Beam Trawl Research Articles

Flume tank trials to investigate the snagging of towed demersal fishing gears on boulders

The snagging of towed demersal fishing gears on seabed features and obstructions can have economic, safety, ecological and environmental consequences. Nevertheless, very little is known about the snagging process, the extent to which it occurs and how best to mitigate it. Here we present the results of a systematic flume tank study to investigate which gear-types are more likely to snag on boulders, which part of a given gear snagging is more likely to occur, and what are the characteristic features of the boulders shapes and size that increase the likelihood of snagging. As a case study we focus on gears that are typical of Jammerbugt, Denmark and show that tickler chain beam trawls are more likely to snag, while the snagging likelihood of the otter trawl, Danish seine and chain mat beam trawl are similar. Our approach and the methodology we develop will help design safer and more sustainable gears that interact less with the seabeds habitats and features. They will provide insights as to which gears can be used on which fishing grounds, contribute to a reduction of abandoned, lost and discarded fishing gears (ALDFG), improve fisher safety, and help fisheries managers develop measures that will promote more environmentally friendly and sustainable fisheries.

Spatio-temporal analysis of potential factors explaining fluctuations in population size of Spisula subtruncata in the Dutch North Sea

Bivalves play a key role in coastal ecosystems by supporting food web, modifying habitats, and their economic value for fisheries. Many bivalve species are under pressure, showing large variations in population sizes and distributions, with climate change and human activities considered as important drivers. The Dutch North Sea hosts high densities of bivalve species, dominated by the cut trough shell Spisula subtruncata, with strong interannual variations and a patchy distribution. To explore the causes of this variation, data of an extensive long-term spatial benthic monitoring program (1995-2021) was analysed using a Bayesian spatio-temporal hurdle model. We considered indicators related to human activities, biological processes, climate change and habitat preference as explanatory variables for the observed long-term temporal and spatial variations. Results revealed that medium sediment grain size was key determinant of S. subtruncata occurrence and density. Increasing sea water temperatures during winter and the post-settlement phase positively affected annual population densities, while strong north-westerly winds led to lower densities. These climate change related factors had an overall positive effect on this species in the region. Human activities like shellfish dredging and sand nourishment had no measurable impact. However, shrimp and flatfish beam trawling overlapped with S. subtruncata occurrence and were negatively related to densities, suggesting higher beam trawling intensity in these areas may negatively impacts densities. Overall, the effects were stronger at medium to finer sediments where the highest densities occurred, indicating a strong habitat-dependent effect. Despite identifying multiple drivers, unexplained annual variation suggests other not included factors like predation pressure, also play a role. More detailed studies on the combined effects of climate change-driven environmental stressors and human activities are needed to fully understand the population dynamics. This knowledge is essential for developing more adequate fisheries and coastal management strategies to sustain biodiversity.

Assessing the overlap between fishing and chondrichthyans exposes high‐risk areas for bycatch of threatened species

AbstractChondrichthyans (sharks, rays, skates, and chimaeras) make up one of the oldest and most ecologically diverse vertebrate groups, yet they face severe threats from fishing, necessitating improved management strategies. To effectively manage these species, we need to understand their spatial interactions with fisheries. However, this understanding is often challenged by limited data on chondrichthyan catches and species identification. In such cases, assessing potential risks from fishing activities can provide valuable insights into these spatial interactions. Here, we propose a method combining geostatistical models fitted to a fishery‐independent dataset with vessel monitoring system (VMS) data to estimate the spatial overlap between chondrichthyans and fishing. Our case study focuses on the western Adriatic Sea in the Mediterranean, examining the overlap between bottom trawling (including otter bottom trawling and beam trawling) and demersal chondrichthyans. We find that the northwestern part of the basin is a hotspot where threatened chondrichthyans (classified as Vulnerable, Endangered, or Critically Endangered by the International Union for Conservation of Nature Red List) greatly overlap with bottom trawling activities. Moreover, some areas, such as the northernmost part of the Adriatic and the “area dei fondi sporchi” in the north‐central offshore part, exhibit minimal overlap between threatened chondrichthyans and bottom trawling, potentially serving as refuges. We recommend prioritizing the management of otter bottom trawling in the northwestern basin to protect these threatened species, while also paying attention to the possible impacts of beam trawling on skates and chondrichthyan habitats. Despite certain limitations, our findings demonstrate that combining geostatistical models of species distributions with VMS data is a promising method for identifying areas of concern for species vulnerable to fishing. This approach can inform targeted management measures and cost‐effective onboard monitoring programs.

Updated state of small scale fisheries on the Romanian Black Sea area

Romanian small-scale fisheries are practiced along the Black Sea coast in five fishing ports (Sulina, Cape Midia, Tomis, Constanta and Mangalia) and 18 other small fishing stations, located between Sulina - Vama Veche, at depths ranging between 2 - 20 m and sometimes up to 50 m, when practicing specialized turbot fisheries. Of significant importance is fishing with divers for the Rapana venosa, the species with the greatest impact on the landed catches. In the coastal area, between Vama Veche and Sulina, which also represents an important area for the reproduction, feeding and rearing of some important fish species, the small-scale fishing is practiced with fixed and active gear, throughout the year, mainly using the following types of fishing gears: pound nets, gillnets, longlines, beach seines, cages/traps, handlines and from 2013 with beam trawl. Catch and fishery productivity vary yearly, depending on environmental conditions, fishing effort, status of main commercial species, and human factors. During the analyzed period (2019 - 2023), catches in shallow waters were between 7149 and 3127 tons, which has an increasing trend compared to the previous period (2012 – 2017).

The relative effects of bottom trawling, organic enrichment, and natural environmental factors on coastal seabed communities

Coastal regions are under intense and growing pressure from human activities. Here, we examine how human and natural drivers interact with benthic communities, species, and life-history traits across four distinct coastal areas. Sediment organic content was a key driver of seabed community characteristics, with positive (increased benthic biomass) and strongly adverse (depauperate communities) effects observed. Similarly, environmental factors such as bottom currents were highly influential. In contrast, bottom trawling impacts varied by location. Beam trawling in areas of low organic enrichment was most damaging to seabed fauna, even in the presence of strong bottom currents. However, we did not observe any faunal impacts of trawling under chronic enrichment, despite the fishery using relatively heavy gears (e.g. otter trawls) at high intensities. Lastly, we discuss how human and natural factors interact and shape seabed ecosystems under different conditions, and how management measures can be adapted to improve coastal seabed health.

Crustacean species off the coast of Kıyıköy (Black Sea, Türkiye) with a new record

Examination of hard- and soft-bottom samples collected off the coast of Kıyıköy (Black Sea, Türkiye) using grabs, quadrats and trawls revealed a total of 39 crustaceans belonging to eight orders. Among the species, Medorippe lanata was recorded in the Black Sea for the first time. Amphipoda dominated on hard and soft substrates in terms of the number of species and individuals. A total of 898 individuals belonging to 27 species were identified on the hard bottom, of which Ampithoe ramondi was the most dominant species (47.4%). On the other hand, a total of 123 individuals belonging to 16 species were recorded on the soft bottom, with Diogenes pugilator (21.1%) being the most dominant species (21.1%). A total of 441 individuals belonging to nine species were found following bottom and beam trawl hauls, with Liocarcinus navigator and L. depurator being the most frequent species. Community parameters were estimated in both hard- and soft-bottom samples.

Eucarid and Peracarid Fauna of the Valencia Seamount, a Deep-Isolated Seamount of the Western Mediterranean: Colonisation Capacity and Historical Changes

Seamounts can have a strong influence on the distribution and diversity of species, creating an oasis effect that may favour diversification. In order to assess how and to what extent supra- and epibenthic crustaceans can colonise these environments, the eucarid and peracarid fauna collected from the summit of the Valencia Seamount (VS), a small deep seamount (summit depth: 1056 m), rising from a depth of ca. 1850 m, in the oligotrophic Balearic Basin, was analysed. Based on a first sampling (beam trawls, plankton nets and stomach contents), and a faunal reconstruction from a sediment core (MC2, at 1151 m), the supra(epi)benthic crustaceans at the VS summit (to 1300 m) were composed of nine Eucarida and 25 Peracarida. Polycheles typhlops, Munida tenuimana, and Aristeus antennatus were the dominant species among eucarids. Among Peracarida the most abundant species were the Mysida Boreomysis arctica, the Amphipoda Rhachtropis caeca, and the Isopoda Munnopsurus atlanticus. Among Decapoda, a species with a wide amplitude in their depth distribution and small eggs (i.e., with planktotrophic larvae), showed a higher colonisation capacity. In the absence of larvae, the colonisation of peracarids depends on the amplitude of their depth distribution and only those species that reach the highest depths in the entire Balearic Basin, at least 1600–1800 m, were able to colonise the summit of VS. The natatory capacity of the species also has some influence and whole groups with low natatory capacity, such as the Desmosomatidae, were completely absent on the VS summit; however, they are distributed throughout the Balearic Basin to depths (up to about 1500 m) exceeding the depth of the seamount summit. Therefore, colonisation by peracarids must not have occurred by swimming through the entire water column, but by swimming along or just above the bottom. Remains of some suprabenthic species (mainly the isopod M. atlanticus) in MC2 and another core collected in NW Mallorca (MC3, 1114 m), i.e., out of the VS, showed how isopod diversity and size distribution changed historically. Also, after the 1960s, a decrease in primary production due to a decrease in rainfall and river runoff associated with river damming could have reduced the abundance of M. atlanticus. These types of historical studies can be useful in interpreting long-term changes in deep-sea communities and optimising the management of these vulnerable areas.

A report of sea cucumbers collected on the first dedicated deep-sea biological survey of Australia’s Indian Ocean Territories around Christmas and Cocos (Keeling) Islands (Echinodermata: Holothuroidea)

The marine benthic biodiversity survey Investigating the IOT took place in the waters of Christmas and Cocos (Keeling) Islands in Australia’s Indian Ocean Territories (IOT) on two voyages over 2021 and 2022. Both voyages on the RV Investigator collected sea cucumbers using a beam trawl from the seamounts and seafloor of the area. A report of sea cucumbers collected is included below, including taxonomic treatments, shipboard and ossicle images, range extensions, and genetic data for species where available. One new species, Deima oloughlini Mackenzie and Davey sp. nov., is described. Sea cucumbers collected are now housed in the collections at the Museums Victoria Research Institute in Melbourne, Australia. Range extensions and new species records for Australia will be supplied to compliers, including the Australian Faunal Directory and Atlas of Living Australia, and genetic data will be lodged with GenBank. This report was initiated through funding by an Australian Biological Resources Study Bush Blitz grant, and subsequently supported through funding by Ocean Census. Investigating the IOT voyages were supported by Parks Australia, Bush Blitz, Museums Victoria, and other Australian institutions. Voyage time on the RV Investigator was supported by the Marine National Facility (CSIRO), and additional travel for holothuroid taxonomic work was supported by a Council of the Heads of Australian Faunal Collections grant.

Vertical and horizontal environmental DNA (eDNA) patterns of fish in a shallow and well-mixed North Sea area

The integration of eDNA metabarcoding into monitoring programs provides valuable information about fish community structures. Despite the growing body of evidence supporting the method's effectiveness in distinguishing fine-scale eDNA signals, there is a limited understanding of eDNA distribution in shallow, well-mixed environments, especially related to sampling depth. We analyzed 167 samples collected from the surface and bottom water at 17 locations of the Belgian Part of the North Sea (BPNS), where the deepest sampling point was 31 m, and compared this to beam trawl catch data collected simultaneously at the same locations. eDNA metabarcoding identified an additional 22 species compared to beam trawl catch data. Diversity measures and patterns were very similar between surface and bottom samples and revealed community patterns that were previously described by long-term beam trawl catch data. Surface and bottom samples had 39 fish species in common, while six and eight rare species were uniquely detected, respectively. Our results demonstrate that eDNA metabarcoding effectively identifies spatial community patterns of fishes in the highly dynamic environment of the BPNS regardless of sampling depth. Out of the six most common species tested, eDNA metabarcoding read abundances correlated strongly with catch-based abundance data for one species, but moderately for two others, indicating that inferring fish abundance and biomass via eDNA metabarcoding remains challenging.

Investigating the nursery function of the Alboran MPA on the Mediterranean coast of Morocco

Coastal habitats provide shelter and food for juvenile fish, ensuring their survival and supporting a range of species that are both commercially and ecologically important. The Alboran Marine Protected Area (MPA) off the Mediterranean coast of Morocco has been identified as a nursery area, although this role has never been the subject of characterisation. This study investigates the nursery function of habitats at six sites, two of which have seasonally flooded rivers with small persistent lagoons (transition systems) actively connected to the sea. Mixed sand-and-gravel beaches and transition systems were surveyed using a beach seine (four hauls) during two consecutive summer periods (June 2019 and July 2020), and a beam trawl was used in July 2020 in order to survey shallow waters at three depths: 3, 5 and 7 m. The use of both fishing methods provided a comprehensive assessment of juvenile fish communities. Different habitats in these coastal areas supported juvenile fish of 31 different species, with higher species richness and densities of young-of-the-year (YOY; first year of life) fish in transition systems despite their limited surface area and depth. Shallow marine waters supported fish species with specific microhabitat requirements despite lower overall YOY fish densities. The Alboran MPA coast has a nursery function, with different habitats acting as nurseries for juveniles of different fish species, creating a seascape of interconnected nursery habitats. As low densities of juvenile fish were a common concern across species and habitats, protecting these nursery habitats through enforcement of their protection regime appears to be a priority.

Environmental DNA for monitoring the impact of offshore wind farms on fish and invertebrate community structures

AbstractTo reach the renewable energy targets set by the European Commission, a tenfold expansion of the installed offshore wind farms is needed. Since the construction of offshore wind farms may affect local soft‐sediment fauna, an efficient monitoring technique is needed to monitor the potential effects on the marine ecosystem. Here, we assess whether eDNA metabarcoding is a suitable alternative to monitor fish and epibenthos biodiversity in these difficult to access marine habitats. Water sampling and trawl surveys were conducted in parallel in 12 coastal and 18 offshore sites, the latter located inside and outside two offshore wind farms in the Belgian part of the North Sea. 12S eDNA metabarcoding retrieved 85.7% of the fish species caught in the beam trawls, whereas the COI eDNA metabarcoding only identified 31.4% of the epibenthic invertebrate species. Furthermore, the 12S marker resulted in an additional detection of 26 unique fish species, whereas the COI marker detected an additional 90 invertebrate species. Spatial patterns in alpha diversity recovered with eDNA metabarcoding were not significantly different from those observed with morphological determination. Significant differences were found in fish and invertebrate community structures between the coastal, transition and offshore zones as well as on the smaller wind farm scales, which agreed with the morphological beam trawl data. Indicator species found with morphological beam trawl monitoring for each of the three zones (coastal, transition, offshore) were also detected with 12S eDNA metabarcoding, and the latter method detected an additional 31 indicator species. Our findings show the need for adequate quality control of the obtained species lists and reveal that 12S eDNA metabarcoding analyses offers a useful survey tool for the monitoring of fish communities in offshore wind farms, but the used COI assay did not adequately capture the epibenthic communities as observed with beam trawl data.

Trawling through time: reconstructing a late nineteenth century beam trawl for scientific inshore fishery investigations

Understanding long-term change in fish populations often relies on comparing catches from historical and contemporary trawl surveys. However, such comparisons may not resolve biases associated with differences in fishing gears and their relative catchabilities. It is possible to reduce these uncertainties by replicating historical trawl gear and practices. With the availability of unique historical catch data, we investigated the trawl gear employed by the Northumberland Sea Fisheries Committee (NSFC) during scientific surveys conducted between 1892–1913 in inshore waters of the Northumberland coast (UK), and describe our attempt to reconstruct the gear using currently available materials. We reviewed the historical literature, photographs and acquired technical expertise to reconstruct a late nineteenth century beam trawl used by the NSFC. The replica gear consisted of a 6.7 m beam connected by two Brixham style wrought-iron trawl heads, which held open a triangular-shaped trawl net with rounded ground-rope. Following construction, we tested the performance and catchability of the replica gear by conducting comparative trawls using a modern otter trawl in August 2018 and March 2019. Both trawl gears exhibited similar catches for flatfish in August trials, yet a higher proportion of individuals were landed by the otter trawl in March. Zero or negligible catches were exhibited by the replica gear during this period. This work collates relevant information to describe the evolution, design and functioning of late nineteenth century beam trawls used around the British Isles, providing an important repository for investigators interested in trawl technology and survey designs.

Comparative analysis of bottom trawl and nanopore sequencing in fish biodiversity assessment: The sylt outer reef example

The assessment of fish diversity is crucial for effective conservation and management strategies, especially in ecologically sensitive regions such as marine protected areas. This study contrasts the effectiveness of environmental DNA (eDNA) metabarcoding analysis employing Nanopore technology with compare beam trawl surveys at the Sylt Outer Reef, a Natura 2000 site in the North Sea, Germany.Out of the 17 fish species caught in a bottom trawl (using a 3m beam trawl), 14 were also identified through eDNA extracted from water samples. The three species not detected in the eDNA results were absent because they lacked representation in public DNA databases. The eDNA method detected twice as many fish species as the beam trawl, totalling 36 species, of which 14 were also detected by the trawl. Additionally, the selection of primers (Mifish) facilitated the identification of one marine mammal species, the harbour porpoise.In conclusion, the findings underscore the potential of eDNA coupled with MinION sequencing (Long read technology) as a robust tool for biodiversity assessment, surpassing traditional methods in detecting species richness.

Predicting the penetration depth and towing resistance of beam trawl fishing gears in sand

Accurate characterization of mechanical perturbations on the seabed is essential for developing models assessing the environmental impacts from physical disturbances. Furthermore, understanding the relationship between (1) seabed resistance and (2) penetration depth, can also facilitate the development of more efficient and less impactful fishing gears. This study examines these two aspects of tickler chain rigged beam trawling via large-scale physical experiments. Three scaled down models (“light,” “medium,” and “heavy” designs) were developed to represent the impacts from typical beam trawl configurations used in the North Sea and were towed at various speeds on a saturated sand bed. Results reveal that increasing the towing speed reduces the mean penetration depth and the steady-state towing resistance of the gears. Smaller scale physical model tests incorporating tickler chains in sand, demonstrate that the towing resistance is significantly influenced by the soil compaction and particle sizes. Moreover, our study offers a simple and efficient method to estimate the penetration depth and towing resistance of prototype beam trawl gears in sand. This approach, along with the associated research, may be valuable for marine scientists assessing trawling impacts and demersal fishing gear designers seeking to optimize efficiency while minimizing seabed disturbance.

Species c omposition and community structure of aquatic organisms caught by the coastal beam trawl in the Gomso Bay, Jeollabuk-do of South Korea

Species c omposition and community structure of aquatic organisms caught by the coastal beam trawl in the Gomso Bay, Jeollabuk-do of South Korea

Technical and economic feasibility study on reducing CO2 emissions of Dutch beam trawlers

This paper examines the technical and economic influence of CO2 reduction measures on the design and operation of Dutch beam trawlers. This is done by means of a parametric model used to assess the influence on the overall design of the vessel. Technical feasibility is determined by meeting operational effectiveness requirements, maximum added draught, maximum added length, and a reduction of CO2 emission by at least 40%. Secondly the model evaluates the new energy carrier and fish storage layout as a result of additional required volume. Additional volume is gained within the net store, fish hold, or by hull extension. Additionally, various propeller configurations, waste heat recovery, and regenerative braking systems are explored to reduce energy consumption. The economic performance is assessed using yearly operational requirements, capital expenses of configuration, and total cost of ownership.

Long-term change in a North Sea inshore fish assemblage between 1899-1913 and 2018-2019

Marine communities have been impacted by human activities for centuries, yet historical data are rarely incorporated into modern conservation efforts and restoration targets. For inshore waters, survey data sets are typically lacking because they extend back by only a few decades, despite their ecological significance as nursery grounds for many fish species. We investigated long-term change in a demersal fish assemblage from inshore waters of the Northumberland coast (UK). We collated unique historical data (1899-1913) that were sampled using a wooden beam trawl during scientific trawling investigations, shortly after the onset of widespread mechanised trawling in the North Sea. Twelve decades later (2018-2019), we re-surveyed the same bays using a modern otter trawl. The results revealed marked declines in the abundance and diversity of the entire fish and flatfish assemblage as well as among individual species. Elasmobranchs and formerly abundant species such as grey gurnard Eutrigla gurnardus were completely absent in contemporary surveys, while dab Limanda limanda and plaice Pleuronectes platessa were the most dominant species in both periods. Changes were also detected in the size distributions of the entire fish and flatfish assemblages, with proportionally fewer large individuals recorded in contemporary surveys. These findings suggest that over a century of trawling and climate change, combined with pollution, habitat alteration and increased predation risk are likely contributors to changes in the inshore fish assemblage. This work provides further evidence of long-term decline in North Sea inshore waters and offers an invaluable benchmark for improving coastal ecosystem status.

Length-weight relationships of four difficult-to-sample Caspian endemic gobies (Teleostei: Gobiidae): Benthophilus persicus, Benthophilus baeri, Knipowitschia longecaudata, and Hyrcanogobius bergi

The present study provides the length-weight relationships (LWRs) for four difficult-to-sample Caspian endemic gobies for the first time: Benthophilus persicus, Benthophilus baeri, Knipowitschia longecaudata, and Hyrcanogobius bergi. They were collected from shallow and deep waters of the southwestern Caspian Sea using various methods, including beach seining, scuba diving, and deepwater bottom beam trawls. The slope (b) of LWRs ranged from 2.874 for B. baeri, to 3.408 for H. bergi with coefficient of determination higher than 0.918. The b values showed significant differences between the sexes of all species.

Bayesian analysis of biodiversity patterns via beam trawl versus video transect—a comparative case study of Svalbard rhodolith beds

Knowledge of spatial biodiversity patterns is important for ecosystem assessment. Rhodoliths, free-living calcareous algae, are biotic components that structure the sea floor through their complex calcareous skeletons and their tendency to accumulate in an area to form rhodolith beds. Thereby, rhodoliths are considered to act as ecosystem engineers promoting local biodiversity. In this study, the biodiversity of rhodolith beds in Mosselbukta, Svalbard, was investigated to analyse the proposed link between local biodiversity and the presence of rhodoliths by evaluating beam trawl and underwater video transect data. The comparative analysis of two sampling methods addressing the same research question allowed us to assess the suitability of these two methods. To test our hypothesis and the utility of the two methods, evaluations of the two data sets were carried out separately by using Bayesian statistics. The results confirm a positive relationship between the presence of rhodoliths and local biodiversity with a posterior probability of 70% for the video transects and 85% for the beam trawl data. The similarity of the results of the two methods suggests that both methods are well-suited for the analysis of local biodiversity patterns. The combination of the two methods, with their individual strengths and weaknesses, has provided stronger support for the results and a broader view on different components of the biodiversity in the Svalbard rhodolith beds.

Behavioural response thresholds of marine fish species for pulsed electric fields

Electrical pulse trawling is an alternative to conventional beam trawling for common sole (Solea solea), with substantially less discards, lower fuel consumption, and reduced impact on the benthic ecosystem. Pulsed electric fields are used to drive the fish from the seafloor and immobilise them in front of the nets. Concerns exist, however, that the electric fields may affect fishes outside the trawl track. Here, we address these concerns by measuring amplitude thresholds for behavioural responses and by comparing these response thresholds to simulated field strengths around fishing gear. Electroreceptive small-spotted catshark (Scyliorhinus canicula) and thornback ray (Raja clavata) as well as non-electroreceptive European seabass (Dicentrarchus labrax), turbot (Scophthalmus maximus), and common sole were, one at the time, placed in a ø2.5 m circular tank with seven, individually controlled, evenly spaced electrode pairs, spanning the diameter of the tank. Behavioural responses were assessed from camera recordings for different pulse amplitudes and for different fish positions relative to the stimulating electrodes. Electrical stimulation consisted of a Pulsed Bipolar Current at 45 Hz and 0.3 ms pulse width, similar to that used in commercial gears. Computer simulations of the electric field, verified with in situ measurements, were used to determine the field strength at the location of the animal. Thresholds for different species varied between 6.0 and 9.8 V m–1, with no significant difference between electroreceptive and non-electroreceptive species. The thresholds correspond to a distance of maximally 80 cm from the electrode arrays in simulated electric fields around commercial fishing gears. These findings suggest that electrical pulses as used in pulse trawling are unlikely to elicit a behavioural response outside the nets that surround the electrode arrays.