Otter Trawl Research Articles

Single-species quotas drive discards by multi-species trawlers in the Celtic Seas ecoregion when their relative abundance fluctuates

Abstract Our study investigated discarding patterns by bottom otter trawlers over 17 years prior to the full implementation of the Landing Obligation. A generalized additive modelling approach was applied to at-sea sampling data to examine the most important drivers of the discards per unit effort (DPUE) of cod, whiting, hake, and haddock in the Celtic Seas ecoregion from 2002 to 2018. Many operational, environmental, regulatory, and spatio-temporal factors were tested. Fish above and below the minimum conservation reference size (MCRS) were modelled separately to compare drivers of discarding of these categories of unwanted catch. In the full time period analysis, the three most important factors in determining DPUE were geographic location, an interaction between geographic location and year, and year interacting with month. Further analysis of a subset of the time series indicated that quota availability significantly impacted the DPUE for <MCRS haddock, <MCRS whiting, and >MCRS hake, while the quota allocated for one species often significantly influenced the DPUE of other species and size classes. Quota interacting with abundance had a significant impact for all >MCRS species and <MCRS hake. This indicates that changes in relative abundance compound discarding under quota constraints. Collectively, these results empirically demonstrate that single-species quotas majorly contribute to discards in a mixed-fisheries context.

Physical and geochemical responses to bottom trawling on naturally disturbed sediments in the eastern Bering Sea

Abstract Recent concerns that commercial bottom trawling can contribute to a significant release of sequestered marine carbon have highlighted a need for research in this area. Here, a Before-After Control-Impact (BACI) experimental design was utilized in a previously untrawled area of the eastern Bering Sea. Six pairs of experimental and control corridors were sampled before, after, and 1 year after a trawl disturbance. Each experimental corridor was fished four consecutive times over ∼12 h with a commercial otter trawl. Results were contextualized with minimum detectable effects (MDE), and showed no evidence of a trawl effect on total organic carbon (P = .999, MDE ± 0.05% TOC), total nitrogen (P = .999, MDE ± 0.02% TN), δ13C, and δ15N isotope ratios and sediment size classes. Interannual changes observed in δ15N, sand, silt, and clay are attributed to natural variation. The study suggests that the characteristics of the study site, such as storm disturbances, high sand content, and low carbon content, limited the bottom-trawl effect on sediment composition following this initial trawl disturbance. The findings highlight the importance of site-specific studies that account for local conditions to support best management practices for commercial bottom trawling.

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.

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.

Dynamic performance of strategy for transitioning from conventional bottom otter trawling to semi-pelagic trawling through towing tank experiments and numerical simulations

An innovative trawling strategy for transitioning from conventional bottom trawling to semi-pelagic trawling (elevating the otter board but allowing the trawl net to contact the seabed) was developed to mitigate the effects of seabed impact, and its dynamic performance was evaluated. Experiments were carried out using a 1/18 scale physical model of the otter trawl at a speed of 0.6 m/s, and the warp length was tuned in the range of 4–8 m under constant-speed control of the trawl winch for validating the numerical simulations. Numerical simulations were then conducted to investigate the effects of towing speed and winch speed on the dynamic loads of the otter trawl system and movement of the otter board, eventually develop a fuzzy or proportion-integration-differentiation (PID) controller for the trawl system. Numerical results showed the sharp increase of the warp tension and the overshoot of the otter board at the constant-speed control occurred, and the magnitudes of both raised as the towing speed and winch speed increased. The otter board spread was significantly reduced during the transition to semi-pelagic trawling at a low towing speed. The use of fuzzy and PID control successfully eliminated the overshoot and diminished the high warp tension.

Broad-scale genetic population connectivity in the Moreton Bay Bug (Thenus australiensis) on Australia’s east coast

Understanding population connectivity helps inform resource and conservation managers about appropriate boundaries for management units. However, for many species facing recent increases in fishing or environmental pressure, accurate information on population structure is lacking. Reef Bugs (Thenus australiensis), commonly known as Moreton Bay Bugs, are iconic shovel-nosed lobsters in northern Australia and an increasingly important fisheries resource. Around 80% of landings occur in the Queensland East Coast Otter Trawl Fishery (ECOTF) where the first stock assessment of the species is underway. However, knowledge about population structure to inform stock assessment is lacking. We used genome complexity reduction-based sequencing to characterise high-quality Single Nucleotide Polymorphisms (SNPs) used to evaluate population structure among three management zones of the ECOTF. Post-filtering, a total of 3,031 SNPs were used to infer no genetic differences among locations indicating strong genetic population connectivity. The presence of a single panmictic population was further supported by cluster and kinship analyses. Broad-scale genetic connectivity likely results from pelagic larval dispersal due to limited adult movements. Findings of high gene flow among connected populations indicate a single biological stock of T. australiensis on Australia’s east coast and will inform future fisheries management initiatives.

Spatial Distribution and Potential Impact of Drifted Thalli of the Invasive Alga Rugulopteryx okamurae in Circalittoral and Bathyal Habitats of the Northern Strait of Gibraltar and the Alboran Sea

The arrival of a new invasive alga, Rugulopteryx okamurae, in the Strait of Gibraltar (SoG) in 2015 marked an unprecedented milestone in the North African and, later, in the European marine ecosystems. Nowadays, it is colonising vast infralittoral areas and significantly modifying some habitats and associated communities of the southern Iberian Peninsula. In recent expeditions, a high amount of free drifted thalli of this alga has been detected in different circalittoral and bathyal habitats of the northern SoG and the Alboran Sea. The present study combines quantitative data of this alga obtained with the use of a remotely operated vehicle (ROV) and a bottom otter trawl. The coverage–entanglement level of the drifted thalli on circalittoral and bathyal benthic invertebrates (e.g., not covering, covering only the basal part, covering one-third of the invertebrate, etc.) was also annotated from picture frames taken in locations with abundant drifted thalli. In underwater images, drifted thalli were mainly detected in circalittoral and bathyal bottoms of the northern SoG and the north-western Alboran Sea, between 50 to ca. 450 m depth. Nevertheless, abundant drifted thalli were also detected in bottom otter trawl samples from circalittoral bottoms of the north-central and north-eastern Alboran Sea. Small benthic organisms (e.g., encrusting sponges, hydrozoans, etc.) generally displayed low coverage–entanglement levels of drifted thalli. Nevertheless, large sessile and colonial benthic organisms with a complex three-dimensional morphology (e.g., gorgonians, colonial scleractinians) reached high levels of R. okamurae thalli entangled in different parts of their colonies. The drifted R. okamurae thalli entangled in these colonial suspension feeding organisms may hinder their feeding capability in the long term, resulting in habitat deterioration in the near future.

Spatial Distribution of Major Fish Species Catches and Their Relationship with Environmental Factors in the Beibu Gulf, South China Sea

This study focused on major fish species caught from different ecological habitats to analyze the habitat changes in economically important fish in the Beibu Gulf. The maximum entropy model was constructed based on the data from 26 voyages obtained through the otter trawl fishery stock surveys conducted in the Beibu Gulf from 2006 to 2018. A total of 10 taxa of major fish catches, belonging to 4 families, 1 genus, and 5 species, were analyzed for their distribution characteristics in potential habitats during various ecological periods, specifically the withered and high-water periods, as well as their relationships with crucial environmental factors. During both the withered and high-water periods, the average area under the curve was 0.927, and all models had values exceeding 0.9. Salinity was identified as the principal factor during both periods. The salinity niche of Acropoma japonicum and the primary productivity niche of Sciaenidae were identified as the most restricted factors. The total distribution area of potentially suitable regions for major fish catches extended between 106°30′–109°45′ E and 17°30′–20°45′ N, and the area was lesser during the withered period. During the withered period, the distribution areas of Sciaenidae, Leiognathidae, and Saurida increased, while the distribution area of Trachurus japonicus increased during the high-water period. Sciaenidae and Trachurus japonicus exhibited the highest rates of change at 6.22% and 10.92%, respectively. This indicates that the high-water period may expand the range of suitable habitats for large catches that have an ideal habitat status in the Beibu Gulf. Therefore, it is crucial to anticipate the potential fish habitats in the Beibu Gulf and clarify their spatial distribution patterns.

Ecological Assessment of Fishery Communities in an Otter-Trawl-Restricted, Semi-Enclosed Gulf in Greece

A fishery-independent survey with a commercial bottom otter trawl was conducted in the Pagasitikos Gulf, a semi-enclosed, trawl-restricted gulf in Greece. The study aimed to ecologically assess the fishery communities that are experiencing a decline in fishery landings. Twelve hauls of 30 min duration each were conducted in the eastern, western, and central parts of the gulf at depths between 62 and 97 m. In total, 57 species were captured, with the highest species number recorded in the west (35 species), followed by the center (32 species) and east (29 species). The highest numerical abundance was recorded at the center, followed by the east and west, with an opposing trend exhibited for biomass; however, GLM detected no significant spatial differences (in area or depth) or interaction. Ecological indices exhibited significantly lower values in the west–east area comparison. Linear Discriminant Analysis, mMDS, and hierarchical clustering indicated the presence of two main groups (east and west), with PERMANOVA showing a significant difference in the demersal communities among the identified groups. The results indicated moderately disturbed demersal communities and an increasing level of disturbance from east to west. Considering the economic value of Pagasitikos to the local fishing community, additional fishery management measures are deemed necessary to protect the fishery resources and mitigate the potential risks of overexploitation.

Commercially and economically important fish species from an otter trawling vessel of Bay of Bengal, Bangladesh

The study was conducted on the commercially and economically important fish species in the Bay of Bengal (BoB) that were collected from an otter trawling vessel in March 2020. Within the study period, a total of 52 species were identified, including 17 orders, and 43 families. Perciformes were found to be the most dominant order over all others, contributing about 46.15% of the fish species (24 species under 23 families). A record of catching immature species has been found, which can reduce the sustainability of fisheries. We have found one critically endangered (CR), two near threatened (NT), twenty-five least concerned (LC), four data deficient (DD), and twenty not evaluated (NE) species among the fifty-two species in the BoB during the study period. Many commercially important fish species within the bay need to be exploited properly to get maximum economic benefits. J. Asiat. Soc. Bangladesh, Sci. 49(1): 13-25, June 2023

Improved size selection and estimated at-vessel mortalities for an Australian whiting (Sillago spp.) boat seine

In response towards more species in New South Wales (NSW), Australia being managed via quotas, efforts have recently focused on developing more efficient fishing methods with concomitantly low unaccounted fishing mortality and/or other environmental impacts. The present study contributes information towards this initiative by investigating the relative selectivity of a boat seine with a traditional vs modified codend when targeting eastern school whiting, Sillago flindersi and stout whiting, S. robusta—species historically caught in NSW using otter trawls. The traditional boat seine represented those used in other Australian jurisdictions, tapering from an 85-mm stretched mesh opening in the body to a codend comprising 38.5-mm diamond-shaped mesh ('T0') throughout, and was alternately fished with a modified codend made entirely from 40.9-mm mesh to match the grith of mature individuals of both whiting species and orientated 90° ('T90') with shortened lastridge ropes. Regardless of codend, the boat seine was very efficient at quickly harvesting large quantities of whiting (i.e. often >3 tonnes 60 min deployment–1), with a total discarded-to-retained catch weight ratio (0.44:1) much less than for conventional otter trawls used across similar areas (e.g. >2:1). At-vessel mortalities were high (>95%) for both whiting species, but all were retained. Mortalities were lower for two key discards, bluespotted, Platycephalus caeruleopunctatus (61%) and longspine flathead, P. grandispinis (82%) and both were negatively affected by the total catch weight. The mortality of bluespotted flathead was also negatively correlated to their total length. The T90 codend allowed many immature eastern school whiting to escape, however there were issues with fish being entangled in meshes. We conclude boat seining could represent an effective and relatively selective method for harvesting whiting in NSW, but future work is required to progress an appropriate codend configuration (possibly with fewer T90 meshes) and also address any impacts of rapid, regional depletions on the overall stock structures of both whiting species.

Contemporary analyses of comparative fishing data: a case study of Thorny skate on the Grand Banks (NAFO Divisions 3LNOP)

We re-analyze Thorny skate data from two comparative fishing experiments conducted by DFO in 1995 and 1996 using improved and more contemporary methods to estimate the relative efficiency of the Campelen 1800 demersal shrimp trawl survey protocol compared to the Engel 145 otter trawl. We correct possible bias in the method previously applied to these data. We investigate if there are size-based differences and if depth or spatial regions have important effects on results. We also investigate the influence and robustness of the estimation procedures, which was a concern in the original analyses of these data for other groundfish species. We did not find strong evidence that the relative efficiency of the Campelen trawl protocol compared to the Engel was different for smaller-sized Thorny skate compared to larger ones. However, we conclude that there is a potential that size-based differential catchability existed but there is insufficient information to reliably estimate these effects for Thorny skate. We also found evidence of significant differences in relative efficiency among NAFO Divisions and experiments, which is similar to other flatfish species. However, the mechanisms for these differences are unknown and it is not clear if spatial estimates should be used when converting Engel indices to Campelen equivalents. Hence, we do not recommend a different Engel-Campelen conversion factor than the one currently used in stock assessments for Thorny skates on the Grand Banks (NAFO Divisions 3LNOPs).

Identification of navigation characteristics of single otter trawl vessel using four machine learning models

Identification of navigation characteristics of single otter trawl vessel using four machine learning models

SFA를 이용한 근해어업의 온실가스 배출 효율성 및 감축잠재량 추정

The purpose of this study is to estimate greenhouse gas(GHG) emission efficiency(GEE) and GHG mitigation potential(GMP) of offshore fisheries in preparation for carbon neutral and negative promotion in the ocean and fisheries sector, and to suggest policy improvements related to GHG mitigation. To this end, this study used stochastic frontier analysis(SFA) considering exogenous determinants of GHG emission inefficiency. As a result, the GEE of fleet and drag net fisheries with high fuel cost and vessel age was lower than other fisheries. In addition, the GMP and mitigation ratio of large purse seine, large pair trawl, large otter trawl, and anchovy drag net were higher than those of other fisheries. Lastly, as policy improvements to reduce GHG emission from offshore fisheries, fleet size reduction, development of low-energy used fishing gear, easing of conditions for participation in fishing vessel modernization projects, revising laws to supply eco-friendly fishing vessel, and improvement of the tax-free petroleum supply system were proposed.

Influence of strain-rate on the interaction between towed fishing gears and the seabed

The ability to predict the seabed penetration and the drag force of the gear components of demersal trawlers is of significant benefit to the fisheries industry. It allows for the design of gears of reduced environmental impact and of improved fuel efficiency. This study presents a single-phase strain rate dependent soil model that can accurately predict deformation of a saturated granular soil. Elements of an otter trawl system are modelled as simplified discs which are then translated across a seabed at given speed where horizontal drag force and vertical penetration is measured. This is facilitated using an explicit Finite Element (FE) model developed in ABAQUS alongside a Coupled Eulerian-Lagrangian (CEL) mesh. Comparisons against laboratory experiments showed that the model was correctly able to capture the increase in drag force with towing speed. Further comparisons against full scale sea trials indicated the model generally compared well against test data and correctly identified the trends and magnitudes of drag force against towing speed. From these results, the influence of strain rate in the soil was studied in detail and conclusions drawn on the resultant drag force and penetration of towed fishing gears on the seabed.

Life-history characteristics of Theodore’s threadfin bream, Nemipterus theodorei (Ogilby, 1916), and the yellow-lip butterfly bream, Nemipterus aurifilum (Ogilby, 1910), from southern Queensland, Australia

Theodore’s threadfin bream (Nemipterus theodorei) and the yellow-lip butterfly bream (Nemipterus aurifilum) are two of the most common nemipterids in eastern Queensland. These two species are caught incidentally and at times retained for sale as ‘permitted’ species in Australia’s largest trawl fishery, the Queensland East Coast Otter Trawl Fishery (QECOTF). Despite their prevalence, little biological information is available for these species. This paper reports key life-history characteristics of these nemipterids. Growth and length-at-maturity parameters were estimated from samples collected in southern Queensland. Growth parameters were estimated using back-calculation of fork length (FL) from otolith increment data and modelled within a Bayesian framework to overcome bias resulting from the small number of larger, older animals in the retained bycatch. The von Bertalanffy growth function (VBGF) was identified as the most appropriate growth model with significant differences in sex-specific growth rates evident for both species. Maximum ages were six and four years for N. theodorei and N. aurifilum respectively, with individuals maturing within their first year of life. The length-at-maturity for females was 91 mm FL and 77 mm FL for N. theodorei and N. aurifilum respectively. Increased reproductive activity was observed in the austral spring and summer months. The results from this study can be used to assess the ecological risk posed to these species by the QECOTF.

Species composition and assemblage analysis of fishes caught as bycatch by the Patagonian shrimp fishery in the southwest Atlantic.

Bottom trawl fishing is the most used worldwide gear generating large amounts of discards due to bycatch of a variety of species. Shrimp fisheries are recognized for their high incidence in global discards. In waters of Patagonia Argentina (43°S - 47°S) an industrial shrimp fishery of high economic value is developed whose target species is the Patagonian shrimp Pleoticus muelleri. The information presented in this study comprises a period of 12 years (2003-2014) and it was gathered by the On-board Observer Program. The Program collects information of all species captured in the fishing fleets. The data analyzed corresponds to the double-rigged otter trawler fleet and the coastal fleet. The fish bycatch composition was characterized in both fleets and the frequencies of occurrence of species and the assemblage areas were analyzed. A total of 101 fish species were identified (59 families) of which 69 were bony fishes, 29 cartilaginous fishes and three species of jawless fishes. The assemblages described correspond to coastal and deep waters, and they are integrated by temperate and subtropical species pointing out the area as an ecotonal zone.

Gain or Loss for the Inshore Trawling Ban within Three Miles? Preliminary Data

From 1 June 2010 in the Italian coastal waters of the Northern Adriatic Sea, trawl fishery within three nautical miles became banned. This activity was previously allowed for some species as an exception to legislation. In order to evaluate the consequences both on demersal resources and economic yields of the trawl which will oblige fishermen to trawl beyond three miles, a pilot study was performed. Twenty hauls comparing catch discard and income between hauls within and external to three nautical miles were performed. Results highlighted differences in catch composition both for landing and discard. Landing per unit of effort and discard per unit of effort did not differ in relation to distance from the coast, while income was higher for offshore hauls than inshore ones even if not significantly. Fishery management is a complex task, and the results of this study can contribute to the debate providing new insights into the consequences of the regulation on the trawling within three nautical miles. Considering the high amounts of discard, the habitat damages caused by otter trawling, the presence of juveniles in coastal waters and data regarding fishermen income, this study supports the actual European Community regulation on coastal trawling.

Application of a multi-species bio-economic modelling approach to explore fishing traits within eligible cetacean conservation areas in the Northern Ionian Sea (Central Mediterranean Sea)

The assessment of the spatial overlap between eligible cetacean conservation areas (CCAs) and fishing grounds could be a strategic element in the implementation of effective conservation measures in the pelagic offshore areas. A multi-species bio-economic modelling approach has been applied to estimate the fishing traits in eligible CCAs in the Northern Ionian Sea (NIS, Central Mediterranean Sea) between 10-800 m of depth, adopting the Spatial MAnagement of demersal Resources for Trawl fisheries model (SMART). Four possible CCAs were defined according to the distribution of cetacean species, their bio-ecological needs, as well as socio-economic needs of human activities, identifying a Blue, Red, Orange and Green CCAs in the NIS. SMART spatial domain was a grid with 500 square cells (15×15 NM). The analysis was conducted for the period 2016-2019, considering the Otter Trawl Bottom (OTB) fleet activities in the study areas through the Vessel Monitoring System. The spatial extension of fishing activities, hourly fishing effort (h), landings (tons) and economic value (euros) for each CCA and the NIS were estimated as yearly median values. Fishing activities were absent in the Blue CCA, where the presence of the submarine canyon head does not offer accessible fishing grounds. The hourly fishing effort in the Green area accounted for about 22% (3443 h) of the total hourly effort of the NIS, while the Orange and Red areas were about 8% (1226 h) and 2% (295 h), respectively. The Green CCA corresponded to about 14% (36 tons) of the total landings in the NIS, whereas the Orange and Red areas represented about 9% (22 tons) and 6% (16 tons), respectively. The Green CCA accounted for about 13% (156 thousand euros) of the total economic value of the NIS, while the Orange and Red areas represented about 6% (69 thousand euros) and 4% (44thousand euros), respectively. Results showed no or negligible negative effects on trawl activities by potential spatial restrictions due to the establishment of CCAs highlighting the importance to consider spatially integrated information during the establishment process of conservation areas for cetacean biodiversity according to the principles of Ecosystem Based Management.

Linking Species Functional Traits to Specific Biogeochemical Processes under Trawling Pressure.

Simple SummaryBottom trawls when fishing move over large areas with different parts of the gears physically impacting the sea bottom, including the trawling wires, doors, ground rope and net. In this way, the trawl nets remove animals from bottom waters, the sediment surface and shallow sub-surface. The animals that live in the sea bottom with their activities and lifestyle play an important role in major ecosystem processes such as nutrient cycling. In this study, we investigated the relationship between species functional characteristics and ecosystem functions under trawling pressure. Our results indicated that under trawling, more opportunistic lifestyles and deposit feeders were associated with the ecosystem processes while in the undisturbed areas these processes were connected with bioturbating and burrowing species. Finding these links helps scientists and policy makers to better predict the impact of fishing disturbance on marine environment and set appropriate thresholds for marine ecosystem impacts.The impact of otter trawling on the relationship between functional traits of benthic invertebrates and specific biogeochemical processes were investigated in the oligotrophic Cretan Sea. The fishery is managed through a seasonal closure during the summer. During two seasons (winter and summer) replicate samples were taken from the field from a commercial trawl ground and an adjacent control area. Environmental parameters related to sediment biogeochemistry were measured including particulate organic carbon, sedimentary organic carbon, bottom water and sedimentary chlorophyll a and phaeopigment concentrations as well as benthic oxygen consumption. A significant impact of trawling was recorded only for bottom water chlorophyll and sedimentary organic carbon. Furthermore, the links between species traits and specific ecosystem processes were affected by trawling, highlighting the importance of unique functional modalities on ecosystem functioning. The traits that mostly influenced benthic biogeochemistry in the control sites were related to bioturbation and burrowing activities. In contrast, in the trawled sites, the associated traits were related to more opportunistic lifestyles and deposit feeding species that do not act as bioturbators. Thus, under trawling disturbance, this shift can decouple the species-sediment relations and affect nutrient cycling.