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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. This research was supported by travel funds from the University of South Alabama Department of Marine Science.

Ocean microplastic concentrations are known to vary significantly by location, with especially high levels in the North Atlantic and North Pacific gyres. Most direct measurements come from plankton net trawling made in these regions; concentrations in other regions have been estimated by microplastic transport models that depend on large-scale ocean circulation patterns. However, global measurements of microplastic distribution and its temporal variability are lacking. A new method is presented for detecting and imaging the global distribution of ocean microplastics from space. The method uses spaceborne bistatic radar measurements of ocean surface roughness and relies on an assumed reduction in responsiveness to wind-driven roughening caused by surfactants that act as tracers for microplastics near the surface. Annual mean microplastic distributions estimated by the radars are generally consistent with model predictions. The spaceborne observations are also able to detect temporal changes that are not resolved by the models. For example, seasonal dependencies are observed at mid-latitudes in both Northern and Southern Hemispheres, with lower concentrations noted in the winter months. Time lapse images at finer spatial and temporal scales reveal episodic bursts of microplastic tracers in the outflow from major river discharges into the sea. This new method will provide better monitoring of ocean microplastics and will support future model development and validation.

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.

The offshore Greenland halibut (Reinhardtius hippoglossoides) fishery, west Greenland, employs demersal trawl gear at depths of 800–1400 m. In contrast to many deep-sea fisheries, the target stock appears stable and the fishery is of significant economic importance. Recent Marine Stewardship Council certification of this fishery highlighted the paucity of knowledge of benthic habitats and trawling impacts, which this study aimed to address using a towed benthic video sled. The spatially discrete northern and southern areas of the fishery were found to be distinct in terms of the communities present, which non-metric multidimensional scaling suggests is primarily driven by temperature. Extensive physical evidence of trawling was observed. Trawling effort was significantly linked with community composition, with a negative association between trawling effort and abundance of some taxa, including some vulnerable marine ecosystem (VME) indicator species. Three potential VMEs are identified: (i) Flabellum alabastrum cup coral meadows; (ii) a Halipteris finmarchica sea pen field; and (iii) areas exhibiting mixed assemblages of VME indicators. Of immediate conservation concern is a H. finmarchica field, which seems to be at least regionally rare, is situated within the fringes of existing trawling effort and is currently afforded no protection by management measures.

Sea pen communities are United Nations General Assembly-designated Vulnerable Marine Ecosystems which occur worldwide in soft-bottom sediments where trawling often occurs. However, the ability of marine managers to assess, monitor and mitigate impacts to sea pens at national scales has been constrained by a limited understanding of their environmental requirements, geographical distribution and responses to trawling. In this study, we used random forest species distribution modelling (SDM) to predict the distribution of suitable habitat for 3 sea pen species (tall sea pen Funiculina quadrangularis, slender sea pen Virgularia mirabilis and phosphorescent sea pen Pennatula phosphorea) on the UK continental shelf, exploring the results relative to the distribution of fishing activity. Occurrence of all 3 species corresponded to areas of low current and wave velocity, where suspended matter in the water column was also low. However, for F. quadrangularis, the largest species, the models indicated substantially different drivers of distribution between the Greater North Sea and Celtic Seas ICES Ecoregions. This disparity appears to reflect modification to the range and realised niche of this species in the Greater North Sea, due to trawling impacts. P. phosphorea and V. mirabilis appear to be more resilient to trawling, with no clear negative relationships observed. Our findings illustrate the value of broadscale qualitative comparisons between SDMs and human activity data for insights on pressure-state relationships. When combined with robust distribution maps, this improved understanding of vulnerability will enable marine managers to make ecologically sound, defensible decisions and deliver tangible conservation outcomes for sea pen communities.

The objective of this study was to analyze the brachyuran crab assemblages associated with shrimp fishing on the central-southern coast of Veracruz. Information was collected using 46 trawls organized within nine fishing quadrants. The total catch shrimp, bycatch, and discard were recorded and standardized (CPUE kg h−1). Value index by species, species richness, diversity using Shannon and Weaver index, and equitability were determined. A total of 3055 individuals were collected, which corresponded to nine families, 13 genera, and 14 species. Achelous spinicarpus species were identified at the greatest relative abundance (77.74%). Four new species records for the zone: Hepatus pudibundus, Iliacantha liodactylus, Leiolambrus punctatissimus, and Platylambrus granulatus. Species richness varied according to fishing quadrant and depth interval assessed. The highest value of species richness was eight, and observed Margalef species richness index values ranged from 0 to 2.23. The diversity values ranged from 0 to 2.41 bits ind−1; this may indicate that a few species share the greatest impact of trawling. The presence of lagoon systems was determined to define a portion of the composition of the assemblage. Understanding assemblage structure is important to improve knowledge on the impact of shrimp trawling activity on the ecosystem.

The spatial and vertical distribution of larvae, juveniles, and adults of meso- and bathypelagic fish during the dark period of the day was analyzed at three areas in the tropical part of the Mid-Atlantic Ridge, located north and south of the Cape Verde Fault in the zone of the Russian exploration area. The material was collected at four standard layers of 250–0, 700–0, 1500–0, and 2500–0 m. In the study area, 127 species of juveniles and adult fish, belonging to 29 families, and 81 species of larvae, representing 32 families, were recorded. Species abundance and total abundance of deep-sea fish communities at different areas did not differ statistically, regardless of the trawling layer. In the night, the species diversity and average abundance of the fishes gradually increased ( from 25.9 to 531.6 sp./100 m2) with an increase of fishing depth from the surface up to a zone of 1500 m. The maximum fish abundance was observed nearby the summits and slopes of seamounts at a depth range of 700–1500 m. No signs of nighttime peaks in the abundance of deep-sea fish in the 250–0 m layer in the tropical part of the Mid-Atlantic Ridge were found. With increasing of the depth of fishing, the number of warm-water species of lanternfishes (Myctophidae), belonging to tropical and equatorial habitats, decreases, whereas the number of species with bicentral and central-peripheral ranges on the contrary increases. At greater depths there are also appear the subtropical species, preferring less warm water masses, and the species, inhabiting the continental slope and seamounts.

Most studies about benthic community use small-scale sampling methods focused on the infauna such as grabs or box-corers. The benthic data collected by scientific trawl surveys in all European waters, in the frame of the Common Fishery Policy Data Collection Multiannual Program, can be used to study the impact of large-scale fisheries such as trawling. However, the catchability of trawls is very dependent on the nature of the seabed as well as resulting ground-gear adaptations. Due to its non-destructive nature and its ability to focus on benthic macro-epifauna, towed video sampling appears to be a good alternative to monitor the impact of trawling on benthic communities. In the present work, we studied the influence of fishery induced seabed abrasion and video characteristics on nine indices, which can be used to monitor the effect of trawling on benthic communities, was studied. Among them, three indices specific to fishery effect detection based on biological traits appeared to be the best performing benthic indices with video data: modified-Trawling Disturbance Index, partial-Trawling Disturbance Index, and modified sensitivity index. The effectiveness of these indices to monitor the effect of trawling was evaluated and compared between trawl and video sampling. This work has highlighted that video sampling could be a good alternative, or at least a complementary method, to scientific trawling to monitor the effect of trawling on benthic communities in European waters.

14 pages, 5 figures, 4 tables, supplementary data https://doi.org/10.1093/icesjms/fsac123.-- Data availability statement: Data available on request, 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, The study was performed within and financed by the MICYT project RECOMARES (RTI2018-094066-B-I00) funded by Ministerio de Ciencia e Innovación, MICYIT, With the institutional support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

In the summer period of 2017, the threaded sculpin Gymnocanthus pistilliger occurred at depths from 14 (minimum depth of trawling) to 64 m in the Sea of Okhotsk off the western coast of Kamchatka. Areas of the maximum G. pistilliger concentrations are only partially similar in terms of fish mass and abundance. The maximum average catches in terms of biomass were recoded between 55° and 56° N, where a high abundance of the species was also recorded. The maximum average catches in terms of abundance were obtained southerly, between 53° and 54° N. The species is the most common and abundant to the depths of 40−50 m. The length of specimens varies within 6−26 (on average 18.3) cm. The ratio of males to females is 0.4 : 1. The smallest sizes of specimens of both sexes were recorded in the depth range of 14−20 m; the average sizes of males and females increase with depth. In the summer period, G. pistilliger occurs in a wide temperature range between 0.4 and 12.1°С on the West Kamchatka shelf. The highest catches of the species were recorded at the temperature of 1.0−3.5°С in the main part of the bathymetric interval, and at 3.5−6.0°С in a shallow zone. According to the results of summer surveys off the western coast of Kamchatka the estimated abundance of G. pistilliger was 146 million ind., and the biomass was 11200 t.

Seamounts and oceanic islands of the Chilean Exclusive Economic Zone at the intersection of the Nazca and Salas y Gómez ridges lie within one of the least explored areas in the world. The sparse information available, mainly for seamounts outside Chilean jurisdiction and shallow-water fauna of the Desventuradas Islands, suggests that the area is a hotspot of endemism. This apparent uniqueness of the fauna motivated the creation of the large Nazca-Desventuradas Marine Park (NDMP, ~ 300,000 km2) around the small islands San Felix and San Ambrosio in 2015. We report for the first time a detailed description of benthic microhabitats (i.e., centimeter to meter scale), macrohabitats (i.e., meter to kilometer-scale) and associated megafauna within the NDMP. Descriptions were based on analysis of fauna collected by trawling and ROV video observations from ~ 50 to 370 m depth. Rocky, coarse sand and silty sediment bottom habitats were observed at island slopes. In contrast, rocky and coarse sandy bottom habitats with a predominance of rhodoliths, thanatocoenosis, and other biogenic components were observed at seamounts. Mobile fauna and predators dominated the oceanic islands and nearby seamounts, whereas seamounts farther from the islands were dominated by sessile and hemisessile fauna that were mainly suspension and deposit feeders. Based on the register of 118 taxonomic units, our results provide an expanded and updated baseline for the benthic biodiversity of NDMP habitats, which seemed pristine, without evidence of trawling or anthropogenic debris.

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

On the northeastern flank of the Bay of Bengal, the St. Martin’s Island, a sedimentary continental formation, is the only maritime island and an Ecologically Critical Area of Bangladesh. Rock beds fringing the island from supratidal to subtidal zone with a subtidal depth around 10 m and presence of non-reef forming scleractinian corals from lower rocky intertidal to about 200–600 m offshore comprise a rich but least-explored rocky tidal habitat. Addressing the knowledge gap, during December 2017, an expedition was conducted to observe fish diversity caught in beach seines, gillnets and drifting handlines. Studying morphological and meristic characters of the collected specimens revealed 7 bony fish species for the first time in Bangladesh and northern seaboard of the Bay of Bengal. These are Ablennes hians, Callionymus erythraeus, Ellochelon vaigiensis, Grammatobothus polyophthalmus, Istiblennius dussumieri, Omobranchus punctatus, and Trichonotus setiger. The family Trichonotidae and the genera Ablennes, Callionymus, Grammatobothus, and Istiblennius, too, represent the first record for Bangladesh. Omobranchus punctatus, I. dussumieri, C. erythraeus and T. setiger were strongly associated with the tidal boulder beds. Grammatobothus polyophthalmus, a flounder threatened by shrimp harvesting, was caught in trawling gillnet operated in the surrounding subtidal waters. Ellochelon vaigiensis, a catadromous mullet known to spend natal stages near shoreline, was collected from a rock-pool. Fish diversity of the St. Martin’s Island is not well understood; the last comprehensive checklist dated back to 1997. Thus, these results remarkably obtained from a cursory expedition entail a thorough diversity assessment of the island.

Significant concentrations of Chub mackerel (Scomber japonicas) were found in 2014 in the area of the Southern Kuril Islands (Northwestern Pacific Ocean (NWPO)). Commercial fishing for Chub mackerel was resumed in the NWPO in 2016. In this connection, exploratory work and acoustic-trawl surveys are carried out to identify distribution and abundance of Chub mackerel in the NWPO. Acoustic abundance estimates of the stock size of Chub mackerel is important for fishing. However, the reflectivity of Chub mackerel is not well understood. Collections of in situ target strength (TS) signals and corresponding fish size measurements for Chub mackerel were obtained as a result of research in the NWPO (2015–2017). The calibrated scientific echo-sounder “EK‑60 Simrad” with two split-beam echo sounders of respectively 38 and 120 kHz was used to collect sonar data. Measurement of the TS of Chub mackerel was conducted at the trawl layer, which corresponds to the trawl opening per the trawling area. The echogram selection process and the filtering process of single targets of Chub mackerel are realize in the “SALTSE” software package (“TINRO”). The dependence of mean target strength (TS, dB) on mean fish length (L, cm) for was estimated as 20 log (L) — 72,8 dB at 38 kHz and as 20 log (L) — 73,6 dB at 120 kHz. The obtained values backscattering strength (Sv) of Chub mackerel in the NWPO are compared with the values Sv of other studies of the reflective properties of Scombridae.

Bottom trawling can cause acute depletion of benthic invertebrate biomass, thus reducing competition among surviving organisms and increasing food availability by generating carrion. As ectotherms are generally smaller and grow faster with increasing temperature, they may be less vulnerable to trawling and quicker to replenish biomass in warmer waters. Therefore, the chronic effect of bottom trawling on benthic invertebrate biomass may depend on local sea temperature and, hence, be under the influence of climate change. We tested this hypothesis using benthic grab samples from 200 sites spanning the North Sea and data on trawling pressure in the areas where samples were collected. The relationship between benthic community biomass and swept area ratio (the average number of times the seabed is trawled per year) was negative where annual bottom water temperature was low (8°C), positive in relatively warm water (11°C) and approximately neutral at intermediate temperature (9.5°C). These relationships were attributed to changes in mean body mass, not community abundance. Our results are consistent with theoretical expectations and suggest that climate modulates the chronic effect of bottom trawling on benthic invertebrate biomass. Confirming causality and determining the broader consequences for community structure and ecosystem functioning should be priorities of future research.

This study describes shore-based competitive fishing events in Ilhéus, southern Bahia (Brazil), including catch composition, and provides information on the profile of recreational fishers participating in these events. Information was collected in all events promoted by the Clube de Pesca de Ilhéus (CLUPESIL) in 2007-2008. A total of 26 competitive fishing events were organized during this period, with 47 species caught. The top species were: Cathorops spixii, Menticirrhus littoralis, Trachinotus goodei, Eucinostomus melanopterus, Polydactylus virginicus, Atherinella brasiliensis, and Eucinostomus argenteus. These seven species represented 87% of the total catch in number and 78% in weight. Menticirrhus littoralis and Polydactylus virginicus are species of commercial interest and their catch was dominated by juveniles. Local recreational fishers were predominately middle-aged men, who tended to use small hooks and mainly shrimp as bait. They were consumption-oriented, but also released small fishes. During competitions, fishers used even smaller hooks. Most of them perceived shrimp trawling as the main factor affecting recreational fisheries. The use of larger hooks and a minimum size of 20 cm are suggested to decrease the capture of juveniles, mainly those of commercial importance. This study sets a baseline from which new studies can be proposed to access the current status of local recreational fisheries.

Este artículo contiene 14 páginas, 7 figuras, 3 tablas., 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., project funded by the European Community (Grant agreement n◦ 312762). L.E.H. was supported by the Natural Environmental Research Council (grant number NE/L002531/). C.L.I. was supported by the H2020 MSC Action HABISS (GA 890815). We are grateful to the staff at the Environmental Sequencing facility at the National Oceanography Centre Southampton and to members of the EU-FP7 ISLAND (Exploring SiciLian CAnyoN Dynamics) Cruise. Finally, this work acknowledges the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S) to ICM-CSIC.

The city of Tarakan, Indonesia, benefits economically from abundant marine biological resources, one of which is the layur fish, known commercially as ribbonfish. The purpose of this study was to analyze the growth character of the layur fish (Lepturacanthus savala) obtained from the juata waters of Tarakan City. The method of this quantitative and descriptive study was to analyze the growth of layur fish Lepturacanthus savala in the Juata waters off the coast from the city of Tarakan. Body shape, length, weight, and ratio sex data were collected from sites selected by the purposive sampling method based on trawl fishing catch. Secondary data, collected from interviews of fishing personnel, included the number of catches using trawling gear and trawl fishing location. The length ranges of male from 20,4 to 54,0 cm with an average length of 37,2±16.8 cm (n = 255) and the length ranges of female from 20,5 to 68 cm with an average length of 44,25±23.75 cm (n = 275). The results showed that maximum length of male layur fish was smaller than the maximum length of female fish, which were 59.352 cm at 267 d and 72.638 cm at 315 d, respectively. The result shows a negative allometric growth pattern male and female layur fish was found to be the same and sex ratio of male to female has a ratio of 1,0: 1,8 with a percentage of males at 48.11% and females at 51.89%. The majority of male and female fish exhibited a thin body shape (51,4% of male and 52% of female).

Background. The interaction between Pterygoplichthys and Florida manatee (Trichechus manatus latirostris) was recorded approximately 13 years ago in Florida, United States. In Mexico, this interaction has not been documented neither in the wild nor in captivity. Until now it was supposed that Pterygoplichthys attach to manatees to forage the epibiota of the skin without causing any damage. However, some behaviour displayed suggests pain, stress, and discomfort when these fish attach to the manatee’s skin. Goals. To determine if the skin wounds found in three captive manatees are associated with the presence of Pterygoplichthys in the facilities where they are housed. Methods. By trawling a large artificial lagoon (AL) for three consecutive days, every six months for two and a half years we decimated the local population of Pterygoplichthys; in the management pool (MP), fish were removed manually. Additionally, we reduced the time individuals spent in the management facilities by releasing them into the AL. Results. Total disappearance of the skin wounds was achieved in three years, due to their decreased interaction with the catfish (both through the reduction of the population of Pterygoplichthys and of the time spent by the manatees in the MP). Conclusions. Injuries were caused by the fact that manatees lived in a small space, without food available for the catfish, which caused an increase in the frequency and aggressiveness of the encounters. Therefore, we recommend creating and implementing strategies to reduce Pterygoplichthys populations in places where manatees inhabit, because in the future the wounds they cause could be a potential threat for the long-term population viability of the endangered Antillean manatee.

Fisheries using bottom trawls are the most widespread source of anthropogenic physical disturbance to seafloor habitats. To mitigate such disturbances, the development of fisheries-, conservation-, and ecosystem-based management strategies requires the assessment of the impact of bottom trawling on the state of benthic biota. We explore a quantitative and mechanistic framework to assess trawling impact. Pressure and impact indicators that provide a continuous pressure–response curve are estimated at a spatial resolution of 1 × 1 min latitude and longitude (∼2 km2) using three methods: L1 estimates the proportion of the community with a life span exceeding the time interval between trawling events; L2 estimates the decrease in median longevity in response to trawling; and population dynamic (PD) estimates the decrease in biomass in response to trawling and the recovery time. Although impact scores are correlated, PD has the best performance over a broad range of trawling intensities. Using the framework in a trawling impact assessment of ten métiers in the North Sea shows that muddy habitats are impacted the most and coarse habitats are impacted the least. Otter trawling for crustaceans has the highest impact, followed by otter trawling for demersal fish and beam trawling for flatfish and flyshooting. Beam trawling for brown shrimps, otter trawling for industrial fish, and dredging for molluscs have the lowest impact. Trawling is highly aggregated in core fishing grounds where the status of the seafloor is low but the catch per unit of effort (CPUE) per unit of impact is high, in contrast to peripheral grounds, where CPUE per unit of impact is low.

Two alternative stimulation techniques to reduce mortality in benthic megafauna were tested relative to standard tickler chain beam trawling: longitudinal electrodes (pulse trawl) and longitudinal chains. Longitudinal chains caused higher mortality than pulse trawling in 3 species. Standard trawling gave higher mortality in Echinocardium cordatum than pulse trawling. Between longitudinal chain and standard trawling were no significant differences. This trend in decreasing mortality from longitudinal, to standard and then pulse trawling was confirmed by a similar decline in: i) numbers of significant species mortalities per trawl type, ii) average mortalities, i.e. longitudinal chain caused 41% more mortality than standard trawling and pulse trawling 43% less, iii) pre- and post-trawling community dissimilarities. A significant majority of species showed higher mortalities after longitudinal than after standard trawling and, conversely, lower mortalities after pulse trawling. Trawls with longitudinal chains instead of cross tickler chains increase megafaunal impact. On the contrary, pulse trawling can reduce the impact, although average mortality remains substantial (25%) even in impoverished benthic test assemblages in the southern North Sea. Power, generally was low and reference areas, free of (pulse) trawling, and inhabited by more vulnerable taxa will facilitate higher powered studies on the impact of standard and alternative trawling techniques.

The Mediterranean Sea shows a trend of increasing temperature and decreasing productivity from the western to the eastern basin. In this work we investigate whether this trend is reflected in the cephalopod assemblages found throughout the Mediterranean. Data obtained with bottom trawl surveys carried out during the last 22 years by EU Mediterranean countries were used. In addition to analysing spatial differences in cephalopod assemblages, we also analysed putative temporal changes during the last two decades. For this purpose, the basin was spatially divided into bioregions, the trawling grounds were subdivided into depth strata, and the dataset was split into two time series of 11 years each. All analyses were done using PRIMER software. The species richness did not vary with the longitudinal gradient, though in most bioregions it showed a mild decrease with depth before plummeting in the deepest waters. Cluster analysis revealed four different bathymetric assemblages in all bioregions. Despite the contrasting conditions between basins and the claims of biodiversity loss, our study revealed that spatial and temporal differences during the last two decades were restricted to changes in the relative abundance of species from a common pool of species inhabiting the whole Mediterranean. El mar Mediterráneo muestra un patrón de aumento de la temperatura y disminución de la productividad de la cuenca occidental a la oriental. En este trabajo se investiga si este patrón se refleja en las comunidades de cefalópodos que habitan el Mediterráneo. Se utilizaron datos obtenidos en campañas de arrastre de fondo realizadas durante los últimos 22 años por la mayoría de países mediterráneos de la UE. Junto con el análisis de las diferencias espaciales en las comunidades de cefalópodos, también se analizaron cambios temporales durante las dos últimas décadas. Para ello, la cuenca se dividió espacialmente en diferentes bioregiones, mientras que el conjunto de datos se dividió en dos series temporales de 11 años cada una. Todos los análisis se realizaron utilizando el software PRIMER. La riqueza específica no varió con el gradiente longitudinal, aunque en la mayoría de las bioregiones mostró una leve disminución con la profundidad antes de desplomarse en el estrato más profundo. El análisis cluster reveló cuatro comunidades batimétricas diferentes en todas las bioregiones. A pesar de las contrastadas condiciones ambientales entre las cuencas y las afirmaciones de pérdida de biodiversidad, nuestro estudio reveló que las diferencias espaciales y temporales durante las dos últimas décadas se limitaron a cambios en la abundancia relativa de las especies a partir de un conjunto faunístico común que habita todo el Mediterráneo.

The paper presents the results from a study of the population structure of alien snow crabs Chionoecetes opilio in the western Kara Sea near the Kara Strait using two methods: Sigsby trawling and video surveillance. The towed unmanned underwater vehicle Videomodule was used to estimate the population density of crabs: 0.55 ind/m2 in 2016, and 0.17 and 0.09 ind/m2 in 2017. No differences were revealed when comparing the size structure of the crab population based on the two methods. An exception is possible underestimation of younglings with a carapace width

Although fishing with electricity is illegal in the European Union, a number of temporary licences allowed converting beam trawlers to pulse trawling. To analyse how the adaption of pulse trawling changed this fishery, we studied fishing speeds and landings per unit effort as proxies for catch efficiencies for the main target species. Compared to conventional tickler chain beam trawls, pulse trawls were towed at lower speeds (small vessels −10%, large vessels −23%). Large vessels that switched from conventional beam trawls to pulse trawls at the end of 2009 gradually increased catch efficiency for sole over the period of almost 1 year. While pulse trawling was found to have higher catch rates (kg/h) for sole (small vessels +74%, large vessels +17%), lower catch rates were observed for plaice (small vessels −31%, large vessels −32%). Vessels that switched later achieved immediate gains in catch efficiency for sole. The change in catch efficiency is likely due to the difference in cramp response between the species.

The accumulation of human debris in the marine ecosystem is one of the main hidden negative impacts of the economic and social development that humanity has witnessed after industrialization era which comes accompanied with the evolution of productions, the consumerism, as well as the emergence of the throw-away culture. In this paper, we studied the marine debris pollution on the seafloor of the North and Central Moroccan Atlantic waters from Tangier (35° N) to Sidi Ifni(29° N). The data were collected during two scientific trawling surveys conducted aboard the Charif Elidrissi Vessel in February–March 2015 and March 2018. The prospection operations allowed to collect a total of 329 kg of Seafloor Marine Debris (SMD) with an average abundance ranging between 16.84 ± 20 kg/km2 to 30.15 ± 43 kg/km2. The plastic materials represented the higher percentage of collected items with more than 40% followed by textile debris which mainly composed of knotted fishing ropes used by the longliners in the area. The analysis of SMD composition and their Spatio-temporal pattern combined with the environmental and socio-economic parameters of the prospected area using GIS tools showed that the majority of collected items comes from fishing activities, and the rest comes from the coastal anthropogenic activities. Then the analysis of hydrodynamic properties of the area using AVISO data showed that the horizontal current in area that controls the exchange of water from the coastal area to the ocean interior plays a major role in scattering debris in this area far from their origins to the open ocean.

Of particular concern in commercial fishing catch is 'size bycatch', i.e., the death of early stages of resources that would reach a marketable value when they turn into adults. This event is frequently associated with trawling because of the lower size selectivity of this gear as compared to gillnets. However, this is expected when small-scale fisheries (SSF) employ gillnets simultaneously in setnets + driftnets that mix multiple mesh sizes. This work analyzes fishing captures and compares characteristics of fish catch from gillnets and trawlers with respect to size at first maturation, legal size of capture, and expected discards. Data were obtained from 2007-2021 for SSF in Southern Brazil. A total of 112 fish species were represented in the data. Gillnets exploited fewer species than trawlers; however, most of these constitute fishing resources in the study region. Of the 19 species whose maturation size is known, nine occurred in gillnets as juveniles, and of the 14 species for which the legal size of capture is established, seven occurred in gillnets in prohibited sizes. Gillnets and trawlers presented size bycatch and affected different species between them, with four resources that were present in bycatch from both gillnets and trawlers. The broad range of mesh sizes employed by SSF warns of the discarding of undersized captures, and stresses the importance of policies addressing gillnet management.

The objective was to analyse the relative growth and size structure of Achelous spinicarpus associated with trawling in Veracruz. The organisms came from shrimp trawls carried out in July 2013. There were 45 trawls organized in two depth intervals (B: 22 to 46 m and C: &gt, 46 m) and 14 fishing quadrants. Abundance, mean and standard deviation, by sex and depth interval, and sex ratio were determined. An ANOVA was applied to compare CW means, depth intervals and fishing quadrants. The CW-weight relationship was obtained, and growth type was also determined. Length-frequency analyses were carried out. A total of 2377 crabs were collected, 1164 males and 713 females. The overall average CW was 3.65 ± 0.7677 cm, the minimum value was 1.50 cm, and the maximum was 6.00 cm. For males, the average CW was 3.65 ± 0.8242 cm, with1.50 cm minimum value and 6.00 cm maximum value. The average CW of females was 3.64 ± 0.6164 cm, with 1.60 cm minimum value and 5.90 cm maximum value. There were no statistically significant differences in CW between males and females. However, there were significant differences between depth intervals (B and C) for the total and sex CW data. The sex ratio was 2.94:1 and 2.05:1 for depth intervals B and C, and 2.33:1 for the total data set. Growth type was allometric negative for both sexes and overall, with significant differences in slopes between sexes. There was a unimodal pattern for the two fishing depth intervals and for each sex, crabs were between 2.40 and 4.00 cm (77.64%) and between 2.56 and 5.12 (91.12%) for the B and C intervals, respectively. In males, 88.46% were between 2.40 and 4.80 cm, and 90.46% of females were between 2.72 and 4.64 cm. Achelous spinicarpus is an essential species in the structure of the brachyuran assemblage and in benthic communities, as well as a food resource for various species of demersal fish. Thus, the present study provides information on the population subjected to the impact of fishing activity in the area, allowing comparisons between different populations in the species’ area of distribution.

International audience; 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 (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.

In the Mediterranean Sea, where bottom trawling for demersal species is the most important fishery in terms of landings, around 75% of the assessed fish stocks are overfished. Its status as one of the world’s most heavily exploited seas and the one subject to the highest trawling pressure has become a global concern. An extensive review of bottom trawl selectivity studies was performed to assess the sustainability of this fishery in the Mediterranean; the selectivity parameters were collected from 93 peer-reviewed publications of 10 countries, totalling 742 records and 65 species. The review highlighted that i) the catch of bottom trawls commonly employed in the Mediterranean, even complying with current regulations on codend meshes, still includes immature individuals for 64-68% of the species investigated, and individuals under the minimum conservation reference size (MCRS) for 78% of the species investigated, and that ii) the MCRS set for 59% of the species analyzed is well below their length at first maturity, and is therefore ecologically inadequate. Although square-mesh codends are slightly more selective, the models developed herein demonstrate that improving size and species selectivity would require considerably larger meshes, which may significantly reduce profitability. The urgent need to reduce the biological impacts of bottom trawling in the Mediterranean should be addressed by promoting the adoption of more ecologically sustainable fishing gears through the introduction of more selective meshes or gear modifications.

In the Mediterranean Sea, the catch of bottom trawl fisheries is composed of a complex mix of fish and invertebrates with a considerable amount of discards. Seasonal composition of catches and discards of bottom trawls operating at different depths in the central Tyrrhenian Sea were investigated from October 2014 to October 2015. The mean total catch per unit effort (CPUE) ranged between 30.93±8.43 and 27.52±9.88 kg/h in shallow and deep fishing grounds, respectively. The discarded fraction of the catch was 39.9 % in shallow and 43.3% in deep fishing grounds. The mean CPUE of commercial target species were similar in shallow and deep trawling (10.81+5.82 vs 8.92±3.16 kg/h). The commercial bycatch was lower in shallow (6.66±1.25 kg/h) than in deep grounds (8.24±2.91 kg/h), whilst the discards were lower in deep (10.43±5.14 kg/h) than shallow grounds (13.43±5.29 kg/h). Overall, 246 species were caught during fishing operations, out of which 209 were included in discards. The number of species recorded in shallow grounds (199 caught species with 166 discarded) was higher than that recorded in deep grounds (116 caught species with 102 discarded). Fish were the most represented taxa in the shallow discards, followed by echinoderms; crustaceans, and were the main discarded taxa in deep water. Depth was the main factor affecting both commercial catches and discards composition, whereas the season affected the CPUE of main target species only. The results confirmed that discards were higher in shallow than in deep trawling, suggesting that the latter is more efficient than the former in catching fishery resources for human consumption. Understanding the factors that affect discarding is the starting point for adopting management measures to mitigate negative impacts of trawl fisheries on marine resources and benthic communities.

Conservation management of wildlife species should be underpinned by knowledge of their distribution and abundance, as well as impacts of human activities on their populations and habitats. Common dolphins (Delphinus delphis) are subject to incidental capture in a range of Australia’s commercial fisheries including gill netting, purse seining and mid-water trawling. The impact these fishery interactions have on common dolphin populations is uncertain, as estimates of abundance are lacking, particularly for the segments of the populations at risk of bycatch and in greater need of protection. Here we used double-observer platform aerial surveys and mark-recapture distance sampling methods to estimate the abundance of common dolphins in 2011 over an area of 42,438 km2 in central South Australia, where incidental mortality of common dolphins due to fisheries bycatch is the highest. We also used the potential biological removal (PBR) method to estimate sustainable levels of human-caused mortality for this segment of the population. The estimated abundance of common dolphins was 21,733 (CV = 0.25; 95% CI = 13,809–34,203) in austral summer/autumn and 26,504 in winter/spring (CV = 0.19; 95% CI = 19,488–36,046). Annual PBR estimates, assuming a conservative maximum population growth rate of Rmax = 0.02 and a recovery factor of Fr = 0.5 for species of unknown conservation status, ranged from 95 (summer/autumn) to 120 dolphins (winter/spring), and from 189 (summer/autumn) to 239 dolphins (winter/spring) with an Rmax = 0.04. Our results indicate that common dolphins are an abundant dolphin species in waters over the central South Australian continental shelf (up to 100 m deep). Based on the 2011 abundance estimates of this species, the highest estimated bycatch of common dolphins (423 mortalities in 2004/05) in the southern Australian region exceeded the precautionary PBR estimates for this population segment. Recent bycatch levels appear to be below PBR estimates, but low observer coverage and underreporting of dolphin mortalities by fishers means that estimates of dolphin bycatch rates are not robust. The effects of cumulative human impacts on common dolphins are not well understood, and thus we recommend a precautionary management approach to manage common dolphin bycatch based on local abundance estimates.

The coronavirus disease 2019 (COVID-19) has brought a global socio-economic crisis to almost all sectors including the fishery one. In order to limit the infection, the Governments adopted several containment measures. In Italy, Croatia and Slovenia a lockdown period was imposed from March to May 2020, during which many activities, including restaurants, had to close or limit their business. All of this caused a strong reduction in seafood request and consequently a decrease in fishing activities. The aim of this work is to investigate the indirect effect of the COVID-19 in the Northern and Central Adriatic fleet, by comparing the fishing activities in three periods (before, during and after the lockdown) of 2019 and 2020. The use of the Automatic Identification System (AIS) data allowed us to highlight the redistribution of the fishing grounds of the trawlers, mainly located near the coasts during the 2020 lockdown period, as well as a reduction of about 50% of fishing effort. This reduction resulted higher for the Chioggia trawlers (-80%) and, in terms of fishing effort decrease, the large bottom otter trawl was the fishing segment mainly affected by the COVID-19 event. Moreover, analysing also the landings of the fleet of the Chioggia and of the Venice lagoon fleets it was possible to point out a strong reduction both in landings and profits ranging from -30%, for the small-scale fishery operating at sea, to -85%, for the small bottom otter trawl.

Bottom trawling is known to affect benthic faunal communities but its effects on sediment suspension and seabed biogeochemistry are less well described. In addition, few studies have been carried out in the Baltic Sea, despite decades of trawling in this unique brackish environment and the frequent occurrence of trawling in areas where hypoxia and low and variable salinity already act as ecosystem stressors. We measured the physical and biogeochemical impacts of an otter trawl on a muddy Baltic seabed. Multibeam bathymetry revealed a 36 m-wide trawl track, comprising parallel furrows and sediment piles caused by the trawl doors and shallower grooves from the groundgear, that displaced 1,000 m3 (500 t) sediment and suspended 9.5 t sediment per km of track. The trawl doors had less effect than the rest of the gear in terms of total sediment mass but per m2 the doors had 5× the displacement and 2× the suspension effect, due to their greater penetration and hydrodynamic drag. The suspended sediment spread >1 km away over the following 3–4 days, creating a 5–10 m thick layer of turbid bottom water. Turbidity reached 4.3 NTU (7 mgDW L–1), 550 m from the track, 20 h post-trawling. Particulate Al, Ti, Fe, P, and Mn were correlated with the spatio-temporal pattern of suspension. There was a pulse of dissolved N, P, and Mn to a height of 10 m above the seabed within a few hundred meters of the track, 2 h post-trawling. Dissolved methane concentrations were elevated in the water for at least 20 h. Sediment biogeochemistry in the door track was still perturbed after 48 h, with a decreased oxygen penetration depth and nutrient and oxygen fluxes across the sediment-water interface. These results clearly show the physical effects of bottom trawling, both on seabed topography (on the scale of km and years) and on sediment and particle suspension (on the scale of km and days-weeks). Alterations to biogeochemical processes suggest that, where bottom trawling is frequent, sediment biogeochemistry may not have time to recover between disturbance events and elevated turbidity may persist, even outside the trawled area.

In 2020, the developing COVID-19 pandemic disrupted fisheries surveys to an unprecedented extent. Many surveys were cancelled, including those for walleye pollock (Gadus chalcogrammus) in the eastern Bering Sea (EBS), the largest fishery in the United States. To partially mitigate the loss of survey information, we deployed three uncrewed surface vehicles (USVs) equipped with echosounders to extend the ship-based acoustic-trawl time series of pollock abundance. Trawling was not possible from USVs, so an empirical relationship between pollock backscatter and biomass established from previous surveys was developed to convert USV backscatter observations into pollock abundance. The EBS is well suited for this approach since pollock dominate midwater fishes in the survey area. Acoustic data from the USVs were combined with historical surveys to provide a consistent fishery-independent index in 2020. This application demonstrates the unique capabilities of USVs and how they could be rapidly deployed to collect information on pollock abundance and distribution when a ship-based survey was not feasible. We note the limitations of this approach (e.g. higher uncertainty relative to previous ship-based surveys), but found the USV survey to be useful in informing the stock assessment in a situation where ship-based surveys were not possible.

Riverine outflow is one of the major pathways for microplastic transportation to coastal environments. Research on the output of microplastics in small- or medium-sized rivers will help accurately understand the status of their marine loads. In this study, we used both trawling and pumping methods to collect microplastics of different sizes in the Jiulong River Estuary and Xiamen Bay. We found that the abundance of small microplastics (44 μm–5.0 mm) was at least 20 times higher than the large particles (0.33–5.0 mm). The abundance of the large particles ranges from 4.96 to 16.3 particles/m3, and that of the small particles ranged from 82.8 to 918 particles/m3. Granule was the dominant shape (>60%), and polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) were the most common components. The riverine flux of small microplastics (44 μm–5 mm, 472 ± 230 t/y) was at a medium level and was eight times greater than that of large particles (0.33–5.0 mm, 61.2 ± 2.6 t/y). The behavior of the large microplastics was relatively conservative, whose abundance had a significant correlation with salinity (R2 = 0.927) and was mainly influenced by physical factors. In contrast, results of statistical analysis revealed that more complicated factors influenced the small microplastics.

Trawl fisheries have been shown to cause overfishing and destruction of benthic habitats in the seabed. To mitigate these impacts, a trawling ban has been enforced in Hong Kong waters since December 31, 2012 to rehabilitate the ecosystem and enhance fisheries resources. Previous studies demonstrated that reduced trawling activities would increase the heterogeneity of benthic habitats, thereby enhancing species richness and abundance of benthic fauna and providing more prey resources for predatory fishes. This study aimed to test a hypothesis that the population and trophic dynamics of the Bartail flathead Platycephalus indicus, a heavily fished benthic predatory fish, at inner and outer Tolo Channel of Hong Kong (i.e., EI and EO) improved with increases in their body size, abundance, biomass, trophic niche, and trophic position after the trawl ban. Samples were collected from trawl surveys before and after the trawl ban to compare the pre-ban and post-ban populations of P. indicus from EI and EO. Body size, abundance, and biomass were assessed in 2004, 2013–2014, and 2015–2016, whereas trophic niche and trophic position were analyzed based on stable isotopes of fish samples collected in dry season of 2012, 2015, and 2018. Following the trawl ban, the abundance and biomass of P. indicus increased in EO, with body size increased in EI. Furthermore, as indicated by the results of stable isotope analysis (SIA) on their tissues and prey items, trophic niche, and trophic position of P. indicus increased in EI and EO, respectively. Our study demonstrated that the trawl ban had promoted the recovery of a predatory fish population through restoring size structure and trophic dynamics.

International audience; Realistic assessments of the ecological status of benthic habitats, as requested by European directives such as the Water Framework Directive and the European Marine Strategy Framework Directive, require biotic indices capable of detecting anthropogenic impact without having preliminary knowledge of the occurring pressures. In this context, a new general-purpose biotic index (GPBI) based on the deviation of benthic macrofauna community composition and structure from a valid reference (i.e., good ecological status) is proposed. GPBI is based on the assumption that as a site becomes impacted by a pressure, the most sensitive species are the first to disappear, and that stronger impacts lead to more important losses. Thus, it explicitly uses the within-species loss of individuals in the tested station in comparison to one or several reference stations as the basis of ecological status assessment. In this study, GPBI is successfully used in four case studies considering the impact of diversified pressures on benthic fauna: (1) maerl extraction in the northern Bay of Biscay, (2–3) dredging and trawling in the North Sea, and (4) hypoxic events at the seafloor in the Gullmarfjord. Our results show that GPBI was able to efficiently detect the impact of the different physical disturbances as well as that of hypoxia and that it performs better than commonly used pressure-specific indices (M-AMBI and TDI). Signal detection theory was used to propose a sound good/moderate ecological quality status boundary, and recommendations for future monitoring are also provided based on the reported performance of GPBI.

Length-length relationships (LLRs) and length-weight relationships (LWRs) were determined for four marine fish from Iranian waters of the Strait of Hormuz: Pseudotriacanthus strigilifer, Rhinobatos annandalei, Muraenesox cinereus, Nematalosa nasus belonging to four families Triacanthidae, Rhinobatidae, Muraenesocidae, Clupeidae. Specimens were collected monthly between October to December 2018 from artisanal shrimp vessels equipped with non-selective bottom trawl net (with mesh size of 20 and 40 mm, respectively at cod-end and body of trawl net). Trawling operation carried out in a depth range of 2 to 20 m. Total length (TL) (nearest to 0.1 cm) and body weights (nearest 0.1 g) were taken each individual. The result of this research provides first length-weight relationship references for R. annandalei and P. strigilifer and first LLR for R. annandalei and new maximum total length for M. cinereus. Estimated parameters of the LLR and LWR models (a and b value) of the equation WB = a(TL)b and TL = a + b(SL) were highly significant (P

The Acoupa weakfish Cynoscion acoupa (Lacepí­¨de, 1801) is a large inshore sciaenid of commercial and social importance found along the entire Brazilian coast. In spite of this, there is few information on the species, both in terms of biological aspects and fishery yields, particularly off southeastern Brazil. Within this context, this study aimed to an evaluation of Acoupa weakfish fishery production off São Paulo coast (23°22’í 25°18’S) based on publicly available statistical data collected between 1998 and 2016. Acoupa weakfish fishery in this State takes place on both industrial and artisanal scales, and employs at least 22 different fishing gears. The pair-trawling fishery was the most important Acoupa weakfish producer during the period surveyed, with a sharp decline in the catches from 2007 onward due to the establishment of Marine Protected Areas off São Paulo coast, which banned trawling in depths shallower than 26 meters. Acoupa weakfish yields were relatively low in São Paulo when compared with other demersal fishes exploited, despite the high retail prices commanded by the species in regional markets and restaurants.

Bottom trawling accounts for nearly a quarter of wild-capture seafood production, but it is associated with physical disturbance of the seabed leading to changes in benthic abundance, habitat structure, and biogeochemical processes. Understanding the processes of benthic depletion and recovery in relation to different types of fishing gears, and in different seabed types, is an important pre-requisite to inform appropriate management measures to limit or reduce the effects of trawling on the seabed. The combined approaches of meta-analysis and modelling that link fishing-gear penetration of the seabed to benthic depletion, and recovery to taxon longevity, have enabled the development of a modelling framework to estimate relative benthic status in areas subject to trawling. Such estimations are highly sensitive to the spatial resolution at which fishing footprint (trawl track) data are aggregated, and this leads to overinflated estimates of fishing impacts on benthos when coarse-level aggregation is applied. These approaches present a framework into which other “sustainability” criteria can be added, e.g., the consideration of carbon footprints of fishing activities.

Based on experiments, a trawling-induced erosion dynamics was included in a 3D realistic and pre-validated hydro-sedimentary model so as to assess its contribution to the overall regional sediment dynamics in the specific case of the Bay of Biscay continental shelf. The effect of trawling was investigated throughout a 5-year period in terms of horizontal/vertical fluxes and changes in seabed mud content, and compared to the natural variability of sediment fluxes at different spatio-temporal scales. Trawling is shown in the model to significantly contribute to sediment re-suspension, and changes in the seabed at the scale of the shelf. The contribution of trawling to re-suspension is >80% during the high fishing season at many locations on the outer shelf and over the Grande-Vasiere area (a large and intensively trawled muddy zone located in the middle of the shelf). The contribution of trawling is significantly weaker in winter and at annual scale, particularly over zones with (muddy-) sand facies (between 1‰ and 1%), but remains high, and reaches 20% of the annual erosion over muddy areas (e.g. northern part of the Grande-Vasiere). This significant trawling-induced erosion dynamics results in high sediment fluxes which increase natural poleward dynamics from a few percent up to 40%, and contributes to the natural offshore export of sediment on the outer shelf (e.g. +35% of mud fluxes along the 130 m isobath). It is noteworthy that trawling-induced fluxes are larger in winter although the corresponding re-suspension is lower than in summer: this is due to stronger near-bottom flows occurring at this period (largely influenced by energetic wind conditions). In contrast, on the inner shelf, trawling-induced sediment fluxes are rather oriented towards the coast. Finally, simulation results reveal a trawling signature on changes in the seabed. A significant decrease (between 10% and >50%) in mud content is simulated over trawling hotspots, especially over the internal part of the Grande-Vasiere and on mud patches located in front of the Gironde estuary. Conversely, trawling causes or intensifies mud deposition on both sides of these preferentially trawled areas.

Two separate efforts to characterize epibenthic communities in the northern Bering and Chukchi seas using video imagery from a drop camera system have now been completed. In the initial phase in 2008, we acquired video imagery from the USCGC Healy while drifting on station during the multidisciplinary Bering Sea Program and used cluster analysis and non-metric multidimensional scaling to identify epibenthic assemblage types and associated sediment characteristics based upon along-track epifaunal counts. We also quantified the areal density of easily recognizable organisms such as brittle stars (Ophiura sp.) and sea stars, which were abundant and easily identified. While sampling was not extensive enough to rigorously compare the density of epifauna with trawling data available from prior years, our observations confirmed the characteristics of epifaunal communities sampled through much more labor-intensive trawling. Densities of epifauna that could be readily enumerated were of the same order of magnitude in both types of observations. During the second phase in 2016 and 2017 of video observations from the CCGS Sir Wilfrid Laurier, we improved the quality of imagery, and obtained seafloor video footage from each station in the internationally coordinated sampling grid in the Distributed Biological Observatory (DBO). This grid lies in the productive waters of the northern Bering and Chukchi seas. Quantitative analysis was not undertaken in this second phase, but the imagery confirms the presence of specific organismal community assemblages that can be related to environmental factors such as sediment grain size and water mass identity that are available from other project data collected during the Bering Sea and DBO projects. For example, sandier sediments typically had diverse epifaunal communities including filter feeders as significant community components. In muddier sediments, deposit feeders such as brittle stars predominated. All the second phase video footage has been posted in both abbreviated form on the video-sharing website youtube.com, and longer (10 min per station) versions are freely downloadable from a Google Drive server. Future videography may help identify changes in epibenthic diversity and community composition and could be successfully evaluated with crowd-sourced citizen science and/or more traditional scientific documentation.

In world fisheries, incidental non target species mortality have turned in a permanent debate issue. Although many studies have dealt with these interactions from a descriptive overview, there is little information based on fishing operations data. One of the most important species that have awakened scientific concern are seabird, being southern Chile one of the areas with the highest levels in this kind of interactions. In order to improve our understanding on these relationships, we analyze records of fishing hauls of industrial trawlers off the coast of Chile between 39 and 57°S. The results showed that incidental seabird mortality appears to be affected mainly by the collisions with net monitoring systems (net-sonde cable), the duration of fishing hauls, the year period, and the fishing zones, these last related to the breeding period and areas of albatross colonies. We indirectly address a probable relationship between seabird mortality and fishing discards, and some hypothesis are proposed to explain the results. Finally, we demonstrated that longer fishing hauls are less efficient for fishing, beside to a high seabird mortality. Our findings suggest mitigation actions that would harmonize fishing activity with the ecosystem, in particular, for trawl fishing management and operations off far southern Chile.

The abundance and distribution of Northern anchovy (Engraulis mordax) and young of the year (YOY) rockfish (Sebastes spp.) are critical for the survival and reproduction of seabirds, mammals, and predatory fish within the California Current Ecosystem. Traditional detection and quantification of forage fish by trawling can be time consuming and expensive, and may not provide the spatio-temporal resolution needed to examine ecological relationships in quickly-changing marine environments. In an effort to accurately sample forage fish with less expense and higher resolution, this study combined seabird diet and acoustic descriptors to quantify anchovy schools and YOY rockfish in hydroacoustic surveys conducted between 2004 and 2015. Anchovy-like schools were selected from echograms assuming a volume backscattering strength (Sv) range of −47.6 to −42.9 dB. YOY rockfish-like single targets were selected considering a target strength (TS) range between −52.8 to −50.9 dB, calculated from lengths of fish consumed locally by three piscivorous seabirds. Acoustics indices of forage fish were significantly correlated with abundance catches from trawl data collected from an ecosystem assessment survey and relative abundance estimated from breeding seabird diet data. Inter-annual and seasonal indices of forage fish indicated strong anchovy occurrence during 2004–2008 and increased YOY rockfish from 2011 to 2015. These observations confirm previously described changes in upwelling and forage fish variability off central California. Importantly, these results provide new information on the spatio-temporal variability of the vertical and cross-shelf distribution of anchovy schools and will benefit the design of habitat preference models for anchovy and predators. To verify the acoustics, indices were compared to trawl data from an ecosystem assessment survey and relative abundance estimated from seabird diet data collected from locally-breeding piscivorous seabirds. Results add to the existing knowledge of how these species distribute in the water column, and with regards to anchovy provide insight on how they distribute across the shelf in opposing ocean phases. In addition, acoustic indices derived for both forage fish species showed a significant coherence with both the trawl surveys and seabird diets. Combining acoustic methodologies with trawl data and predator diet can be used to monitor distribution and temporal variability of forage fish species to benefit conservation of top marine predators.

Source at https://doi.org/10.3354/meps12803. The Arctic Barents Sea is experiencing a record temperature increase, a poleward shift in the distributions of commercial fish stocks, and invasion by the snow crab, a new predator. To evaluate benthic community vulnerability when exposed to seawater warming, bottom trawling, and predation from a new predator, we used a trait-based approach and applied this to an extensive dataset of >450 megabenthic taxa, from a 1.5 million km2 area. Taxon rank values were obtained after sorting the taxa by temperature median and temperature range, i.e. the temperature sensitivity trait, and by body height, mean weight, and mobility, i.e. the trawl vulnerability trait, and were given as a size-based prey classification, i.e. the predation trait. The taxon rank values were then used to calculate the mean community sensitivity. Our study showed a recent significant increase in community mean temperature ranks, indicating an increased importance of species with affinity for warmer waters and a reduced importance of coldwater species. Commercial fish stocks and snow crabs are expanding into the western part of the Barents Sea, thereby simultaneously increasing the exposure of large immobile species to trawling and of small prey species to crab predation. Overall, we found a high level of vulnerability to the 3 investigated stressors in the northwestern Barents Sea, which may lead to alterations in community structure and diversity. Mapping vulnerability to multiple stressors enables authorities managing human activities to identify vulnerable areas that warrant special measures, including protection from trawling and reduction of the snow crab stock.

High-resolution vessel monitoring (VMS) data have led to detailed estimates of the distribution of fishing in both time and space. While several studies have documented large-scale changes in fishing distribution, fine-scale patterns are still poorly documented, despite VMS data allowing for such analyses. We apply a methodology that can explain and predict effort allocation at fine spatial scales; a scale relevant to assess impact on the benthic ecosystem. This study uses VMS data to quantify the stability of fishing grounds (i.e. aggregated fishing effort) at a microscale (tens of meters). The model links effort registered at a large scale (ICES rectangle; 1° longitude × 0.5° latitude, ˜3600 km2) to fine spatial trawling intensities at a local scale (i.e. scale matching gear width, here 24 m). For the first time in the literature, the method estimates the part of an ICES rectangle that is unfavourable or inaccessible for fisheries, which is shown to be highly stable over time and suggests higher proportions of inaccessible grounds for either extremely muddy or courser substrates. The study furthermore shows high stability in aggregation of fishing, where aggregation shows a positive relationship with depth heterogeneity and a negative relationship with year-on-year variability in fishing intensity.