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We reflect on the innovation process that led to the development of the pulse trawl that was successfully trialed at a commercial scale, but eventually ended with the European Parliament passing legislation to ban its use. The ban was imposed despite published and emerging evidence that suggested that the environmental performance and catch efficiency of the pulse trawl was superior to the conventional beam trawl design. We used a stakeholder questionnaire to understand which factors undermined wider acceptance of the pulse trawl. The main factors where a lack of involvement of certain key stakeholders earlier in the process that would have ensured better co-development of innovation and a shared vision of the environmental or governance questions that needed to be addressed. Although the stakeholder process itself was seen to be positive, it was implemented too late in the innovation process, as was the implementation of an independent peer review process. We conclude by identifying a pathway for future fishing gear innovation processes that integrate the lessons learnt from the pulse trawl innovation process.

In the context of marine conservation, trawl fishing activity is the most important ecosystem stressor in demersal Mediterranean waters. Limited management measures in bottom trawling have caused deep-sea stocks of the iconic Norway lobster Nephrops norvegicus to decrease over the last decade. This crustacean acts as an umbrella species for co-existing megafauna. Here, we used non-invasive Remote Operated Vehicle (ROV) video-surveys to investigate the status of a pilot deep-sea no-take reserve implemented in the northwestern Mediterranean by quantifying demographic indicators of Norway lobsters and the co-existing benthic community, seafloor restoration, and the presence of marine litter. The results revealed that in the no-take reserve the Norway lobster stock showed higher abundance and biomass, and slightly larger body sizes than in the control area without fishing prohibition. Some taxa, such as the fishes Helicolenus dactylopterus and Trigla lyra and anemones of the family Cerianthidae, increased in abundance. We also observed that all trawling marks were smoothed and most of the seafloor was intact, clear indicators of the recovery of the muddy seafloor. The accumulation of marine debris and terrestrial vegetation was similar in the no-take reserve and the fished area. On the basis of the results of this study, we suggest that the use of no-take reserves might be an effective measure for recovering the Norway lobster stock, its co-existing megafauna community, and the surrounding demersal habitat. We also suggest that ROV video-survey might be a useful, and non-invasive method to monitor megafauna and seafloor status in protected deep-sea environments

The seafloor of the Mediterranean Sea accumulates marine litter (ML), an area where bottom trawlers operate and can accidentally catch the litter from the seafloor. This study aims to describe and quantify the ML caught by bottom trawlers along the Catalan coast (NW Mediterranean Sea) and estimate the potential of the bottom trawl fleet to extract ML from the area as a Fishing for Litter (FFL) initiative to tackle the ML issue. Marine litter was collected from commercial trawlers and was classified as metal, plastic, rubber, textile, wood, and other waste and weighed (kg) from 305 hauls performed during three years (2019–2021) from 9 different ports at 3 different depths. ML was present in 97 % of the hauls, with plastic being the most abundant material. The composition varied according to zone, port and depth, with the highest densities found in highly urbanized areas (13.75 ± 3.25 kg km−2), which mainly contained plastics (74.3 %). The port of Barcelona had the highest presence of plastics (23.62 ± 6.49 kg km−2), mainly wet wipes. Regarding depth, the continental shelf had the highest density of ML, with 12.24 ± 2.40 kg km−2. The potential ML removal (t year−1) was calculated using fishing effort (hours). It is estimated that the bottom trawlers may potentially remove 237 ± 36 t year−1 of ML in the Catalan coast. FFL initiatives should be part of a multidisciplinary approach to tackle marine litter, which must include prevention, monitoring, and cleaning actions

Substantial losses of the seagrass Posidonia oceanica have initiated investigations into localized resilience declines related to anthropogenic disturbances. In this study, we determined reconstructed shoot age and interannual growth metrics can detect anthropogenic impact effects on P. oceanica production. Interannual rhizome vertical growth, leaf production, and demographics of shoots collected from sewage and trawling impacted areas were examined using mixed effects modeling. Detected impact effects were specific to the type of impact, manifesting as an older-skewed age distribution of sewage outfall shoots and reduced vertical growth and reduced leaf production of trawling site shoots. A stress event period was also detected for all shoots >5 years old, with trawling impacted shoots indicating little recovery. Reconstructed age and growth metrics are simple to measure, incorporate multiple years of in situ shoot development, and are advantageous for identification of declining P. oceanica resilience prior to catastrophic losses.

Several Mediterranean fisheries are experiencing flaws in the application of the management system based on input control, including Algeria, where the state of fisheries and stocks remain unclear. This paper focused on the characterization of the catches from bottom trawling by professional fishing vessels in the Mostaganem fishery (West of Algeria). Catch data were collected on board between 2017 and 2020 in two different fishing areas between isobaths 30 and 100 meters in depth. Out of a total of 87 species caught, discards represented a greater variety of species (74) than landings (57). Quantitatively, the landing weights were estimated at 7.8 tons, while the discard weights were lower, accounting for 1.8 tons. Between the two fishing areas, a significant difference was detected in the composition of discards and landings, while for the weights, the two areas were similar. Generally, the Mostaganem fishery is similar to other bottom trawl Mediterranean fisheries both for target and discard species. Otherwise, this research highlighted the existence of an uncontrolled black market, which sustains the practice of illegal, unregulated and unreported fishing, and potentially increases the rate of overexploitation.

Subtidal marine sediments are one of the planet's primary carbon stores and strongly influence the oceanic sink for atmospheric CO2. By far the most widespread human activity occurring on the seabed is bottom trawling/dredging for fish and shellfish. A global first-order estimate suggested mobile demersal fishing activities may cause 0.16–0.4 Gt of organic carbon (OC) to be remineralized annually from seabed sediment carbon stores (Sala et al., 2021). There are, however, many uncertainties in this calculation. Here, we discuss the potential drivers of change in seabed sediment OC stores due to mobile demersal fishing activities and conduct a literature review, synthesizing studies where this interaction has been directly investigated. Under certain environmental settings, we hypothesize that mobile demersal fishing would reduce OC in seabed stores due to lower production of flora and fauna, the loss of fine flocculent material, increased sediment resuspension, mixing and transport and increased oxygen exposure. Reductions would be offset to varying extents by reduced faunal bioturbation and community respiration, increased off-shelf transport and increases in primary production from the resuspension of nutrients. Studies which directly investigated the impact of demersal fishing on OC stocks had mixed results. A finding of no significant effect was reported in 61% of 49 investigations; 29% reported lower OC due to fishing activities, with 10% reporting higher OC. In relation to remineralization rates within the seabed, four investigations reported that demersal fishing activities decreased remineralization, with three reporting higher remineralization rates. Patterns in the environmental and experimental characteristics between different outcomes were largely indistinct. More evidence is urgently needed to accurately quantify the impact of anthropogenic physical disturbance on seabed carbon in different environmental settings and to incorporate full ev

The Eastern Corsican Coast (ECC) is distinguished by its shallow sandy shelf, extensive Posidonia seagrass meadows, and the relatively limited exploitation of fish in this region. To understand ECC trophic functioning and the effects of fishing in this region of the Mediterranean Sea, we applied the Ecopath and EcoTroph approaches. Our model encompassed 5 groups of primary producers and detritus, 14 invertebrate groups, two groups of Chondrichthyes, 16 teleost groups, one seabird group, and one group of cetaceans. The ECC ecosystem was structured into five trophic levels, regulated top–down by Sphyraenidae, Epinephelus marginatus, and Dentex dentex. The ecosystem displayed a high degree of benthic–pelagic coupling, confirmed by keystone groups/species located at intermediate trophic levels (Seriola dumerilii, planktivorous teleosts, benthic cephalopods, shrimps, zooplankton). The ECC demonstrated the lowest exploitation rate (F/Z) of all exploited Mediterranean ecosystems, with trawling representing 55% of catches, followed by the lobster net (27%) and fish net (18%) fisheries. Catches often included untargeted groups—often discarded dead—in particular sharks and rays, and several protected species. Moreover, Palinurus elephas, Scorpaena scrofa, and Dentex dentex had elevated F/Z values, highlighting their vulnerabilities to fishing. Although the fishing simulations suggested that the ECC could support a greater exploitation, they also revealed that these fisheries have a marked impact on upper trophic levels. Our study draws attention to the critical habitat the ECC provides for Chondrichthyes, evidenced by the significant biomass for these taxa and the low fishing pressure relative to other exploited Mediterranean systems. This first modelling of the ECC is an initial step towards modelling all Corsican marine ecosystems to serve as a guide for preserving these ecosystems through appropriate management measures.

The Eastern Corsican Coast (ECC) is distinguished by its shallow sandy shelf, extensive Posidonia seagrass meadows, and the relatively limited exploitation of fish in this region. To understand ECC trophic functioning and the effects of fishing in this region of the Mediterranean Sea, we applied the Ecopath and EcoTroph approaches. Our model encompassed 5 groups of primary producers and detritus, 14 invertebrate groups, two groups of Chondrichthyes, 16 teleost groups, one seabird group, and one group of cetaceans. The ECC ecosystem was structured into five trophic levels, regulated top–down by Sphyraenidae, Epinephelus marginatus, and Dentex dentex. The ecosystem displayed a high degree of benthic–pelagic coupling, confirmed by keystone groups/species located at intermediate trophic levels (Seriola dumerilii, planktivorous teleosts, benthic cephalopods, shrimps, zooplankton). The ECC demonstrated the lowest exploitation rate (F/Z) of all exploited Mediterranean ecosystems, with trawling representing 55% of catches, followed by the lobster net (27%) and fish net (18%) fisheries. Catches often included untargeted groups—often discarded dead—in particular sharks and rays, and several protected species. Moreover, Palinurus elephas, Scorpaena scrofa, and Dentex dentex had elevated F/Z values, highlighting their vulnerabilities to fishing. Although the fishing simulations suggested that the ECC could support a greater exploitation, they also revealed that these fisheries have a marked impact on upper trophic levels. Our study draws attention to the critical habitat the ECC provides for Chondrichthyes, evidenced by the significant biomass for these taxa and the low fishing pressure relative to other exploited Mediterranean systems. This first modelling of the ECC is an initial step towards modelling all Corsican marine ecosystems to serve as a guide for preserving these ecosystems through appropriate management measures.

The bamboo coral Isidella elongata is an engineering species that forms a characteristic biogenic habitat in the bathyal mud of the Mediterranean Sea. This habitat has been severely reduced in recent decades due to trawling impacts, and there is a growing concern about its conservation status. In this work, the habitat loss of I. elongata was computed using a novel approach that combines the realized niche of the species with the estimation of its past distribution (before trawling) to delineate potential areas of habitat loss with different levels of uncertainty. The realized niche of the species was modelled using only live colonies and including trawling effort as explanatory variable whereas the past distribution was estimated also using the leftovers of dead colonies as presences. Trawling effort had a statistically significant negative effect on the extent of the realized niche of I. elongata, confirming previous results on the impact of this pressure on its distribution. The novel approach used in this work has allowed us to map for the first time several areas of potential habitat loss for I. elongata in the studied area, opening new opportunities to provide this essential information for future management and restoration actions of vulnerable marine ecosystems worldwide.

Although considerable research progress on the effects of anthropogenic disturbance in the deep sea has been made in recent years, our understanding of these impacts at community level remains limited. Here, we studied deep-sea assemblages of Sicily (Mediterranean Sea) subject to different intensities of benthic trawling using environmental DNA (eDNA) metabarcoding and taxonomic identification of meiofauna communities. Firstly, eDNA metabarcoding data did not detect trawling impacts using alpha diversity whereas meiofauna data detected a significant effect of trawling. Secondly, both eDNA and meiofauna data detected significantly different communities across distinct levels of trawling intensity when we examined beta diversity. Taxonomic assignment of the eDNA data revealed that Bryozoa was present only at untrawled sites, highlighting their vulnerability to trawling. Our results provide evidence for community-wide impacts of trawling, with different trawling intensities leading to distinct deep-sea communities. Finally, we highlight the need for further studies to unravel understudied deep-sea biodiversity.

Although considerable research progress on the effects of anthropogenic disturbance in the deep sea has been made in recent years, our understanding of these impacts at community level remains limited. Here, we studied deep-sea assemblages of Sicily (Mediterranean Sea) subject to different intensities of benthic trawling using environmental DNA (eDNA) metabarcoding and taxonomic identification of meiofauna communities. Firstly, eDNA metabarcoding data did not detect trawling impacts using alpha diversity whereas meiofauna data detected a significant effect of trawling. Secondly, both eDNA and meiofauna data detected significantly different communities across distinct levels of trawling intensity when we examined beta diversity. Taxonomic assignment of the eDNA data revealed that Bryozoa was present only at untrawled sites, highlighting their vulnerability to trawling. Our results provide evidence for community-wide impacts of trawling, with different trawling intensities leading to distinct deep-sea communities. Finally, we highlight the need for further studies to unravel understudied deep-sea biodiversity.

Although considerable research progress on the effects of anthropogenic disturbance in the deep sea has been made in recent years, our understanding of these impacts at community level remains limited. Here, we studied deep-sea assemblages of Sicily (Mediterranean Sea) subject to different intensities of benthic trawling using environmental DNA (eDNA) metabarcoding and taxonomic identification of meiofauna communities. Firstly, eDNA metabarcoding data did not detect trawling impacts using alpha diversity whereas meiofauna data detected a significant effect of trawling. Secondly, both eDNA and meiofauna data detected significantly different communities across distinct levels of trawling intensity when we examined beta diversity. Taxonomic assignment of the eDNA data revealed that Bryozoa was present only at untrawled sites, highlighting their vulnerability to trawling. Our results provide evidence for community-wide impacts of trawling, with different trawling intensities leading to distinct deep-sea communities. Finally, we highlight the need for further studies to unravel understudied deep-sea biodiversity.

The bamboo coral Isidella elongata is an engineering species that forms a characteristic biogenic habitat in the bathyal mud of the Mediterranean Sea. This habitat has been severely reduced in recent decades due to trawling impacts, and there is a growing concern about its conservation status. In this work, the habitat loss of I. elongata was computed using a novel approach that combines the realized niche of the species with the estimation of its past distribution (before trawling) to delineate potential areas of habitat loss with different levels of uncertainty. The realized niche of the species was modelled using only live colonies and including trawling effort as explanatory variable whereas the past distribution was estimated also using the leftovers of dead colonies as presences. Trawling effort had a statistically significant negative effect on the extent of the realized niche of I. elongata, confirming previous results on the impact of this pressure on its distribution. The novel approach used in this work has allowed us to map for the first time several areas of potential habitat loss for I. elongata in the studied area, opening new opportunities to provide this essential information for future management and restoration actions of vulnerable marine ecosystems worldwide

Mussel beds are an important habitat in many coastal systems, harboring a high diversity of biota. They are threatened by anthropogenic impacts that affect mussels and their associated assemblages. Pollution, harvesting, trampling, dredging and trawling are major threats faced by these communities. Most of the studies on the effects of such impacts on the mussel beds overlook the associated fauna. Since mussels are very resilient, especially to pollution, the associated fauna can provide a better footprint of the impacts’ effects. In this review, we looked into the main remarks regarding the effects of anthropogenic impacts in mussel bed communities. Organic pollution was the best studied impact and the Atlantic region was the best studied zone. Low values of abundance, biomass, diversity, evenness and species richness were reported for all categories of impacts, with some studies describing declines in at least three of these descriptors. Among the associated fauna, some tolerant species benefited from the impacts, particularly organic enrichment, and became more abundant, but sensitive species suffered considerable declines in density, mainly in dredging and trawling impacts. Therefore, fauna associated with mussel beds is a suitable indicator of anthropogenic disturbances.

Global shrimp catches are reported primarily in association with large industrial trawling, but they also occur through small-scale fishing, which plays a substantial role in traditional communities. We developed an Ecopath model in north-eastern Brazil, and applied a temporally dynamic model (Ecosim) to evaluate the potential effects of different fishing effort control policies and environmental changes on marine resources and ecosystem between 2015 to 2030 with a case study for small-scale shrimp fishing, novelty for tropical region. These scenarios included different management options related to fishing controls (changing effort and closed season) and environmental changes (primary production changes). Our findings indicate that it is possible to maintain the same level of landings with a controlled reduction of bottom trawlers activities, for example, close to 10 %, without compromising the ecosystem structure. This scenario provided better results than 3–4 months of closing the fishing season, which led to significant losses in catches of high market-value target species (white shrimp, Penaeus schmitti and pink shrimp, Penaeus subtilis). However, intense negative effects on biomass, catch and biodiversity indicators were reported in scenarios with decreasing primary production, from 2 %, reinforcing the need to simulate and project the possible impacts caused by environmental change. However, the control of bottom trawling activity may help to reduce, even at low levels, the highly adverse effects due to primary production reduction. The impacts of climate change in a near future on organisms and ecosystems is an imminent reality, and therefore the search for measures for mitigating and even minimizing these impacts is crucial.

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

Global shrimp catches are reported primarily in association with large industrial trawling, but they also occur through small-scale fishing, which plays a substantial role in traditional communities. We developed an Ecopath model in north-eastern Brazil, and applied a temporally dynamic model (Ecosim) to evaluate the potential effects of different fishing effort control policies and environmental changes on marine resources and ecosystem between 2015 to 2030 with a case study for small-scale shrimp fishing, novelty for tropical region. These scenarios included different management options related to fishing controls (changing effort and closed season) and environmental changes (primary production changes). Our findings indicate that it is possible to maintain the same level of landings with a controlled reduction of bottom trawlers activities, for example, close to 10 %, without compromising the ecosystem structure. This scenario provided better results than 3–4 months of closing the fishing season, which led to significant losses in catches of high market-value target species (white shrimp, Penaeus schmitti and pink shrimp, Penaeus subtilis). However, intense negative effects on biomass, catch and biodiversity indicators were reported in scenarios with decreasing primary production, from 2 %, reinforcing the need to simulate and project the possible impacts caused by environmental change. However, the control of bottom trawling activity may help to reduce, even at low levels, the highly adverse effects due to primary production reduction. The impacts of climate change in a near future on organisms and ecosystems is an imminent reality, and therefore the search for measures for mitigating and even minimizing these impacts is crucial.

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

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

Unprecedented and dramatic transformations are occurring in the Arctic in response to climate change, but academic, public, and political discourse has disproportionately focussed on the most visible and direct aspects of change, including sea ice melt, permafrost thaw, the fate of charismatic megafauna, and the expansion of fisheries. Such narratives disregard the importance of less visible and indirect processes and, in particular, miss the substantive contribution of the shelf seafloor in regulating nutrients and sequestering carbon. Here, we summarise the biogeochemical functioning of the Arctic shelf seafloor before considering how climate change and regional adjustments to human activities may alter its biogeochemical and ecological dynamics, including ecosystem function, carbon burial, or nutrient recycling. We highlight the importance of the Arctic benthic system in mitigating climatic and anthropogenic change and, with a focus on the Barents Sea, offer some observations and our perspectives on future management and policy., SCOPUS: ar.j, info:eu-repo/semantics/published

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

In the Mediterranean and the Black Sea, the assessment of demersal stocks mainly relies on scientific surveys (bottom and beam trawl) while the assessment of pelagic stocks is essentially based on acoustic surveys using acoustic techniques with mid-water trawling. These routine surveys-at-sea provide essential information, which in turn are crucial to fine-tune the assessments of the status of resources and to estimate more precisely indicators at the population and fish community levels. However, survey practices differ from one subregion to another, each approach having its own strengths and limitations. In addition, there is still a lack of large-scale standardized surveys aimed at analysing the diversity and distribution of the main demersal and pelagic species across the Mediterranean and the Black Sea. One way of tackling this issue is to carry out international scientific surveys covering the main demersal and pelagic stocks based on a common methodology. The methodology presented in this publication aims at supporting the planning and implementation of regional demersal (bottom and beam) trawl and pelagic acoustic surveys. It can be useful for the implementation of new surveys-at-sea in areas where demersal trawl and pelagic acoustic surveys are not regularly carried out. It can also contribute to increasing comparability between existing surveys thanks to the standardization of methods, sampling of catches and data recording and analysis. Finally, it represents a valuable tool to define minimum requirements towards sustainability and management objectives at the regional and subregional level.

Marine landings in Portugal have decreased at a higher rate than fishing effort in the last 20 years. Identifying the variables driving the quantity and composition of landings is pivotal to understand the dynamics of the fisheries sector, which entails complex social and environmental aspects. In this study, we investigate the main drivers of marine fish landings in continental Portugal between 1989 and 2014. To identify common trends in time series, and quantify the importance of environmental factors, we applied a dynamic factor analysis considering four regions and three types of gear (trawling, purse-seine, and a multi-gear fishery). Our results show the importance of fishing effort as the most relevant factor driving marine landings in Portugal, both at the long and short terms. In addition, the effect of environmental factors such as the winter river discharge and the spring East Atlantic Teleconnection index should not be neglected, probably through mechanisms affecting coastal productivity. We provide a comprehensive amount of information that permits to improve our understanding of the trends of the most important commercial species in Portugal during the period of study.

In the Mediterranean and the Black Sea, the assessment of demersal stocks mainly relies on scientific surveys (bottom and beam trawl) while the assessment of pelagic stocks is essentially based on acoustic surveys using acoustic techniques with mid-water trawling. These routine surveys-at-sea provide essential information, which in turn are crucial to fine-tune the assessments of the status of resources and to estimate more precisely indicators at the population and fish community levels. However, survey practices differ from one subregion to another, each approach having its own strengths and limitations. In addition, there is still a lack of large-scale standardized surveys aimed at analysing the diversity and distribution of the main demersal and pelagic species across the Mediterranean and the Black Sea. One way of tackling this issue is to carry out international scientific surveys covering the main demersal and pelagic stocks based on a common methodology. The methodology presented in this publication aims at supporting the planning and implementation of regional demersal (bottom and beam) trawl and pelagic acoustic surveys. It can be useful for the implementation of new surveys-at-sea in areas where demersal trawl and pelagic acoustic surveys are not regularly carried out. It can also contribute to increasing comparability between existing surveys thanks to the standardization of methods, sampling of catches and data recording and analysis. Finally, it represents a valuable tool to define minimum requirements towards sustainability and management objectives at the regional and subregional level.

Marine landings in Portugal have decreased at a higher rate than fishing effort in the last 20 years. Identifying the variables driving the quantity and composition of landings is pivotal to understand the dynamics of the fisheries sector, which entails complex social and environmental aspects. In this study, we investigate the main drivers of marine fish landings in continental Portugal between 1989 and 2014. To identify common trends in time series, and quantify the importance of environmental factors, we applied a dynamic factor analysis considering four regions and three types of gear (trawling, purse-seine, and a multi-gear fishery). Our results show the importance of fishing effort as the most relevant factor driving marine landings in Portugal, both at the long and short terms. In addition, the effect of environmental factors such as the winter river discharge and the spring East Atlantic Teleconnection index should not be neglected, probably through mechanisms affecting coastal productivity. We provide a comprehensive amount of information that permits to improve our understanding of the trends of the most important commercial species in Portugal during the period of study.

In the Mediterranean and the Black Sea, the assessment of demersal stocks mainly relies on scientific surveys (bottom and beam trawl) while the assessment of pelagic stocks is essentially based on acoustic surveys using acoustic techniques with mid-water trawling. These routine surveys-at-sea provide essential information, which in turn are crucial to fine-tune the assessments of the status of resources and to estimate more precisely indicators at the population and fish community levels. However, survey practices differ from one subregion to another, each approach having its own strengths and limitations. In addition, there is still a lack of large-scale standardized surveys aimed at analysing the diversity and distribution of the main demersal and pelagic species across the Mediterranean and the Black Sea. One way of tackling this issue is to carry out international scientific surveys covering the main demersal and pelagic stocks based on a common methodology. The methodology presented in this publication aims at supporting the planning and implementation of regional demersal (bottom and beam) trawl and pelagic acoustic surveys. It can be useful for the implementation of new surveys-at-sea in areas where demersal trawl and pelagic acoustic surveys are not regularly carried out. It can also contribute to increasing comparability between existing surveys thanks to the standardization of methods, sampling of catches and data recording and analysis. Finally, it represents a valuable tool to define minimum requirements towards sustainability and management objectives at the regional and subregional level.

Marine landings in Portugal have decreased at a higher rate than fishing effort in the last 20 years. Identifying the variables driving the quantity and composition of landings is pivotal to understand the dynamics of the fisheries sector, which entails complex social and environmental aspects. In this study, we investigate the main drivers of marine fish landings in continental Portugal between 1989 and 2014. To identify common trends in time series, and quantify the importance of environmental factors, we applied a dynamic factor analysis considering four regions and three types of gear (trawling, purse-seine, and a multi-gear fishery). Our results show the importance of fishing effort as the most relevant factor driving marine landings in Portugal, both at the long and short terms. In addition, the effect of environmental factors such as the winter river discharge and the spring East Atlantic Teleconnection index should not be neglected, probably through mechanisms affecting coastal productivity. We provide a comprehensive amount of information that permits to improve our understanding of the trends of the most important commercial species in Portugal during the period of study.

Bottom trawling accounts for almost one quarter of global fish landings but may also have significant and unwanted impacts on seabed habitats and biota. Management measures and voluntary industry actions can reduce these impacts, helping to meet sustainability objectives for fisheries, conservation and environmental management. These include changes in gear design and operation of trawls, spatial controls, impact quotas and effort controls. We review nine different measures and actions and use published studies anda simple conceptual model to evaluate and compare their performance. The risks and benefits of these management measures depend on the extent to which the fishery is already achieving management objectives for target stocks and the characteristics of the management system that is already in place. We offer guidance on identifying best practices for trawl-fisheries management and show that best practices and their likelihood of reducing trawling impacts depend on local, national and regional management objectives and priorities, societal values and resources for implementation. There is no universalbest practice, and multiple management measures and industry actions are required to meet sustainability objectives and improve trade-offs between food production and environmental protection.

Bottom trawling in the deep sea is one of the main drivers of sediment resuspension, eroding the seafloor and altering the content and composition of sedimentary organic matter (OM). The physical and biogeochemical impacts of bottom trawling were studied on the continental slope of the Gulf of Castellammare, Sicily (southwestern Mediterranean), through the analysis of two triplicate sediment cores collected at trawled and untrawled sites (∼550 m water depth) during the summer of 2016. Geochemical and sedimentological parameters (excess 210Pb, excess 234Th, 137Cs, dry bulk density, and grain size), elemental (organic carbon and nitrogen) and biochemical composition of sedimentary OM (proteins, carbohydrates, lipids), as well as its freshness (phytopigments) and degradation rates were determined in both coring locations. The untrawled site had a sedimentation rate of 0.15 cm yr−1 and presented a 6 cm thick surface mixed layer that contained siltier sediment with low excess 210Pb concentrations, possibly resulting from the resuspension, posterior advection, and eventual deposition of coarser and older sediment from adjacent trawling grounds. In contrast, the trawled site was eroded and presented compacted century-old sediment highly depleted in OM components, which were between 20 % and 60 % lower than those in the untrawled site. However, the upper 2 cm of the trawled site consisted of recently accumulated sediments enriched in excess 234Th, excess 210Pb, and phytopigments, while OM contents were similar to those from the untrawled core. This fresh sediment supported protein turnover rates of 0.025 d−1, which doubled those quantified in surface sediments of the untrawled site. The enhancement of remineralization rates in surface sediment of the trawled site was associated with the arrival of fresh particles on a chronically trawled deep-sea region that is generally deprived of OM. We conclude that the detrimental effects of bottom trawling can be temporarily and parti

Bottom trawling in the deep sea is one of the main drivers of sediment resuspension, eroding the seafloor and altering the content and composition of sedimentary organic matter (OM). The physical and biogeochemical impacts of bottom trawling were studied on the continental slope of the Gulf of Castellammare, Sicily (southwestern Mediterranean), through the analysis of two triplicate sediment cores collected at trawled and untrawled sites (∼550 m water depth) during the summer of 2016. Geochemical and sedimentological parameters (excess 210Pb, excess 234Th, 137Cs, dry bulk density, and grain size), elemental (organic carbon and nitrogen) and biochemical composition of sedimentary OM (proteins, carbohydrates, lipids), as well as its freshness (phytopigments) and degradation rates were determined in both coring locations. The untrawled site had a sedimentation rate of 0.15 cm yr−1 and presented a 6 cm thick surface mixed layer that contained siltier sediment with low excess 210Pb concentrations, possibly resulting from the resuspension, posterior advection, and eventual deposition of coarser and older sediment from adjacent trawling grounds. In contrast, the trawled site was eroded and presented compacted century-old sediment highly depleted in OM components, which were between 20 % and 60 % lower than those in the untrawled site. However, the upper 2 cm of the trawled site consisted of recently accumulated sediments enriched in excess 234Th, excess 210Pb, and phytopigments, while OM contents were similar to those from the untrawled core. This fresh sediment supported protein turnover rates of 0.025 d−1, which doubled those quantified in surface sediments of the untrawled site. The enhancement of remineralization rates in surface sediment of the trawled site was associated with the arrival of fresh particles on a chronically trawled deep-sea region that is generally deprived of OM. We conclude that the detrimental effects of bottom trawling can be temporarily and parti

Highly diverse megabenthic assemblages dominated by passive and active suspension feeders have been recently reported in shelf edge environments of the Mediterranean Sea. Due to their frequent association with species of commercial interest, these assemblages have been heavily impacted by fishing. The vulnerability and low resilience of these assemblages, composed mainly by long-living and slow-growing species, have motivated the implementation of management measures such as the restriction of bottom trawling, and the establishment of large protected areas embracing these environments. The Menorca Channel is one of such areas recently included in the European Union Natura 2000 network. Quantitative analysis of video transects recorded at 95–360 m depth by manned submersible and remotely operated vehicles were used to characterize megabenthic assemblages and to assess their geographical and bathymetric distribution. Six different assemblages were identified, mainly segregated by substrate type and depth. Hard substrates hosted coral gardens and sponge grounds, whereas soft sediments were mainly characterized by large extensions of the crinoid Leptometra phalangium and the brachiopod Gryphus vitreus. The good preservation of most of the observed assemblages is probably related to a low bottom trawling pressure, which mainly concentrates deeper on the adjacent continental slope. Because of their biological and ecological value, management and conservation measures need to be established to preserve these benthic assemblages

For a successful implementation of an Ecosystem Approach to Fisheries (EAF) management, it is necessary that all stakeholders involved in fisheries management are aware of the implications of fishing impacts on ecosystems and agree with the adopted measures to mitigate these impacts. In this context, there is a need for tools to share knowledge on the ecosystem effects of fisheries among these stakeholders. When managing bottom trawl fisheries under an EAF framework, one of the main concerns is the direct and indirect consequences of trawling impacts on benthic ecosystems. We developed a platform using the ExtendSim® software with a user-friendly interface that combines a simulation model based on existing knowledge, data collection and representation of predicted trawling impacts on the seabed. The platform aims to be a deliberation support tool for fisheries’ stakeholders and, simultaneously, raise public awareness of the need for good benthic community knowledge to appropriately inform EAF management plans. The simulation procedure assumes that trawling affects benthic communities with an intensity that depends on the level of fishing effort exerted on benthic communities and on the habitat characteristics (i.e. sediment grain size). Data to build the simulation comes from epifaunal samples from 18 study sites located in Mediterranean continental shelves subjected to different levels of fishing effort. In this work, we present the simulation outputs of a 50% fishing effort increase (and decrease) in four of the study sites which cover different habitats and different levels of fishing effort. We discuss the platform strengths and weaknesses and potential future developments

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons’ morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities.

Discarding is considered globally among the most important issues for fisheries management. The recent reform of the Common Fisheries Policy establishes a landing obligation for the species which are subject to catch limits and, in the Mediterranean, for species which are subject to Minimum Conservation Reference Size (MCRS) as defined in Annex III to Regulation (EC) No 1967/2006. Additionally, several other initiatives aim to reduce unwanted catches of target and bycatch species, including species of conservation concern. This raises the need to study discarding patterns of (mainly) these species. In this work we collated a considerable amount of historical published information on discard ratios and lengths at discarding for species caught in EU Mediterranean bottom trawl fisheries. The main aim was to summarize the available historical records and make them more accessible for scientific and managerial needs, as well as to try identifying patterns in discarding. We show discard ratios and lengths at which 50% of the individuals were discarded (L50) for 15 species (9 bony fishes, three crustacean decapods, and three elasmobranchs). Discard ratios were usually low for target species such as hake, red mullets and highly commercial shrimps and exemptions from the landing obligation under the de minimis rules could be sought in several cases. Discard ratios were usually higher for commercial bycatch species. Discarding is affected by a combination of factors and for a given species, especially for non-target ones, discards are likely to fluctuate within a fishery, across seasons, years, and regions. For most species considered, L50s were lower than the MCRS (when in place) and length at first maturity. L50s of target species, such as hake, were very small due to the existence of market demands for small sized individuals. However, for species of low demand, like horse mackerels, a higher retention size was observed, often exceeding MCRS. Lengths at discarding are affe

Many studies highlight that fish trawling activities cause seafloor erosion, but the assessment of the remobilization of surface sediments and its relocation is still not well documented. These impacts were examined along the flanks and axes of three headless submarine canyons incised on the Barcelona continental margin, where trawling fleets have been operating for decades. Trawled grounds along canyon flanks presented eroded and highly reworked surface sediments resulting from the passage of heavy trawling gear. Sedimentation rates on the upper canyon axes tripled and quadrupled its natural (i.e. pre-industrialization) values after a substantial increase in total horsepower of the operating trawling fleets between 1960 s and 1970 s. These impacts affected the upper canyon reaches next to fishing grounds, where sediment resuspended by trawling can be transported towards the canyon axes. This study highlights that bottom trawling has the capacity to alter natural sedimentary environments by promoting sediment-starved canyon flanks, and by enhancing sedimentation rates along the contiguous axes, independently of canyons’ morphology. Considering the global mechanisation and offshore expansion of bottom trawling fisheries since the mid-20th century, these sedimentary alterations may occur in many trawled canyons worldwide, with further ecological impacts on the trophic status of these non-resilient benthic communities.

Bottom trawling is the most widespread human activity affecting seabed habitats. Here, we collate all available data for experimental and comparative studies of trawling impacts on whole communities of seabed macroinvertebrates on sedimentary habitats and develop widely applicable methods to estimate depletion and recovery rates of biota after trawling. Depletion of biota and trawl penetration into the seabed are highly correlated. Otter trawls caused the least depletion, removing 6% of biota per pass and penetrating the seabed on average down to 2.4 cm, whereas hydraulic dredges caused the most depletion, removing 41% of biota and penetrating the seabed on average 16.1 cm. Median recovery times posttrawling (from 50 to 95% of unimpacted biomass) ranged between 1.9 and 6.4 y. By accounting for the effects of penetration depth, environmental variation, and uncertainty, the models explained much of the variability of depletion and recovery estimates from single studies. Coupled withlarge-scale, high-resolution maps of trawling frequency and habitat, our estimates of depletion and recovery rates enable the assessment of trawling impacts on unprecedented spatial scales.

Maërl habitats are of great biological value due to their high biodiversity and productivity, but they are also very fragile. The subaqueous dune field on the continental shelf off the Mar Menor exhibits sediment characteristics that favour the presence of maërl habitats. However, this seabed is altered by two kinds of disturbance: biogenic disturbance caused mainly by the feeding and burrowing activities of the sea urchin Spatangus purpureus, and anthropogenic disturbance caused by trawling activities

Turbidity currents in submarine canyons are the main contribution for sediment transfer across the continental margins. Geological studies of submarine canyons and associated turbiditic systems for more than 30 years led to an extraordinary breakthrough in the understanding of how turbidite systems evolve. However, these studies remain limited to a posteriori interpretations, based on the distribution of deposits and morphological evidences. The overarching aim of this thesis is to apply a 2DH process-based model to simulate large-scale turbidity currents on two different submarine canyons in the western Mediterranean coast.The work in La Fonera canyon, in the Catalan margin, focuses on the modelling of sediment transport and accumulation resulting from trawling activities on the canyon flanks. The numerical process-based provides a 3D visualization of potential trawling impacts on sediment dynamics. The study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins. The present work can help in the identification of trawling areas with lesser impacts. The Var Sedimentary System, located in the vicinity of Nice (France), is connected to the Var River during both low and high-stands and it can be considered as a natural laboratory for the study of the climatic control on the turbiditic activity. The influence of Coriolis forces on the spatial evolution of the hyperpycnal flows and hence in the construction of the Var Sedimentary Ridge (VSR) is evidenced and supported for the first time.The major drawback is the limited amount of information for the necessary initial and boundary conditions; hence modelling results might not be of predictive quality. However, modelling results provide a full-scale vision of the system allowing the identification of sediment pathways and deposition areas on the basis of physical processes and enlarge the present knowledge of the canyons studied. The results obtained may hel, Les courants de turbidité dans les canyons sous-marins contribuent largement au transfert sédimentaire à travers des marges continentales. L’étude géologique des canyons sous-marins et des systèmes turbiditiques associés a permis des avancées fondamentales dans la compréhension de l’évolution des courants de turbidité.Ces études sont cependant limitées à des interprétations a posteriori, basées sur la répartition des dépôts et des évidences morphologiques. Cette thèse vise à l’application de la modélisation numérique des courants de turbidité, sur la base des processus physiques, à deux canyons sous-marins de la côte Méditerranée Occidentale.Des courants de turbidité liés au chalutage de fond sont modélisés dans le canyon de La Fonera. Les résultats du modèle permettent de spatialiser ce transport; ainsi le modèle peut être un point de départ pour l’identification de zones de pêche au chalut avec un moindre impact. L’absence d’un plateau continental au niveau de Nice a permis une alimentation continue du système turbiditique du Var indépendamment des variations du niveau marin. Ainsi ce système s’avère un laboratoire naturel pour l’étude du contrôle climatique sur l’activité turbiditique. L’influence des forces de Coriolis dans l’évolution spatiale des courants de turbidité et dans la construction de la Ride sédimentaire du Var est modélisée et mise en évidence pour la première fois.La modélisation numérique des courants de turbidité ne peut pas fournir à présent des résultats de qualité prédictive du fait de la quantité limitée d’information disponible pour établir les conditions initiales de l’écoulement qui impactent largement son évolution et dépôts. Malgré ce fait, la modélisation numérique permet d’élargir les interprétations du fonctionnement sédimentaire des canyons étudiés, d’identifier les chemins empruntés par les écoulements et leur dépôt final et de mieux préparer des cibles (mouillages et carottage) lors des campagnes à la mer.

La pesca de arrastre en el mar Mediterráneo genera un gran número de descartes, es decir, especies que no se comercializan. Estas especies se ven igual o más afectadas que las especies comerciales y por eso son motivo de estudio. Se ha estudiado todos los descartes de un arrastre a 600 metros de profundidad en el canal de Ibiza, tomando datos de tallas y pesos, y observando los contenidos estomacales de las especies capturadas con mayor número de individuos. En la mayoría de las especies se han obtenido resultados similares al de otros estudios en zonas similares, excepto las especies Chalinura mediterranea y Mora moro que se han encontrado a menor profundidad, según la bibliografía, a la que habitualmente se encuentran., Trawling in the Mediterranean Sea generates a large number of discards, species that are not sold . These species are equally or more affected than commercial species and therefore are subject to study . We have studied all the discards of a drag to 600 meters deep in the channel of Ibiza, taking height and weight data , and observing the stomach contents of harvested species with the greatest number of individuals . In most species we have obtained similar results to other studies in similar areas , except species Chalinura mediterranea and Mora moro that found at shallower depths , according to

The northern shrimp (Pandalus borealis L.) stock in the Skagerrak is shared by Sweden, Norway, and Denmark. Although the fishery is regulated by an annual agreement between the EU and Norway, there are also national regulations as well as differences in fleet composition and shrimp markets. In early 2014, the World Wildlife Fund gave all Skagerrak shrimp a red light in their seafood consumer guide, which led to an extensive debate, especially in Sweden, about the sustainability of this fishery. The aim of this study was to quantify a set of indicators that together give a broad picture of the sustainability of the three fisheries to provide an objective basis for a discussion on needed measures. The different indicators concerned environmental, economic or social aspects of sustainability and were quantified per tonne of shrimp landed by each country in 2012. The Danish fishery was most efficient in terms of environmental and economic indicators, while the Swedish fishery provided most employment per tonne of shrimp landed. Fuel use in all fisheries was high, also when compared with other shrimp fisheries. Interesting patterns emerged, with smaller vessels being more fuel efficient than larger ones in Sweden and Norway, with the opposite trend in Denmark. The study also demonstrated major data gaps and differences between the countries in how data are collected and made available. Various improvement options in the areas data collection and publication, allocation of quotas and enforcement of regulations resulted. Product-oriented studies could be useful to follow-up performance of fisheries over time and to identify how to best utilize the Skagerrak shrimp stock. This could involve evaluating novel solutions in terms of technology and management, based on current and future scenarios aiming to maximize societal benefits generated from this limited resource, at minimized environmental impacts.

The northern shrimp (Pandalus borealis L.) stock in the Skagerrak is shared by Sweden, Norway, and Denmark. Although the fishery is regulated by an annual agreement between the EU and Norway, there are also national regulations as well as differences in fleet composition and shrimp markets. In early 2014, the World Wildlife Fund gave all Skagerrak shrimp a red light in their seafood consumer guide, which led to an extensive debate, especially in Sweden, about the sustainability of this fishery. The aim of this study was to quantify a set of indicators that together give a broad picture of the sustainability of the three fisheries to provide an objective basis for a discussion on needed measures. The different indicators concerned environmental, economic or social aspects of sustainability and were quantified per tonne of shrimp landed by each country in 2012. The Danish fishery was most efficient in terms of environmental and economic indicators, while the Swedish fishery provided most employment per tonne of shrimp landed. Fuel use in all fisheries was high, also when compared with other shrimp fisheries. Interesting patterns emerged, with smaller vessels being more fuel efficient than larger ones in Sweden and Norway, with the opposite trend in Denmark. The study also demonstrated major data gaps and differences between the countries in how data are collected and made available. Various improvement options in the areas data collection and publication, allocation of quotas and enforcement of regulations resulted. Product-oriented studies could be useful to follow-up performance of fisheries over time and to identify how to best utilize the Skagerrak shrimp stock. This could involve evaluating novel solutions in terms of technology and management, based on current and future scenarios aiming to maximize societal benefits generated from this limited resource, at minimized environmental impacts.

Turbidity currents in submarine canyons are the main contribution for sediment transfer across the continental margins. Geological studies of submarine canyons and associated turbiditic systems for more than 30 years led to an extraordinary breakthrough in the understanding of how turbidite systems evolve. However, these studies remain limited to a posteriori interpretations, based on the distribution of deposits and morphological evidences. The overarching aim of this thesis is to apply a 2DH process-based model to simulate large-scale turbidity currents on two different submarine canyons in the western Mediterranean coast.The work in La Fonera canyon, in the Catalan margin, focuses on the modelling of sediment transport and accumulation resulting from trawling activities on the canyon flanks. The numerical process-based provides a 3D visualization of potential trawling impacts on sediment dynamics. The study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins. The present work can help in the identification of trawling areas with lesser impacts. The Var Sedimentary System, located in the vicinity of Nice (France), is connected to the Var River during both low and high-stands and it can be considered as a natural laboratory for the study of the climatic control on the turbiditic activity. The influence of Coriolis forces on the spatial evolution of the hyperpycnal flows and hence in the construction of the Var Sedimentary Ridge (VSR) is evidenced and supported for the first time.The major drawback is the limited amount of information for the necessary initial and boundary conditions; hence modelling results might not be of predictive quality. However, modelling results provide a full-scale vision of the system allowing the identification of sediment pathways and deposition areas on the basis of physical processes and enlarge the present knowledge of the canyons studied. The results obtained may hel, Les courants de turbidité dans les canyons sous-marins contribuent largement au transfert sédimentaire à travers des marges continentales. L’étude géologique des canyons sous-marins et des systèmes turbiditiques associés a permis des avancées fondamentales dans la compréhension de l’évolution des courants de turbidité.Ces études sont cependant limitées à des interprétations a posteriori, basées sur la répartition des dépôts et des évidences morphologiques. Cette thèse vise à l’application de la modélisation numérique des courants de turbidité, sur la base des processus physiques, à deux canyons sous-marins de la côte Méditerranée Occidentale.Des courants de turbidité liés au chalutage de fond sont modélisés dans le canyon de La Fonera. Les résultats du modèle permettent de spatialiser ce transport; ainsi le modèle peut être un point de départ pour l’identification de zones de pêche au chalut avec un moindre impact. L’absence d’un plateau continental au niveau de Nice a permis une alimentation continue du système turbiditique du Var indépendamment des variations du niveau marin. Ainsi ce système s’avère un laboratoire naturel pour l’étude du contrôle climatique sur l’activité turbiditique. L’influence des forces de Coriolis dans l’évolution spatiale des courants de turbidité et dans la construction de la Ride sédimentaire du Var est modélisée et mise en évidence pour la première fois.La modélisation numérique des courants de turbidité ne peut pas fournir à présent des résultats de qualité prédictive du fait de la quantité limitée d’information disponible pour établir les conditions initiales de l’écoulement qui impactent largement son évolution et dépôts. Malgré ce fait, la modélisation numérique permet d’élargir les interprétations du fonctionnement sédimentaire des canyons étudiés, d’identifier les chemins empruntés par les écoulements et leur dépôt final et de mieux préparer des cibles (mouillages et carottage) lors des campagnes à la mer.

La pesca de arrastre en el mar Mediterráneo genera un gran número de descartes, es decir, especies que no se comercializan. Estas especies se ven igual o más afectadas que las especies comerciales y por eso son motivo de estudio. Se ha estudiado todos los descartes de un arrastre a 600 metros de profundidad en el canal de Ibiza, tomando datos de tallas y pesos, y observando los contenidos estomacales de las especies capturadas con mayor número de individuos. En la mayoría de las especies se han obtenido resultados similares al de otros estudios en zonas similares, excepto las especies Chalinura mediterranea y Mora moro que se han encontrado a menor profundidad, según la bibliografía, a la que habitualmente se encuentran., Trawling in the Mediterranean Sea generates a large number of discards, species that are not sold . These species are equally or more affected than commercial species and therefore are subject to study . We have studied all the discards of a drag to 600 meters deep in the channel of Ibiza, taking height and weight data , and observing the stomach contents of harvested species with the greatest number of individuals . In most species we have obtained similar results to other studies in similar areas , except species Chalinura mediterranea and Mora moro that found at shallower depths , according to

La pesca de arrastre en el mar Mediterráneo genera un gran número de descartes, es decir, especies que no se comercializan. Estas especies se ven igual o más afectadas que las especies comerciales y por eso son motivo de estudio. Se ha estudiado todos los descartes de un arrastre a 600 metros de profundidad en el canal de Ibiza, tomando datos de tallas y pesos, y observando los contenidos estomacales de las especies capturadas con mayor número de individuos. En la mayoría de las especies se han obtenido resultados similares al de otros estudios en zonas similares, excepto las especies Chalinura mediterranea y Mora moro que se han encontrado a menor profundidad, según la bibliografía, a la que habitualmente se encuentran., Trawling in the Mediterranean Sea generates a large number of discards, species that are not sold . These species are equally or more affected than commercial species and therefore are subject to study . We have studied all the discards of a drag to 600 meters deep in the channel of Ibiza, taking height and weight data , and observing the stomach contents of harvested species with the greatest number of individuals . In most species we have obtained similar results to other studies in similar areas , except species Chalinura mediterranea and Mora moro that found at shallower depths , according to

La pesca de arrastre en el mar Mediterráneo genera un gran número de descartes, es decir, especies que no se comercializan. Estas especies se ven igual o más afectadas que las especies comerciales y por eso son motivo de estudio. Se ha estudiado todos los descartes de un arrastre a 600 metros de profundidad en el canal de Ibiza, tomando datos de tallas y pesos, y observando los contenidos estomacales de las especies capturadas con mayor número de individuos. En la mayoría de las especies se han obtenido resultados similares al de otros estudios en zonas similares, excepto las especies Chalinura mediterranea y Mora moro que se han encontrado a menor profundidad, según la bibliografía, a la que habitualmente se encuentran., Trawling in the Mediterranean Sea generates a large number of discards, species that are not sold . These species are equally or more affected than commercial species and therefore are subject to study . We have studied all the discards of a drag to 600 meters deep in the channel of Ibiza, taking height and weight data , and observing the stomach contents of harvested species with the greatest number of individuals . In most species we have obtained similar results to other studies in similar areas , except species Chalinura mediterranea and Mora moro that found at shallower depths , according to

The northern shrimp (Pandalus borealis L.) stock in the Skagerrak is shared by Sweden, Norway, and Denmark. Although the fishery is regulated by an annual agreement between the EU and Norway, there are also national regulations as well as differences in fleet composition and shrimp markets. In early 2014, the World Wildlife Fund gave all Skagerrak shrimp a red light in their seafood consumer guide, which led to an extensive debate, especially in Sweden, about the sustainability of this fishery. The aim of this study was to quantify a set of indicators that together give a broad picture of the sustainability of the three fisheries to provide an objective basis for a discussion on needed measures. The different indicators concerned environmental, economic or social aspects of sustainability and were quantified per tonne of shrimp landed by each country in 2012. The Danish fishery was most efficient in terms of environmental and economic indicators, while the Swedish fishery provided most employment per tonne of shrimp landed. Fuel use in all fisheries was high, also when compared with other shrimp fisheries. Interesting patterns emerged, with smaller vessels being more fuel efficient than larger ones in Sweden and Norway, with the opposite trend in Denmark. The study also demonstrated major data gaps and differences between the countries in how data are collected and made available. Various improvement options in the areas data collection and publication, allocation of quotas and enforcement of regulations resulted. Product-oriented studies could be useful to follow-up performance of fisheries over time and to identify how to best utilize the Skagerrak shrimp stock. This could involve evaluating novel solutions in terms of technology and management, based on current and future scenarios aiming to maximize societal benefits generated from this limited resource, at minimized environmental impacts.

Turbidity currents in submarine canyons are the main contribution for sediment transfer across the continental margins. Geological studies of submarine canyons and associated turbiditic systems for more than 30 years led to an extraordinary breakthrough in the understanding of how turbidite systems evolve. However, these studies remain limited to a posteriori interpretations, based on the distribution of deposits and morphological evidences. The overarching aim of this thesis is to apply a 2DH process-based model to simulate large-scale turbidity currents on two different submarine canyons in the western Mediterranean coast.The work in La Fonera canyon, in the Catalan margin, focuses on the modelling of sediment transport and accumulation resulting from trawling activities on the canyon flanks. The numerical process-based provides a 3D visualization of potential trawling impacts on sediment dynamics. The study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins. The present work can help in the identification of trawling areas with lesser impacts. The Var Sedimentary System, located in the vicinity of Nice (France), is connected to the Var River during both low and high-stands and it can be considered as a natural laboratory for the study of the climatic control on the turbiditic activity. The influence of Coriolis forces on the spatial evolution of the hyperpycnal flows and hence in the construction of the Var Sedimentary Ridge (VSR) is evidenced and supported for the first time.The major drawback is the limited amount of information for the necessary initial and boundary conditions; hence modelling results might not be of predictive quality. However, modelling results provide a full-scale vision of the system allowing the identification of sediment pathways and deposition areas on the basis of physical processes and enlarge the present knowledge of the canyons studied. The results obtained may hel, Les courants de turbidité dans les canyons sous-marins contribuent largement au transfert sédimentaire à travers des marges continentales. L’étude géologique des canyons sous-marins et des systèmes turbiditiques associés a permis des avancées fondamentales dans la compréhension de l’évolution des courants de turbidité.Ces études sont cependant limitées à des interprétations a posteriori, basées sur la répartition des dépôts et des évidences morphologiques. Cette thèse vise à l’application de la modélisation numérique des courants de turbidité, sur la base des processus physiques, à deux canyons sous-marins de la côte Méditerranée Occidentale.Des courants de turbidité liés au chalutage de fond sont modélisés dans le canyon de La Fonera. Les résultats du modèle permettent de spatialiser ce transport; ainsi le modèle peut être un point de départ pour l’identification de zones de pêche au chalut avec un moindre impact. L’absence d’un plateau continental au niveau de Nice a permis une alimentation continue du système turbiditique du Var indépendamment des variations du niveau marin. Ainsi ce système s’avère un laboratoire naturel pour l’étude du contrôle climatique sur l’activité turbiditique. L’influence des forces de Coriolis dans l’évolution spatiale des courants de turbidité et dans la construction de la Ride sédimentaire du Var est modélisée et mise en évidence pour la première fois.La modélisation numérique des courants de turbidité ne peut pas fournir à présent des résultats de qualité prédictive du fait de la quantité limitée d’information disponible pour établir les conditions initiales de l’écoulement qui impactent largement son évolution et dépôts. Malgré ce fait, la modélisation numérique permet d’élargir les interprétations du fonctionnement sédimentaire des canyons étudiés, d’identifier les chemins empruntés par les écoulements et leur dépôt final et de mieux préparer des cibles (mouillages et carottage) lors des campagnes à la mer.

Turbidity currents in submarine canyons are the main contribution for sediment transfer across the continental margins. Geological studies of submarine canyons and associated turbiditic systems for more than 30 years led to an extraordinary breakthrough in the understanding of how turbidite systems evolve. However, these studies remain limited to a posteriori interpretations, based on the distribution of deposits and morphological evidences. The overarching aim of this thesis is to apply a 2DH process-based model to simulate large-scale turbidity currents on two different submarine canyons in the western Mediterranean coast.The work in La Fonera canyon, in the Catalan margin, focuses on the modelling of sediment transport and accumulation resulting from trawling activities on the canyon flanks. The numerical process-based provides a 3D visualization of potential trawling impacts on sediment dynamics. The study represents a starting point for the assessment of the sedimentary impact of bottom trawling in deep continental margins. The present work can help in the identification of trawling areas with lesser impacts. The Var Sedimentary System, located in the vicinity of Nice (France), is connected to the Var River during both low and high-stands and it can be considered as a natural laboratory for the study of the climatic control on the turbiditic activity. The influence of Coriolis forces on the spatial evolution of the hyperpycnal flows and hence in the construction of the Var Sedimentary Ridge (VSR) is evidenced and supported for the first time.The major drawback is the limited amount of information for the necessary initial and boundary conditions; hence modelling results might not be of predictive quality. However, modelling results provide a full-scale vision of the system allowing the identification of sediment pathways and deposition areas on the basis of physical processes and enlarge the present knowledge of the canyons studied. The results obtained may hel, Les courants de turbidité dans les canyons sous-marins contribuent largement au transfert sédimentaire à travers des marges continentales. L’étude géologique des canyons sous-marins et des systèmes turbiditiques associés a permis des avancées fondamentales dans la compréhension de l’évolution des courants de turbidité.Ces études sont cependant limitées à des interprétations a posteriori, basées sur la répartition des dépôts et des évidences morphologiques. Cette thèse vise à l’application de la modélisation numérique des courants de turbidité, sur la base des processus physiques, à deux canyons sous-marins de la côte Méditerranée Occidentale.Des courants de turbidité liés au chalutage de fond sont modélisés dans le canyon de La Fonera. Les résultats du modèle permettent de spatialiser ce transport; ainsi le modèle peut être un point de départ pour l’identification de zones de pêche au chalut avec un moindre impact. L’absence d’un plateau continental au niveau de Nice a permis une alimentation continue du système turbiditique du Var indépendamment des variations du niveau marin. Ainsi ce système s’avère un laboratoire naturel pour l’étude du contrôle climatique sur l’activité turbiditique. L’influence des forces de Coriolis dans l’évolution spatiale des courants de turbidité et dans la construction de la Ride sédimentaire du Var est modélisée et mise en évidence pour la première fois.La modélisation numérique des courants de turbidité ne peut pas fournir à présent des résultats de qualité prédictive du fait de la quantité limitée d’information disponible pour établir les conditions initiales de l’écoulement qui impactent largement son évolution et dépôts. Malgré ce fait, la modélisation numérique permet d’élargir les interprétations du fonctionnement sédimentaire des canyons étudiés, d’identifier les chemins empruntés par les écoulements et leur dépôt final et de mieux préparer des cibles (mouillages et carottage) lors des campagnes à la mer.

Fishing disturbance on ecosystems leads to changes in community structure and composition, which may have drastic implications for ecosystem functional performance. Functional redundancy, defined as species sharing similar functional roles, is a community property that plays an important role in preventing functional changes in ecosystems under pressure. In this study, we suggest that functional redundancy may be achieved through trait abundance (i.e. large amounts of a trait, hereafter “common traits”), or through trait richness (i.e. large numbers of distinct taxa exhibiting the same trait, hereafter “widespread traits”). We assessed the variability of both measures obtained from epifaunal and infaunal communities in soft-bottom trawling grounds. Sampling sites were located in four Mediterranean areas that were subjected to different levels of trawling effort. Common and widespread traits measures were based on the analysis of biological traits linked to key soft-bottoms functions such as nutrient cycling, bentho-pelagic coupling and habitat provision. The role of rare species in both measures was also assessed and we observed that, in our study sites, rare species generally exhibited the same traits as the most abundant species. Common and widespread traits measures provided complementary information on benthic functional redundancy. Thus, we suggest that a combination of the two measures should be used to appropriately assess benthic functional redundancy in trawling grounds. As redundancy is a component of ecosystem resilience, functional redundancy evaluation is important to assess the overall integrity of ecosystems

We investigated the natural and anthropogenic drivers controlling the spatiotemporal distribution of the meiofauna in the submarine Blanes Canyon, and its adjacent western slope (NW Mediterranean margin of the Iberian Peninsula). We analyzed the relationships between the main sedimentary environmental variables (i.e. grain size, Chl-a, Chl-a: phaeopigments, CPE, organic carbon and total nitrogen) and the density and structure of the meiofaunal assemblages along a bathymetric gradient (from 500 to 2000 m depth) in spring and autumn of 2012 and 2013. Twenty-one and 16 major taxa were identified for respectively the canyon and slope, where the assemblages were always dominated by nematodes. The gradual decreasing meiofaunal densities with increasing depth at the slope showed little variability among stations and corresponded with a uniform pattern of food availability. The canyon was environmentally much more variable and sediments contained greater amounts of food resources (Chl-a and CPE) throughout, leading not only to increased meiofaunal densities compared to the slope, but also different assemblages in terms of composition and structure. This variability in the canyon is only partly explained by seasonal food inputs. The high densities found at 900 m and 1200 m depth coincided with significant increases in food availability compared to shallower and deeper stations in the canyon. Our results suggest that the disruption in expected bathymetric decrease in densities at 900–1200 m water depth coincided with noticeable changes in the environmental variables typical for disturbance and deposition events (e.g., higher sand content and CPE), evoking the hypothesis of an anthropogenic effect at these depths in the canyon. The increased downward particle fluxes at 900–1200 m depth caused by bottom trawling along canyon flanks, as reported in previous studies, support our hypothesis and allude to a substantial anthropogenic factor influencing benthic assemblages at these d