In fisheries, greenhouse gas accounting has largely focused on fuel use during resource extraction. Beyond its climate impact, fuel use affects the economic viability of the fishing industry and its capacity to mitigate emissions and adapt to climate change. Understanding fuel use and efficiency is critical to the long-term sustainability of fisheries and should inform the UK’s climate mitigation roadmap. Fuel use estimates and relevant indicators are available for a limited number of species and gear types, calculated using different methods. This study addresses the availability and granularity of fleet-wide fuel metrics, using the UK as a case study. Using primary data on days at sea, engine power, and fuel use to estimate fleet-wide fuel use, this study provides fuel use estimates for 78% of UK-caught wild-capture seafood and conducts a Fuel Use Intensity (Litres/Tonne) and Fuel Cost Intensity (£fuel/£revenue) analysis of UK fishing vessels. This study finds that the UK pelagic fleet burns the most fuel per active vessel annually. Some beam trawl fleets have the highest Fuel Use Intensity and Fuel Cost Intensity. Species typically caught by beam trawlers have a higher weighted Fuel Use Intensity, yet species targeted by fleets with lower Fuel Use Intensity are still vulnerable to economic and policy impacts relating to fossil fuels and fuel use due to their dependence on fossil fuels and total annual fuel use. Climate mitigation cannot single out gear types or species; it must use multiple strategies tailored to each fleet's needs to reduce emissions.

Bottom-tow gear fisheries (trawls and dredges) produce similar to 24 million mt of harvest annually, representing a globally important animal-sourced food system. While many are currently sustainably managed, growing concern over the potential for ecosystem impacts from bottom-tow gears has increased pressure to improve these fisheries. We assembled an international working group of > 30 contributors, including fishing industry participants, managers, non-governmental ocean conservation organization representatives, and scientists to synthesize obstacles to bottom-tow fisheries sustainability and to develop expert-based recommendations to operationalize sustainability advancements moving forward. We identified 30 key gaps impeding bottom-towed fisheries sustainability spanning 6 core challenge areas including: seafloor disturbance, bycatch and discards, management design and implementation, fishing operations, cross-sector conflicts, and public perception and communication. We generated 28 priority recommendations to address bottom-tow fisheries sustainability obstacles with themes including: addressing data gaps, advancing mechanistic understanding and modelling tools, strengthening management processes, and improving knowledge sharing and communication. Cross-disciplinary and diverse system experience among fisheries and marine ecosystem stakeholders will be critical for operationalizing bottom-tow fisheries sustainability advancements. As the global human population approaches 10 bn in the next 30 years, ensuring sustainable wild capture fisheries is an imperative for feeding the world. Outputs from this synthesis serve as a resource for fishing and marine ecosystem stakeholders to identify key challenge areas and associated entry points for solutions-oriented efforts to improve the sustainability of bottom-tow fisheries.

Mangrove forests are increasingly threatened by selective deforestation, yet understanding of the implications of different modes of deforestation for the functioning of these ecosystems is limited. Benthic macroinfaunal communities are integral components of mangrove ecosystems, supporting biogeochemical cycling and providing food to higher trophic levels, but their response to selective deforestation is unknown. Macroinfaunal community structure, biodiversity, and functioning were compared among 4 estuarine mangrove systems exposed to varying degrees of deforestation along the coast of Ghana. At higher tidal elevations, biomass, bioturbation potential, and secondary production estimates were significantly larger in the intact mangroves compared to selectively deforested and clear-felled sites. Differences in canopy cover were important in explaining the significant differences in macroinfaunal community composition between the intact and selectively deforested sites. Biological traits analysis showed that macroinfaunal assemblages were distinct between the intact and deforested mangroves, with deforested areas exhibiting reduced trait diversity. Both modes of mangrove deforestation degraded ecosystem functioning through their impact upon macroinfaunal communities. In clear-felled mangroves, secondary production and bioturbation potential were reduced by 94 and 90%, respectively, while in selectively deforested mangroves, both metrics were reduced by 98% compared to intact mangroves. This case study provides clear evidence that both clear-felling and selective mangrove deforestation can have a significant impact on benthic macroinfaunal communities and their functioning.

ABSTRACT The scallop fishing sector is central to UK fisheries. Traditional dredging with Newhaven dredges poses ecological risks, creating pressure to adopt more sustainable practices. This study assessed the catch and environmental outcomes of modified scallop dredge designs aimed at reducing environmental impact without compromising catch efficiency. Four gear designs were tested: (1) N‐Viro dredge with conventional belly bag, (2) N‐Viro dredge with skid belly bag, (3) Newhaven dredge with skid belly bag, compared to the (4) standard Newhaven dredge with conventional belly bag. Results showed that the N‐Viro dredge alone did not increase catches of market‐sized king scallops (Pecten maximus); however, pairing it with a skid belly bag improved catches by 14%–19%. The N‐Viro dredge reduced undersized scallop catch by 42% and stones by 67%, with further reductions when combined with a skid belly bag. Bycatch levels remained unchanged. Fuel consumption fell by 30% with N‐Viro dredges, equating to annual CO2 reductions of 164,571 kg CO2‐e/year for vessels over 15 m and 37,235 kg CO2‐e/year for vessels under 15 m, alongside annual fuel cost savings of £46,250 and £10,465, respectively. Seabed impact assessment indicated that skid belly bags reduced gear footprint by 55%, with the lowest impact from the N‐Viro dredge with skid belly bag. These findings demonstrate that combining N‐Viro dredges with skid belly bags can substantially cut environmental impacts and emissions while maintaining catch efficiency, offering a promising pathway towards more sustainable scallop dredging in UK waters.

The European Natura 2000 (N2000) network aims to protect Europe's most valuable habitats and species. As the EU advances its "30% by 2030" target, prohibiting bottom trawling within all N2000 sites has been proposed. We evaluated the effectiveness of such closures for seafloor protection by quantifying network coverage across benthic habitats and ten mobile bottom-contacting fishing metiers in four northeast Atlantic regions, and by assessing ecological implications under multiple fishing-redistribution scenarios. N2000 coverage and its overlap with fishing grounds varied strongly across habitats, metiers, and regions. The network covered 23% of the assessment area and contained 22% of annual average fishing effort (2016-2020), with particularly high values in the Bay of Biscay & the Iberian Coast (44% coverage; 43% effort). Nearshore habitats were disproportionally represented in the network, whereas deeper offshore habitats were underrepresented. Several metiers relied heavily on N2000 sites, especially beam trawls targeting crustaceans (85% of effort), followed by otter trawls for small pelagic fish (41%), Danish seines (40%), and beam trawls for molluscs (38%). Ecological outcomes of N2000 closures varied across displacement scenarios. Habitat quality increased within closures, but regional declines occurred outside them under certain redistribution strategies, particularly in habitats with limited N2000 coverage. Consequently, some scenarios yielded habitat-specific net losses. Closing all N2000 sites could contribute to the EU's 30 & times; 30 target, but would still yield uneven habitat protection and disproportionate consequences for specific fisheries. The dependence of net conservation gains on displacement dynamics highlights the need for strategic MPA design and active redistribution management.

Bottom trawling affects seabed habitats, but its large-scale impacts remain poorly quantified. Assessment of trawling impacts is essential to support monitoring and achieving sustainability objectives under international conventions, sustainable development goals, and seafood certification programs. We present a Europe-wide quantitative assessment of bottom trawling impacts, accounting for regional seabed-community sensitivity drivers, across the Baltic, Atlantic, Mediterranean and Black Sea continental shelves. Using two risk-based indicators of seabed status-Relative Benthic Status determined as benthic community biomass relative to seabed fauna carrying capacity (RBStot) and RBSsen (biomass of the 10% most sensitive fauna relative to carrying capacity)-we found substantial regional and habitat differences. The Black, Baltic and Aegean-Levantine Seas showed low trawling intensity and high seabed status across habitats. In contrast, the Western Mediterranean, Ionian and Central Mediterranean and Adriatic Seas were the most severely impacted. Trawling affected the sensitive species biomass fraction more strongly than the total community biomass. RBStot was in good condition (here chosen as RBS > 75% for epifauna) for over 79% of habitat-ecoregion combinations. In contrast, RBSsen met this threshold in only 46% of these. A strong correlation emerged between the mean trawling intensity and RBStot and RBSsen, allowing the use of SAR to estimate ecosystem status. This relationship can support decisions on where, and by how much, SAR reductions are needed to achieve good environmental status in regions where no detailed assessment is available. Our approach provides a quantitative framework to balance fishery production with ecosystem sustainability, offering tools for environmental and fisheries management in Europe.

Cetaceans face a multitude of well-recognised anthropogenic threats, many of which can be attributed to the activities of marine vessels that are increasing in number throughout the world's oceans. This study applies a systematic map methodology to better understand the current state of knowledge on vessel impacts to cetaceans, and to identify data gaps relating to specific geographies, vessel types and species. Literature searches were undertaken in January 2023 using three databases (Scopus, Web of Science, ProQuest), yielding 28,452 results. After duplicate removal and title, abstract and full-text screening, 568 documents were included in this review, resulting in 661 records of empirical evidence being extracted for further analysis. These records highlighted a focus on certain species (bottlenose dolphins (n = 133) and humpback whales (n = 89)) and vessel types (e.g., eco-tourism boats (n = 145)), and the majority of records were from North American waters (n = 274). There was also limited evidence demonstrating impacts of vessels for entire groups of species including porpoises (n = 21) and beaked whales (n = 22). Given the global distribution of marine mammals and vessels, there were few published records available for African waters and international waters. However, for 41.4% of the records it was not possible to classify the type(s) of vessels represented. Therefore, greater clarity and recognition of the heterogeneity of vessels and their associated impacts would both help improve our understanding of potential knowledge gaps and, importantly, help refine our ability to holistically evaluate and assess the risk(s) maritime traffic poses to cetaceans.

Abstract Background : Seafood is a vital global resource, yet the rapid growth of aquaculture – which now supplies over half the world’s blue food – has introduced significant ecological and social challenges. As a major importer and consumer, Europe is central to these global supply chains. While the industry bolsters rural economies, it is frequently linked to nutrient pollution, habitat loss, disease, and labour exploitation. This systematic map evaluates the biodiversity and societal impacts of European blue food consumption, specifically regarding salmon, cod, sea bass, and sea bream. Methods : We searched 10 bibliographic databases/indexes and a suite of grey literature sources for evidence. Following a rigorous screening of over 28,000 results from bibliographic and grey literature sources, a random 60% subsample (210 studies) was analysed through metadata extraction and coding using a tried-and-tested form. Consistency checking prior to screening and data extraction ensured operationalisation and consistency. Results : The findings reveal a fragmented and deeply uneven evidence base. Research focus largely mirrors production volume; Atlantic salmon is the most studied species, with data concentrated in Norway, Chile, Canada, and the UK. While Mediterranean sea bass and sea bream are well-documented, evidence for cod remains negligible. A stark thematic imbalance exists between ecological and social research. Most studies prioritise ecological outcomes, such as benthic health, sea lice, and wild fish mortality. In contrast, social impacts are severely under-represented; critical issues like food security and labour conditions in producing or feed-extracting regions are almost entirely absent. Furthermore, the map highlights an under-representation of interdisciplinarity, with only one study integrating both social and ecological outcomes. The evidence also suffers from production stage bias. Most research focuses on the “grow-out” phase in offshore pens, leaving upstream activities like feed production and downstream stages like processing largely unexamined. Crucially, only six studies evaluated the effectiveness of mitigation measures, creating a significant barrier to evidence-based policy. Discussion : Ultimately, the current evidence base is insufficient for a holistic understanding of the implications of European blue food consumption. Research remains narrowly focused on specific species and production stages, overlooking cumulative and supply-chain-wide effects. To support the European Biodiversity Strategy for 2030 and foster equitable food systems, future research must prioritise the social dimensions of production and investigate mitigation strategies across the entire value chain.

Marine mammals have long been affected by human activities. To understand the state of knowledge regarding anthropogenic threats, we systematically mapped peer-reviewed and grey literature on this topic for 19 marine mammal species found in the North Atlantic. Searches in 2022 and 2024 resulted in 3390 relevant documents for review. Relevant records were extracted from each document ( n  = 6964 records), and threats were grouped into 13 major classes (e.g., climate change, fisheries, acoustic disturbance). Of the 19 species, bottlenose dolphins had the most records ( n  = 1365), and of the threat classes, fisheries had the most records ( n  = 2124), with 59% being associated with mortality. Mapping the study locations highlighted how records were unevenly distributed across each IUCN-defined species range. Furthermore, species of conservation concern (i.e., globally assessed by IUCN as ‘Endangered’) often received comparatively little study effort. We highlight the species and threats that have to date received limited attention and discuss the potential reasons for disparities in research effort. Increased efforts to understand and appropriately mitigate threats are critical, given the continued co-existence of marine mammals and human threats in the ‘Anthropocene’.

Organic carbon stored in continental margin sediments might be at risk by widespread mobile bottom fishing, potentially leading to reductions of organic carbon stocks, increased ocean acidification, additional atmospheric carbon dioxide emissions and a reduction of the buffering capacity of the ocean. Spatially explicit studies that have been conducted to inform marine management have so far looked at organic carbon stocks that have already been affected by mobile bottom fishing. Here, we focus instead on areas on the Norwegian continental margin that are currently not fished, based on fishing data covering the years 2009–2020. Using these data and spatial prediction methods, we estimate that the surface sediment layer (0–2 cm) in unfished areas covering 765 600 km2 contains 139.2 Tg of organic carbon. Based on data from a meta-analysis of demersal fishing impacts on organic carbon density and estimated reductions in sediment thickness due to fishing-induced erosion, we estimate that 18.7 Tg (1.9–33.5 Tg) of organic carbon might be lost due to mobile bottom fishing in a scenario where each grid cell is fished evenly over the entire area and down to the full depth of the surface layer. Approximately one third of this vulnerable organic carbon is currently located in existing area-based protection measures. Additional protection could be guided by hotspots of vulnerable organic carbon, which are mainly found in the Barents Sea. We argue that the protection of vulnerable organic carbon that is at high risk of being lost e.g. in areas becoming accessible to fishing due to sea ice retreat such as in the northern Barents Sea should be given a high priority.

Marine sediments represent a hot spot of ecosystem services, but their integrity is increasingly put at risk by anthropogenic disturbance, most notably by demersal fisheries. The need for global action to minimize the impacts of destructive fishing techniques on the marine environment is urgent. The urgency to act, however, needs to be met with caution, as scientists are pushed for action, global predictions of trawling impacts are tempting, yet poor validation and oversimplified assumptions can lead to large uncertainties. We visit the scientific literature on trawl studies to map out current evidence from the literature and report on a global meta-analysis to quantify the effects of demersal fishing on sedimentary and biogeochemical properties. Studies examining the direct impacts of bottom fishing revealed significant reductions in total organic carbon (TOC; -10%), chlorophyll-a (Chl-a, -10%), phaeopigments (-21%) and proteins (-24%), and largest impact was detected on surficial sediment (0-2 cm). Implications of methodological biases as a result of inappropriate sampling in trawl studies and the importance of context-dependency for effect size is flagged up. Environmental parameters such as bottom current velocity and surface primary productivity significantly influenced both the direction and magnitude of fishing effects. We highlight where the lack of evidence lies that might create bias in regional and global models that require empirical data for validation. The objective is to summarize current knowledge and to direct future studies towards more robust analysis of the impacts of bottom trawling, which will provide a basis of sound advice to fisheries managers and policy makers.

Marine sediments are a significant sink for anthropogenic carbon dioxide (CO2)1. Bottom trawl fisheries constitute the most widespread physical disturbance to carbon-rich seabed habitats2. Recent research has sparked concern that this disturbance can turn marine sediments into a large source of CO23, but this is subject to ongoing debate4,5,6. Uncertainties exist regarding the effect of bottom trawling on carbon sequestration, remineralisation, and storage. To address this, we conducted a systematic review and meta-analysis of the existing literature to assemble a comprehensive, up-to-date database looking at how demersal mobile fishing affects: (i) the amount and type of carbon found in benthic sediments; (iii) the geochemical, biological, and physical parameters which control the fate of benthic carbon; (iii) the magnitude and direction of benthic-pelagic carbon fluxes; and (iv) the geochemical, biological, and physical parameters which control the fate of resuspended carbon. Here we present methodological details alongside preliminary findings of the resultant meta-analysis. We highlight the parameters which carry the greatest and least uncertainties and suggest key knowledge gaps to help target future field and laboratory studies to help better constrain the effect of bottom trawling on the benthic-pelagic carbon fluxes and processing.1. Atwood et al., 2020. Global patterns in marine sediment carbon stocks. Frontiers in Marine Science; 2. Hiddink et al., 2017. Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance. PNAS; 3. Sala et al., 2021. Protecting the global ocean for biodiversity, food and climate. Nature; 4. Hilborn and Kaiser, 2022. A path forward for analysing the impacts of marine protected areas. Nature; 5. Hiddink et al., 2023. Quantifying the carbon benefits of ending bottom trawling. Nature; 6. Atwood et al., 2023. Reply to: Quantifying the carbon benefits of ending bottom trawling. Nature.

The potential threat of fisheries on seabed carbon is a topic of growing concern, yet existing literature presents inconsistencies leaving experts divided on the topic. We conducted a global meta-analysis to synthesize the current knowledge and quantify how demersal fishing impacts various biogeochemical properties. Direct impact studies revealed overall reductions in chlorophyll-a (Chl-a, 17%), phaeopigments (24%), and proteins (32%). Effects on these reactive compounds were more pronounced on surface sediment (0-2 cm), where the impact on total organic carbon (TOC) also became significant, demonstrating the effect of gear penetration, and highlighting that sampling strategies combining sediment layers can mask observed effects. Current velocity and primary productivity significantly influenced the direction and magnitude of fishing impacts. Trawling-induced subsurface reductions of TOC in low-energy habitats may affect carbon sequestration due to the preferential removal of semi-reactive carbon. Intriguingly, fishing intensity gradient studies showed an average increase in TOC in chronically fished areas, possibly reflecting fishing preferences for meso-eutrophic grounds. We estimate a similar to 300-day recovery period post-fishing for Chl-a, though values for other parameters are less certain. Limited data on seasonality, gear types, and an under-representation of studies in tropical and deep-sea areas pose challenges to quantifying global scale geochemical impacts of demersal fisheries. Knowledge gaps persist in understanding the fate of disturbed organic matter including its mineralization, transport, and sequestration. Nonetheless, our insights and estimates provide foundational knowledge that can contribute to science-based approaches for spatial fisheries management while preserving natural carbon dynamics on the seabed.

Marine sediments are among the largest carbon reservoirs on the planet and play a key role in the global cycling of organic matter. Bottom fisheries are the most widespread anthropogenic physical disturbance to seabed habitats, prompting NGOs and governments to act on regulating mobile bottom-contacting fishing gear. However, the scientific evidence of the effects of bottom trawling on sediment biogeochemistry is highly diverse and presents contrasting results. Here we present a global harmonized dataset of 71 independent studies that assess the effects of demersal fisheries on sedimentological (i.e. grain size, porosity) and biogeochemical (i.e. organic carbon, phytopigments, nutrient fluxes) properties: the Demersal fishery Impacts on Sedimentary Organic Matter (DISOM) database (Paradis, 2023; https://doi.org/10.3929/ethz-b-000634336). We identify considerable gaps, namely in the geographical extension of the data; coverage of environmental predictors (i.e. seasons); fishing descriptors such as the availability of true controls, quantification of fishing effort, and distribution of fishing gear types; and biogeochemical variables that study the remineralization of organic matter. Future studies should address these data gaps to enhance the comprehensiveness of the dataset. With this harmonized database, we aim to allow researchers to explore the effects of demersal fisheries in variable environmental settings to disentangle the effects of this disturbance and provide efficient management strategies.

Global scallop fisheries are economically important but are associated with environmental impacts to seabed communities resulting from the direct physical contact of the fishing gear with the seabed. Gear modifications attempting to reduce this contact must be economically feasible such that the catch numbers for the target species is maintained or increased. This study investigated the outcome of reducing seabed contact on retained catch of scallops and bycatch by the addition of skids to the bottom of the collecting bag of scallop dredges. We used a paired control experimental design to investigate the impact of the gear modification in different habitat types. The modified skid dredge generally caught more marketable scallops per unit area fished compared with the standard dredge (+5%). However, the skid dredge also retained more bycatch (+11%) and more undersize scallops (+16%). The performance of the two dredges was habitat specific which indicates the importance of adjusting management measures in relation to habitat type. To realize the potential environmental benefits associated with the improvement in catchability of this gear modification, further gear modification is required to reduce the catch of undersize scallops and bycatch. Furthermore we advocate that technical gear innovations in scallop dredging need to be part of a comprehensive and effective fisheries management system.

Abstract Background Marine sediments represent one of the planet’s largest carbon stores. Bottom trawl fisheries constitute the most widespread physical disturbance to seabed habitats, which exert a large influence over the oceanic carbon dioxide (CO2) sink. Recent research has sparked concern that seabed disturbance from trawling can therefore turn marine sediments into a large source of CO2, but the calculations involved carry a high degree of uncertainty. This is primarily due to a lack of quantitative understanding of how trawling mixes and resuspends sediments, how it alters bioturbation, bioirrigation, and oxygenation rates, and how these processes translate into carbon fluxes into or out of sediments. Methods The primary question addressed by this review protocol is: how does mobile bottom fishing affect benthic carbon processing and storage? This question will be split into the following secondary questions: what is the effect of mobile bottom fishing on: (i) the amount and type of carbon found in benthic sediments; (ii) the magnitude and direction of benthic-pelagic carbon fluxes; (iii) the biogeochemical, biological, and physical parameters that control the fate of benthic carbon; and (iv) the biogeochemical, biological, and physical parameters that control the fate of resuspended carbon. Literature searches will be conducted in Web of Science, SCOPUS, PROQUEST, and a range of grey and specialist sources. An initial scoping search in Web of Science informed the final search string, which has been formulated according to Population Intervention Comparator Outcome (PICO) principles. Eligible studies must contain data concerning a change in a population of interest caused by mobile bottom fishing. Eligible study designs are Before and After, Control and Impact, and Gradient studies. Studies included at full-text screening will be critically appraised, and study findings will be extracted.Extracted data will be stored in an Excel spreadsheet. Results will be reported in narrative and quantitative syntheses using a variety of visual tools including forest plots. Meta-analysis will be conducted where sufficient data exists.