacean’s catch (e.g., edible crab, Cancer pagurus Linnaeus, 1758; European lobster, Homarus gammarus (Linnaeus, 1758); European spider crab, Maja brachydactyla Balss, 1922) was almost impossible to track before the 2000s. Important fluctuations were observed in catch volume reports along time that might be related to two phenomena: technological advances that would have improved the fishery performances and the decline of some previously targeted species that might have led to a transfer in fishing effort.

Do marine food subsidies predict large scale distribution of scavenging seabirds within the Bay of Biscay?

Article

Oct 2024

Structural and functional changes in Artificial Reefs ecosystem stressed by trophic modelling approach: Case study in the Bay of Biscay

Article

Jul 2023

When bioregionalisation emphasises the presence of Vulnerable Marine Ecosystem indicator species in Nephrops fishing grounds: evidence in the Bay of Biscay/Irish Sea continuum

Article

Apr 2023
PROG OCEANOGR

Under the apparent homogeneity of soft-bottom ecosystems hides an heterogeneity of habitats driven by variations in sediment composition and environmental conditions. Using an extensive underwater video survey dataset, we explored the taxonomic diversity of soft-bottom Nephrops fishing grounds and their environmental drivers on a large latitudinal scale from the Bay of Biscay to the Irish Sea (Northeast Atlantic). Biogeographical network clustering highlighted indicator species of the different communities and a Between-Class Analysis characterised the abiotic factors influencing each community. Our analyses confirmed a biogeographical limit between the Bay of Biscay and the northern areas driven by a latitudinal temperature gradient and highlighting the distribution of Lusitanian and Boreal species. Mobile fish and crustaceans, and sessile filter-feeder assemblages differed along a depth, bottom current and fishing gradient. Some species assemblages covered the whole latitudinal range, implying a greater influence of optimal environmental surroundings rather than their geographical position. Vulnerable Marine Ecosystem indicator taxa such as Virgularia mirabilis and Pennatula phosphorea are potential indicator species of some clusters, while harvested species such as Nephrops norvegicus or mobile fish characterized other bioregions. Spatial knowledge produced in this study could be integrated as biodiversity layers together with fisheries activities layers in decision support tools such as Marine Spatial Planning in order to define compromise between conservational and fishing objectives. Outcomes of management scenarios would then consider the whole species stock (e.g. Nephrops) rather that local populations independently.

Effects of spatial and temporal scale on the assessment of biodiversity and ecosystems health, under the scope of the Marine Strategy Framework Directive" Final Version, PhD in Marine Sciences

Thesis

Full-text available

Dec 2021

Inês Machado

The environmental assessment and monitoring of marine systems aim is to reveal the condition of ecosystem components, assess the effects of anthropogenic pressures and evaluate the effects of management measures. In Europe, the Marine Strategy Framework Directive aims to assess and manage the quality of the European seas to achieve Good Environmental Status. This directive uses indicators to analyse the environmental status and anthropogenic pressures on the European seas. Even though the Directive provides an unparallel comprehensive set of information, several issues are still undermining the correct assessment, masking the effects of anthropogenic activities and natural variability (e.g., climate change.). To overcome such difficulties the present dissertation thesis has addressed issues such as: 1) the implementation of the directive and the congruency of the scales used by the Member States (MSs) to report biodiversity indicators; 2) the use of distinctive spatial scales to assess the time series of biodiversity indicators, focusing on indicators addressing the status of sensitive fish species with no commercial value; 3) disaggregation of the spatial and temporal scales used in food webs assessment focusing on fish community indicators to identify the scales that detect prevailing patterns; and 4) food webs reporting in the NE Atlantic and the capability of food webs indicators detecting the effects of natural and anthropogenic drivers. Results showed that MSs used a wide range of criteria, metrics, and scales, which were selected independently and led to wide incongruencies in reporting. The evaluation of scales for biodiversity and food web indicators highlighted that spatial scales need to be downsized to detect species and community patterns. Downscaling allowed showing local and regional areas where indicators presented significant variability and were below the threshold, revealing that the spatial scales currently used are masking the effects of existing drivers. To validate these results, spatial scales were disaggregated for the assessment of the Portuguese continental waters, showing that smaller sized scales based on depth, sector and 1000km2 units reveal estimates below the established threshold for fish communities in the South coast and on intermediary depths of the Southwest of the continental platform. On the contrary, temporal scales explained extremely low variance. Lastly, this study showed that anthropogenic drivers significantly influencing food web trends for fish elements were fishing and climate anomalies in the southern Bay of Biscay and Iberian coast, while eutrophication and chemical contamination had effects on trends in the Celtic seas and the North Sea. Results allowed to establish a direct relation between anthropogenic effects and food web patterns. Nonetheless, these were constrained since food webs data is still limited at relevant scales. Keywords: Good environmental status, ecosystem-based assessment, detection of anthropogenic pressures, spatial boundaries, temporal scales.

Impact of ocean warming on sustainable fisheries management informs the Ecosystem Approach to Fisheries

Article

Full-text available

Oct 2017

An integrated ecosystem model including fishing and the impact of rising temperatures, relative to species’ thermal ranges, was used to assess the cumulative effect of future climate change and sustainable levels of fishing pressure on selected target species. Historically, important stocks of cod and whiting showed declining trends caused by high fisheries exploitation and strong top-down control by their main predators (grey seals and saithe). In a no-change climate scenario these stocks recovered under sustainable management scenarios due to the cumulative effect of reduced fishing and predation mortalities cascading through the food-web. However, rising temperature jeopardised boreal stenothermal species: causing severe declines in grey seals, cod, herring and haddock, while eurythermal species were not affected. The positive effect of a higher optimum temperature for whiting, in parallel with declines of its predators such as seals and cod, resulted in a strong increase for this stock under rising temperature scenarios, indicating a possible change in the contribution of stocks to the overall catch by the end of the century. These results highlight the importance of including environmental change in the ecosystem approach to achieve sustainable fisheries management.

Natural and human-induced hypoxia and consequences for coastal areas: synthesis and future development

Article

Full-text available

Jan 2010
BG

Hypoxia has become a world-wide phenomenon in the global coastal ocean and causes a deterioration of the structure and function of ecosystems. Based on the collective contributions of members of SCOR Working Group #128, the present study provides an overview of the major aspects of coastal hypoxia in different biogeochemical provinces, including estuaries, coastal waters, upwelling areas, fjords and semi-enclosed basins, with various external forcings, ecosystem responses, feedbacks and potential impact on the sustainability of the fishery and economics. The obvious external forcings include freshwater runoff and other factors contributing to stratification, organic matter and nutrient loadings, as well as exchange between coastal and open ocean water masses. Their different interactions set up mechanisms that drive the system towards hypoxia. Coastal systems also vary in their relative susceptibility to hypoxia depending on their physical and geographic settings. It is understood that coastal hypoxia has a profound impact on the sustainability of ecosystems, which can be seen, for example, by the change in the food-web structure and system function; other influences include compression and loss of habitat, as well as changes in organism life cycles and reproduction. In most cases, the ecosystem responds to the low dissolved oxygen in non-linear ways with pronounced feedbacks to other compartments of the Earth System, including those that affect human society. Our knowledge and previous experiences illustrate that there is a need to develop new observational tools and models to support integrated research of biogeochemical dynamics and ecosystem behavior that will improve confidence in remediation management strategies for coastal hypoxia.

Development of the Ecosystem Approach to Fisheries Management (EAFM) in European seas

Article

Full-text available

Jan 2010

Development of the Ecosystem Approach to Fisheries Management (EAFM) in European seas

Working Document to present to the ICES Working Group on the Assessment of Southern Shelf Stocks of Hake, Monk and Megrim

Technical Report

Full-text available

Jan 2008

Patricia Gonçalves

Macroscopically it is not possible to distinguish immature from resting females, for several species. European hake (Merluccius merluccius) is included in this case. Misclassification of resting females, that have already contributed to the removal of the stock in a given year, as immature, will lead to an SSB underestimation of that year. The use of GSI and HIS to differentiate these two stages was investigated but does not give an accurate answer. Only histology can allow the correct classification of resting females. Taking to account that the proportion of resting females is lower during the peak of the spawning season than the rest of the year, maturity ogives should only be based on data collected during the peak of the spawning season. It is recommended to collect for both sexes immature/resting gonads for histology purposes in a length class basis to estimate a correction factor that could be applicable to the macroscopic data. A standard macroscopic maturity stage key was proposed, based on an agreed macroscopic gonads photos interpretation. This standard stage key is in accordance with the histological knowledge of this species.

Limits to transparency - Exploring conceptual and operational aspects of the ICES framework for providing precautionary fisheries management advice

Article

Full-text available

Apr 2007

Hauge, K. H., Nielsen, K. N., and Korsbrekke, K. 2007. Limits to transparency—exploring conceptual and operational aspects of the ICES framework for providing precautionary fisheries management advice. – ICES Journal of Marine Science, 64: 738–743. ICES precautionary approach to fisheries management advice is based on limit reference points (LRPs) reflecting stock status and precautionary reference points (PRPs) reflecting risk levels. As LRPs are exclusively science-based, while PRPs are management-based, this framework is deployed towards satisfying the ideal of a clear division of science and management's responsibilities. We discuss the variety of technical definitions of reference points and their use in the advisory process. There are inconsistencies in the use of reference points and a tendency to downplay uncertainty. Although the framework can be improved, we argue that some dilemmas will remain. First, transparency of uncertainty presupposes a simple and understandable framework. However, translation of the complexity of natural and human interactions into simple concepts leads to problematic standardization. Second, a clear-cut division of responsibility between science and management is not feasible because LRPs cannot be purely science-based and PRPs cannot be purely management-based. Such dilemmas set fundamental limits to what can be expected from the framework in terms of handling and communicating uncertainty. We suggest that comprehensive dialogue between science and management and explicit reflection on their respective roles will prove more effective at enhancing precautionary and transparent advice on fisheries than adhering to the ideal of strict separation.

A Response to the GREEN PAPER: Reform of the Common fisheries Policy

Article

Full-text available

Jan 2009

Interpreting the large fish indicator for the Celtic Sea

Article

Full-text available

Aug 2011
ICES J MAR SCI

Shephard, S., Reid, D. G., and Greenstreet, S. P. R. 2011. Interpreting the large fish indicator for the Celtic Sea. – ICES Journal of Marine Science, 68: 1963–1972. The large fish indicator (LFI) was developed in the North Sea as a size-based indicator of fish community state. It is now established as OSPAR's fish community Ecological Quality Objective (EcoQO) metric and will be applied across all OSPAR regions. To produce a protocol for use when developing regional LFIs, the North Sea experience is interpreted using data from the Celtic Sea. Differences in fish community species composition and size distribution were reflected in a different species complex and large fish threshold (50 cm) for the Celtic Sea LFI. However, a lag of 12–14 years in the relationship between assemblage-averaged fishing mortality Fcom,y and the LFI suggested similar underlying ecological mechanisms to the North Sea. The indicator responded to changes in small fish biomass that follow fishing-induced changes in the level of predation by large demersal piscivores. The Celtic Sea LFI showed maximum observed values >0.40 before 1990, and 0.40 is here proposed as an EcoQO. Development of regional LFIs demands a flexible process rather than a strictly prescriptive protocol.

A meta-analysis of the status of ICES fish stocks during the past half century

Data

Full-text available

May 2007

Sparholt, H., Bertelsen, M., and Lassen, H. 2007. A meta-analysis of the status of ICES fish stocks during the past half century. – ICES Journal of Marine Science, 64: 707–713. Based on a meta-analysis of time-series of stock size, recruitment, and fishing mortality, the general status of fish stocks within the ICES Area (i.e. the Northeast Atlantic) is evaluated. The analysis is based on data for 34 (7 pelagic, 27 demersal) commercial stocks. The stocks were selected based on the quality of the data and the length of the time-series. The analysis indicates that most pelagic stocks recovered to sustainable levels with high productivity after several had collapsed in the 1960s and 1970s. In contrast, most demersal stocks have continued to decline over the past half century and are now recruitment-overfished. By reducing fishing mortality on demersal stocks on average by half and building up the stocks by a factor of about two, management could be brought in line with international agreements. If recruitment-overfishing is avoided for all demersal stocks and discarding is minimized, their yield might be almost doubled over the current yield. Among the major management initiatives during the past half century, only the closure of the pelagic fisheries in the mid-1970s can be clearly identified in the time-series as having had a direct effect on stock status.

Trends in fish biomass off Northwest Africa, 1960-2000.

Conference Paper

Full-text available

Jan 2005

Sensitivity of marine systems to climate and fishing: Concepts, issues and management responses

Article

Full-text available

Feb 2010
J MARINE SYST

Modern fisheries research and management must understand and take account of the interactions between climate and fishing, rather than try to disentangle their effects and address each separately. These interactions are significant drivers of change in exploited marine systems and have ramifications for ecosystems and those who depend on the services they provide. We discuss how fishing and climate forcing interact on individual fish, marine populations, marine communities, and ecosystems to bring these levels into states that are more sensitive to (i.e. more strongly related with) climate forcing. Fishing is unlikely to alter the sensitivities of individual finfish and invertebrates to climate forcing. It will remove individuals with specific characteristics from the gene pool, thereby affecting structure and function at higher levels of organisation. Fishing leads to a loss of older age classes, spatial contraction, loss of sub-units, and alteration of life history traits in populations, making them more sensitive to climate variability at interannual to interdecadal scales. Fishing reduces the mean size of individuals and mean trophic level of communities, decreasing their turnover time leading them to track environmental variability more closely. Marine ecosystems under intense exploitation evolve towards stronger bottom–up control and greater sensitivity to climate forcing. Because climate change occurs slowly, its effects are not likely to have immediate impacts on marine systems but will be manifest as the accumulation of the interactions between fishing and climate variability — unless threshold limits are exceeded. Marine resource managers need to develop approaches which maintain the resilience of individuals, populations, communities and ecosystems to the combined and interacting effects of climate and fishing. Overall, a less-heavily fished marine system, and one which shifts the focus from individual species to functional groups and fish communities, is likely to provide more stable catches with climate variability and change than would a heavily fished system.

The impact of global positioning systems and plotters on fishing power in the northern prawn fishery, Australia

Article

Full-text available

Jul 1998
CAN J FISH AQUAT SCI

The impact of global positioning systems (GPS) and plotter systems on the relative fishing power of the northern prawn fishery fleet on tiger prawns (Penaeus esculentus Haswell, 1879, and P. semisulcatus de Haan, 1850) was investigated from commercial catch data. A generalized linear model was used to account for differences in fishing power between boats and changes in prawn abundance. It was found that boats that used a GPS alone had 4% greater fishing power than boats without a CPS. The addition of a plotter raised the power by 7% over boats without the equipment. For each year between the first to third that a fisher has been working with plotters, there is an additional 2 or 3% increase. It appears that when all boats have a GPS and plotter for at least 3 years, the fishing power of the fleet will increase by 12%. Management controls have reduced the efficiency of each boat and lowered the number of days available to fish, but this may not have been sufficient to counteract the increases. Further limits will be needed to maintain the desired levels of mortality.

Natural and human-induced hypoxia and consequences for coastal areas: Synthesis and future development

Article

Full-text available

May 2010
BG

Trends in the abundance of marine fishes

Article

Full-text available

Jul 2010

The Convention on Biological Diversity (CBD) established a target in 2002 to reduce the rate of biodiversity loss by 2010. Using a newly constructed global database for 207 populations (108 species), we examine whether the 2010 target has been met for marine fishes, while accounting for population biomass relative to maximum sustainable yield, BMSY. Although rate of decline has eased for 59% of populations declining before 1992(a pattern consistent with a literal interpretation of the target), the percentage of populations below BMSY has remained unchanged and the rate of decline has increased among several top predators, many of which are below 0.5BMSY. Combining population trends, a global multispecies index indicates that marine fishes declined 38% between 1970 and 2007. The index has been below BMSY since the mid-1980s and stable since the early 1990s. With the exception of High Seas pelagic fishes and demersal species in the Northeast Pacific and AustraliaNew Zealand, the multispecies indices are currently below BMSY in many regions. We conclude that the 2010 CBD target represents a weak standard for recovering marine fish biodiversity and that meaningful progress will require population-specific recovery targets and associated time lines for achieving those targets.

Fuel Price Increase, Subsidies, Overcapacity, and Resource Sustainability

Article

Full-text available

Apr 2008
ICES J MAR SCI

Sumaila, U. R., Teh, L., Watson, R., Tyedmers, P., and Pauly, D. 2008. Fuel price increase, subsidies, overcapacity, and resource sustainability. – ICES Journal of Marine Science, 65: 832–840. Global fisheries are currently overcapitalized, resulting in overfishing in many of the world’s fisheries. Given that fuel constitutes a significant component of fishing costs, we expect recent increases in fuel prices to reduce overcapacity and overfishing. However, government fuel subsidies to the fishing sector reduce, if not completely negate, this positive aspect of increasing fuel costs. Here, we explore the theoretical basis for the expectation that the increasing fuel prices faced by fishing enterprises will reduce fishing pressure. Next, we estimate the amount of fuel subsidies to the fishing sector by governments globally to be in the range of US$4.2–8.5 billion per year. Hence, depending on how much of this subsidy existed before the recent fuel price increases, fishing enterprises, as a group, can absorb as much as this amount of increase in their fuel budget before any conservation benefits occur as a result of fuel price increases.

Reconsidering the Consequences of Selective Fisheries

Article

Full-text available

Mar 2012
SCIENCE

Concern about the impact of fishing on ecosystems and fisheries production is increasing (1, 2). Strategies to reduce these impacts while addressing the growing need for food security (3) include increasing selectivity (1, 2): capturing species, sexes, and sizes in proportions that differ from their occurrence in the ecosystem. Increasing evidence suggests that more selective fishing neither maximizes production nor minimizes impacts (4–7). Balanced harvesting would more effectively mitigate adverse ecological effects of fishing while supporting sustainable fisheries. This strategy, which challenges present management paradigms, distributes a moderate mortality from fishing across the widest possible range of species, stocks, and sizes in an ecosystem, in proportion to their natural productivity (8), so that the relative size and species composition is maintained

Life history correlates of fisheries exploitation

Article

Full-text available

Feb 1998

We use an approach based on phylogenetic comparisons to identify life history correlates of abundance trends in 18 intensively exploited fish stocks from the north-east Atlantic. After accounting for differences in fishing mortality, we show that those fishes that have decreased in abundance compared with their nearest relatives mature later, attain a larger maximum size, and exhibit significantly lower potential rates of population increase. Such trends were not evident in a more traditional cross-species analysis. This is the first phylogenetically independent evidence to link life histories with abundance trends, and provides a quantitative basis for assessing vulnerability of fish populations to exploitation. Our approach can be applied to the conservation and management of other exploited taxa.

Continental Shelf-Wide Response of a Fish Assemblage to Rapid Warming of the Sea

Article

Full-text available

Sep 2011

Climate change affects marine biological processes from genetic to ecosystem levels [1-3]. Recent warming in the northeast Atlantic [4, 5] has caused distributional shifts in some fish species along latitudinal and depth gradients [6, 7], but such changes, as predicted by climate envelope models [8], may often be prevented because population movement requires availability of suitable habitat. We assessed the full impacts of warming on the commercially important European continental shelf fish assemblage using a data-driven Eulerian (grid-based) approach that accommodates spatial heterogeneity in ecological and environmental conditions. We analyzed local associations of species abundance and community diversity with climatic variables, assessing trends in 172 cells from records of >100 million individuals sampled over 1.2 million km(2) from 1980-2008. We demonstrate responses to warming in 72% of common species, with three times more species increasing in abundance than declining, and find these trends reflected in international commercial landings. Profound reorganization of the relative abundance of species in local communities occurred despite decadal stability in the presence-absence of species. Our analysis highlights the importance of focusing on changes in species abundance in established local communities to assess the full consequences of climate change for commercial fisheries and food security.

Impacts of Fishing Low-Trophic Level Species on Marine Ecosystems

Article

Full-text available

Jul 2011
SCIENCE

Low–trophic level species account for more than 30% of global fisheries production and contribute substantially to global food security. We used a range of ecosystem models to explore the effects of fishing low–trophic level species on marine ecosystems, including marine mammals and seabirds, and on other commercially important species. In five well-studied ecosystems, we found that fishing these species at conventional maximum sustainable yield (MSY) levels can have large impacts on other parts of the ecosystem, particularly when they constitute a high proportion of the biomass in the ecosystem or are highly connected in the food web. Halving exploitation rates would result in much lower impacts on marine ecosystems while still achieving 80% of MSY.

The Trophic Fingerprint of Marine Fisheries

Article

Full-text available

Nov 2010
NATURE

Biodiversity indicators provide a vital window on the state of the planet, guiding policy development and management. The most widely adopted marine indicator is mean trophic level (MTL) from catches, intended to detect shifts from high-trophic-level predators to low-trophic-level invertebrates and plankton-feeders. This indicator underpins reported trends in human impacts, declining when predators collapse ("fishing down marine food webs") and when low-trophic-level fisheries expand ("fishing through marine food webs"). The assumption is that catch MTL measures changes in ecosystem MTL and biodiversity. Here we combine model predictions with global assessments of MTL from catches, trawl surveys and fisheries stock assessments and find that catch MTL does not reliably predict changes in marine ecosystems. Instead, catch MTL trends often diverge from ecosystem MTL trends obtained from surveys and assessments. In contrast to previous findings of rapid declines in catch MTL, we observe recent increases in catch, survey and assessment MTL. However, catches from most trophic levels are rising, which can intensify fishery collapses even when MTL trends are stable or increasing. To detect fishing impacts on marine biodiversity, we recommend greater efforts to measure true abundance trends for marine species, especially those most vulnerable to fishing.

Fishery development patterns are driven by profit but not trophic level

Article

Full-text available

Jul 2010
P NATL ACAD SCI USA

Successful ocean management needs to consider not only fishing impacts but drivers of harvest. Consolidating post-1950 global catch and economic data, we assess which attributes of fisheries are good indicators for fishery development. Surprisingly, year of development and economic value are not correlated with fishery trophic levels. Instead, patterns emerge of profit-driven fishing for attributes related to costs and revenues. Post-1950 fisheries initially developed on shallow ranging species with large catch, high price, and big body size, and then expanded to less desirable species. Revenues expected from developed fisheries declined 95% from 1951 to 1999, and few high catch or valuable fishing opportunities remain. These results highlight the importance of economic attributes of species as leading indicators for harvest-related impacts in ocean ecosystems.

Fisheries Ecology and Management

Book

Jan 2005

Biologie et niveau d'exploitation des stocks de langoustine, de merlu, des baudroies et de sole dans le proche Atlantique

Article

Jan 1978

A. Guillou

The Bay of Biscay, France: 1998 and 1970 models

Article

Jan 2001

Life history correlates of responses to fisheries exploitation

Article

Jan 1998

International Commission for the Conservation of Atlantic Tunas (ICCAT)

Chapter

Jan 1981

The fishing of tunas in the Atlantic began in the mid-fifties. At the present time about 20 states are fishing this species, having a total catch of 4.5 million tons in 1975. The main portion of catch is of Spain and Japan (in 1973 68.5 and 48.0 thousand tons respectively).

Fishing down the food webs

Article

Jan 1998

Correction: Primary production required to sustain global fisheries (Nature (1995) 374 (255-257))

Article

Jul 1995

International Commission for the Conservation of Atlantic Tunas Basic Texts 5th Revision

Article

Jan 2007

ICCAT

Possible ecosystem impacts of applying MSY policies from single-species assessment

Article

May 2005

Ecosim models have been fitted to time-series data for a wide variety of ecosystems for which there are long-term data that confirm the models' ability to reproduce past responses of many species to harvesting. We subject these model ecosystems to a variety of harvest policies, including options based on harvesting each species at its maximum sustainable yield (MSY) fishing rate. We show that widespread application of single-species MSY policies would in general cause severe deterioration in ecosystem structure, in particular the loss of top predator species. This supports the long-established practice in fisheries management of protecting at least some smaller “forage” species specifically for their value in supporting larger piscivores.

Evolution of the state of fish stocks in the Northeast Atlantic within a precautionary framework, 1970-2003: A synoptic evaluation

Article

Dec 2005

The state and trajectory of some of the stocks assessed by ICES in the North Atlantic in the period 1970e2003 are synoptically represented on a single system of representation of fishing mortality and biomass with precautionary reference points used as limits and thresholds. The results indicate that for nearly 30 years, the status of the stocks in relation to the precautionary reference points has been degrading in terms of spawning biomass and excess fishing mortality, driving most resources down close to and often beyond those reference points. The situation seems to have improved during the past decade, with some exceptions, as shown by progressive shift of the mean position of the stocks away from excessive mortality (since the early 1990s) and, after a time-lag, away from low biomass (since the early 2000s). The proposed representation system sticks to the reference points and value judgements used in the ICES context, but could be used with any equivalent precautionary system of representation.

Time changes in fishing power in the Danish cod fisheries of the Baltic Sea

Article

Feb 2001

Using nominal fishing effort to control fishing mortality and using cpue data from commercial fisheries as abundance indices require ability to correct fishing power for temporal development. It is often assumed in ICES stock assessments that fishing power is constant over time. However, experience has suggested that this assumption may be false. This study investigates the time dynamics of an Index of Fishing Power (IFP). This index is based on the fleet's cpue, relative to the cpue of a subset of vessels from the same fleet. The primary characteristic of the reference vessels is that their fishing power has not varied much over time. IFP is calculated for some of the Danish cod fisheries in the Baltic Sea. IFP appeared to be independent of the vessel composition of the reference sub-fleet and for the fleets fishing in the Eastern Baltic Sea, but less so for the Western Baltic Sea fleets. Variations in IFP are analysed by a GLM (General Linear Model). Results suggest that fishing power has developed in the Eastern Baltic Sea cod fishery at an annual rate of 2% and 6% for trawlers and gillnetters respectively. Mechanisms of fishing power creeping may include increased technical efficiency and also changes in vessel composition of the fleets over the period of analysis.

Defining Overfished Stocks: Have We Lost the Plot?

Article

Mar 2010
FISHERIES

In recent years, there has been increasing emphasis on prevention of overfishing and agencies such as the National Oceanic and Atmospheric Administration now report the proportion of stocks that are overfished as a primary indicator of the agencies' performance. Almost all national and international legislation makes specific reference to maximum sustainable yield (MSY) and most definitions of overfishing are related in some way to achievement of MSY. We show that many of the definitions of overfishing now being adopted by fisheries agencies are increasingly unrelated to achievement of MSY and have become, to a great extent, arbitrary. We argue that overfishing definitions and management targets are generally better based on levels of historical stock size rather than the growing trend to setting targets in relation to theoretical unfished stock sizes. Resumen Recientemente se le ha dado especial énfasis a la prevención de la sobrepesca y agencias como la Nacional de Administración Oceánica y Atmosférica reportan como su principal indicador de desempeño, la proporción de stocks sobreexplotados. Casi toda la legislación existente, nacional e internacional, hace referencia específica al Rendimiento Máximo Sostenible (RMS) y la mayor parte de las definiciones de sobrepesca se relacionan de alguna forma a la adquisición de dicho nivel de rendimiento. En la presente contribución se muestra que muchas de las definiciones de sobrepesca que adoptan las agencias de pesquerías, se alejan cada vez más del nivel de RMS y que se han convertido, en buena medida, en algo arbitrario. Se discute que las definiciones de sobrepesca y objetivos de manejo generalmente tienen una mejor base en los niveles históricos del tamaño del stock que en la tendencia creciente de establecerlos en relación al tamaño teórico del stock en estado virgen.

A future for marine fisheries in Europe (Manifesto of the Association Fran?? aise d'Halieum??trie)

Article

Apr 2011
FISH RES

Perish legally and ecologically: The ineffectiveness of the minimum landing sizes in the Mediterranean Sea

Article

Sep 2009
FISHERIES MANAG ECOL

Abstract Minimum landing size (MLS) is one technical measure used to manage fisheries with the aim of allowing enough juveniles to survive and spawn. In this study the practical and ecological efficiency of the MLSs set by European Union (Regulation 1967/2006) and Greek legislation for 13 fish species caught with five gears in the Ionian Sea was tested using length measurements from 22 382 individuals. The percentage of individuals with lengths smaller than MLS was estimated. In addition, MLSs were compared against length at 50% maturity (L50) and the percentages of individuals caught per species and gear with lengths smaller than the L50 were also estimated. The mean percentage of individuals caught with lengths smaller than MLS ranged from 5.9% for longliners to 42.6% for beach-seiners, showing the practical inefficiency of this measure. In addition, all MLS were smaller than the corresponding L50 and L50 − SE values and across species the mean percentage of the immature individuals caught was very high, ranging from 55% for longliners to 92% for beach-seiners, indicating that the vast majority of the individuals caught did not have the chance to spawn even once. Thus, the existing MLSs are ecologically inefficient for sustainable management.

Decline of demersal resources in North-West Africa: An analysis of Mauritanian trawl-survey data over the past 25 years

Article

Dec 2007

Mauritania is characterised by fast-growing fisheries that have developed over the past decades. Since 1982, scientific trawl surveys have been conducted regularly, allowing assessment of the impact of this increasing fishing pressure on exploited species as well as on demersal communities. Based on 55 bottom trawl surveys and using linear model techniques, the annual abundances were estimated for a selection of 24 fish stocks and for the whole demersal biomass. Changes in the demersal community structure were also investigated, using Biomass Trophic Spectra representations. It is shown that the demersal biomass has been reduced by 75% on the Mauritanian continental shelf over the past 25 years, corresponding to a biomass loss of around 20 000t per year. Top predators abundance has been reduced by 8–10-fold and in some case up to 20-fold. The trophic structure has been significantly modified and the mean trophic level of the catchable biomass decreased from >3.7 to <3.5. The results are discussed at the regional scale, taking into account recent studies in Senegal and Guinea in which a similar decline in demersal biomass was observed. This decline was due to severe overexploitation that affected the various groups in succession.

Long-term changes in the trophic level of the Celtic Sea fish community and fish market price distribution

Article

Jun 2002
J APPL ECOL

The intensive exploitation of fish communities often leads to substantial reductions in the abundance of target species, with ramifications for the structure and stability of the ecosystem as a whole. We explored changes in the mean trophic level of the Celtic Sea (ICES divisions VII f–j) fish community using commercial landings, survey data and estimates of trophic level derived from the analysis of nitrogen stable isotopes. Our analyses showed that there has been a significant decline in the mean trophic level of survey catches from 1982 to 2000 and a decline in the trophic level of landings from 1946 to 1998. The decline in mean trophic level through time resulted from a reduction in the abundance of large piscivorous fishes and an increase in smaller pelagic species which feed at a lower trophic level. Similar patterns of decline in the trophic level of both catches and landings imply that there have been substantial changes in the underlying structure of the Celtic Sea fish community and not simply a change in fishery preferences. We suggest that the reported changes in trophic structure result from reductions in the spawning stock biomass of traditional target species associated with intensive fishing, together with long‐term climate variability. The relative distribution of fish market prices has changed significantly over the past 22 years, with high trophic level species experiencing greater price rises than lower trophic level species. Although decreased abundance of high trophic level species will ultimately have negative economic consequences, the reduction in mean trophic level of the fish community as a whole may allow the system to sustain higher fishery yields. Management objectives in this fishery will depend on the relative values that society attaches to economic profit and protein production.

Modification of marine habitats by trawling activities: Prognosis and solutions

Article

Jun 2002
FISH FISH

Fishing affects the seabed habitat worldwide on the continental shelf. These impacts are patchily distributed according to the spatial and temporal variation in fishing effort that results from fishers' behaviour. As a consequence, the frequency and intensity of fishing disturbance varies among different habitat types. Different fishing methodologies vary in the degree to which they affect the seabed. Structurally complex habitats (e.g. seagrass meadows, biogenic reefs) and those that are relatively undisturbed by natural perturbations (e.g. deep-water mud substrata) are more adversely affected by fishing than unconsolidated sediment habitats that occur in shallow coastal waters. These habitats also have the longest recovery trajectories in terms of the recolonization of the habitat by the associated fauna. Comparative studies of areas of the seabed that have experienced different levels of fishing activity demonstrate that chronic fishing disturbance leads to the removal of high-biomass species that are composed mostly of emergent seabed organisms. Contrary to the belief of fishers that fishing enhances seabed production and generates food for target fish species, productivity is actually lowered as fishing intensity increases and high-biomass species are removed from the benthic habitat. These organisms also increase the topographic complexity of the seabed which has been shown to provide shelter for juvenile fishes, reducing their vulnerability to predation. Conversely, scavengers and small-bodied organisms, such as polychaete worms, dominate heavily fished areas. Major changes in habitat can lead to changes in the composition of the resident fish fauna. Fishing has indirect effects on habitat through the removal of predators that control bio-engineering organisms such as algal-grazing urchins. Fishing gear resuspend the upper layers of sedimentary seabed habitats and hence remobilize contaminants and fine particulate matter into the water column. The ecological significance of these fishing effects has not yet been determined but could have implications for eutrophication and biogeochemical cycling. Simulation results suggest that the effects of low levels of trawling disturbance will be similar to those of natural bioturbators. In contrast, high levels of trawling disturbance cause sediment systems to become unstable due to large carbon fluxes between oxic and anoxic carbon compartments. In low energy habitats, intensive trawling disturbance may destabilize benthic system chemical fluxes, which has the potential to propagate more widely through the marine ecosystem. Management regimes that aim to incorporate both fisheries and habitat conservation objectives can be achieved through the appropriate use of a number of approaches, including total and partial exclusion of towed bottom fishing gears, and seasonal and rotational closure techniques. However, the inappropriate use of closed areas may displace fishing activities into habitats that are more vulnerable to disturbance than those currently trawled by fishers. In many cases, the behaviour of fishers constrains the extent of the impact of their fishing activities. Management actions that force them to redistribute their effort may be more damaging in the longer term.

Generic Harvest Control Rules for European Fisheries

Article

Sep 2011
FISH FISH

In European fisheries, most stocks are overfished and many are below safe biological limits, resulting in a call from the European Commission for new long-term fisheries management plans. Here, we propose a set of intuitive harvest control rules that are economically sound, compliant with international fishery agreements, based on relevant international experiences, supportive of ecosystem-based fisheries management and compatible with the biology of the fish stocks. The rules are based on the concept of maximum sustainable yield (MSY), with a precautionary target biomass that is 30% larger than that which produces MSY and with annual catches of 91%MSY. Allowable catches decline steeply when stocks fall below MSY levels and are set to zero when stocks fall below half of MSY levels. We show that the proposed rules could have prevented the collapse of the North Sea herring in the 1970s and that they can deal with strong cyclic variations in recruitment such as known for blue whiting. Compared to the current system, these rules would lead to higher long-term catches from larger stocks at lower cost and with less adverse environmental impact.

Hundred-year decline of North Atlantic predatory fish

Article

Mar 2003
FISH FISH

We estimate the biomass of high-trophic level fishes in the North Atlantic at a spatial scale of 0.5° latitude by 0.5° longitude based on 23 spatialized ecosystem models, each constructed to represent a given year or short period from 1880 to 1998. We extract over 7800 data points that describe the abundance of high-trophic level fishes as a function of year, primary production, depth, temperature, latitude, ice cover and catch composition. We then use a multiple linear regression to predict the spatial abundance for all North Atlantic spatial cells for 1900 and for each year from 1950 to 1999. The results indicate that the biomass of high-trophic level fishes has declined by two-thirds during the last 50-year period, and with a factor of nine over the century. Catches of high-trophic level fishes increased from 2.4 to 4.7 million tonnes annually in the late 1960s, and subsequently declined to below 2 million tonnes annually in the late 1990s. The fishing intensity for high-trophic level fishes tripled during the first half of the time period and remained high during the last half of the time period. Comparing the fishing intensity to similar measures from 35 assessments of high-trophic level fish populations from the North Atlantic, we conclude that the trends in the two data series are similar. Our results raise serious concern for the future of the North Atlantic as a diverse, healthy ecosystem; we may soon be left with only low-trophic level species in the sea.

Rebuilding fish stocks no later than 2015: will Europe meet the deadline?

Article

Jun 2010
FISH FISH

Maintaining or restoring fish stocks at levels that are capable of producing maximum sustainable yield is a legal obligation under the United Nations Convention on the Law of the Sea (UNCLOS) and has been given the deadline of no later than 2015 in the Johannesburg Plan of Implementation of 2002. Here, we analyse stock assessment data of all major fish stocks of the Northeast Atlantic to determine whether Europe will be able to deliver on this commitment, which it has helped to bring about. The analysis shows that, if current fishing pressure continues, 91% of the European stocks will remain below target. If European ministers in charge of fisheries were serious about meeting their obligations, they would have to reduce drastically fishing pressure and halt fishing completely on some stocks. But even if fishing were halted in 2010, 22% of the stocks are so depleted that they cannot be rebuilt by 2015. If current trends continue, Europe will miss the 2015 deadline by more than 30 years. We argue that, from a legal perspective, such repeated enactment of fisheries management measures, which are incapable of maintaining or restoring Bmsy, does not comply with the requirements contained in UNCLOS and may constitute a breach of the precautionary principle of European Community law.

Fisheries for small pelagic species: an empirical approach to management targets

Article

Dec 1992

Kenneth Patterson

Long-term management targets based on MSY, Fmax or F0.1 are inappropriate for small pelagic fish because of the possibility of stock collapse owing to a stock-recruit relationship at low biomasses. Better reference points such as Fmed and Fhigh that take account of stock and recruit data cannot be used in developing fishery situations because they are too demanding of data. A simple model was fitted to medium-term (about 10 year) periods in exploited small pelagic fisheries, relating change in stock biomass to exploitation rate. Data from 28 stocks and 11 species were used. The fitted model was used to estimate likelihood of stock decrease at different exploitation rates. The pelagic stocks included in the model appeared to be in equilibrium for an exploitation rate F/Z=0.4, which may be used as a guideline for the appropriate exploitation of pelagic stocks.

The trophic spectrum: Theory and application as an ecosystem indicator

Article

May 2005

Trophic spectra represent the distribution of biomass, abundance, or catch by trophic level, and may be used as indicators of the trophic structure and functioning of aquatic ecosystems in a fisheries context. As a theoretical background, we present a simple ecosystem model of biomass flow reflecting predation and ontogenetic processes. Biomass trophic spectrum of total biomass can be modelled as the result of three major factors and processes: trophic efficiency, transfer kinetics, and extent of top-down control. In the simulations, changes in the spectrum highlight fishing impacts on trophic structure and reveal some functional characteristics of the underlying ecosystem. As examples of potential applications, three case studies of trophic spectra are presented. Catch trophic spectra allow description of structural differences among European fishing areas and periods. Abundance trophic spectra of coral-reef fish assemblages display different trophic signatures, characterizing different reef habitats in New Caledonia and highlighting fishing effects in a marine protected area context. Biomass trophic spectra of demersal resources off Northwest Africa show a shift in ecosystem structure that can be attributed to the rapid increase in fishing pressure during the past few decades. Off Senegal, total biomass remained fairly constant, suggesting a strong top-down control linked to fisheries targeting high trophic level species. Off Guinea, exploitation rates are spread over a wider range of trophic levels, and the total biomass of demersal resources tended to decrease. The trophic spectrum is concluded to be a useful indicator describing and comparing systems in time and space, detecting phase shifts linked to natural or anthropogenic perturbations, and revealing differences in ecosystem functioning. (c) 2004 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.

Size matters: How single-species management can contribute to ecosystem-based fisheries management

Article

May 2008
FISH RES

In this study we show how substantial gains towards the goals of ecosystem-based fisheries management (EBFM) can be achieved by different single-species management. We show that fishing has much less impact on stocks if fish are caught after they have reached the size (Lopt) where growth rate and cohort biomass are maximum. To demonstrate our point we compare the impact of three fishing scenarios on 9 stocks from the North Sea and the Baltic. Scenario (1) is the current fishing regime, scenario (2) is a new management regime proposed by the European Commission, aiming for maximum sustainable yield obtained from all stocks, and scenario (3) is set so that it achieves the same yield as scenario (2), albeit with fishing on sizes beyond Lopt. Results show that scenarios (2) and (3) are significant improvements compared to current fishing practice. However, scenario (3) consistently shows least impact on the stocks, with seven-fold higher biomass of demersal fishes and an age structure similar to an unfished stock. This allows juveniles and adults to better fulfil their ecological roles, a major step towards the goals of ecosystem-based fisheries management. We give examples where scenario (3) is practiced in successful fisheries. We present a new interpretation of the relative yield per recruit isopleth diagram with indication of a new target area for fisheries operating within the context of EBFM. We present a new expression of the relative biomass per recruit isopleth diagram, which supports our analysis. We conclude that size matters for precautionary and ecosystem-based fisheries management and present a list of additional advantages associated with fishing at Lopt.

Global assessment of the European Union fishing fleet: An update

Article

May 2010
MAR POLICY

Sebastian Villasante

This paper provides a global analysis of recent trends in the EU fishing fleet. Analysis of the capital productivity, labour rates, and economic benefits of the fleet revealed that considerable replacement of fishermen by better technology and well-equipped vessels occurred between 1990 and 2006. The analysis confirms that the Common Fisheries Policy (CFP) has been ineffective in reducing fishing capacity. In addition, the changes in capacity that occurred in this time interval differed among the different sectors of the fleet. Some members of the high sea fishing fleet increased their capacity (range 11–57%), and the deep-sea sector, which has greater tonnage and fishing power, increased its fishing capacity by 34–44%. These results confirm the ineffectiveness of the CFP in reducing overcapacity and illustrate the continuing threat of overcapacity to the long-term sustainability of fishery resources.

Ecopath, Ecosim, and Ecospace as tools for evaluating ecosystem impact of fisheries

Article

Jun 2000

Since its development in the early 1980s, the mass-balance approach incorporated in the Ecopath software has been widely used for constructing food-web models of marine and other ecosystems. Generalizations on the structure and functioning of such ecosystems, relevant to the issue of fisheries impacts, have been developed and these have affected the evolution of the Ecopath approach. Thus, the description of the average state of an ecosystem, using Ecopath proper, now serves to parametrize systems of coupled difference and differential equations, which are used to depict changes in biomasses and trophic interactions in time (Ecosim) and space (Ecospace). The outcomes of these simulations can then be used to modify the initial parametrization, and the simulations are rerun until external validation is achieved. This reconceptualization of the Ecopath approach as an iterative process, which helps address issues of structural uncertainty, does not increase its input requirements markedly. Rather, it has become possible, through a Bayesian resampling routine, to explicitly consider the numerical uncertainty associated with these inputs. We present the key features of the reconceptualized approach, and two indices based thereon for quantifying the ecosystem impacts of fisheries. We conclude with a brief discussion of its limitations, both present and intrinsic.

Anecdotes and the shifting baseline syndrome of fisheries

Article

Oct 1995
TRENDS ECOL EVOL

Daniel Pauly

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Report of the Working Group on Anchovy and Sardine (WGANSA)

Article

ICES

The Working Group on Anchovy and Sardine (WGANSA) met at IPIMAR, Lisbon 24- 28 June 2010, chaired by Dankert Skagen, Norway. There were 10 participants from France, Portugal, Spain and Norway. The main task was to assess the state of the stock and to provide short term predictions for the stocks of Anchovy in Subarea VIII and in Division IXa, and for Sardine in Divisions VIIIc and IXa. All assessments were updates of previous assessments. The time interval between finalizing the key surveys and the managers decision is short, and the timing of the WG has been problematic. This year, it was held 9 days later than last year, which allowed a better control of the input to the assessment. The Anchovy in Subarea VIII is improving, as the recruitment in 2010 is at an intermediate level, breaking a long series of poor recruitments. Hence, it can be recommended to open the fishery again. Reasons for the recent recruitment failure are not known, despite extensive investigations.

Note préliminaire à l'étude de la biologie de la langoustine dans le golfe de Gascogne

Article

Jan 1967

Fontaine Bernard

La langoustine, Nephrops norvegicus (LINNÉ, 1758), forme une fraction importante du tonnage de crustacés débarqué dans les ports du golfe de Gascogne. Les apports ont deux origines : la "grande vasière" d'une part ; le canal Saint-Georges, le banc de la Chapelle et les Smalls d'autre part. Ils sont le fait des petits chalutiers bretons, vendéens et charentais qui arment à la langoustine et approvisionnent le marché en crustacés vivants, et aussi des navires hauturiers travaillant en mer Celtique et dans le canal St-Georges qui ne fournissent que des langoustines conservées dans la glace. Cette note est consacrée aux premiers résultats des recherches entreprises en 1965 à bord du "Roselys" sur l'état du stock de langoustines de la partie nord du golfe de Gascogne. La biologie de l'espèce a également été étudiée et en particulier l'état sexuel des femelles capturées en avril et en septembre, ainsi que la nourriture et la faune associée. Ce travail n'est qu'un préliminaire à une étude plus importante qui se poursuivra au cours de l'année 1967.

Of precautionary reference points in providing management advice on North Sea fish stocks

Article

Dec 2004

For 17 stocks in the North Sea, the performance and effectiveness of management advice using precautionary reference points was evaluated. Three criteria were used to identify whether a stock was within safe biological limits: SSB < Bpa, F > Fpa, or SSB < Bpa and F > Fpa. Four scenarios were considered, comparing the advice in the assessment year with what is retrospectively (2002 assessment) known to be the status of the stock at that time: (1) stock outside safe biological limits, advice to reduce fishing; (2) stock outside safe biological limits, advice for status quo harvesting; (3) stock within safe biological limits, advice to reduce fishing; and (4) stock within safe biological limits, advice for status quo (or increased) harvesting. Signal Detection Theory was applied to these scenarios, and the proportion of Hits (1 and 4), Misses (2), and False Alarms (3) were determined for each year as the proportion of the stocks for which the respective scenarios applied. Using both Bpa and Fpa was deemed the approach with the lowest error rate, and it resulted in about the same proportion of Hits in management advice as when Bpa alone was used (62Œ but the proportion of Misses was slightly lower (24␟s. 26Ž Therefore, the suggested EcoQ element would be the proportion of commercial fish stocks within safe biological limits (i.e. SSB > Bpa, F < Fpa), and the Ecological Quality Objective (EcoQO) should be that this EcoQ should be at or above a desired level. This desired level is a societal/political decision relative to the EcoQ reference level (i.e. where the anthropogenic influence on the ecological system is minimal), which by definition is 100ÐAt present, probably <10␘f North Sea fish stocks are within safe biological limits, despite the relatively high Hit rate of >60ÐA possible explanation is that most of these stocks (e.g. flatfish and roundfish) are caught in a mixed fishery, for which TAC management is less effective.

An investigation of the cumulative impacts of shrimp trawling on mud-bottom fishing grounds in the Gulf of Maine: effects on habitat and macrofaunal community structure

Article

Nov 2006

The cumulative impacts (i.e. collective, multi-year effects) of seasonal commercial shrimp trawling on habitat and macrofaunal community structure were investigated for two mud-bottom. fishing grounds and adjacent untrawled areas in the Gulf of Maine. Habitat structure on mud-bottom fishing grounds did not differ significantly from that in similar untrawled areas. Moreover, sediment resuspension associated with shrimp trawling did not appear to result in net loss of deposited material on fishing grounds, but there is evidence that trawling may alter sediment mixing regimes. Visual inspection of the sediment surface in trawled areas revealed minimal evidence of fishing gear disturbance (such as door, bobbin, or net marks), but biological disturbance features including numerous large burrows, pits, and dense aggregations of the brittle star Ophiura sarsi, were present in both trawled and untrawled areas. Macrofaunal communities on the two fishing grounds exhibited different responses to shrimp trawling, which were attributed to disparities in levels of fishing activity during the 2000-2001 shrimp season. The results suggest that seasonal shrimp trawling produced at least short-term changes (< 3 months) in macrofaunal community structure, but did not appear to result in long-term cumulative changes. Resilience to trawling disturbance may be due in part to high levels of biological disturbance generated by benthic megafauna, such as lobsters and fish. By burrowing, pit-digging, and possibly foraging, these animals rework sediments to a depth of 16-17 cm, creating a natural level of disturbance that appears to maintain macrofaunal communities in a perpetually low successional state, so potentially minimizing trawling impacts. (c) 2006 International Council for the Exploration of the Sea. Published by Elsevier Ltd. All rights reserved.

Analyse de l'évolution des puissances de pêche par l'analyse des cohortes: Application aux senneurs exploitant l'albacore (Thunnus albacares) dans l'Atlantique Est

Article

May 1993

Une méthode d'ajustement de l'analyse des cohortes, combinant calcul en mode inverse et calcul en mode direct, est présentée; elle permet d'analyser l'évolution des puissances de pêche par flottille et par âge, à partir de la matrice des capturabilités nominales. La méthode est appliquée aux deux principales flottilles exploitant l'albacore dans l'Atlantique Est, entre 1980 et 1990 : les senneurs franco-ivoiro-sénégalais (FIS) et les senneurs espagnols. A l'aide d'un modèle linéaire généralisé, les puissances de pêche globales sont décomposées en deux termes : puissances locales et efficiences globales. Les évolutions tendancielles des trois grandeurs, puissances globales, puissances locales et efficiences globales, par catégorie d'âge ou en moyennes, sont analysées en calculant des taux d'accroissement inter-annuels sur des intervalles pluriannuels. Les changements de tactiques de pêche sont étudiés au travers des corrélations entre puissances de pêche résiduelles appliquées à des groupes d'âge différents

Shifting baselines in European fisheries: The case of the Celtic Sea and Bay of Biscay

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