Commercial Trawl Research Articles

Spatio-temporal dynamics in the discards of trawl fisheries in the eastern Mediterranean

Discarded catches in the main fishing areas of the Turkish coasts of the Aegean Sea were studied using data from commercial trawlers. The study area spans the Turkish coast of the Aegean Sea from Saros Bay (north) to Güllük Bay (south), and data were collected from trawl fishing grounds between April 2010 and 2012. Particular attention is paid to discard per unit effort (DPUE) and discard ratio. Generalized additive modelling (GAM) techniques with Tweedie family and log-link function were used to examine various predictor variables (duration, season, depth, longitude and latitude) on the DPUE of total catch. Discard ratio varied from 0.01 in winter at Çanakkale to 0.90 in summer at Güllük. Total discard ratio was calculated to be 0.33 for pooled data. The DPUE values ranged between 0.2 kg h–1 in autumn at Sığacık and 45.5 kg h–1 in spring at Güllük, with a mean value of 7.6±5.7 kg h–1. Modelling DPUE values in relation to season vs coordinates revealed spatio-temporal differences. The relationship between the dependent variable (DPUE) and the independent variable (depth) showed fluctuations, but haul duration displayed a decreasing trend in the modelling. It was determined that a considerable amount of trawl discards was obtained in the Aegean Sea. The results of this paper should be considered to create a regional discard policy and management plan in the eastern Mediterranean.

First record of marine goby Priolepis profunda (Weber, 1909) (Teleostei: Gobiidae) from Taiwan

The marine goby Priolepis profunda (Weber, 1909) is recorded for the first time from Taiwan, based on three specimens (33.2–36.4 mm SL) collected from fishery by-catches of commercial trawling that landed at Da-shi fish port in Ilan County and Keziliao fishing harbor in Kaohsiung, Taiwan. The redescription of current newly recorded species would be provided in this paper.

Estimation of Growth and Mortality Parameters for the Annular Seabream Diplodus annularis (Linnaeus, 1978) in the Southern Aegean Sea

The growth and mortality parameters were examined for the annular seabream Diplodus annularis collected from the Didim coast, Southern Aegean Sea. A total of 654 annular seabream individuals, 263 female (40.21%) and 391 male (59.79%), were sampled by commercial trawlers and gillnets from September 2022 to January 2024. The total length varied between 9.0 and 24.3 cm for females, 8.6 and 24.0 cm for males, and the weight varied between 8.60 and 146.57 g for females, 7.00 and 128.96 g for males. The length-weight relationships were calculated for females, males, and all individuals as W = 0.0115 x L2.9641, W = 0.0131 x L2.8995, and W = 0.0118 x L2.9440, respectively. The growth pattern was determined as negative allometric. The maximum age class was V for both females and males. The von Bertalanffy growth parameters were L∞ = 25.27 cm, k = 0.424 year-1, t0 = -0.308 years for females; L∞ = 25.63 cm, k = 0.338 year-1, t0 = -0.935 years for males; L∞ = 27.43 cm, k = 0.283 year-1, t0 = -1.121 years for all individuals. The growth performance index (Φ´) for females, males, and all individuals were 2.432, 2.347, and 2.329, respectively. This study provides the first information on the growth and mortality parameters of D. annularis along the Didim coast, southern Aegean Sea.

Length-based assessment of penaeid shrimp fishery stocks along the north-eastern Arabian Sea

Penaeid shrimps are a key resource in marine fisheries and are of great ecological and economic importance. The north-west (NW) coast of India contributes significantly (~30%) to the penaeid shrimp landings in India. Four species of penaeid shrimps, namelyParapenaeopsis stylifera, Solenocera crassicornis, Metapenaeus affinis, and M. monoceros, were assessed using Length-based spawning potential ratio (SPR) based on the length frequency data collected during 2017-21, from commercial trawlers operating in the depth range of 20-100 m along the north-west coast of India bordering the north-eastern Arabian Sea. The current status (2021) of P. stylifera, S. crassicornis and M. affinis was found to be healthy, with a spawning potential ratio of ≥ 0.40. For M. monoceros, the SPR was slightly below 0.40 (0.34-35), however, considering the fast growth and short generation time for the resources, the stock status can be considered fair. Significant reduction in fishing pressure (F/M < 1.0) and increase in SPR (>0.40) during COVID-19 affected years (2020-21) were evident. The reduction in fishing hours during the pandemic has allowed the resource to regain the target reference point (TRP) for SPR. Declining catches over the past decade for the group are not due to resource depletion but for the shift in species preference and the diversification of trawls in the region, with bottom trawling giving way to pelagic trawling. Keywords: Sustainability, Spawning potential ratio, COVID-19, Penaeid shrimps

Growth, mortality, and exploitation rates of the mantis shrimp Erugosquilla massavensis (Kossman, 1880) (Malacostraca: Stomatopoda) in Iskenderun Bay, north-eastern Mediterranean of Türkiye

ABSTRACT Lessepsian Erugosquilla massavensis is one of the three Stomatopod species reported on the Levantine coast of Türkiye. Its natural habitat is the Red Sea and it is the first Red Sea stomatopod species reported from the Mediterranean. This study aims to determine the morphometric relationships, growth parameters, sex ratio, age, mortality, and exploitation rates of non-native E. massavensis in the north-eastern Mediterranean. Samples were collected monthly by commercial trawl surveys between September 2016 and March 2017 in Iskenderun Bay. Relationships between the carapace length (CL)–total length (TL) and the total length (TL)–total weight (TW) were estimated. Negative allometric growth was observed between the CL–TL and TL–TW relationship for females, males, and all. The von Bertalanffy growth parameters (vBGP) were found L ∞ = 155.4 mm, K = 0.520 year−1, t 0 = −0.199, ø′ = 4.099 for females, L ∞ = 157.5 mm, K = 0.600 year−1, t 0 = −0.127, ø′ = 4.173 for males. This research provided the first-ever data on the vBGP of E. massavensis. The study found that both sexes had a higher fisheries mortality coefficient than natural mortality (Z = 2.01, M = 0.71, F = 1.3) and were exploited (E = 0.65).

Length-Weight Relationship of Diamondback puffer Lagocephalus guentheri from the northeastern Mediterranean Sea

The length-weight relationship data is important basic information that helps to compare species between populations and habitats. In this study, we provide detailed information on the length-weight relationships and condition factors of Lagocephalus guentheri from the Iskenderun Bay, northeastern Mediterranean Sea. A total of 408 (262 Female, 146 Male) specimens were collected on commercial trawlers by local fishermen caught between December 2022 to December 2023 from Iskenderun Bay. The total length range was 11.0-36.9 cm and 11.2-36.7 cm for females and males, respectively. The total weight values of females and males ranged from 20.30-1080.50 g and 20.50-1012.36 g, respectively. The length-weight relationship of L. guentheri was calculated as W = 0.0098 × L3.2145 (R2 = 0.9960) for females, W = 0.009 × L3.2399 (R2 = 0.9963) for males, and W = 0.0095 × L3.2243 (R2 = 0.9962) both sexes. The Fulton’s condition factor was observed as 1.2384 for females, 1.2504 for males, and 1.2335 for both sexes. This study is the most recent reference on length-weight relationships and condition factors for L. guentheri after correction of species identification. It is very important to determine the population parameters of pufferfish species to shed light on the studies to be carried out to restore the ecological balance in the Mediterranean ecosystem. This study will provide basic information that will be useful for fisheries scientists and managers in the Mediterranean Sea.

New insights into the reproduction and migration of the porbeagle shark Lamna nasus (Bonnaterre 1788) in the Southwest Atlantic Ocean.

The objective of this study was to estimate the reproductive parameters of porbeagle shark in the Southwest Atlantic Ocean and thus characterize the adult fraction of this population. Therefore, 1012 specimens were measured by scientific observers on board the commercial trawl fleet operating south of 50° S. The size range of the specimens was from 77 to 292 cm fork length (LF). The mean size at maturity was estimated to be 153 cm LF for males and 172 cm LF for females. Porbeagle shark catches were recorded throughout the year, with the highest frequency occurring between November and June. The presence of pregnant females was observed from December to July, along with an increase in the average size of embryos in each litter. The information presented in this study improves the knowledge of the reproductive biology and allows to propose a migratory pattern of adult porbeagle females in the Southwest Atlantic Ocean. The likely seasonal increase in vulnerability of this shark to austral trawl fishery, despite all conservation management measures established in Argentina, underscores the importance of promoting its proper management and conservation given the need to improve understanding of porbeagle population dynamics in the Southern Hemisphere.

Analysis of bycatches from mid-water trawl fishery targeting ribbonfish Trichiurus lepturus on the north-west coast of India

Commercial trawl fisheries are closely associated with bycatch and discards and itsignificantly affects the non-target resources, biodiversity, ecosystem function and habitat.The present study analysed bycatch based on data obtained from commercially operatedmultiday midwater trawlers operating off the north-west coast of India during August2017-December 2019. The data revealed that bycatch and discards constituted about 53and 6% respectively of the trawl catch. Mid-water trawl bycatch comprised 92 Teleosts,8 Cephalopods, 12 Crustaceans and 11 Elasmobranch species. The bycatch is mainlycomprised of cuttlefishes, squids, threadfin breams, sciaenids, bullseye and lizardfishes.Further, 93.68% of the bycatch consisted of commercially important fish, hence it wasretained in the vessel. The bycatch rate was high in September (72.81±37.44 kg h-1) whereas,for discards, it was in August (16.25±10.84 kg h-1). Keywords:Arabian Sea. Bycatch, Discard, Midwater trawl,Ribbonfish

Sığacık Körfezi (Ege Denizi, Türkiye)’nin derin deniz dekapod tür listesi ve körfezden yeni kayıtlar

Decapod crustaceans were sampled monthly from May 2008 to April 2009 using a commercial trawl vessel at depths between 292 and 550 m from Sığacık Bay. 16 species were identified, of which 3 are Brachyura, 5 Caridea, 3 Dendrobranchiata, 1 Polychelida, 1 Astacidea, 3 Anomura. Of these, 4 species (Bathynectes maravigna, Munida intermedia, Pontophilus spinosus, and Processa canaliculata) are new records for Sığacık Bay. Furthermore, all of the previous studies were reviewed on the deep-sea decapod crustaceans of Sığacık Bay, depth range of each species is given.

Coordinate-Aware Mask R-CNN with Group Normalization: A underwater marine animal instance segmentation framework

Unsustainable fishing, driven by bycatch and discards, harms marine ecosystems. Addressing this, we propose a Coordinate-Aware Mask R-CNN (CAM-RCNN) method to enhance fish detection in commercial trawls. Leveraging CoordConv and Group Normalization, our approach improves generalisation and stability. To tackle class imbalance, a compound Dice and cross-entropy loss is employed, and image data are enhanced through multi-scale retinex and colour restoration. Evaluating on two fishing datasets, CAM-RCNN excels in accuracy and generalisation, achieving the best Average Precision (AP) for instance mask and BBOX prediction in both source (39.7%, 40.2%) and target domains (24.4%, 24.2%). This method promotes sustainable fishing by selectively capturing desired fish, reducing harm to non-target species.

Spatial analysis of fishing tows with Automatic Identification System (AIS) data to inform offshore wind layouts

AbstractObjectiveThe coexistence of fisheries and offshore wind depends in part on the feasibility of fishing within turbine arrays. This paper explores the value of the Automatic Identification System (AIS) to measure tows of commercial trawl and dredge vessels as quantitative indications of their spatial characteristics to inform offshore wind assessments.MethodsPublic records from the AIS provide objective, detailed data supporting the measurement of fishing tows from recent years. Patterns and dimensions were examined from 45 trawl and dredge trips of 35 vessels.ResultAlthough vessels spread some trips over large areas, they also make multiple passes in swaths as narrow as 0.3 nautical miles (NM). Turns are made by towing the gear through an arc ranging from 0.2 NM to more than 1 NM in diameter or by hauling gear to the boat and turning in less than 0.1 NM. These practices are confirmed by fishing captains.ConclusionThese objective data from actual fishing trips could be valuable in considering the feasibility of fishing in wind farms and planning appropriate layouts. This first effort provides too small a sample to be considered representative, but it may demonstrate the concepts and encourage further research. Techniques could be refined and extended to other regions and activities, as expanding marine interests share limited space.

Reproductive biology of two small-bodied sharks, Carcharhinus coatesi and Rhizoprionodon acutus, in the Northern Territory, Australia

Sharks and rays are widely perceived to have slow reproductive rates and, thus, are often considered highly susceptible to population declines from commercial fishing. However, the reproductive biology of sharks is highly diverse, and some species can sustainably support significant commercial harvest. Small sharks are commonly caught and discarded as bycatch in several Australian and international fisheries. This represents either a wasted resource that could potentially be sustainably utilised, or a potential conservation issue if overharvesting occurs. This study examines the reproductive biology of two small-bodied sharks in the Northern Territory, Australia. Carcharhinus coatesi (n = 726) and Rhizoprionodon acutus (n = 179) were collected between May 2018 and November 2019 from commercial trawl fisheries. Maximum lengths in both species were higher in females than males (C. coatesi: F = 862 mm, M = 822 mm; R. acutus: F = 862 mm, M = 835 mm). Size at 50% maturation size C. coatesi: F = 655 mm, M = 664 mm; R. acutus: F = 682 mm. Size-at-maturity that the logistic model predicted for male R. acutus (715 mm) appears to represent size at full maturation and this study could not determine 50% maturation size. Litter sizes were small in both species, with C. coatesi producing 1–2 pups (mean 1.9) and R. acutus producing 1–4 pups (mean 2.8). Both species gave birth to large pups when compared to other shark species (C. coatesi: 370 - 450 mm; R. acutus: 315 – 400 mm), with C. coatesi size-at-birth being 47.6% of maximum female total length, while R. acutus size-at-birth was 41.5% of maximum female total length). Both species reproduced throughout the year, complicating estimation of the gestation period. The reproductive biology of C. coatesi and R. acutus showed considerable spatial and temporal variability when compared to studies from other regions and a past study from the Northern Territory in 1991. Although C. coatesi and R. acutus are currently abundant in the Northern Territory, the low fecundity of both species compared to other small-bodied sharks may limit their potential to sustain high levels of commercial harvest. Any expansion of commercial fishing for these species should be based on detailed consideration of their reproductive biology—in particular their low fecundity—to avoid the declines experienced by other formerly abundant elasmobranchs globally.

Spatial analysis of demersal food webs through integration of eDNA metabarcoding with fishing activities

The evaluation of the status of marine communities, and especially the monitoring of those heavily exploited by fisheries, is a key, challenging task in marine sciences. Fishing activities are a major source of disruption to marine food webs, both directly, by selectively removing components at specific trophic levels (TL), and indirectly, by altering habitats and production cycles. Food web analysis can be very useful in the context of an Ecosystem Approach to Fisheries, but food web reconstructions demand large and expensive data sets, which are typically available only for a small fraction of marine ecosystems. Recently, new technologies have been developed to easily, quickly and cost-effectively collect environmental DNA (eDNA) during fishing activities. By generating large, multi-marker metabarcoding data from eDNA samples obtained from commercial trawlers, it is possible to produce exhaustive taxonomic inventories for the exploited ecosystems, which are suitable for food-web reconstructions. Here, we integrate and re-analyse the data of a recent study in which the α diversity was investigated using the eDNA opportunistically collected during fishing operations. Indeed, we collect highly resolved information on species feeding relationships to reconstruct the food webs at different sites in the Strait of Sicily (Mediterranean Sea) from eDNA and catch data. After observing that the trophic networks obtained from eDNA metabarcoding data are more consistent with the available knowledge, a set of food web indicators (species richness, number of links, direct connectance and generality) is computed and analysed to unravel differences in food webs structure through different areas (spatial variations). Species richness, number of links and generality (positively) and direct connectance (negatively) are correlated with increasing distance from the coast and fishing effort intensity. The combined effects of environmental gradients and fishing effort on food web structure at different study sites are then examined and modelled. Taken together, these findings indicate the suitability of eDNA metabarcoding to assist and food web analysis, obtain several food web-related ecological indicators, and tease out the effect of fishing intensity from the environmental gradients of marine ecosystems.

К ВОПРОСУ ОБ ОПРЕДЕЛЕНИИ ПРОМЫСЛОВОГО ЗАПАСА АНТАРКТИЧЕСКОГО КРИЛЯ EUPHAUSIA SUPERBA В РАЙОНЕ АНТАРКТИЧЕСКОГО ПОЛУОСТРОВА ПО ДАННЫМ ТРАЛОВЫХ УЛОВОВ КОММЕРЧЕСКИХ СУДОВ

Background. The assessment of the density and total biomass of the Antarctic krill aggregations has been conducted based on the commercial catches by the fishing and krill harvesting trawlers (supertrawlers) “Konstruktor Koshkin” (“Design Engineer Koshkin”) in 2006 and “More Sodruzhestva” (“Commonwealth Sea”) in 2017 in the Bransfield Strait (FAO Subarea 48.1). Relevance. Recommencement of the Russian krill harvesting necessitates timely strategical characterization of the krill aggregations with regard to their prospective exploitation. This work is aimed at the identification of the density and biomass of the Antarctic krill aggregations in 2006 and 2017, which have been calculated by the volumetric (net) method based on the catches by the commercial vessels in the Bransfield Strait. Methods. A midwater rope trawl of the 74/600 m design with the mesh size 20 mm in the krill-targeting insertion was used as a fishing gear. Estimation of the biomass was done using the isoline method. The catchability coefficient was considered to be 1. Mapping of the biomass density values was conducted with Golden Software Surfer 9 and QGIS 2.18.16. Confidence intervals for the average variation were calculated with 95 % probability. Results. The decrease in the average density of the krill biomass at the harvesting sites in the Bransfield Strait in 2017 (18.0±0.23 g/m3) as compared to 2006 (32.5±0.40 g/m3) has been identified; it resulted from the krill aggregations scattering over the increased area. The total krill biomass in the aggregations in 2006 and 2017 was 2678.3±65.07 thousand t and 2743.1±68.70 thousand t, respectively. Conclusion. Based on the commercial trawl catches, the volumetric method allows for the expedient estimation of the density and biomass of the krill aggregations with the size composition optimal for their exploitation. Taking into consideration that the commercial trawls capture the relatively large-sized krill preferred by the krill-dependent predators, the volumetric method makes it possible to estimate the volume of their food reserves. Exploitable krill stock in the aggregations in the Bransfield Strait in 2017 remained virtually unchanged as compared to that of 2006 and amounted to 2.7 million t.

Regional assessment of important biological indices in the population of red cornetfish (Fistularia petimba Lacepède, 1803) along the eastern Mediterranean coasts of Türkiye

The Lessepsian migrants of the family Fistulariidae, which are widely distributed in the Eastern Mediterranean coasts of Türkiye, are represented by two species, Fistularia commersonii and Fistularia petimba. This study focused on estimating various biological indices of red cornetfish Fistularia petimba Lacepède 1803, eastern Mediterranean coast of Türkiye. The biological indices determined were: FI- Fullness index, HSI-Hepatosomatic index, GSI-Gonadosomatic index, EQ-Encephalization quotient, VSI-Visceral index, IWL-Zihler index, Fulton-K: Fulton-Condition. For this study, 65 red cornetfish specimens (♀:40, ♂:23, immature: 2) caught as by-catch in the nets of commercial trawlers, operating in the study area in the winter of 2021 were studied. The estimated length-weight relationship (LWR) was W=0.0001L3.34 (R2= 0.89) and the species exhibits a positive allometric growth. The mean index (M±SD) and range values calculated from the obtained data are as follows: FI 1.05±0.13 (0.83-1.26); HSI 0.43±0.05 (0.23-0.62); GSI 1.27±0.20 (1.08-1.46); EQ 0.0024±0.0003 (0.0022-0.0025); VSI 3.14±0.39 (2.08-4.20); IWL 12.37±1.54 (4.41-20.3) and Fulton-K 0.47±0.06 (0.43-0.51). According to these results, it can be hypothesized that this Lessepsian species is well established and thrives in the eastern Mediterranean coasts of Türkiye. Although it is evaluated as the least concern category (LC) in the IUCN Red List 2013, we believe that the species has an invasive potential. Therefore, this study, in which biological index parameters were presented for Fistularia petimba, may be important in terms of fisheries management, planning measures to reduce distribution and combating invasiveness.

The Relationships of Otolith Dimensions (Length-Breadth) with Weight and Total Length of Greater Forkbeard (Phycis blennoides (Brünnich, 1768)) Captured from northeastern Mediterranean Sea

The greater forkbeard, Phycis blennoides is captured by commercial trawler, has minor commercial value in Türkiye. This study is the first knowledge on otolith biometry-fish size relationships of Phycis blennoides living in the northeastern Mediterranean Sea. A total of 202 the greater forkbeard individuals were caught by commercial bottom trawl at a depth of 200 to 400 m in the northeastern Mediterranean. Minimum-maximum total length and weight of obtained fish specimens were found as 16.9-38.7 cm and 31.06-415.0 g for females and 16.3-38.3 cm and 27.14-504.08 g for males respectively. The difference of the total length and weight between the females and males of P. blennoides was statistically insignificant (P>0.05). The determination coefficient value showed that there were a moderate relationships between total length-right and left otolith lengths, total length-right and left otolith breadths.

The Escape Intensity and Its Influencing Factors in Antarctic Krill (Euphausia superba) Passing through Large Mesh at the Front End of a Commercial Trawl

The purpose of this study was to comprehend the escape intensity and its influencing factors in Antarctic krill (Euphausia superba) that escaped through large mesh located at the front end of commercial trawl nets. Two pocket nets were employed to collect escaped krill that passed through the mesh opening in the first section (400 mm mesh size, without liner) and second section (16 mm mesh size liner) of the trawl body. The results show that krill escape primarily took place in the first section of the trawl body. Meanwhile, there was almost no krill escape observed in the second section of the trawl body, primarily attributable to the presence of a 16 mm mesh size liner. In terms of body length composition, the average PSI (percentage similarity index) was 67.31 (95% CI: 61.86–72.87) for krill from the pocket net on the larger mesh part and the codend. In addition, the PSI was significantly different (p < 0.05) between the day (60.96, 95% CI: 55.68–66.71) and night (83.62, 95% CI: 76.80–89.46). The escape intensity of krill ranged from 20.83 to 213.13 g·m−2 per ton per hour in the area at the front end of trawl body, with a mean value of 76.52 (95% CI: 55.22–101.09) g·m−2 per ton per hour during the daytime, and 144.66 (95% CI: 110.44–180.03) g·m−2 per ton per hour at night. These results indicate that krill can see and avoid contacting the netting easily during the day, particularly for larger individuals. This provides insight into the design of krill trawls, specifically on the arrangement of liners, which should be integrated from the front part of the trawl body.

OCCURRENCE OF Bregmaceros nectabanus (WHITLEY, 1941) IN THE GULF OF ANTALYA

With the opening of the Suez Canal in 1869, a connection was established between the Red Sea and the Mediterranean. Because of this connection, many organisms of Red Sea origin migrated to the Mediterranean. These migratory organisms also include fish. For this reason, we monitor and determine the number of fish originating from the Red Sea in the Gulf of Antalya. One of the fishing methods in the Gulf of Antalya is trawler fishing. One of the fish species caught during commercial trawling is horse mackerel. A small and different type of fish was found in the stomach of horse mackerel caught during trawling on October 26, 2021 in the Gulf of Antalya. During the species identification of these fish samples, which were intact in the stomach content of horse mackerel and preserved their integrity, it was determined that these fish were Bregmaceros nectabanus, which is included in the Bregmacerotidae family. With this study, the presence of B. nectabanus identified in the Gulf of Antalya was one more addition to the number of Red Sea origin fish species in the Gulf.

The use of cameras on commercial deep-water trawls to investigate habitat associations and scampi trawl efficiency in New Zealand scampi Metanephrops challengeri

AbstractThis study assessed the effectiveness of using video cameras mounted on commercial trawls for a deep-sea lobster, the New Zealand scampi Metanephrops challengeri, for acquiring information on habitat associations of demersal species and fishing efficiency. Randomly selected frames from 1 h of recording replicated over 12 trawls and conducted over three fisheries management areas (FMA), were analysed for counts of visible scampi, scampi burrows, visible topographical features and visible epifauna and fish taxa. Poisson regression analysis indicated a positive relationship between the distribution of scampi burrows (a proxy of scampi abundance) and conical mounds (formed by bioturbators), but a negative relationship with smooth topography. Counts of scampi burrows were also positively associated with counts of visible scampi for four trawls, while significant relationships were seldom found between counts of scampi burrows and other commonly observed individual taxa. Scampi trawl efficiency was low, with only 56 of the 186 observed scampi (30%) passing over the footrope and into the trawl net. The results confirm the effectiveness of video sampling from commercial trawls to improve our understanding of habitats and fishing efficiency in deep-sea fisheries.

Spatial overlap between South American fur seal foraging effort and commercial trawl fisheries in the Falkland Islands

Spatial overlap between South American fur seal foraging effort and commercial trawl fisheries in the Falkland Islands