Bottom Trawl Research Articles

Observations on the Biology and Fishery of the Marbled Spinefoot (Siganus rivulatus Forsskål & Niebuhr, 1775) in the Eastern Red Sea

This study aims to enhance our understanding of the marbled spinefoot (Siganus rivulatus) population along the Red Sea coast of Saudi Arabia. It investigates whether the stock is subject to overfishing and tests the hypothesis that current fishing mortality exceeds sustainable thresholds. A total of 6192 specimens were sampled during a comprehensive survey conducted from 2022 to 2024, utilizing a range of fishing methods, including handline, trap, gillnet, and demersal trawl fisheries. The sampled fish ranged in total length (TL) from 100 to 335 mm and in total weight (W) from 17 to 470 g. The length–weight relationship was W = 0.0175 × TL2.92. Growth parameters derived from the von Bertalanffy model were TL∞ = 43.5 cm, K = 1.12 year−1, and t0 = −0.18 year. The median size at first maturity was estimated at 14.83 cm TL for both sexes. Virtual Population Analysis revealed fishing mortality rates ranging from 0.01 year−1 to 0.89 year−1 across age classes 1 to 5 years, with exploitation levels of 0.6, 0.55, and 0.5 at ages 3, 4, and 5, respectively, indicating slight overfishing. The annual average catch of marbled spinefoot along the Saudi Arabian Red Sea coast was approximately 211 tonnes, contributing an estimated 1.8 million USD to the national economy. Maintaining the current fishing effort at sustainable levels is essential to ensure the long-term viability of this stock.

Diet Composition and Feeding Intensity of Four-Spotted Megrim, Lepidorhombus boscii (Risso, 1810), in the Eastern Adriatic Sea

Feeding habits of the four-spotted megrim, Lepidorhombus boscii, from the eastern Adriatic Sea were examined. A total of 1070 individuals collected using a bottom trawl net between July 2020 and June 2021 were analyzed. A high percentage of empty stomachs (63.27%) was recorded. The food composition proved that L. boscii is a carnivorous species. The identified prey of L. boscii was divided into seven groups: Teleostei, Bivalvia, Gastropoda, Cephalopoda, Isopoda, Mysida, and Decapoda. Decapods were the most important prey (%IRI = 58.18), followed by cephalopods (%IRI = 10.93). At the species level, the most important prey were the decapods Parapeneus longirostris (%IRI = 11.48) and Goneplax rhomboides (%IRI = 5.92). Statistically significant seasonal variations in diet were recorded; decapods dominated in spring, summer, and winter, whereas cephalopods prevailed in autumn. There were no statistically significant differences in the food composition between the three size categories. Decapods were the most important prey in all size categories (%IRI > 50). The lowest feeding intensity, as well as the highest percentage of empty stomachs, was recorded in winter, which is also the main spawning season of this species in the Adriatic Sea.

Unraveling Fish Community Diversity and Structure in the Yellow Sea: Evidence from Environmental DNA Metabarcoding and Bottom Trawling.

The use of environmental DNA (eDNA) metabarcoding to analyze fish species diversity across different aquatic ecosystems is well documented. Nonetheless, there is a gap in validating eDNA metabarcoding studies on the diversity and structure of fish communities in coastal ecosystems, particularly in comparing these findings with bottom trawl catch data. In this study, we employed eDNA metabarcoding to explore species composition and relative abundance in fish communities, taxonomic-level diversity variations, and the interplay between community structures and environmental factors in the Yellow Sea and compared these results with those obtained from bottom trawl catches. In addition, we compared the various methods used to estimate the distributions of taxonomic, phylogenetic, and functional diversity factors. We found that eDNA metabarcoding detected a greater number of species (86 vs. 41), genera (73 vs. 37), and families (42 vs. 25) than bottom trawl results at each sampling station. eDNA metabarcoding provided higher Shannon, Simpson, and Chao1 alpha diversity indices than the bottom trawl results. The PCoA results showed that eDNA metabarcoding samples could be more clearly separated at the sampling sites in the Zhuanghe (ZH) and Lianyungang (LYG) areas than bottom trawling samples. The RDA analysis indicated that temperature, along with NO3- and NH4+ concentrations, were pivotal in shaping the geographical patterns of fish communities, as identified through eDNA metabarcoding, echoing findings from bottom trawling studies. Furthermore, our findings suggest that eDNA barcoding surpasses bottom trawling in detecting taxonomic and phylogenetic diversity, as well as in uncovering greater functional diversity at the local level. Conclusively, eDNA metabarcoding emerges as a valuable complement to bottom trawling, offering a multifaceted approach to biodiversity monitoring that not only boosts efficiency but also reduces environmental impact on coastal ecosystems.

Newfoundland and Labrador Shelf ecosystem dynamics post cod collapse

In highly dynamic systems, a key challenge of modern fisheries management is to promote ecosystem and stock health in the face of fishing pressure combined with environmental and ecological perturbations. Failing to account for changes in ecosystem productivity or structure can result in overexploitation that, when left undetected, can severely limit the ability of an ecosystem or stock to recover. Here, we evaluate the dynamics of the Newfoundland and Labrador Shelf ecosystem following the groundfish collapse of the early 1990s. Using data from an annual bottom trawl survey, we analyzed ecosystem structure across space and time. The past 3 decades have been characterized by shifting ecosystem structure across the Shelf, from invertebrate-dominated to groundfish-dominated. Total ecosystem biomass remains far below pre-collapse levels and spatial heterogeneity of species distribution has increased. Several factors, including system productivity and prey availability, are explored for their role in the decoupling of ecosystem biomass and community composition. Measures of ecosystem structure and productivity have important fisheries and management implications when determining appropriate reference points and harvest control rules. Our study demonstrates the importance of considering ecosystem-scale processes to sustainably manage fisheries.

Identifying spatiotemporal variations in four-spot megrim (Lepidorhombus boscii) fishery nurseries to enhance management and stock assessment

IntroductionThe identification of recruitment areas and other essential fish habitats of exploited stocks is a fundamental requirement for the development of marine spatial planning and ecosystem conservation measures. Reducing recruitment mortality is particularly relevant on the northern continental shelf of the Iberian Peninsula and is one of the key prerequisites for the future sustainability of trawl fisheries.MethodsIn this study, the distribution of nursery areas of four-spot megrim (Lepidorhombus boscii) was analyzed using time series of scientific bottom trawl survey data to assess whether recruitment areas are persistent over time. Four environmental variables were considered as potential predictors of recruit distribution, as they may influence habitat selection by this species: sea bottom temperature, sea bottom salinity, bathymetry, and sediment type. Additionally in a second stage and based on the spatial findings during this work, the recruitment abundance index within the a4a stock assessment model currently used to provide scientific advice for this species was divided into two spatial areas.ResultsSpatial analyses revealed a specific depth preference for four-spot megrim recruits, with higher abundance in shallower waters, particularly within the 150 to 300 m depth range, respect deeper ones. More importantly, our findings showed significant spatial-temporal variability in four-spot megrim nursery areas. Furthermore, the results of the updated assessment model showed differences in biological reference points (BRPs) compared to the existing model.DiscussionThis suggests that static spatial management approaches may be ineffective due to environmental variability and underscoring the importance of incorporating spatial structure into the assessment process. This approach enables more accurate stock evaluations and more effective, sustainable management, thus laying the groundwork for a potential implementation of spatial stock assessment for this species.

Implementation of Marine Environmental Impact Assessment Mechanism for Marine Spatial Planning in Taiwan

To undertake a detailed and comprehensive research on the marine environmental impact assessment mechanism of marine spatial planning in Taiwan with a specific focus on the environmental impact assessment (EIA) technique. The present research adopts methodological model based on the principles of environmental impact assessment (EIA) for analysis of the Taiwan marine ecosystem. The cumulative environmental impact of human activities within the area of scope of the study is computed as the sum of the impacts of identified human activities on selected components of the ecosystem. The collection of data related to the human activities and ecosystem components variables was limited to the last five years, between 2018 and 2023, and the pre-existing data that were openly available were sourced from different sources including the Taiwan marine spatial planning (MSP) related governmental agencies, consultancies and academic research. The impactful human activities on the Taiwan marine environment include ocean bottom trawls, oil spill shipping and sand loss extraction activities as well as turbidity ocean bottom trawl, boating effects, mining activities and marine infrastructural projects and the most affected ecosystem components include the artificial and natural coastal reefs, the shoreline shallows, the deep ocean spaces and the biological components which include the plants and the animals. The most impactful human activity on the Taiwan marine environment is attributed to dumping activities within the coast zone areas which has had the most significant impact on the coastal zone ecosystem.

Molecular Insights into the Marine Gastropod Olivancillaria urceus: Transcriptomic and Proteopeptidomic Approaches Reveal Polypeptides with Putative Therapeutic Potential.

The marine environment is a rich source of new biotechnologies and products. Bottom trawling for shrimp species such as Xiphopenaeus kroyeri and Farfantepenaeus brasiliensis leads to the unintentional capture of non-target species, known as bycatch, which includes a variety of marine life that are often discarded without economic value. A common bycatch species on the southeast coast of Brazil is Olivancillaria urceus (O. urceus), a carnivorous gastropod that feeds mainly on bivalves. Despite its abundance, this species is still little studied, especially for biotechnological applications. Other gastropods such as Conus are known for their diverse and potent toxins, which offer great potential for pharmacological discoveries. In this study, an omics approach, including transcriptomics and proteopeptidomics, was applied to explore O. urceus at the molecular level. The transcriptome of the muscle foot/mantle led to the annotation of 19,097 genes via Gene Ontology, identifying 20 toxin-like transcripts identified considering the Gastropod class. The proteome fraction confirmed 2179 transcripts, including sequences with toxin activity, such as conotoxin precursors, Conodipine-P3, and BPTI/Kunitz domain-containing proteins. In addition, 9663 peptides of 1484 precursor proteins were detected in the peptide fraction, including 2 sequences representing neurotoxins. The identification of these sequences could lead to the discovery of new molecules with therapeutic potential.

Bottom Temperature Effect on Growth of Multiple Demersal Fish Species in Flemish Cap, Northwest Atlantic.

This study investigates the effects of warming water on growth in seven demersal fish species including Atlantic cod (Gadus morhua), American plaice (Hippoglossoides platessoides), Greenland halibut (Reinhardtius hippoglossoides), roughhead grenadier (Macrourus berglax) and three species of redfish (Sebastes spp.) in the Northwest Atlantic and compares the changes in growth across species. Length-at-age data were collected from EU bottom trawl surveys from 1993 to 2018, and bottom temperature data were obtained from the Copernicus Marine Service. Generalised additive mixed models (GAMMs) were used to describe the temperature effects on growth. The analysis was carried out separately for males and females. Both sexes of all species except American plaice showed significant temperature effects on growth. To obtain the growth parameters, von Bertalanffy growth functions (VBGFs) were fitted to the predictions from best-fit GAMMs for all species and both sexes under five different bottom temperature scenarios (3, 3.5, 4, 4.5 and 5 °C). The predictions from all best-fit GAMMs were broadly similar in form to the fitted von Bertalanffy growth functions (R2 > 90%). Increased bottom temperature generally resulted in a decrease in the asymptotic length (L∞) and an increase in the growth rate (k). The species with the most dramatic increase in k over the temperature range of 3 °C to 5 °C was Atlantic cod, for which k increased from 0.05 to 0.13 year-1 in females and from 0.08 to 0.14 year-1 in males. The maximum length (Lmax), predicted by the VBGF at maximum age generally declined from 3 °C to 5 °C. The species with the most pronounced decline in Lmax was beaked redfish (S. mentella). An increase in the proportion of smaller individuals could impact population productivity and result in lower biomass available to fisheries. Uneven changes in fish growth in the warming ocean could also have wider ecological implications and alter the trophic landscape.

Under pressure: deep-sea elasmobranchs experience high mortality and stress in a crustacean trawling fishery

Crustacean bottom trawling in southern Portugal is an economic and culturally important fishing activity but may result in considerable bycatch of deep-sea elasmobranchs (DSE). Due to DSE life-history strategies, at-vessel mortality (AVM) rates in crustacean bottom trawl fisheries are expectedly high but require further investigations. This study assessed the at-vessel condition of 18 species of DSE, and AVM rates and stress of four deep-sea shark species (Etmopterus pusillus, E. spinax, Galeus melastomus, and Scymnodon ringens), to understand the impact of bottom trawling on these animals. Opportunistic sampling on a crustacean trawler in the southern Portuguese coast, revealed that 95% of specimens were either dead (n = 1,258) or in poor condition (n = 224) upon collection, underscoring their minimal chance of post-release survival. General linear model analyses showed that AVM was species-specific and highest in smaller sharks, as well as in those from hauls that exhibited larger temperature differences between bottom and surface waters, and those caught in hauls with heavier codend weight using a 55 mm codend mesh (targeting shrimp and prawns) instead of those caught in hauls using a 70 mm codend mesh (targeting Norway lobster). Stress, evaluated through metabolites and electrolytes levels in sharks' plasma, indicated significant differences in potassium, urea, and magnesium levels between live and deceased specimens of E. pusillus and G. melastomus, suggesting these as reliable mortality markers. Elevated lactate levels in G. melastomus further pointed to high post-release mortality risk. These findings highlight an urgent need to find solutions to mitigate the impacts of bottom trawling on those DSE, which are thoroughly discussed. A coordinated, multi-stakeholder approach involving researchers, the fishing industry, and regulatory bodies is crucial for developing and implementing effective, and more sustainable fisheries management and protection of DSE populations.

Insight into the biology, ecology and population trends of the brown skate, Raja miraletus Linnaeus, 1758, in the Balearic Islands.

We studied the life-history traits of the brown skate (Raja miraletus) population off the Balearic Islands, which is a species commonly caught as bycatch by the bottom trawl fishery in the Western Mediterranean. Samples and data were collected year-round from commercial catches and yearly during spring-summer from the International Bottom Trawl Survey in the Mediterranean. The maximum total length observed was 43 cm, consistent with other Mediterranean regions but smaller than in Tunisia and Egypt. Recruitment was higher in winter, aligning with the observed summer spawning peak. The smallest sexually active individuals were 34 and 32 cm for females and males, respectively; with L50 values of 35.9 and 33.4 cm for females and males, respectively. Length-weight relationships differed between sexes for total weight but not for eviscerated weight, highlighting variations in the mass of the organs rather than the sexual dimorphism of carcasses. Growth parameters indicated slower growth (K = 0.14) and smaller L∞ (49.63 cm) in the Balearic Islands compared to other Mediterranean areas. The estimated trophic level from stomach contents was 3.72 ± 0.63, with crustaceans appearing as its main prey (accounting for 96% of Index of Relative Importance), with an ontogenetic dietary shift observed between adults and juveniles, transitioning from a diet based on a greater proportion of small crustaceans to one that includes larger crustaceans and fish. Juvenile and adult populations are not bathymetrically segregated. Both mean annual density and frequency of occurrence showed stability over two decades, potentially linked to the decrease in fishing pressure on the shelf and the implementation of protected areas. However, the historical context of overexploitation in the area emphasizes the need to consider this stability cautiously. The results presented here enhance the understanding of R. miraletus in the Balearic Islands, providing critical data for potential management and conservation purposes.

Effects of Climate‐Responsive, Fjordscape, and Aquaculture‐Associated Environmental Drivers on Fjord Hyperbenthic Community Structure

AbstractMarine community sensitivity to climate change can be informed by examining community patterns along current environmental gradients. Fjords provide natural laboratories for such studies due to their variable oceanographic conditions that can differ from basin to basin. Bottom trawl samples were collected from 17 fjord basins and nearshore coastal stations (59–63°N) from 2011 to 2022. We examined how climate‐responsive (temperature, salinity, and oxygen) and fixed environmental variables (bottom depth, sill depth, and distance to coastline) as well as aquaculture impact score (calculated using biomass capacity within a 5 km radius) correlate with differences in hyperbenthic community biomass, diversity, and composition. We focused on fish and crustacean species composition, diversity, and biomass as well as the biomass and distribution of a recently proliferating jellyfish, Periphylla periphylla. Our results indicate that fixed environmental variables (e.g., bottom depth and sill depth) are important predictors of community biodiversity; biodiversity decreased with bottom depth and was highest in fjord basins with 151–250 m deep sills. Fish and crustacean biomass was negatively correlated with distance to coastline. Four community‐types were identified which separated mainly by depth, geographic location (fjord or coastal), and presence of P. periphylla. We found limited evidence of climate‐responsive or aquaculture‐associated drivers being strong predictors of hyperbenthic community differences. The exception was that P. periphylla biomass was negatively correlated with temperature. Oxygen was not a significant predictor of any community patterns. Since West‐Norwegian fjord species are common to the N. Atlantic, the study offers broader insights into community sensitivity to environmental change.

TinyVAST: R Package With an Expressive Interface to Specify Lagged and Simultaneous Effects in Multivariate Spatio‐Temporal Models

ABSTRACTAimMultivariate spatio‐temporal models are widely applicable, but specifying their structure is complicated and may inhibit wider use. We introduce the R package tinyVAST from two viewpoints: the software user and the statistician.InnovationFrom the user viewpoint, tinyVAST adapts a widely used formula interface to specify generalised additive models and combines this with arguments to specify spatial and spatio‐temporal interactions among variables. These interactions are specified using arrow notation (from structural equation models) or an extended arrow‐and‐lag notation that allows simultaneous, lagged and recursive dependencies among variables over time. The user also specifies a spatial domain for areal (gridded), continuous (point‐count) or stream‐network data. From the statistician viewpoint, tinyVAST constructs sparse precision matrices representing multivariate spatio‐temporal variation, and parameters are estimated by specifying a generalised linear mixed model (GLMM). This expressive interface encompasses vector autoregressive, empirical orthogonal functions, spatial factor analysis and ARIMA models.Main ConclusionTo demonstrate, we fit to data from two survey platforms sampling corals, sponges, rockfishes and flatfishes in the Gulf of Alaska and Aleutian Islands. We then compare eight alternative model structures using different assumptions about habitat drivers and survey detectability. Model selection suggests that towed‐camera and bottom trawl gears have spatial variation in detectability but sample the same underlying density of flatfishes and rockfishes and that rockfishes are positively associated with sponges while flatfishes are negatively associated with corals. We conclude that tinyVAST can be used to test complicated dependencies representing alternative structural hypotheses for research and real‐world policy evaluation.

Seasonal spatial distribution patterns of AmphiOctopus ovulum in the East China Sea: current status future projections under various climate change scenarios

Currently, there is also little up to date information on the the current population status and life history traits of AmphiOctopus ovulum, a very often seen cephalopod species in the East China Sea. It is therefore important to figure out the seasonal spatial distribution of this species, both in terms of number and biomass, and the environmental variables which determine them. Additionally, climate change plays an important role in determining the characteristics of individual species and thus on the ecosystems they inhabit. We set out to understand the responses of A. ovulum to habitat variables and to make projections based on the climate change scenarios described in the IPCC’s SSP1-2.6 and SSP5-8.5 criteria. We carried out seasonal bottom trawling surveys in the East China Sea region during 2018 and 2019 to fill this knowledge gap. Our results showed that the average individual size values ranged from 17.80−43.00 g·ind-1 in spring and 23.49−33.00 g·ind-1 in summer; the measured sea bottom temperature, sea bottom salinity, and depth value ranges were 10.81−27.06°C, 31.73–35.25‰, and 91–103 m independently in spring to winter. Our study showed that A. ovulum was distributed in the area between 27°–29°N, 122.5°–125°E during spring to autumn, and expanded into the area between 26.5°–32.5°N, 121°–124.5°E in winter. The core habitat of A. ovulum was centered on the area between 27.5°–28°N, 122.5°–123.5°E, and can be expected to expand to the northeast and southwest independently under the most likely global warming scenarios. Our results will benefit the development of suitable conservation measures for cephalopod habitats, and incorporate the impacts of climate change into fisheries management programs.

Spatial Change of Dominant Baltic Sea Demersal Fish Across Two Decades.

The arange and biomass distribution of marine fish species offer insights into their underlying niches. Quantitative data are rare compared to occurrences and remain underused in species distribution models (SDMs) to explore realized niches-the actual space occupied by a species shaped by abiotic and biotic factors. Local densities drive differences in species contributions to ecological processes and ecosystem function rather than through presence alone. If a species growth rate is strongly controlled by macro-environmental conditions, then predicting geographical abundance or densities should be possible. We collated 20 years (2001-2020) of standardized scientific bottom trawl data to fit several versions of hierarchical generalized additive models using biomass (kg km-2) of four dominant demersal species (Common dab, European flounder, European plaice, Atlantic cod) within yearly and seasonal (winter and autumn) time windows. Covariates were represented with trawl-level geographic information (position, depth) and high-resolution oceanographic features. This work illustrates species-specific spatiotemporal biomass patterns across two decades and demonstrates superior predictive performance with seasonally variable smoothing terms, revealing seasonally different responses to oceanographic predictors. Firstly, we find relative stasis in Common dab biomass which is linked to the macro-environmental salinity gradient in the western Baltic Sea but with different temperature responses across seasons. Secondly, we show both European flounder and plaice have increased in biomass in the western Baltic Sea with different seasonal relationships to bottom temperature, and that flounder switches between salinity conditions based on season during spawning/feeding periods. Lastly, both juvenile and adult Atlantic cod life stages are shown to have declined most significantly in the Bornholm Deeps and the Gdańsk Deeps. For cod, we conclude that biomass was less reliably predicted in comparison to the other major Baltic demersals studied here, warranting dynamic fishing covariates as a formerly major commercial fishing target. These models approach more dynamic species distribution models and are increasingly valuable to constrain uncertainties in biogeographic forecasting which often rely on annually-averaged response curves, occurrence data, and suitability maps which rarely discriminate between areas of high and low biomass areas in space and time.

A new species of supergiant Bathynomus A. Milne-Edwards, 1879 (Isopoda: Cirolanidae) from the Paracel Islands, South China Sea.

Bathynomusparacelensis sp. nov., a medium-sized supergiant Bathynomus, is described from specimens obtained at Zhengbin fishing port in Keelung, Taiwan and had been caught in the water near Paracel Islands, South China Sea. Due to its similar shape to B.jamesi, this species has often been mistaken for juveniles or immatures of B.jamesi by fishermen working in this area. Species of Bathynomus can be distinguished morphologically and genetically. The differences from B.jamesi are in the shorter body, clypeus shape, uropod endopod and gene sequence. The difference from B.vaderi is in the body shape, clypeus shape, hook number of maxilliped endite and spines number of maxilulla. Based on the morphological and genetic data results, the specimen is a hitherto undescribed species. The samples were collected as a bycatch species in the deep-sea bottom trawl fishery. The distribution area and depth of this new species and population size are still unclear. B.paracelensis sp. nov. is the third supergiant Bathynomus discovered in the South China Sea after B.jamesi and B.vaderi. Its remarkable feature is its short body length and sub-parallel shape. In addition, it is different from B.jamesi and B.vaderi in features such as clypeus shape, number of maxillula keratinised spine and pleotelson spine almost straight. Phylogenetic and barcoding gap analyses confirm that B.paracelensis sp. nov. is not the same species as B.jamsei. Many morphological differences also indicate that it should be a different species from B.vaderi. B.paracelensis sp. nov. may be an intermediate species between giant and supergiant, possessing characteristics of both categories, which can increase researchers' understanding of Bathynomus biodiversity.

Retrieval of abandoned, lost, or otherwise discarded fishing gear through different retrieval modes and analysis of biota on the retrieved gear.

Abandoned, lost, or otherwise discarded fishing gear (ALDFG) contribute significantly to marine debris, and studies regarding this subject are getting coign of vantage worldwide. This study assessed ALDFG through retrieval exercises in three prominent fishing locations, viz., Enayam, Vizhinjam, and Kochi along the southwest coast of India. The retrieval of ALDFG was carried out by scuba diving, creeper/grapple retrieval, and a bottom trawling survey by covering an area of 1.1 km2, 1.25 km2, and 32 km2, respectively, in the three study locations, Enayam, Vizhinjam, and Kochi. A total of 55.6kg ALDFG were retrieved which mainly composed of whole or parts of lobster traps, trawl cod ends, fish traps, gillnets, long lines, head ropes/foot ropes, and squid jigs contributing 46, 25, 14, 9, 4, 2, and 0.5%, respectively, to the total retrieved gear. Lobster traps dominated the retrieved ALDFG. The scuba diving mode of retrieval was most effective in Enayam and Vizhinjam due to water clarity and suitable depth range. Bottom trawling was effective in Kochi as the trials were carried out in commercial trawling grounds, where concentrations of ALDFG were reported as bycatch in trawl operations. The creeper/grapple retrieval trial along the Kochi coast failed due to the design's incompetency for deep muddy ground at the test site. Overall, 670 organisms were attached/caught in the retrieved gear of which 62% were live and 38% were dead. Perna viridis (green mussel) was the dominant species among the three study sites. The traps retrieved from Enayam and Vizhinjam did not show any signs of ghost fishing but were in a state of initiating a new ecosystem for benthic organisms. The traps of Enayam were made of HDPE webbing which contributes to marine plastic pollution, while traps of Vizhinjam were made of natural materials. Other retrieved gear types also did not show any evidence of ghost fishing. However, the polyamide (PA) monofilament gillnets disrupted the benthic mussel bed and coral reef in Enayam and Vizhinjam, respectively, by covering the habitat and hindering the growth of organisms native to the habitat. This highlights the occurrence of ALDFG and its subsequent impact on the biota in the studied area. This study, covering a smaller area, points to the need for further extensive research in this direction for the responsible management of fishing gears along the Indian coast.

Long‐term recovery and food web response of benthic macrofauna following cessation of bottom trawling in a marine protected area

AbstractThe understanding of the depletion of species and communities and recovery following the reduction of pressures is fundamental in conservation biology. The impact of bottom trawl fisheries on benthic communities has been well studied, but there are few studies of the long‐term recovery after the cessation of bottom trawling. Here we followed the recovery of the benthic macrofaunal community over 12 years in a large (426 km2) no‐take zone (NTZ) area in the south Kattegat after demersal trawling was stopped and compared it to a nearby area where trawling continued. Using multivariate analyses, we found shifts in the community composition. Two species of burrowing brittle stars, Amphiura filiformis and Amphiura chiajei, dominated abundance and biomass and decreased in the closed area (abundance effect size A. filiformis 48%; A. chiajei 45%). In parallel, there was an increase in benthivore flatfish. Stomach contents of the dominating flatfishes matched the availability of benthic prey taxa, and brittle stars were the staple food. Food web effects thus appear to override the decrease in mortality of the dominant macrofauna caused by the cessation of trawling in the NTZ. The recovery response in the species community in the NTZ correlated with the pattern in community composition along a chronic bottom trawling intensity gradient in the same area. This indicates that the recovery of the benthic community is not random but follows a successional pattern that can also be observed in chronic states of disturbance from bottom trawling. This is important information from the perspective of management efforts to restore marine ecosystems from the impact of bottom trawl fisheries, as it indicates that reduced effort may lead to predictable recovery.

Deep-sea ecosystems in the north-eastern Alboran Sea (western Mediterranean): quantifying assemblages and anthropogenic activity in the Seco de los Olivos Bank

Seafloor elevations (e.g., seamounts, banks, mounds) are essential underwater features for supporting and maintaining global marine biodiversity. Such geomorphological features might be of particular relevance to preserve biodiversity in the Mediterranean Sea, where a high number of anthropogenic impacts threaten deep-sea ecosystems. Using imagery from a remotely operated vehicle (ROV), deep-sea megabenthic and demersal fish assemblages were identified and quantified in some of the less studied areas of the Seco de los Olivos Bank (also known as Chella Bank), a seafloor elevation considered a hotspot of biodiversity in the Alboran Sea, Western Mediterranean. The 62 taxa identified were grouped into five well-defined benthic and demersal assemblages, mainly influenced by substrate type and typified by massive sponges, cold-water corals, sea pens, and ray-finned fishes. Nine taxa were identified as indicators of vulnerable marine ecosystems (VMEs) and/or endangered species. The heterogeneous distribution of substrate types plays a key role in assemblage composition, with hard substrates enhancing biodiversity at the local scale. A wide variety of indicators of anthropogenic activities were found, including bottom trawling marks, remains of fishing gears, and other types of marine litter, whose presence seemed to reduce the diversity of the observed assemblages. The results presented here improve the still scarce quantitative assessments of deep-sea benthic ecosystems to implement effective management measures in the framework of the main European policies (e.g., Habitats Directive, Marine Strategy Framework Directive) to reach 2030 conservation goals.

Seasonal Spatial Distribution Patterns of Abralia multihamata in the East China Sea Region: Predictions Under Various Climate Scenarios.

The enoploteuthid squid species Abralia multihamata plays an important role in the epi- and mesopelagic food web. However, little is known about its seasonal and spatial distribution, life history traits, and environmental threats that may affect it. In this study, we used independent scientific bottom trawling surveys conducted in the southern Yellow and East China Seas during 2018-2019 to identify the seasonal spatial distribution characteristics of biomass, number, and size of this species as well as the relationships among these features and measured environmental factors. We also predicted the habitat distribution variations of the species under different climate scenarios (the present, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) and seasons. The results revealed a continuously increasing individual size from the southern Yellow Sea to the East China Sea in spring, summer, and autumn, which suggests the possibility of growth differences in different water temperature conditions. The seasonal order of regional mean biomass and number was autumn > spring > summer and winter in the study area, and, for size, it was spring > summer and autumn > winter. This result shows that the majorities of recruitment and breeding groups occurred in autumn and spring, respectively. In addition, our results showed that the most beneficial case in terms of average habitat area was SSP3-7.0 in 2050, and the most loss occurred under SSP1-2.6 and SSP5-8.5 in 2100. Few benefits were predicted for the other cases under the various climate scenarios. This study provides a new understanding of the distribution and life history of A. multihamata in the East China Sea region.

Regional Variation in Active Bottom‐Contacting Gear Footprints

ABSTRACTFishing with active bottom‐contacting gears (here collectively described as 'bottom trawling') is considered the greatest source of anthropogenic disturbance to marine sediments. However, uncertainties are apparent in studies evaluating the severity of their impacts from fishing with these gears at the global scale. A major uncertainty is the estimation of the area of seabed disturbed by applying European‐based vessel size to gear footprint (i.e., gear width) relationships to the global fleet, thereby assuming these relations hold worldwide. To test the strength of this assumption, we conducted a structured review to understand global variation in fishing gear parameters and, thus, footprint of bottom trawling gears. While we find a European bias in the primary literature, we find that the relationship between vessel size and gear footprint differs significantly among FAO Major Fishing Areas, suggesting that European‐based relationships are not representative of fleets worldwide. For example, otter trawler footprints in the Mediterranean and the Black Sea increase by 10.2 m for every meter increase in overall vessel length compared to just 3.3 m for otter trawlers in the Northwest Atlantic. These findings challenge the reliability of previous estimates of the global footprint of bottom trawling gears, thus highlighting the urgent need for improved availability of commercial data to create a globally representative data set that can address uncertainties in the quantification of anthropogenic disturbance of the benthic environment and the consequential impacts on biodiversity, ecosystem integrity and carbon losses.