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Disentangling the role of factors responsible for juvenile fish dispersal is essential to understand the ecology of individual species, setting the corresponding conservation status and evaluating the potential risk in case of invasion. Because of their small body size and high sensitivity to environmental conditions, juvenile fish movements have largely been explained by external factors such as wind-induced water currents. In this study, early hatched pikeperch (Sander lucioperca) of hatchery origin were marked with oxytetracycline hydrochloride, stocked into a bay near the dam of a deep reservoir, and then monitored at approximately 10-day intervals using fix-frame trawling for 43 and 51 days after stocking, in 2007 and 2008, respectively. In both years, marked pikeperch were captured throughout the study period in the bay and closed dam section of the reservoir. After one month, individuals were captured in the middle section of the reservoir, approximately 5 km upstream from the stocking site. Four individuals were recaptured in the tributary section of the reservoir, about 10 km upstream from the stocking site during the last sampling in 2007. The farthest distance detection followed periods of strong wind. During daytime sampling, marked pikeperch were captured in both the warm epipelagic layer above the thermocline and the cold bathypelagic layer below the thermocline. The later sampling represented a community of vertically migrating individuals originally thought to consist only of reservoir-born and reservoir-experienced fish. This study suggested the high mobility and flexibility of 0+ pikeperch, as well as their unexpected behavioral plasticity.

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.

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

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.

In response to concerns over the mortality of discards and other negative environmental impacts of otter trawling for penaeids, the utility of bottom-set gillnets deployed by artisanal vessels to target Penaeus monodon, Metapenaeus affinis and other retained species by-product was assessed in the Sea of Oman. Two gillnets (each comprising several 80-m panels for total lengths of up to 1.3 km) were diurnally fished at two locations (off Beris and Govater, eastern Iran) within established penaeid fishing grounds. During 30 days, the total catch was 2721 kg, comprising penaeids (981 kg), eight retained by-product species (598 kg and mostly Otolithes ruber, Cynoglossus bilinearus and Carangoides talamparoides) and 19 discarded species (1142 kg). The catch-per-unit-of-effort (CPUE, kg/gillnet-panel · hour-fished) of targeted penaeids and by-product varied significantly between areas (0.5–1.0 kg), but nevertheless reached economically viable levels. The CPUEs of total bycatch were similar at both sites (

Tickler chains are simple additions to the ground gears of benthic trawls that can improve the catches of some target species, albeit with considerable variability. The purpose of this study was to decipher some of the technical variability associated with tickler chains used with generic, paired trawls targeting school prawns, Metapenaeus macleayi. In the first of two experiments, single tickler chains were either attached between the trawl otter boards or the wing ends and compared against each other and a control trawl (no tickler chain). Attaching the tickler chain to the otter boards significantly reduced wing-end spread and the trawled area without significantly affecting catches of school prawns. By comparison, attaching the tickler chain to the wing ends maintained spread and resulted in significantly more school prawns being caught (by 1.11 ×) than in the control trawl, and also fewer numbers of one teleost species, pink-breasted siphonfish, Siphamia roseigaster. In experiment two, a single tickler chain was compared against one with multiple chains and one with a double chain; all attached at the wing ends. Trawls with the multiple- and double-tickler chains had the same wing-end spread as those with the single tickler chain, while retaining up to 1.17 × more school prawns, and for the double-chain tickler, 45% fewer southern herring, Herklotsichthys castelnaui. The results are attributed to mechanical and visual stimuli affecting school prawns and some fish, respectively, and support maximising the surface area of tickler chains within the wing ends as a means for improving penaeid-trawl species selectivity without affecting swept area.

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.

Abstract Fisheries resources in Hong Kong have been overexploited since the 1970s due to intensive bottom trawling and other fishing activities that have depleted stocks and destroyed marine habitat. To rehabilitate depleted fisheries resources, a permanent ban on trawling in Hong Kong territorial waters came into force on December 31, 2012. In order to determine whether the trawl facilitated recovery of fish communities, trawl surveys were conducted at two sites in each of the eastern, southern and western (estuarine) coastal waters of Hong Kong before and three years after the trawl ban. A total of 315 species and 86 families of fishes in nine feeding groups were encountered during the surveys. Mean trophic level of the fish community, abundance and biomass of total fishes and of predatory fishes increased in eastern and western waters after the ban, but no changes or declines in these metrics were observed in southern waters. Although initial recovery in fish community were observed in eastern and western waters, anthropogenic disturbances might hinder the recovery process, including a large-scale reclamation for construction of coastal infrastructures in the west, illegal trawling, and expansion of non-trawling fishing efforts in the southern and eastern waters. Longer term monitoring is needed to evaluate the effects of the trawl ban, and determine whether recovery in the southern waters will continue to be constrained by the anthropogenic disturbances. Graphic abstract

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.

The relationship between fish functional diversity and fishing levels at which its baselines shift is important to identify the consequences of fishing in ecosystem functioning. For the first time, we implemented a trait-based approach in the Argentine Patagonian sea to identify the vulnerability and spatiotemporal changes in functional diversity of fish assemblages bycatch by a trawling fleet targeting the Argentine red shrimp Pleoticus muelleri (Spence Bate, 1888) between 2003 and 2014. We coupled seven fish trophic traits to a reconstructed fish assemblage for the study area and bycatch and evaluated changes in fish species richness and four complementary functional diversity metrics [functional richness, redundancy, dispersion, and community trait values] along with fishing intensity, temporal use, latitudinal location, and depth of fishing grounds. Resident fishes larger than 30 cm in TL, with depressed and fusiform bodies, intermediate to high trophic levels, and feeding in shallow benthic, benthodemersal, and benthopelagic areas were vulnerable to bycatch. Fish assemblages exhibited a low functional trait redundancy, likely related to species influxes in a biogeographic ecotone with tropicalisation signs. Significantly increases in fish trait richness and dispersion polewards and with depth suggested new functional roles in these grounds, matching trends in community body size, reproductive load, maximum depth, trophic level, and diet breadth. Finally, a temporal increase in fish species and functional trait removal in fishing grounds led to trait homogenisation since the first year of trawling. The identified tipping points in temperate fish functional trait diversity highlight trait-based approaches within ecosystem-based fisheries management.

Demersal shrimp trawling is among the least selective fishing methods, posing a considerable threat to marine ecosystems due to the catch of nontarget species (bycatch). Even when bycatch is immediately released, physical damage to organisms may reduce their survival. The probability of long-term survival and oxidative stress markers of two species of Sciaenidae fish, Paralonchurus brasiliensis and Stellifer rastrifer, caught incidentally while trawling for shrimp in the State of Parana—Brazil, were analyzed. The mortality rate for both species was found to be high (P. brasiliensis, 76.94%, n = 337 and S. rastrifer, 69.32%, n = 2.586). Among other factors, mortality was associated with body size and the physical damage suffered. Smaller fish showed a higher incidence of damage, most commonly scale-loss and contusions or haematomas on the head and body. The mortality rate and catch damage index (CDI) were similar for both species, but were aggravated by higher tow durations (15, 30, and 45 min). The CDI can be a good predictor of mortality. The probability of survival improved in winter for both species. Increased lipid peroxidation and protein carbonylation were identified in P. brasiliensis but not in S. rastrifer. This indicates that the two species responded in different ways to the stressful conditions produced by trawling. Considering the oxidative stress markers identified, it appears that the high mortality rate recorded in two species was more closely associated with physical damage than oxidative stress markers.

Made available in DSpace on 2022-04-29T08:32:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Brazilian endemic batoid elasmobranch populations have declined dramatically in the past 40 years due to anthropic activities (e.g., overfishing). The Brazilian guitarfish, Pseudobatos horkelii, included in the IUCN red list of endangered species [Critically Endangered (CR)], has been captured as by-catch by trawling fishing boats to the edge of extinction. Despite governmental conservation initiatives, the species is still caught and commercialized along the Brazilian coast. In this study, the authors report three rare aggregation events for the Brazilian coast of P. horkelii, inside the only nearshore no-entry Brazilian marine protected area. Strategies for its protection are also discussed. Laboratory of Ichthyology Department of Oceanography Federal University of Espírito Santo Marine Macroecology and Biogeography Laboratory Department of Ecology and Zoology Federal University of Santa Catarina Universidade Federal do Rio de Janeiro Instituto de Biodiversidade e Sustentabilidade NUPEM/UFRJ Avenida São José Barreto Biology of Teleosts and Elasmobranchs Laboratory (LABITEL) Department of Ecology and Zoology Federal University of Santa Catarina Elasmobranch Research Laboratory São Paulo State University Campus do Litoral Paulista Pça. Infante Dom Henrique Elasmobranch Research Laboratory São Paulo State University Campus do Litoral Paulista Pça. Infante Dom Henrique

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.

Posljednjih desetljeća brojne ljudske djelatnosti, ponajviše turizam i intenzivno ribarstvo, ostavljaju znatan utjecaj na cjelokupni morski ekosustav. Kao rezultat, zabilježeni su štetni učinci na morske organizme i morska staništa, smanjen je broj morskih vrsta, te manja biomasa istih. Otok Pag osim svojim gastronomskim te turističkim sadržajem, obiluje i nizom ribolovnih djelatnosti. Cilj ovog završnog rada je bio istražiti ribolov koćama na otoku Pagu, odnosno metodom ispitivanja lokalnih ribara prikupljeni su podaci za vremensko razdoblje od 1980. do danas o promjenama u ribolovnim alatima, ulovu, novim vrstama, te mišljenja ribara o akcijama i regulacijama koje bi pridonijele održivom ribolovu. Analizom podataka utvrđeno je kako su se dužine plovila, kao i snaga motora, znatno povećale u odnosu na prošlost, ali usprkos tome, količina ulova te biomasa ribljih vrsta znatno su se smanjili. Ribari danas svoj ulov svode na petnaestak vrsta koje su najčešće prisutne u ulovu, od čega je najzastupljeniji oslić (Merluccius merluccius) koji je ujedno najčešća lovljena vrsta u svim ispitivanim vremenskim periodima. Kada je riječ o novim vrstama, važno je istaknuti kako ribari nisu previše upoznati s istim, ali ističu dvije vrste kao često viđene u posljednjim desetljećima, a to su: žutousne barakude (S. viridensis) i strijelke (P. saltratrix). Iako se većina ispitanika odlučuje na modifikaciju alata, analizom ispitivanja doznajemo kako navedene promjene ne utječu znatno na količinu ulova, već više pri olakšanju poslova. In recent decades, numerous human activities, mainly tourism and intensive fishing, have left a significant impact on the entire marine ecosystem. As a result, harmful effects on marine organisms and marine habitats have been recorded, the number of marine species has decreased, and their biomass is significantly lower. In addition to its gastronomic and tourist content, the island of Pag also abounds in a number of fishing activities. The aim of this final work was to investigate fishing with trawls on the island of Pag, that is, by means of the method of surveying local fishermen, data was collected for the time period from 1980 to the present day about changes in fishing tools, catches, new species, and fishermen's opinions about actions and regulations that would contribute sustainable fishing. The analysis of the data revealed that the length of the vessels, as well as the power of the engines, have increased significantly compared to the past, but despite this, the amount of catch and the biomass of fish species have decreased significantly. Today, fishermen reduce their catch to about fifteen species that are most often present in the catch, of which the most abundant is the hake (Merluccius merluccius), which is also the most frequently caught species in all examined time periods. When it comes to new species, it is important to point out that fishermen are not too familiar with the same, but they point out two species as often seen in recent decades, namely: yellowlipped barracuda (S. viridensis) and arrowhead (P. saltratrix). Although the majority of respondents decide to modify the tool, the analysis of the test reveals that the mentioned changes do not significantly affect the amount of catch, but more in facilitating work.

Bottom trawling is a type of fishing where huge nets are dragged for miles along the seafloor to catch flatfish like flounder or sole. Yet trawl nets also destroy ancient corals and other important habitats as they catch everything in their path. This habitat destruction has cascading impacts to fish and other sea life, ultimately threatening ocean ecosystems. Our oceans face many threats including climate change, pollution, overfishing, bycatch, habitat destruction, and other human impacts. All of these put extreme stress on marine ecosystems. The cold and remote waters of the Gulf of Alaska are no exception; yet there is one human-caused threat that has a practical solution that has already been applied to most U.S. and Canadian waters from the U.S. Arctic to Southern California — freeze the footprint of bottom trawling. According to the National Academy of Sciences, bottom trawling is the most destructive form of fishing on seafloor habitat like corals and sponges. In addition to harming seafloor habitat, bottom trawlers in Alaska catch and often waste nontargeted salmon, halibut, crab and other species central to the lives of Alaskans. The Gulf of Alaska is the last place on the U.S. west coast where industrial bottom trawling can still be conducted in large areas of corals and other ocean habitats vital for fish and other animals. However, there is a solution, one that has been implemented throughout much of the North Pacific. Oceana has worked with fishery managers, fishermen, indigenous communities, and other organizations to save seafloor habitat through a “freeze the footprint” approach to bottom trawling. In this approach, bottom trawling can only continue in areas that have already been trawled, protecting new areas from being destroyed and ensuring untrawled, vibrant habitats remain intact. The freeze the footprint approach also protects key seafloor habitats within the existing footprint such as coral gardens, seamounts, canyon heads, rocky reefs, and sponge beds. Along with limiting bycatch and protecting important ecological areas within the trawl footprint, this approach represents a win-win for healthy fisheries and healthy oceans. It’s time to implement this same approach in the Gulf of Alaska. The North Pacific Fishery Management Council’s “Essential Fish Habitat” review process is currently underway, where conservation measures for ocean habitats in Alaska are considered once every five years. This time measures must include freezing the footprint of bottom trawling in the Gulf of Alaska, limiting waste of nontargeted species like salmon and halibut, and protecting important ecological areas within the existing trawl footprint.

Multi-species bottom trawl fisheries are one of the human activities with a great impact on the benthic habitats and their associated biota. This study provides estimates of the bottom trawling activity (effort), catches and landings of the main commercial species as well as an estimation of the total revenue (TR) generated inside a mud volcano field located in the Spanish margin of the Gulf of Cádiz, during a time series from 2007 to 2012. To date, no studies have been carried out to analyse the temporal evolution of bottom trawling activity and TR in a mud volcano fied, or the economic consequences of possible potential bottom trawling regulation of certain sectors harbouring vulnerable and/or threatened habitats. In this study, Vessel Monitoring System data, logbooks and sales slips were used. The spatial distribution of the bottom trawling activity, catches and TR were related to the seafloor morphology and specific bottom types of the mud volcano field. During the time series, a high bottom trawling activity and associated catches was detected in flat sandy and muddy bottoms, including the Anastasya sector and between the Guadalquivir and Cádiz Diapiric Ridges. Low bottom trawling activity and catches were detected in the deepest areas but also in areas with hard and detritic bottoms such as Gazul and Chica sectors as well as in the Diapiric Ridges. A similar spatial pattern was detected for the TR asociated with these bottom trawling fisheries. An increase in bottom trawling activity was detected during the time series, mainly at the end, probably for increasing the TR and mantaining the economic profit due to the instability and increases in fuel prices and offset the increased costs. Based on the obtained information, bottom trawling regulations should be implemented in certain sectors harboring singular and/or threatened habitats and species. In some of these sectors, a low TR from bottom trawling was detected and, bottom trawling regulation may potentially have a low socioeconomic impact. This specific bottom trawling regulation could provide a sustainable balance between bottom trawling activities and habitat conservation in this mud volcano field according to the aims of the Habitats Directive (92/43/EEC) and the European Marine Strategy Framework Directive (2008/56/EEC)., SI

Liukang Tuppabiring is a waters with marine biodiversity potential large enough to be developed and managed sustainably. Utilization around the coral reefs in the waters of the Liukang Tuppabiring sub-district currently tends to lead to destructive use, so it is necessary to take damage prevention measures immediately. The results showed the condition of coral cover in the medium and damaged, while at stations 1,2,3,4,6 (25,47-41.07%), while conditions were good at station 5 (56.20%). The number of individual reef fish is 290 individuals from 46 species of 22 genera 11 families. At the research location also identified one type of protected biota namely Hawksbill (Eretmochelys imbricata). Coral damage that occurred at 6 observation stations was more caused by the practice of using destructive and environmentally unfriendly fishing equipment such as bombs, trawls, and the use of poisons. The priority strategies undertaken in the management of coral reefs at the study site are 1) Management of environmentally friendly coral reefs where the community as a manager with strong support from the Government; 2) Making clear rules related to utilization in coral reef areas and establishing a POSMAKWAS institution to avoid more severe coral damage; 3) Improve supervision and law enforcement must be firm in relation to the use of fishing gear that can damage coral reef ecosystems.

Parental care is a rather common reproductive strategy in fishes, particularly in species with low fecundity and large eggs as the Antarctic icefish (Channichthyidae). The infrequent use of underwater devices to record fish behaviour and the logistic limitations of operating in the Antarctic marine environment have prevented, so far, the collection of data about rare species. Integrating results from benthic trawling and underwater photographic images, we provide the first demographic and reproductive behavioural data for the channichthyid Neopagetopsis ionah, describing the nesting and parental care behaviour of a spawning population in the south-eastern Weddell Sea. The population sampled by the Agassiz trawl was dominated by females, and consisted of several post-spawning as well as a few mature females spread over a narrow size range. Based on otolith reading, the population included two cohorts estimated as four- and five-year-old fish. Following common trade-off between fecundity and egg size, females of N. ionah spawned few large eggs (733-1810 eggs/female, 4.9-6.5 mm in diameter). The nesting site was characterized by fine sediments with sparse gravel and the accompanying benthic invertebrate community showed low densities and was relatively poor. A total of 93 nests were counted along the video transect, most of them with a single guarding male or left unattended. Fish remains or whole dead specimens were frequently observed in the proximity of the nest. This observation represents the first record of post-spawning mortality associated with parental care which has never been documented before in Antarctic fishes.

In this work, research has been carried out on the technology of fishing for Pacific flying squid with trawls. The substantiation of the use of appropriate net webs with landing ratios to improve filtration in the trawl bag and in the winding part, ensuring the maximum catch and excluding damage, has been carried out.

The interannual and intraseasonal patterns of the spatiotemporal dynamics of the main commercial fishes from Lake Pskov, one of the most productive water bodies in northwestern Russia, are studied. The results of cartographic analysis of the summer–fall fish distributions in the lake are presented. The results of trawl surveys conducted in years that differed by the water level (2003, 2006, and 2008) were used as the input data. The initial data were aggregated into tables of attributes containing information on the trawling dates, trajectories, duration, average speed, water temperature, and the species and size composition of the catch. These tables were used to map the spatial distribution of seven fish species (bream, pikeperch, roach, perch, white bream, burbot, and ruff). Cartographic estimates of abundance are obtained for roach, pikeperch, bream, pike, and perch. An attempt is made to assess the reproduction efficiency of several fish species (pikeperch, perch, and pike) based on an analysis of their abundance variation from spring to autumn. Maps of the spatial distribution of the pikeperch that account for the size composition of the population are created. The discrepancy in the localization of different age groups in different seasons, along with their moving patterns, is ascertained. The patterns in the fish spatiotemporal dynamics are matched with the available hydrological characteristics.

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.

Penaeid trawls often have poor ecological efficiencies measured as unwanted bycatches (with high discard mortality) and

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.

Commercial bottom prawn trawling has been reported to generate a higher proportion of by-catch of up to 70% in Kenya. The Tigertooth croaker, Otolithes ruber is one of the species caught in large quantities as commercial by-catch and also by artisanal fishers. This has led to growing concern that the species could be at risk of over-exploitation. The purpose of this study was to carry out a stock assessment of O. ruber. Stock assessment parameters were estimated using ELEFAN with the generic algorithm as included in the R package TropFishR. The length-converted catch curve and the length-based yield per recruit model were employed. The exploitation rate (F/Z = 0.71) indicates that the stock is overfished based on the length-converted catch curve. The current fishing mortality (F = 2.3) based on the catch curve is larger than the reference level ( = 1.1) based on the yield per recruit analysis and also indicates that the stock is overfished (= 2.09). To reverse the current trend of exploitation, improved management of the stock is required, which should include further studies on other by-catch species and the generation of data to capture the whole fishery for a better estimation of stock status.

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)

This article belongs to the Special Issue 2021 Feature Papers by Diversity’s Editorial Board Members., Mussel beds are an important habitat in many coastal systems, harboring a high diversity of biota. They are threatened by anthropogenic impacts that affect mussels and their associated assemblages. Pollution, harvesting, trampling, dredging and trawling are major threats faced by these communities. Most of the studies on the effects of such impacts on the mussel beds overlook the associated fauna. Since mussels are very resilient, especially to pollution, the associated fauna can provide a better footprint of the impacts’ effects. In this review, we looked into the main remarks regarding the effects of anthropogenic impacts in mussel bed communities. Organic pollution was the best studied impact and the Atlantic region was the best studied zone. Low values of abundance, biomass, diversity, evenness and species richness were reported for all categories of impacts, with some studies describing declines in at least three of these descriptors. Among the associated fauna, some tolerant species benefited from the impacts, particularly organic enrichment, and became more abundant, but sensitive species suffered considerable declines in density, mainly in dredging and trawling impacts. Therefore, fauna associated with mussel beds is a suitable indicator of anthropogenic disturbances., This research was developed under the Project No. 30181 (PTDC/CTA-AMB/30181/2017), co-financed by COMPETE 2020, Portugal 2020 and the European Union, through the ERDF, and by the FCT (Foundation for Science and Technology) through national funds within the scope of UIDB/04423/2020 and UIDP/04423/2020.

Highlight The sex ratio of tiger prawns in the waters of female groceries is 1.08 times higher than that of males. The growth characteristic of male and female tiger prawns is negative allometry, but the male and female body shapes are fat. Fishing mortality, capture mortality, exploitation rate, female tiger prawns are higher than males, but total mortality and natural mortality male tiger prawns are higher than females. The male infinitive growth is longer than the female. Abstract The windu shrimp ( Penaeus monodon ) is an economically important fishery species in the waters of Tarakan. The shrimp is highly demanded for frozen seafood industry that makes its market price range attractive from Rp. 50,000 (USD 3.37) to Rp. 70,000 (USD 4.72)/kg. This can cause the species to be potentially exploited. However, due to lack of data, the exploitation status of the windu shrimp is unknown. Hence, the present study was carried out to determine the absolute growth, mortality, and exploitation level of the windu shrimp in Juata waters of Tarakan. Sampling of the shrimp using experimental trawling net was conducted four times between June and August 2020 in the waters of Tarakan. Morphometric data of the windu shrimps including sex, total length, carapace length, and total weight were recorded and analyzed. The results showed that the sex ratio of male and female tiger prawns was 1:1.08. The maximum growth of male and female shrimps was estimated at 26.875 and 21.435 cm respectively. The size of the male shrimps caught during the sampling ranged between 8.7 and 22.5 cm, and was estimated to be at 13 to 67 days old respectively. Maximum growth of male shrimp was estimated at 26.875 cm that could be achieved within 411 days. The size of female shrimp caught during the sampling ranged from 9.8 to 19.3 cm with an estimated age of 21 to 87 days respectively. The maximum growth for female shrimp was estimated at 21.435 cm, and achievable within 377 days. The mortality of male and female shrimps was not significantly different at 110.3% and 110.1% respectively. The fishing mortality for male and female shrimps was recorded at 19% and 22.5% respectively. The level of exploitation of male and female shrimps was slightly different at 17.2% and 20.5%, respectively. Finally, the natural mortality for male and female shrimps was at 91.3% and 87.5%, respectively.

Seabirds are declining on a global scale, and this trend is concerning as they play an important role in the marine ecosystem. The decline is due to multiple reasons, but harvest fisheries are a major contributor. The impact of fisheries, however, appears to vary; demersal trawlers cause mortality of many birds in some areas and very few in others. Fishery-dependent monitoring is required to understand this impact on seabirds, and particularly to better understand the variable impact of demersal trawling. We employed a targeted observer program to gather data on seabird assemblages, catastrophic interactions with trawl vessels and predictors of vessel attendance by the seabirds. The latter is a useful proxy for catastrophic interactions and provides information on potential mitigation. Throughout the program period, 1040942 seabirds from ~21 species attended New South Wales (NSW) ocean demersal trawlers. These species included 7 species of petrel and albatross listed by the IUCN, including the flesh footed shearwater Ardenna carneipes and wandering albatross Diomedea exulans. Two catastrophic interactions were recorded, and intrinsic and extrinsic predictors of vessel attendance (e.g. offal discharge and wind, respectively) were characterised. The results of the study will provide information to managers, with the goal of ensuring the sustainability of NSW ocean trawling—in particular its coexistence with threatened seabirds. The NSW Ocean Trawl fishery appears to directly harm very few seabirds which is not always the case when considering worldwide trawl fisheries. Predictors of attendance such as space, time and offal discharge can potentially be used to mitigate the attractiveness of trawlers to seabirds.

Recent warming in the Barents Sea has led to changes in the spatial distribution of both zooplankton and fish, with boreal communities expanding northwards. A similar northward expansion has been observed in several rorqual species that migrate into northern waters to take advantage of high summer productivity, hence feeding opportunities. Based on ecosystem surveys conducted during August–September in 2014–2017, we investigated the spatial associations among the three rorqual species of blue, fin, and common minke whales, the predatory fish Atlantic cod, and their main prey groups (zooplankton, 0-group fish, Atlantic cod, and capelin) in Arctic Ocean waters to the west and north of Svalbard. During the surveys, whale sightings were recorded by dedicated whale observers on the bridge of the vessel, whereas the distribution and abundance of cod and prey species were assessed using trawling and acoustic methods. Based on existing knowledge on the dive habits of these rorquals, we divided our analyses into two depth regions: the upper 200 m of the water column and waters below 200 m. Since humpback whales were absent in the area in 2016 and 2017, they were not included in the subsequent analyses of spatial association. No association or spatial overlap between fin and blue whales and any of the prey species investigated was found, while associations and overlaps were found between minke whales and zooplankton/0-group fish in the upper 200 m and between minke whales and Atlantic cod at depths below 200 m. A prey detection range of more than 10 km was suggested for minke whales in the upper water layers.

Otter trawling for fish is one of the world’s most productive yet problematic fishing methods due to its bycatch and discards; issues that have been mitigated in some fisheries by developing more selective trawls. This paper systematically reviews efforts published in international peer-reviewed papers over the past 30 years to identify beneficial (and limiting) factors and propose a way forward in this field. In total, 203 papers were assessed, encompassing many of the world’s fishing regions, and involving > 147 species, although 74% of efforts occurred in Europe mainly focussing on haddock (Melanogrammus aeglefinus) (64 papers) and cod (Gadus morhua) (59 papers). Common, simple modifications have involved increasing lateral-mesh openings to match the morphology of unwanted catches via larger diamond-shaped mesh, or simply turning meshes 45° or 90°, either throughout codends or as strategic windows in the posterior trawl. In some fisheries, more complex grids have improved size or species selection. Fewer attempts have been made to modify the anterior trawl, but varying sweep/bridle lengths, horizontal separator panels and longer headropes have realized benefits depending on species-specific behavioural responses. While the utility of many modifications is indisputable, experimental designs (mostly involving covers, but also alternate hauls and paired comparisons) have, in many cases, suffered low replication and/or confounding variables. These deficits may have compromised some results and contributed to repeated efforts in particular fisheries. We conclude that rigorous empirical assessments, initially focusing on the posterior trawl, but eventually encompassing anterior changes, combined with straightforward interpretation of results for stakeholders, are as important as the simplicity and reliability of modifications. Finally, by assessing the utility, applicability, advantages and disadvantages of the modifications developed, we provide a framework which could be followed in future work to reduce bycatch in these fisheries.

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.

Fishing for krill Euphasia superba has been conducting using midwater trawls of different constructions including beam-trawl for several last decades. Not all krill in harvesting zone of midwater trawl got to catch during trawling. Depending on stock structure, size and physiological state of krill individuals some part of them could pass through cover of net bag and escape of catch. In contact with threads of the net bag some of them may receive possibly lethal mechanical damage. Proposed method is applicable for rating of krill traumatic damage, received by it during trawling from cover of net bag, only for fishing with hauling of full net for catch extraction. The analogous rating for fishing with fishpump needs developing of special methods of source material obtaining to set experiments. But, taking into account the fact that trawl constructions used for these variants of fishing process are analogous or insignificantly different from the first, obtained results could be interpolated for them too. Picking of krill individuals, passed through meshes of net bag cover of fishing gear was carried out with specially made net bags-catchers (traps), set onto the cover of net bag of a studies trawl. While hauling, caught in these special bags krill is took out and then put into a special baths with sea water for conducting of aquarium studies to determine its survival.

Some fish species compose the so-called bycatch caught by pink shrimp trawling, including elasmobranchs (sharks and rays). The objective of the study was to analyze the stomach contents of the captured and compare the items identified in the literature. The material was requested to the commercial vessels that landed in Guaruja, Sao Paulo, being the study area between Rio de Janeiro and Santa Catarina, from 5 to 75 meters deep. In the laboratory, total length-TL and sexing (shark and ray), fork length-FL (shark), disk width- DW (ray) in centimeters, and total weight- TW in kilograms (shark and ray). For the stomach contents, the Degree of Repletion adjusted (empty and full), the Degree of Digestion (undigested and unidentified), frequency of occurrence (%FO) and the numerical frequency (%FN). Sixty-two specimens were analyzed: 20 rays (seven Atlantoraja castelnaui , five A. cyclophora , five Dasyatis hypostigma , one Myliobatis freminvillei , one Gymnura altavela and one Sympterygia bonapartii ); and 42 sharks (29 Squatina guggenheim and 13 S. occulta ), between June 12 to September 19, 2015 and June 15 to December 29, 2016. Most of the food items had been mentioned in the literature, however others only in this study as : Sycionia sp. and Dactylopterus volitans ( D. hypostigma ); Polydactylus sp., Pogonias cromis and Dactylopterus volitans ( S. guggenheim ); and Porichthys porosissimus ( S. occulta ).

The Baltic sprat Sprattus sprattus balticus is an important fishing species and takes the second place in abundance of the commercial catches after the Baltic herring in the eastern part of the Gulf of Finland. Before investigations of the sprat were rarely carried out in Leningradskaya region. Sprat is fished with the pelagic trawls as by-catch of the Baltic herring’s fishing clusters. The supply of the sprat forms in the western part of the Finnish Gulf and the Baltic Sea. This species goes to the eastern part of the gulf due to the forage migration. Materials for the research were the data obtained from the trawl fishery during the periods from January to May and from October to December 2017-2019 in Russian economic zone of the eastern part of the gulf close to the islands Bolshoy and Malyy Tyuters, Moshchnyy and Gogland. The analysis of the sprat distribution in 2019 was carried out based on the generalization of the results of trawl fishing. The review of the season fishing features in considered region is given. The amount of the catch of the species varied in the different fishing areas, changing significantly by months. The biggest catches reached 15-25 tons during 5 to 8 trawling hours were observed in November as well as in the former years. Largest number of the sprat was fished in the western border areas of the gulf which are adjacent to the Estonia and Finland waters.

Using a socioecological metabolism approach to analyze data from the Census of Agriculture, this article examines the underlying soil fertility of two case study areas in the Canadian province of Saskatchewan through the calculation of soil nitrogen balances. The Rural Municipalities of Wise Creek and Livingston are 300 miles apart and therefore have different topography, soil types, and rainfall levels, even though both are within the northern Great Plains. Over 85 years, from first settlement in the 1910s until the beginning of the twenty-first century, Wise Creek agriculture focused increasingly on livestock production while in Livingston farmers began to grow a greater variety of crops, most notably incorporating canola into rotations. Despite the differences between the two case studies, the pattern of soil nitrogen losses was remarkably similar, with biomass yields declining along with soil nitrogen. The addition of chemical nitrogen fertilizers since the 1960s did not produce yields matching historic highs, nor did a renewed focus on livestock. Wise Creek and Livingston showed two different responses to declining yields, but neither one ultimately provided a long-term solution to the problem of soil nutrient depletion and consequent productivity declines.

Biodiversity assessment is an important part of conservation management that ideally can be accomplished with noninvasive methods without influencing the structure and functioning of ecosystems. Environmental DNA (eDNA) metabarcoding has provided a promising tool to enable fast and comprehensive monitoring of entire ecosystems, but widespread adoption of this technique requires performance evaluations that compare it with conventional surveys. We compared eDNA metabarcoding and trawling data to evaluate their efficiency to characterize demersal fish communities in the Estuary and Gulf of Saint‐Lawrence, Canada. Seawater and bottom trawling samples were collected in parallel at 84 stations. For a subset of 30 of these stations, water was also collected at three different depths (15, 50, and 250 m) across the water column. An eDNA metabarcoding assay based on the 12S mitochondrial gene using the MiFish‐U primers was applied to detect fish eDNA. We detected a total of 88 fish species with both methods combined, with 72 species being detected by eDNA, 64 species detected by trawl, and 47 species (53%) overlapped between both methods. eDNA was more efficient for quantifying species richness, mainly because it detected species known to be less vulnerable to trawling gear. Our results indicated that the relative abundance estimated by eDNA and trawl is significantly correlated for species detected by both methods, while the relationship was also influenced by environmental variables (temperature, depth, salinity, and oxygen). Integrating eDNA metabarcoding to bottom trawling surveys could provide additional information on vertical fish distribution in the water column. Environmental DNA metabarcoding thus appears to be a reliable and complementary approach to trawling surveys for documenting fish biodiversity, including for obtaining relative quantitative estimates in the marine environment.

The Northern Adriatic Sea (NAS) is one of the most overexploited marine ecosystems in Europe. Given the gaps in scientific knowledge regarding the NAS, this study sought Fishers’ Ecological Knowledge (FEK) to determine NAS’ historical baselines for conservation. By interviewing 53 fishers in three ports of northern Italy, estimates of the catch rates of four commercial demersal species were generated over a 60-year period, and perceptions of target and non-target species’ diversity and benthic diversity were analysed in three groups of fishers (i.e. novices, experienced and veterans). Results showed a significant decline in perceived abundance of sole (Solea solea), common cuttlefish (Sepia officinalis) and mantis shrimp (Squilla mantis), and evidence was found of a Shifting Baseline Syndrome (SBS) among novices. Given FEK’s ability to complement scientific knowledge, fishers’ participation in marine management policies and intergenerational communication should be enhanced, to improve the status of marine ecosystems and hinder SBS. Electronic supplementary material The online version of this article (10.1007/s13280-020-01452-3) contains supplementary material, which is available to authorized users.

Deep-sea sampling was conducted by a commercial trawl in the International Waters of Mersin Bay between 14 and 17 May 2018. The sampling depth ranged between 274 and 641 meters. A total of 13 trawling operations were performed, and each trawling operation lasted approximately 4 hours. During the sampling, six of the deep-sea cephalopods species were caught. All specimens were preserved in ethyl alcohol and were deposited in the Museum of the Systematic, Faculty of Fisheries, Mersin University (Catalog no: MEUCC-18-11-2- MEUCC-18-11-7). A total of two cuttlefish species belonging to the families of Sepiidae were identified. The others were represented by the families of Sepiolidae, Octopodidae, Bathypolypodidae, and Ommastrephidae.

Fisheries bycatch of non‐target species in the commercial fleet is a major source of anthropogenic injury and mortality for sea turtles and marine megafauna. The Rio de la Plata maritime front (RLPMF) and its adjacent international waters – comprising part of the Argentine and Uruguayan exclusive economic zones, is a highly important fishing ground in the south‐western Atlantic Ocean as well as feeding and development grounds for sea turtles. This paper analyses the distribution of the bottom and pelagic trawling fishery within the RLPMF using information from Vessel Satellite Monitoring System. With this information, areas of highest trawling intensity were defined and further evaluated their overlap with sea turtle habitat‐use areas from available sea turtle satellite tracking information. Results besides identifying high‐susceptibility areas for sea turtle bycatch by the commercial trawler fleet along the RLPMF, provide predictive tools to identify vulnerable areas to interaction of sea turtles and the commercial fishing fleet. Implementation of bycatch mitigation measures, such as reduced fishing effort areas by the Argentine and Uruguayan fisheries management agencies has the potential to benefit the fisheries as well as marine megafauna. Furthermore, there is a need for additional research on the impact that this fleet can have on sea turtles present in the area.

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.