Search

Fish behavior is important to consider when developing selective fishing gear. In studies designed to investigate the size selective properties of towed fishing gears such as trawls, fish behavior is mainly documented by underwater video recordings. Because fishing gear can be operated at great depths or in other low light environments, artificial light is often required for underwater recordings. However, artificial light can influence fish behavior, which casts doubt on the validity of behavioral observations obtained in the presence of artificial light. However, removing artificial light disables video recordings and the possibility to study fish behavior in relation to selectivity devices towed fishing gears in low light environments. To date, little is known about the extent to which artificial light used for video observations affects fish behavior with respect to fishing gear. Therefore, we conducted fishing trials in the Barents Sea demersal trawl fishery to assess the effect of light sources on fish behavior by using size selectivity results in towed fishing gears. We found that the behavior of cod (Gadus morhua) was unaffected by the light sources, whereas the behavior of haddock (Melanogrammus aeglefinus), saithe (Pollachius virens) and redfish (Sebastes spp.) significantly changed when red light and white light were employed. Our results also demonstrated significant differences in fish behavior between white and red light. [ABSTRACT FROM AUTHOR]

Abstract Sorting grids to exclude the juveniles of species targeted by bottom trawl fisheries from the catch are among the most promising solutions to reduce discards. We tested a two-sections Juveniles’ Sorting Grid (JSG) in a Mediterranean fisheries restricted area. First, we provided information on the vitality of individuals escaping from the JSG bars during towing, by analysing underwater footage. Then, we evaluated the catch performance of the JSG-equipped trawl compared to a standard trawl by analysing both the full species community in the catches and the main commercial species. The probability for individuals to be alive while escaping from JSG was always higher than 65% (on average), with some species (e.g. red mullet, gurnards, 91–99% on average) showing significantly higher probability than others (e.g. European hake, crustaceans, 65–82% on average). The installation of a JSG in the trawl net did not change the overall catch composition in the codend, although significant differences were observed at the single species level. The JSG was effective at reducing undersized individuals of European hake, although a loss of legal-sized individuals was observed due to escapement. A significantly lower retention of the JSG-equipped trawl was also observed for other commercial species, such as deep-water rose shrimp and broadtail shortfin squid.

In modern conditions of less number of research expeditions, more information is collected by fishing vessels, where Danish seine is used as a fishing gear. Biostatistical data obtained by bottom trawl and Danish seine were compared in the joint survey in the Ussuri Bay (Japan Sea) and showed good comparability. Availability of the Danish seine using for assessment of fish stocks in this area is concluded.

Borichangar, R.V.; Vyas, U.D.; Parmar, J.N.; Vanza, J.G.; Solanki, H.G., and Pathak, N., 2024. Additional record and taxonomic description of the Arabian carpet shark, Chiloscyllium arabicum, from Dholai Port, southwest coast of Gujarat, India. Journal of Coastal Research, 40(3), 617–622. Charlotte (North Carolina), ISSN 0749-0208. The present study reports an additional record of the Arabian carpet shark, Chiloscyllium arabicum, off Dholai Port, southwest coast of Gujarat, India. Two specimens were caught in a bottom trawl net at a depth of 30–32 m around the southwest coast of Gujarat. The total length and weight of the male and female specimens were recorded as 56.10 cm and 812.5 g and 52.80 cm and 681 g, respectively. In total, 119 morphometric parameters were closely observed and recorded for the taxonomic identification and confirmation of the species. Previously, C. arabicum has been reported from Okha, Mangrol, and Veraval ports along the northwest coast of Gujarat. This study serves as the initial report of the presence of the Arabian carpet shark from Dholai Port, southwest coast of Gujarat. [ABSTRACT FROM AUTHOR]

Abstract It is commonly assumed that beach seining (BS) is more sustainable than bottom trawling because it involves non-motorized operations and limited fishing power. However, no scientific evidence supports this assumption. To address this gap, we evaluated the impact of beach seining, taking a small-scale shrimp fishery in northeast Brazil. Data collected monthly from December 2016 to November 2017 and in literature, were assessed (BS 31,001 individuals, 119 species, 37 families, and 19 orders; BT 6,031 individuals, 58 species, 20 families, and 14 orders). Beach seining demonstrated a lower proportion of bycatch (BS 1:2.3; BT 1:3.2), higher total shrimp catch (BS 87.2 t; BT 65 t), and greater species diversity than bottom trawling catches (BS 119; BT 58). Other aspects were closer associated with bottom trawling, such as the composition of dominant families (Sciaenidae and Pristigasteridae), the proportion of rare species (BS 30%; BT 24%) juveniles (BS 11g; BT 13g), the risk of species extinction, and the composition of ecological guilds. Despite their social significance, both fishing gears showed similar ecological indicators and adverse effects. The findings establish that the ecological concerns related to the impact of bottom trawling are also applicable to beach seine.

In the Mediterranean, one of the main reasons for discarding commercial species is when fishers catch fish smaller than the minimum conservation reference size (MCRS). In reality though, other drivers that vary by country/region have greater impact on the discarding process. A notable illustration of the coexistence of different motives is the Greek bottom trawl fishery. Present work focused on the spatial analysis of discards of three commercial species subjected to MCRS with low market price and often discarded independent of their size (i.e., Trachurus trachurus, Parapenaeus longirostris, Sardina pilchardus). To model and map the spatial distribution of species discards, hierarchical Bayesian spatial models were utilized employing discards dependence on environmental inputs. Further information was gained, by calculating the spatial overlap between the spatial distribution of species discards and their known nurseries. Results showed that S. pilchardus discards had the highest estimated values in shallower waters, whereas T. trachurus and P. longirostris discards were distributed over greater depths. Only a small portion of species nurseries and discard grounds coincided, verifying that the reasons behind discarding were market-driven. Area-specific and species-specific management is essential to reduce discards, since local market demand and fishing restrictions have an impact on the discarding process. [ABSTRACT FROM AUTHOR]

Across the Mediterranean and the Black Sea, an improvement in technological adoption which optimizes the environmental benefits of fisheries is needed. The testing of quality standards in trawl fishing is one of the essential components. In an experiment, we tested four bottom trawl cod-ends in the western Black Sea to determine the characteristics of the catch composition. Fishing trials were conducted by 40 mm diamond (40D), 44 mm diamond (44D), 40 mm square (the 40S), and 40 mm 90-degree turned (40T) mesh cod-ends for 31 bottom trawling hauls. The multivariate analysis of catch composition indicated a significantly higher differentiation between 40D and 40T cod-ends, mainly characterized by five species: Merlangius merlangus, Mytilus galloprovincialis, Trachinus draco, Mullus barbatus, and Uranuscopus scaber. The difference in the shape of cod-end meshes reflected the variation in the catchability and catch composition. However, the 40S and 40T showed 80% similarity in catch composition. Among cod-ends, 40T yielded in lowest catch per unit effort for both commercial and other species. Adoption of gear specially made to catch more target species can help bottom trawl fisheries further improve their ecological and economic sustainability.

Marine Protected Areas require comprehensive monitoring to ensure objectives are achieved; however, monitoring natural ecosystems at scale is challenged by the biodiversity it aims to measure. Environmental DNA (eDNA) metabarcoding holds promise to address this monitoring challenge. We conducted paired sampling at 54 sites for fish and invertebrate assemblages in the Northwest Atlantic using groundfish trawls and eDNA metabarcoding of benthic seawater using four genetic markers (12S rRNA, 16S rRNA, 18S rRNA , and CO1). Compared to trawling, eDNA detected similar patterns of species turnover, larger estimates of gamma diversity, and smaller estimates of alpha diversity. A total of 63.6% (42/66) of fish species captured by trawling were detected by eDNA, along with an additional 26 species. Of the 24 missed detections by eDNA, 12 were inevitable as they lacked reference sequences. Excluding taxa assigned to higher than species level and those without a species name, 23.6% (17/72) of invertebrate species captured by trawling were detected by CO1, which detected an additional 98 species. We demonstrate that eDNA is capable of detecting patterns of community assemblage and species turnover in an offshore environment, emphasizing its strong potential for a non-invasive, comprehensive, and scalable tool for biodiversity monitoring supporting marine conservation programmes. [ABSTRACT FROM AUTHOR]

The Falkland Islands conduct one of the few targeted skate fisheries in the world with total annual catches of several thousand tonnes.  This bottom trawl fishery is characterized by relatively low catch volumes and product yield that challenge commercial profitability. Recently, one Falkland Islands fishing company acquired a large proportion of the skate ITQ, and to optimise its fishing operations, proposed a research collaboration with the Falkland Islands Fisheries Department for assessing the performance of trawls equipped with either standard 110 mm codend mesh, or larger 300 and 400 mm meshes. The results of the trial confirmed the efficiency of larger mesh codends to decrease finfish bycatch by 97–98%. Additionally, trawls with 400 mm mesh significantly decreased the bycatch of commercially valueless small skates that would experience high discard mortality. As a result of the trial, the Falkland Islands Government implemented a regulatory licence condition of 400 mm codend mesh for targeted skate fishing. Besides greater production efficiency, vessel operators are incentivized by possible wider access throughout the fishing zone. Further initiatives are anticipated to develop management measures by individual species, continue improving conservation through bycatch mitigation in all fisheries, and diversify Falklands skate products in global markets. [ABSTRACT FROM AUTHOR]

In Europe, research surveys carried out by state governments provide the great majority of fishery-independent data. Member States (MS) in the European Union (EU) regularly conduct research surveys to provide the necessary data to assess the status of exploited fish stocks and to monitor the general condition of the marine ecosystem. In the surveys, samplings are carried out throughout the distribution range of the targeted fish species using standardized gears (e.g., trawls and seines) and other methods (e.g., hydroacoustics and underwater cameras). In the context of fish stock assessment, survey data are important because they provide indices that help tuning the stock assessment models (e.g., the index of fish abundance) and key information about the size and age distributions of the stock, the size-age relationships, the proportion of fish mature at each age, and information on reproductive performance of the stocks. However, research surveys have a number of shortcomings that include, for example, a high economic cost coupled with complex logistics and a long time required for processing the collected data. In addition, some of the parameters that are needed in stock assessment cannot be estimated from survey data for certain commercially important species. For instance, age is usually determined using hard structures (such as otoliths) in fish target species. However, for European hake, age cannot be determined accurately because there are many difficulties in interpreting the ring patterns of the otoliths. This highlights the need to look for alternative methodologies such as genomics, that have the potential of improving the data obtained from research surveys and hence, improve fish stock assessments. Considering this, we carried out a review of the bottom trawl research surveys in the EU with the purpose of: 1) identifying the current approaches for monitoring fishery resources and the ecosystem and 2) determining how genomic techniques can be used to improve survey data, taking into account the needs of current and future stock assessment in Europe.

Across the Mediterranean and the Black Sea, an improvement in technological adoption which optimizes the environmental benefits of fisheries is needed. The testing of quality standards in trawl fishing is one of the essential components. In an experiment, we tested four bottom trawl cod-ends in the western Black Sea to determine the characteristics of the catch composition. Fishing trials were conducted by 40 mm diamond (40D), 44 mm diamond (44D), 40 mm square (the 40S), and 40 mm 90-degree turned (40T) mesh cod-ends for 31 bottom trawling hauls. The multivariate analysis of catch composition indicated a significantly higher differentiation between 40D and 40T cod-ends, mainly characterized by five species: Merlangius merlangus, Mytilus galloprovincialis, Trachinus draco, Mullus barbatus, and Uranuscopus scaber. The difference in the shape of cod-end meshes reflected the variation in the catchability and catch composition. However, the 40S and 40T showed 80% similarity in catch composition. Among cod-ends, 40T yielded in lowest catch per unit effort for both commercial and other species. Adoption of gear specially made to catch more target species can help bottom trawl fisheries further improve their ecological and economic sustainability. [ABSTRACT FROM AUTHOR]

Seasonal data sampling on the total catch, target catch, bycatch and discard of four commercial bottom trawlers in the south-eastern Black Sea near the coast of Turkey was carried out in the 2016-2017 fishing season. Totally, 217 bottom trawl operations were sampled. Merlangius merlangus and Mullus barbatus were the target species while eight species were discarded, including trash fish and specimens below the legal size of the target species. A total of 28039.86 kg of biomass was caught during the operations, of which 22.98 % was bycatch. The weighed discard rate was 15.12 %. The highest CPUE values calculated for the whiting and red mullet were 69.36 and 23.00, respectively. [ABSTRACT FROM AUTHOR]

The study aims to theoretically determine the total resistance forces acting on bottom trawls used in the commercial trawl fishery around the Turkish Peninsula. For this purpose, a total of 14 (2 for Black Sea, 2 for Sea of Marmara, 6 for Aegean Sea and 4 Mediterranean Sea) trawl gears were ex-amined during the study representing all types of the bottom trawl fishery (e.g., fish targeted, shrimp targeted and mix) in Turkey. The calculation of the hydrodynamic forces of the gears was based on the determination of each gear component; net, floaters, sweep, door, warp and the friction force caused by footrope, sweep and door. The total resistance of trawl gears was calculated according to different towing speeds and warp lengths. Average resistance values of the examined nets with a 500 m warp length indicated that the frictional force of the trawl door composed more than 41.3% of the total resistance, followed by net (39.4%), both doors (6.3%), footrope friction (6.1%), sweep frictions (3.1%) and the rest belonged to sweeps, warps and floaters (totally 3.8%). It was determined that resistance caused by friction including sweeps, footrope and doors constituted more than 50% of the total resistance. Among the examined gears, the greatest resistance values were determined for the 600 meshes tailored-traditional Mediterranean type trawl gear.

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fisheries have important impacts on marine biodiversity. In this work, combined information on the abundance, species richness, diversity indices, species composition, trophic level and vulnerability index were examined for the first-time to detect differences in five units related to trawl fishing: the fish assemblage entering the trawl codend, and the escaping, retained, discarded and landed fractions, derived by the gear and fisher selection practices. The work was based on a case study conducted in the Mediterranean Sea, using three different meshes in the trawl codend (40mm-40D and 50mm-50D diamond meshes, and 40 mm-40S square meshes) and a cover of the codends with small mesh size. In general, trawl fishing produces an escaping fraction that was always lower in abundance, richness, and vulnerability index, similar in diversity indices and trophic level, and different in species composition compared to the fish assemblage entering the codend. In almost all cases, fishers selected as landings a fraction that was the lowest in diversity indices, and the highest in trophic level. In contrast, fishers discarded a fraction that was the highest in diversity and vulnerability index, and the lowest in trophic level. Although the three codends did not differ significantly in the fraction of escapees in terms of diversity indices, trophic level, and vulnerability index, the 40S codend showed a significantly higher percentage in the escaping number of species and individuals, and less differences in the species composition; in addition, lower percentage in abundance of discards and higher of landings in the retained catch (0.6:1) than did the other two codends (0.9:1). It was suggested that an urgent modification of the trawl for the elimination of the discarded highly vulnerable species (e.g. Elasmobranchs) is needed, and that trawl species-selectivity should be improved by allowing escape or avoiding catch of the discarded fraction to minimize biodiversity losses.

A recent rebound of juvenile redfish (Sebastes spp.) in areas where the northern shrimp (Pandalus borealis) bottom trawl fishery in eastern Canada occurs has been challenging the fishing industry to maintain bycatch of this species within acceptable levels. Using self-contained underwater cameras and red lights, this study investigated the behavior of juvenile redfish in response to bycatch reduction devices (BRDs), called Nordmøre grids. Fish behavior was analyzed in grid systems with different bar spacings, including 22- and 19-mm bar spacings. A total of 10.3 h of useable underwater video was collected during commercial fishing conditions, which yielded individual observations of 931 redfish. Generalized linear models (GLMs) and behavioral trees were used to analyze the data. We observed that 52.5% of all redfish passed through the bar spacings and were retained. The duration of the selection process was relatively short (~1.9 s mean), and 57.8% of redfish reacted to the grids by swimming upwards, forward, or towards with respect to the grids. Behaviors exhibited by redfish and redfish retention were similar for both grids. GLM results suggested that as time in front of the grid increased and redfish had upwards or steady grid reactions, retention was drastically reduced. These were important variables that significantly explained the capture fate of redfish. The behavioral sequence that led to higher escape probability was redfish that approached upwards, had no contact with the grid, and reacted to the grid by continuing to move upwards to finally exit through the escape opening. GLM and behavioral trees gave a comprehensive view of redfish behavior, which is extremely useful for perfecting or developing any BRD to address juvenile redfish bycatch.

Demersal fish fauna of the Sea of Marmara, Turkey was determined by bottom trawl surveys between March 2017-December 2018 at 34 stations with the monthly samplings. During the study, a total of 61 teleost and 12 cartilaginous fish species belonging to 42 families were sampled. The target, bycatch and discard rates of CPUE were determined as 13.40%, 69.64% and 16.95%, respectively. In total, 53.9% of the CPUE was stemmed from Trachurus trachurus. Mustelus mustelus, Raja clavata, Merluccius merluccius and Merlangius merlangius had the highest CPUE with a mean of 77.63, 71.86, 71.72 and 72.68 kg/km2, respectively. The highest biodiversity was observed in the southwestern part of the Marmara Sea. With increasing depth, the species number of the teleost fish decreased, whereas the species number of the cartilaginous fish increased. The mean CPUE values of the economical demersal fish species were lower in comparison to those reported from other regions in Turkey. Evidence suggests fish stocks with shallower distribution is under heavier threat against fishing pressure. Since commercial trawling is banned in the Sea of Marmara, beam trawl fishery can be considered as the major threat to demersal fish stocks in the region.

Distribution and biological parameters are considered for eggs and adults of two flatfish species on the data of annual surveys conducted on the shelf of southeastern Kamchatka in summer of 2011–2014 and 2016–2019. The eggs of Pleuronectes quadrituberculatus were sampled mostly at the stage of a germinal strip forming, whereas the eggs of Hippoglossoides elassodon were mostly at the stage of embryo cleavage. The main congestions of the eggs were found in the Kronotsky Bay and northern Avachinsky Bay. The adults of both species concentrated mainly in the northern Kronotsky Bay, at Cape Povorotny. Old age groups prevailed in aggregations of P. quadrituberculatus, but middle-age and young fish — in the aggregations of H. elassodon.

Bloater, Coregonus hoyi , are deepwater planktivores native to the Laurentian Great Lakes and Lake Nipigon. Interpretations of commercial fishery time series suggest they were common in Lake Ontario through the early 1900s but by the 1950s were no longer captured by commercial fishers. Annual bottom trawl surveys that began in 1978 and sampled extensively across putative bloater habitat only yielded one individual (1983), suggesting that the species had been locally extirpated. In 2012, a multiagency restoration program stocked bloater into Lake Ontario from gametes collected in Lake Michigan. From 2012 to 2020, 1,028,191 bloater were stocked into Lake Ontario. Bottom trawl surveys first detected stocked fish in 2015, and through 2020 ten bloater have been caught (total length mean = 129 mm, s.d. = 44 mm, range: 96–240 mm). Hatchery applied marks and genetic analyses confirmed the species identification and identified stocking location for some individuals. Trawl capture locations and acoustic telemetry suggested that stocked fish dispersed throughout the main lake within months or sooner, and the depth distribution of recaptured bloater was similar to historic distributions in Lake Ontario and other Great Lakes. Predicted bloater trawl catches, based on modeled population abundance and trawl survey efficiency, were similar to observed catches, suggesting that post-stocking survival is less than 20% and contemporary bottom trawl surveys can quantify bloater abundance at low densities and track restoration. [ABSTRACT FROM AUTHOR]

The study aims to theoretically determine the total resistance forces acting on bottom trawls used in the commercial trawl fishery around the Turkish Peninsula. For this purpose, a total of 14 (2 for Black Sea, 2 for Sea of Marmara, 6 for Aegean Sea and 4 Mediterranean Sea) trawl gears were examined during the study representing all types of the bottom trawl fishery (e.g., fish targeted, shrimp targeted and mix) in Turkiye. The calculation of the hydrodynamic forces of the gears was based on the determination of each gear component; net, floaters, sweep, door, warp and the friction force caused by footrope, sweep and door. The total resistance of trawl gears was calculated according to different towing speeds and warp lengths. Average resistance values of the examined nets with a 500 m warp length indicated that the frictional force of the trawl door composed more than 41.3% of the total resistance, followed by net (39.4%), both doors (6.3%), footrope friction (6.1%), sweep frictions (3.1%) and the rest belonged to sweeps, warps and floaters (totally 3.8%). It was determined that resistance caused by friction including sweeps, footrope and doors constituted more than 50% of the total resistance. Among the examined gears, the greatest resistance values were determined for the 600 meshes tailored-traditional Mediterranean type trawl gear. [ABSTRACT FROM AUTHOR]

Based on materials for 2016–2020, it has been revealed that yellowfin sole Limanda aspera and Sakhalin sole L. sakhalinensis form the main aggregations in the Avacha (mainly in the northern part) and Kronotsky gulfs. Significant aggregations of L. aspera have been recorded in the upper areas of the shelf, while those of L. sakhalinensis mainly in the lower areas. Small-sized individuals of yellowfin sole (mean length 21.3 cm) occur in the upper shelf areas at depths of less than 40 m, while larger individuals (27.0 cm) at the depth range of 81 to 100 m. Small individuals of Sakhalin sole (17.7 cm) were found at the depth range of 40–80 m and its larger individuals (22.5 cm) at depths of 121–140 m. The dynamics of stocks of both species are multidirectional and tend to decrease during the study period. The biomass values of the studied sole individuals are close to the values recorded in 1981–1985. [ABSTRACT FROM AUTHOR]

The California Current Ecosystem has experienced variable climate regimes, hypoxia, and marine heatwave events that have the potential to impact groundfishes and their associated fisheries. Using bottom trawl survey data collected by NOAA Fisheries, we assessed changes over the last four decades in northern California Current continental shelf (≤200 m) groundfish assemblage composition, species' presence, and relationships to environmental and habitat variables. We focus on the currently understudied continental shelf area, due to its ecological and economic importance, especially after the recent opening of historically important areas to trawling. We found a temporally consistent separation in groundfish assemblages between depth zones based on NMS analysis using species found in over 1% of samples, with shallow, mid‐, and deep shelf groupings. Grain size, species richness, and diversity were associated with assemblage composition. Then, focusing on petrale sole, rex sole, lingcod, arrowtooth flounder, sablefish, English sole, Pacific sanddab, and Dover sole, we examined what factors impact groundfish presence and abundance on the shelf. Bottom temperature, sediment characteristics, and depth were correlated with abundance for all species. These results corroborate previous work indicating recent reductions in presence of hypoxia‐intolerant species. Shallow‐water groundfishes known to tolerate warmer water and low dissolved oxygen concentrations exhibit reductions offshore, possibly a result of low recruitment. There have been significant spatiotemporal changes in the shelf groundfish populations over the past several decades, and while assemblage composition over most of the shelf remains consistent, single species distributional shifts may impact access to target species in newly reopened areas. [ABSTRACT FROM AUTHOR]

Bycatch rates were determined for experimentally-designed bottom trawl, red mullet gillnet and whiting gillnet in the Black Sea off the coast of Turkey. Sampling was performed between January 2010 and July 2011 in the region of Sinop. Bycatch rate was estimated 12±6.02 % in weight and 10±5.14 % in number for the experimental gillnet surveys, and 62±11.16 % in weight and 80±15.32 % in number for the bottom trawl. The sub-samplings showed that bycatch species belonged to various families and many of them were below the minimum landing size. Some bycatch species were endangered. Considering all these problems, we describe the possible effects in near future if measures are not taken to reduce bycatch and ensure the sustainability of the aquatic living resources. [ABSTRACT FROM AUTHOR]

Climate change has been shown to impact marine fish populations and communities. With small population sizes, long reproduction times, and a rapidly warming habitat, thorny skate (Amblyraja radiata) could be particularly vulnerable. To examine this possibility, we used a two‐stage generalized additive model to project future thorny skate abundances under two different climate scenarios. This is the first study in the northeastern United States to compare projections based on different survey methods (bottom trawl and longline), and results were heavily impacted by survey methodology. Models trained with the NOAA Bottom Trawl Survey projected a decrease in abundance of ~60%–80% in the Gulf of Maine and Georges Bank under the RCP 8.5 climate scenario. With aggressive mitigation (RCP 4.5), these decreases could be reduced to ~35%–45%. Models trained with a recent NOAA longline survey indicated that thorny skate abundance would be reduced 22% and 37% under business as usual and mitigation, respectively. There are substantial methodological differences between the two data sets, including capture technique and efficiency, total habitat coverage, and spatio‐temporal coverage. This underscores the importance of continued, methodologically diverse surveys on the Northeast US continental shelf. Our results indicate that climate change will continue to negatively impact thorny skate populations by reducing the amount of thermally suitable habitat in the southern extent of their range. This information should be considered in future management decisions. [ABSTRACT FROM AUTHOR]

The dynamics of fishery resources were analysed and compared before and after artificial reefs were deployed in the Dongshan Sea of Huizhou, Guangdong Province, China based on acoustic detection and trawl sampling methods. Species assessed by acoustic detection were mainly distributed in the middle water layers, and those collected by trawl sampling were mainly benthic organisms. Therefore, it was necessary to integrate the two methods aimed at organisms living in different water layers to improve the reliability of the assessment results. The comprehensive assessment results showed that the densities of fishery resources on artificial reefs and in the surrounding waters after the reefs were deployed were 58,302 inds/km2 and 69658 inds/km2, which were overall higher than that (60159 inds/km2) before artificial reef deployment. Some species, such as Parargyrops edita, usually hide inside the artificial reefs and cannot be detected or caught after the artificial reef deployment, which leads to a lower density being recorded than before artificial reef deployment. Furthermore, according to the results of single echo detection and nautical area backscattering coefficient analysis, the proportion of large- and medium-sized marine organisms increased after artificial reefs were deployed, and these organisms were mainly distributed in middle and deeper water layers. These observations indicated that the construction of artificial reefs could provide sufficient conditions for the growth of marine organisms and induce the large- and medium-sized individuals to deeper water layers. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Taiwan Fisheries Research is the property of Fisheries Research Institute, Council of Agriculture, Executive Yuan and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The invasive crab Charybdis longicollis was first reported in Mersin Bay (Mediterranean Sea/Turkey) in 1954, and since the early 1990s, its populations have been heavily parasitised by the alien rhizocephalan Heterosaccus dollfusi. In Antalya Bay, 46.6% of the trawled catch is constituted by C. longicollis. Monthly biomass values fluctuated between 67 kg km−2 (June) and 704 kg km−2 (October), with a mean of 260 kg km−2. The percentage of change in females ranged from 29% in October to 53% in January. The mean carapace width of uninfected crabs was significantly larger in males (35.1 mm) than females (30.6 mm). Male crabs (34.3%) were more heavily parasitised than females (12.1%). The reduction in size of the chela and broadening of the abdomen are two characteristic modifications of infected males. The size at first maturity was estimated at CW = 24.7 mm. Ovigerous females were found all year-round but were more abundant in spring. Male and female individuals of C. longicollis displayed a maximum of three and one modal groups per year, respectively. Natural mortality (M) was estimated as 1.1 year−1 for male crabs. [ABSTRACT FROM AUTHOR]

The present paper reports the first record of the narrowbar reefgoby, Priolepis profunda (Weber, 1909) from the Indian coast. Two specimens (33.5 and 38.5 mm of TL), were caught during a demersal trawling survey conducted in the area between 9°40.7′N, 76°05.8′E and 9°45.1′N, 76°03.9′E at 33 m in June 2017. The specimens were collected from a coral rock which entered in the trawl net during the demersal resources survey. The morphological descriptions of the specimens collected are compared with those of existing records. [ABSTRACT FROM AUTHOR]

In the survey of fishery resources, the sampling design will directly impact the accuracy of the estimation of the abundance. Therefore, it is necessary to optimize the sampling design to increase the quality of fishery surveys. The distribution and abundance of fisheries resource estimated based on the bottom trawl survey data in the Changjiang River (Yangtze River) Estuary-Hangzhou Bay and its adjacent waters in 2007 were used to simulate the "true" situation. Then the abundance index of Portunus trituberculatus were calculated and compared with its true index to evaluate the impacts of different sampling designs on the abundance estimation. Four sampling methods (including fixed-station sampling, simple random sampling, stratified fixed-station sampling, and stratified random sampling) were simulated. Three numbers of stations (9, 16 and 24) were assumed for the scenarios of fixed-station sampling and simple random sampling without stratification. While 16 stations were assumed for the scenarios with stratification. Three reaction distances (1.5 m, 3 m and 5 m) of P. trituberculatus to the bottom line of trawl were also assumed to adapt to the movement ability of the P. trituberculatus for different ages, seasons and substrate conditions. Generally speaking, compared with unstratified sampling design, the stratified sampling design resulted in more accurate abundance estimation of P. trituberculatus, and simple random sampling design is better than fixed-station sampling design. The accuracy of the simulated results was improved with the increase of the station number. The maximum relative estimation error (REE) was 163.43% and the minimum was 49.40% for the fixed-station sampling scenario with 9 stations, while 38.62% and 4.15% for 24 stations. With the increase of reaction distance, the relative absolute bias (RAB) and REE gradually decreased. Resource-intensive area and the seasons with high density variances have significant impacts on simulation results. Thus, it will be helpful if there are prior information or pre-survey results about density distribution. The current study can provide reference for the future sampling design of bottom trawl of P. trituberculatus and other species. [ABSTRACT FROM AUTHOR]

Groundfish species in the Bering Sea are undergoing pronounced changes in spatial distribution and abundance due to warming ocean temperatures. The main drivers of interannual variability in this ecosystem are the alternating warm and cold thermal stanzas. Yellowfin sole (Limanda aspera ; YFS) and northern rock sole (Lepidopsetta polyxystra ; NRS) are commercially-valuable flatfishes in the Bering Sea and are among the most dominant groundfish species there in numbers and biomass. We examined the variability in the spatial distribution and abundance of juvenile NRS and YFS in relation to the ice and temperature conditions associated with warm-cold thermal shifts from 1982 to 2017. The goal was to assess the implications of the fluctuating thermal environment for Bering Sea flatfish production. We found ice cover and bottom temperature indices in the preceding 1 to 3 years to be the best predictors of NRS juvenile distribution. In contrast, these indices were not significantly correlated with YFS juvenile distribution, which could be an artifact of their relatively low availability to sampling. A warm stanza, as the Bering Sea is currently in, is expected to favor high numbers of NRS juveniles and the northward expansion of their distribution. [ABSTRACT FROM AUTHOR]

This study was performed off the southern coast of Yassıca Island in the Izmir Bay on the Turkish coast of the Aegean Sea to investigate the mortality of red mullet (Mullus barbatus, Mullidae) escaping through 40-mm square-mesh and 44- and 50-mm diamond-mesh codends attached to a conventional demersal trawl net. In total, 48 replicate experimental hauls were performed in the summer and winter of 2011 and 2012. Mean escape mortality for all hauls in winter (33.2%±6.51) was significantly higher (p

Background. The coral reefs and deep water ecosystems of Gulf of Mannar support diverse assemblages of marine fishes vulnerable to indiscriminate mechanized fishing. However, lack of comprehensive information on the fish diversity of these ecosystems is aggravated by the habitat complexity of the fishing grounds, inadequate faunistic surveys and insufficient taxonomic expertise. In view of this, the present paper aims to document rare fishes and supplement the existing species inventory from this region. Materials and methods. Sampling surveys included 23 hauls on-board commercial single-day otter trawlers operating bottom trawls at 15–100 m depths, and mid-water trawls at 100–153 m depths in the Gulf of Mannar. In addition, by-catch landings of commercial trawlers were surveyed at Tuticorin fishing harbour. Specimens were subjected to morphometric and meristic examination and deposited at the Central Marine Fisheries Research Institute, Kochi. Results. he presently reported survey of rare fishes revealed one elasmobranch, Hypogaleus hyugaensis (Miyosi, 1939). In addition, 12 species of teleosts belonging to four orders, 10 families, and 11 genera were identified as Uropterygius micropterus (Bleeker, 1852); Dendrochirus bellus (Jordan et Hubbs, 1925); Snyderina guentheri (Boulenger, 1889); Acropoma japonicum Günther, 1859; Gymnocranius elongatus Senta, 1973; Pomacentrus similis Allen, 1991; Pristotis cyanostigma Rüppell, 1838; Leptojulis cyanopleura (Bleeker, 1853); Naso annulatus (Quoy et Gaimard, 1825); Naso thynnoides (Cuvier, 1829); Pseudalutarius nasicornis (Temminck et Schlegel, 1850); and Lagocephalus suezensis Clark et Gohar, 1953. The present paper provides descriptions of each species supplemented with meristic counts and morphometric measurements. An identification key to these species is provided. Conclusion. Hypogaleus hyugaensis, U. micropterus, D. bellus, P. cyanostigma, N. thynnoides, P. nasicornis, and L. suezensis represent the first records in Indian waters. Additionally, G. elongatus, P. similis, and N. annulatus represent the first records off the Indian mainland, and S. guentheri, A. japonicum, and L. cyanopleura represent the first records off the East coast of India. Among these, D. bellus, S. guentheri, and P. cyanostigma represent the first records outside their known zoogeographical ranges. Patchy zoogeographical distribution and extension of known geographical ranges are attributed to recurrence of vicariance events in the geological past.

Bottom trawl surveys provide fishery‐independent data on relative abundance and life history parameters for a wide range of marine taxa. Survey data are used to assess species distribution, biological interactions, and ecosystem structure and to manage marine resources. Not all bottom types or oceanographic conditions accommodate this survey method. We applied National Ocean Service hydrographic smooth sheets to evaluate physical attributes associated with habitat available to surveys. Random forests were used to evaluate the relative influence of benthic terrain and oceanographic predictors in determining accessibility to bottom trawl gear. We examined the marginal importance of each predictor, quantified the response gradient, and applied piecewise regression to determine threshold breakpoint values. Thresholds were used to develop predictive maps and distinguish untrawlable habitat at the scale of discrete towpaths and survey stations. Untrawlable habitat was associated with increased complexity in terrain, roughness, slope, surface curvature, substrate coarseness, current, and aspect. Maps of critical thresholds suggest different variables constrain the probability of a successful trawl in the nearshore, shelf, and continental slope. Overlay analysis of the model projection demonstrates the utility of archived smooth sheet data and identifies areas where higher resolution data might improve results. The model and maps produced in this analysis might be used to identify habitats available to and impacted by commercial trawl fisheries, inform the relative availability of various species and habitat types to bottom trawl surveys, evaluate bias in assessment indices and ecosystem metrics derived from survey data, and advance habitat‐specific biomass estimates. [ABSTRACT FROM AUTHOR]

• Underwater observations of jumbo squid in a trawl for Chilean hake were made using video cameras. • Quantitative analysis of the selection process using a rigid grid to reduce bycatch was made. • Jumbo squid was positively selected by the rigid grid. • Some obstacles was observed during the selection process, with losing efficiency in the escape. • Redesign components to improve efficiency of the selection system are discussed. Observations via underwater filming were obtained to improve understanding of the behavior and selection process of jumbo squid (Dosidicus gigas) in response to a rigid grid in the Chilean hake (Merluccius gayi gayi) trawl fishery in central Chile. The individual fates of jumbo squid were examined to study the efficiency of the selection system. The number of escaped versus captured specimens was quantified. During the selection process, we observed obstacles that impeded the escape process, leading to retention of jumbo squid and limiting the selectivity effectiveness. The analysis showed that 69.8% of jumbo squid escaped the net and 75.5% faced obstacles that generated retention in the sorting process. Longer retention times led to a saturation of the selection system. The target species was successfully selected by the sorting system, in which 87.1% of Chilean hake entered the codend through the grid. We discuss the need to redesign components of the selection system to improve efficiency. [ABSTRACT FROM AUTHOR]

In the Gulf of Gabes (South-east of Tunisia), the spatial and temporal variations of the demersal fishes communities were examined during two benthic trawl surveys conducted on July 2009 and July 2010 aboard a research fishing vessel. 16 sampling stations were surveyed on inshore bottoms, from 15 to 50 m depth. Seventy-five fish species belonging to two classes were recorded as follows: Elasmobranchii (8 spp.) and Actinopterygii (67 spp.). In the coastal area of the gulf, the inter-annual comparison of the abundance of the demersal fish fauna shows a significant improvement during the summer of 2010 compared to the summer of 2009. This increase is modelled in all surveyed locations especially, in Southern Kerkennah and in Eastern Djerba. This area appeared to be in a good ecological condition hosting an important variety of fish species associated with meadows of Posidonia oceanica and beds of the brown algae Arthrocladia villosa. The species' compositions of the demersal fish assemblage showed clearly that the spatial and temporal analysis represented the differences of abundance of the fish's assemblage during these two cruises (summer 2009 and summer 2010). These differences were closely related to peculiar characters of the fauna and biotopes (improving of bottom type and state of vegetation cover community). [ABSTRACT FROM AUTHOR]

Highlights • Trawlers fishing cod in the Barents Sea often use knotted netting in the codend. • The effect of codend designs was investigated for external damages on cod. • Only 9.4% of the cod caught with the knotted codend was flawless. • Gear marks were the most frequent type of damage. • The new codend designs didn't decrease external damages on cod significantly. Abstract The purpose of this study was to investigate the extent of external damage (gear marks, pressure injuries, ecchymosis and skin abrasion) present on trawl-caught cod (Gadus morhua) and to examine whether the extent of damage could be reduced by introducing changes in the gear. We tested whether changing the 2-panel knotted codend used by the Norwegian trawler fleet operating in the Barents Sea today to a 2-panel knotless codend or a 4-panel knotless codend could decrease the extent of external damage to the fish in the catch. We evaluated 720 fish over 12 hauls carried out with a twin trawl setup and found that the probability for cod to be without any external damage was 9.4% (4.7%–15.8%) with the codend used in the fishery today. Thus, most fish in these catches are likely to have slight or moderate damage. Gear marks were the most frequent type of damage, with only 11.5% (6.0%–18.9%) of the cod being free of this type of injury. When gear marks were not considered in the analysis, 68.4% (58.8%–78.3%) of the fish was estimated to be flawless. Replacing the knotted netting in the codend increased the probability of obtaining fish without gear marks to 15.5% (6.2%–28.0%). However, the confidence intervals were wide, and this effect was not statistically significant. For the other three damage types, the estimated effects of changing the design of the codend were small and not statistically significant. Changing from a 2- to 4-panel codend was estimated to reduce the probability for gear marks by a further 1.7% (−13.4%–16.8%). However, this increase was not significant. Overall, the two codend design changes tested in this study did not significantly decrease the external damage present on trawl-caught cod. [ABSTRACT FROM AUTHOR]

The currently existing Biological Protection Areas (BPAs) are Italian conservation measures specifically oriented to preserve/recover commercial fish stocks through the regulation or ban of few fishing activities. Although BPAs have been well identified/designed within the Italian national waters, neither data on their effects on fishery resources nor on the fishers' compliance with these no-take regulations are yet available. In this context, the present study was aimed to investigate how AIS data processing could be used to map patterns in fishing activity within/around small regulated areas and rate the effectiveness of the conservation measures in place. To do this, it was impossible not to address the issue surrounding well-known and substantial gaps in data coverage and attempt an estimate of them by flagging events when AIS had been switched off within/around BPAs. Results highlighted that almost all the BPAs are illegally trawled and that, unless additional legislation is effected to regulate the use of AIS by fishing vessels, it may provide a useful source of information to map fishing activities stated that the data are interpreted in an appropriate way. • First study addressing the fishers' compliance with the Italian Biological Protection Areas (BPAs). • Almost all the BPAs are illegally trawled. • High resolution AIS data can provide a useful source of information for rating the effectiveness of even small BPAs. • Before AIS data can be used, gaps in the data coverage must be addressed. [ABSTRACT FROM AUTHOR]

Bottom trawling is the most widespread human activity directly affecting seabed habitats. Assessment and effective management of the effects of bottom trawling at the scale of fisheries requires an understanding of differences in sensitivity of biota to trawling. Responses to disturbance are expected to depend on the intrinsic rate of increase in populations (r), which is expected to be linearly related to the reciprocal of longevity.We examine the relationship between the longevity of benthic invertebrates and their response to bottom trawling; both in terms of the immediate mortality following a trawl pass and their subsequent rates of recovery. We collate all available data from experimental and comparative trawling studies, and test how longevity influences these aspects of sensitivity.The shortest lived organisms (<1 year) increased in abundance shortly after experimental trawling but showed no response to trawling in long‐term comparative studies. Conversely, the abundance of biota with a life span >1 year decreased by ~9% immediately following a trawl pass. The effect of bottom trawling in comparative studies increased with longevity, with a 2–3× larger effect on biota living >10 years than on biota living 1–3 years. We attribute this difference to the slower recovery rates of the long‐lived biota.The observed relationship between the intrinsic rate of population increase (r, our metric of recovery rate) and the reciprocal of longevity matches theoretical expectation and predicts that the sensitivity of habitats to bottom trawling is higher in habitats with higher proportions of long‐lived organisms.Synthesis and applications. Where the longevity of a species or the longevity distribution of a community is known or can be inferred, our estimates of depletion and intrinsic rate of increase can be combined with high‐resolution maps of trawling intensity to assess trawling impacts at the scale of the fishery or other defined unit of assessment. Our estimates of r may also be used to estimate recovery times following other forms of seabed disturbance. Where the longevity of a species or the longevity distribution of a community is known or can be inferred, our estimates of depletion and intrinsic rate of increase can be combined with high‐resolution maps of trawling intensity to assess trawling impacts at the scale of the fishery or other defined unit of assessment. Our estimates of r may also be used to estimate recovery times following other forms of seabed disturbance. [ABSTRACT FROM AUTHOR]