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The method for calculation of geometric parameters of trawl system proposed by F.I. Baranov is analyzed. The calculation includes evaluation of spacer force and drag for all elements of trawl system and solution of transcendental equation to find a distance between the otter boards of bottom trawl. Special attention is paid to considering and enhancement of common techniques for determining force and geometric parameters of some elements of trawl system, with identifying the most appropriate ways. The calculations and experimental data are compared for a trawl system using the Scanmar equipment for monitoring of fishing gear. The updated model simulates more adequately the forming of bottom trawl geometry, therefore it can be used for assessment of the catch area during trawl surveys conducted by bottom trawls.

Length‐weight relationships (LWRs) were presented for 15 fish species which caught in the East China Sea during 2009–2014. All of the samples were caught by commercial and scientific survey bottom trawl vessels. The commercial fishery survey used one‐single bottom trawl with the smallest mesh size 25 cm and light seine fishing with the smallest mesh size 38 cm, however, the scientific survey only used one‐single bottom trawl with the smallest mesh size 20 cm. The length and weight of all the fish were measured to the nearest millimeter and milligram, respectively. The application of these estimated values should be limited to the studied waters and observed length ranges. The development and adoption of a standardized sampling format for all studies aiming to determine LWRs should be undertaken. [ABSTRACT FROM AUTHOR]

Background. Bottom trawling is an important fishing technique for catching demersal fish, and selectivity is one of the most important tools for fishery management. This study aimed to determine the selectivity of 40 mm square- (40S) and 90º turned-mesh (40T90) codend for the deepwater rose shrimp, Parapenaeus longirostris, and greater forkbeard, Phycis blennoides (Brünnich, 1768). Materials and methods. Fishing experiments were conducted on the international waters of the Aegean Sea by using a commercial vessel between 24 August and 13 September 2012. The hooped covered codend technique was employed for the estimated codend selectivity. The selectivity parameters were estimated by using CC 2000 software. Results. Nineteen successful hauls, 11 with 40S, and 8 with 40T90 codends, were performed. The mean L50 values (50% retention length) of 40S and 40T90 were found to be a 15.5 ± 0.1 mm and 14.8 ± 0.1 mm carapace lengths for the rose shrimp, and 15.3 ± 0.1 cm and 12.2 ± 0.1 cm total lengths for the greater forkbeard, respectively. Conclusion. In conclusion, 165 square meshes in a codend circumference with 40 mm mesh sizes provided higher L50 values than the 40 mm turned meshes, and 330 meshes around the codend circumference. Halving the number of meshes in the codend with larger turned mesh and different modifications should be investigated for further studies in order to appropriate the L50 values.

Copyright of Marine Pollution Bulletin is the property of Pergamon Press - An Imprint of Elsevier Science 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 dense aggregations of Northeast Atlantic cod ( Gadus morhua ) in the Barents Sea have led to a new fishing practice termed “buffer towing.” In this fishery, many trawlers redeploy the trawl directly after taking the catch onboard in an attempt to secure a continuous supply of fish and avoid any unnecessary stops during processing. If the approximate desired amount of fish is caught or exceeded before the catch from the previous haul is processed, the trawl is lifted off the seabed and towed at a given depth at low speed, usually ∼1–2 knots, until the production capacity of the onboard factory is restored. Both researchers and fishermen onboard trawlers believe that buffer towing has a negative impact on fish quality, as indicated by increased frequency of gear marks and dead fish, poorer exsanguination, ecchymosis, skin abrasion, fillet gaping, and fillet redness. However, the effect that buffer towing has on fish quality has not been scientifically evaluated. The aim of this study was to document the effects of buffer towing on fish quality. The quality was assessed using two different indexes, one for whole cod and one for cod fillets. The results proved that buffer towing has a negative impact on fish quality. Specifically, cod subjected to buffer towing, in contrast to direct haul-back, had an increased relative probability of 371% for poor exsanguination and an increased relative probability of 209% for fillet redness. Furthermore, combining scores of the different quality categories within the indexes (e.g., gear marks, ecchymosis, poor exsanguination, and skin abrasion) proved a significant reduction in the quality of cod subjected to buffer towing. [ABSTRACT FROM AUTHOR]

The Nordmøre grid is widely used in shrimp trawls to reduce the bycatch of fish species. However, small-sized fish species and juveniles still pass through the grid and enter the codend, along with the targeted shrimp. This bycatch of small fish has a negative impact on the ecosystem due to increased fish mortality, and leads to additional sorting work onboard. Some small-sized fish that enter the trawl avoid entering the codend by escaping through the outlet above the grid, without making contact with the grid itself. Design changes that promote this behavior could potentially reduce bycatch in shrimp trawl fisheries. Light-emitting diodes (LEDs) mounted around the escape outlet have previously been found to have either a negative effect, or no effect at all, on fish bycatch species. This study investigates the effect of mounting green LEDs on the lower part of a Nordmøre grid, to determine if their presence would encourage bycatch fish to rise towards the escape outlet prior to contacting the grid. Experimental fishing trials were conducted to assess the size selective properties of a 19 mm bar spaced Nordmøre grid with and without LEDs, mounted on a bottom trawl targeting Deep-water shrimp ( Pandalus borealis ). For the four bycatch species investigated, 51–100% of small fish passed through the Nordmøre grid. The addition of green LEDs to the Nordmøre grid did not significantly affect the escape probability or the size selectivity of any of the investigated species. Very few Deep-water shrimp were found to escape through the escape outlet independent of the presence of the LEDs mounted on the grid. [ABSTRACT FROM AUTHOR]

In this paper, we tested the hydrodynamic characteristics of a new, double-winged otter board that consists of a forewing, a leading edge slat and a trailing edge flap. Flume experiments were conducted in a circulating flume tank by using a model with an aspect ratio (AR) of 0.85 and a horizontal planform area (S) of 0.09 m2. The results indicated that the critical angle (αcr) of the model was 44°, whereas the maximum lift coefficient (CLmax) was up to 1.715, and the door efficiency (K) was 1.122. The attack angle (α) ranged from 30° to 48° and from 10° to 46° when the lift coefficient (CL) and door efficiency (K) were greater than 1.2 and 1.0, respectively. To compare the difference between double-winged otter board and traditional Morgere Polyvalent Ovale, same model of Morgere Polyvalent Ovale was also tested under the same experimental conditions. The critical angle (αcr) and maximum of lift coefficient (CLmax) of the doublewinged otter board were 37.5% and 14.6% larger than those of the Morgere Polyvalent Ovale. Therefore, we concluded that the novel, double-winged otter board was more suitable for bottom trawling fisheries in the deep water of the Mauretania Sea due to its better hydrodynamic characteristics and stability. [ABSTRACT FROM AUTHOR]

SUMMARY: Trawling activities are considered to be one of the main sources of disturbance to the seabed worldwide. We aimed to disentangle the dominance of environmental variations and trawling intensity in order to explain the distribution of diversity patterns over 152 sampling sites in the French trawl fishing-ground, the Grande Vasière. Using a towed underwater video device, we identified 39 taxa to the finest taxonomic level possible, which were clustered according to their vulnerability to trawling disturbance based on functional traits. Using generalized linear models, we investigated whether the density distribution of each vulnerability group was sensitive to trawling intensity and habitat characteristics. Our analyses revealed a structuring effect of depth and substratum on community structure. The distribution of the more vulnerable group was a negative function of trawling intensity, while the distributions of the less vulnerable groups were independent of trawling intensity. Video monitoring coupled with trait-based vulnerability assessment of macro-epibenthic communities might be more relevant than the traditional taxonomic approach to identifying the areas that are most vulnerable to fishing activities in conservation planning. [ABSTRACT FROM AUTHOR]

In this study, length-weight relationship (LWR) parameters are reported for 13 fish species collected from the western Black Sea and a total of 3132 fish individuals were sampled. The b values varied from 2.84 for Scorpaena maderensis to 3.49 for Trachurus mediterraneus, with a mean of 3.13 (±0.074). The LWRS and regressions for all species were highly significant (P<0.05), whereas they were isometric for six species (Merlangius merlangus, Sprattus sprattus, Trachinus draco, Pomatomus saltatrix, Trachurus trachurus and Chelidonichthys lucernus). Two species (Scorpaena porcus, Scorpaena maderensis) showed negative allometry and five species (Mullus barbatus, Merluccius merluccius, Engraulis encrasicolus, Trachurus mediterraneus, Uranoscopus scaber) indicated positive allometry. In this study, LWR for S. maderensis in the Black Sea was investigated for the first time. [ABSTRACT FROM AUTHOR]

Copyright of Review of Hydrobiology is the property of NK Yayincilik Egitim Hizmetleri 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.)

Copyright of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Ürünleri Dergisi is the property of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Urunleri Dergisi 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.)

Copyright of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Ürünleri Dergisi is the property of Ege Journal of Fisheries & Aquatic Sciences (EgeJFAS) / Su Urunleri Dergisi 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.)

Sorting grids and square mesh panels are the two most-applied technical devices to supplement codend size- and species-selection in demersal trawls. In the Barents Sea gadoid fishery, the compulsory size-selectivity system comprises a mesh section with a sorting grid followed by a diamond mesh codend. We tested the size-selective performance of a new sorting section that comprised a sorting grid combined with a square mesh panel as a potential alternative for the grid sections currently in use. The new sorting section was shorter and therefore more maneuverable than the existing sorting grid sections. The investigation was carried out on cod and the bycatch species redfish. The grid was found to contribute to the largest proportion of fish release, and the release through the square mesh panel was low. But, the results showed that the grid was successful at guiding fish not escaping through the grid to a second selection process in the panel. However, the square mesh panel did not result on the intended release efficiency except for the smallest sizes of fish, most likely because the guiding angle of the grid and the square meshes in the panel used did not provide a suitable escape path for the desired size range of fish. Therefore, optimizing the mesh size/shape in the panel and/or the guiding angle for the grid potentially could lead to the desired selectivity pattern in the new sorting section. [ABSTRACT FROM AUTHOR]

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.)

The Argentine stiletto shrimp (Artemesia longinaris) and the Argentine red shrimp (Pleoticus muelleri) currently sustain an important fishery in terms of tonnage and revenues in southern Brazil. This study analyzed the factors affecting the abundance of both species through the application of Generalized Linear Models to landing-per-unit-of-effort (LPUE) data of the trawl fleet operating on the main fishing grounds between 1998 and 2005. The main patterns of LPUE variability of both species were attributed do the effect of seasons and annual cycles. Larger yields were obtained in the southern shallow areas of Rio Grande do Sul State. No tendency either to an increase or a decline in stock abundance was observed, but the effort in one year was affected by the success of the captures of the previous year. In the last two years analyzed the abundance and the total captures declined.

The Gulf of Mannar is a haven for rare species, which along with their pristine reef habitats are under constant threat from natural phenomena and anthropogenic activities. Therefore, the presently reported study aimed at documenting and inventorying rare benthic epi-faunal taxa from the region. We undertook 23 bottom trawl hauls at depths between 14 and 153 m in the Gulf of Mannar. Additionally, we collected rare fishes from the Tuticorin fisheries jetty. Our findings revealed that Parapterois heterura (Bleeker, 1856) is a new record for the Indian waters. Additionally, four species namely Ebosia falcata Eschmeyer et Rama-Rao, 1977, Pseudanthias marcia Randall et Hoover, 1993, Apogon queketti Gilchrist, 1903, and Roa jayakari (Norman, 1939) are new records for the east coast of India outside their known geographical range, whereas five other teleosts (Ostichthys acanthorhinus Randall, Shimizu et Yamakawa, 1982, Apogon semiornatus Peters, 1876, Histiopterus typus Temminck et Schlegel, 1844, Macropharyngodon ornatus Randall, 1978, and Scolopsis xenochroa Günther, 1872) are new records for the east coast of India. The present paper supplements the existing knowledge of benthic invertebrate taxa from this region, which is mandatory to understand the role of these species in ecosystem functioning.

This short-term study on commercial discards was carried out in fishing grounds around Gökçeada Island in the northeastern Aegean Sea, a geographic area where fisheries information is rather limited. A total of 28 bottom trawls were performed between 70 and 410 m depth from December 2009 to February 2010. All the samples were collected on board a commercial trawler under commercial fishing conditions. A total of 3143 kg of biomass was caught in 28 valid hauls. Landings accounted for about 67% of the total catch while the remaining 33% was discarded. Fish species comprised 85% of the total catch and their composition could be divided into four main groups related to depth: shallow shelf (70 to 88 m), deep shelf (155 to 180 m), shelf break (196 to 276 m), and upper slope (307 to 410 m). Fish dominated the abundance and biomass of both landings and discards in all bathymetric strata. Echinoderms also accounted for a large proportion of the discards. Mean total catches varied between 78.4 kg/h on the shallow shelf and 38.1 kg/h on the shelf break with no differences in the landing biomass between groups, but with slightly higher discards over the shallow shelf. Taking into account the preliminary nature of the findings, based on a short-term analysis, the minimum mesh size and minimum landing size currently applied in the Turkish bottom trawl fishery are not sufficient to reduce discards and to protect juveniles of commercially important species in the northeastern Aegean Sea.

Marine litter occurrence and composition were investigated during routine bottom trawl fish surveys type BITS performed in the Polish Maritime Areas (the southern Baltic Sea). Sampling covered a distance of 325 km and an area of 16 km 2 at a depth range of 19–110 m. Litter densities varying between 0 items/ha (34% of tows) and 2.23 items/ha with a mean of 0.20 items/ha (SD = 0.30) are at the bottom range of densities reported from other shelf habitats worldwide at similar water depths. The majority of the items (40%) were found at a depth range of 51–60 m. Overall, plastic was the most common litter type (67% of all items) found in all tows with litter. The results of this study indicate that despite the Baltic being a semi-enclosed basin, with a densely populated coastline and extensive shipping, marine litter pollution of the southern Baltic seafloor is low compared to other coastal areas. [ABSTRACT FROM AUTHOR]

Species that have a high likelihood of surviving the discarding process have become great concern since the European Union reformed the Common Fisheries Policy and enacted a landing obligation prohibiting the discarding any individuals of species under quota. Among species presenting an elevated survival potential, plaice ( Pleuronectes platessa ) is one of the most discarded in the coastal otter trawl fishery in the English Channel. The objective of this study is to provide the most reliable estimates of plaice survival after release in commercial conditions, and to identify the factors that influence survival rates. A captivity experiment was conducted in January–February in the English fishery to assess the survival of discarded plaice as a function of a semi-quantitative index of fish vitality, which has been demonstrated to be a good proxy of fish survival in comparable fishing and environmental conditions. This study examined the potential of this index to estimate discard survival in three trials from the English and French fisheries and at three different seasons. The vitality index was then used to analyse the influence of several factors (fishing practices, environmental conditions and fish biological characteristics) on the discard survival. The survival rates for plaice were accurately estimated at 62.8% in January–February, 66.6% in November and 45.2% in July. While these rates remained substantial whatever the fishing, environmental or fish biological conditions, the time fish spent on the deck, the bottom and air temperatures, the tow depth and the fish length had a significant influence on plaice survival. In practice, plaice survival could be enhanced by releasing the fish early during catch sorting and avoiding exposure to extreme air temperatures. [ABSTRACT FROM AUTHOR]

Species richness has long been used as an indicator of ecosystem functioning and health. Global richness is declining, but it is unclear whether sub-global trends differ. Regional trends are especially understudied, with most focused on island regions where richness is strongly impacted by novel colonisations. We addressed this knowledge gap by testing for multi-decade trends in species richness in nine open marine regions around North America (197 region-years) while accounting for imperfect observations and grounding our findings in species-level range dynamics. We found positive richness trends in eight of nine regions, four of which were statistically significant. Species' range sizes generally contracted pre-extinction and expanded post-colonisation, but the ranges of transient species expanded over the long-term, slowly increasing their regional retention and driving increasing richness. These results provide more evidence that sub-global richness trends are stable or increasing, and highlight the utility of range size for understanding richness dynamics. [ABSTRACT FROM AUTHOR]

The improvement of fishing technology has been detrimental to the sustainability of fisheries, which is particularly clear for the bottom trawl fishery. Reducing its environmental impact is a key point for the development of a more sustainable fishery. The present work analyzed different possibilities to mitigate the impact of gears on the seabed and to increase the efficiency of the bottom trawl fishery of the Western Mediterranean. The analysis of three experiments showed that innovative technical and regulation measures can lead to benefits such as the reduction of fishing effort, the improvement of the cost-benefit relation and the reduction of the direct impact on the seabed and the indirect effect on the ecosystems through reduce discards and the emission of CO 2 into the atmosphere. After years of studies focused on improving the sustainability of this fishery, it's about time to turn this improvement into reality. [ABSTRACT FROM AUTHOR]

Hydrodynamic performance of a 1/8 scale model of traditional bottom trawl was investigated in a flume tank. It was to represent prototype of a bottom trawl with a low engine power of 33 HP at a towing speed of 3-knot, which is commonly used in Kotabaru, Indonesia. At a towing speed of 3-knot (96 cm s-1 in model scale), the net heights at different wing tips distances varied from 7.0 to 9.2 cm, the projective areas of net mouth from 6.35×10² to 8.44×10² cm², water filtering volume from 32.04×10³ to 40.55×10³ m³ and total net resistance from 11.07×10² to 13.46×10² g. In the present study, the values of H/a ratio obtained was low (0.029 to 0.038) because there was no square part on the net body construction. The net height was 3.4 % of net circumference and getting lower at higher towing speeds. Water flow velocity and pressure distribution around trawl can alternate mesh shape from diamond to parallelogram. The average exponent value 1.37 was less than the suggested value (2.0); thus, the shape of net body under towing condition should be refined. [ABSTRACT FROM AUTHOR]

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. The 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. [ABSTRACT FROM AUTHOR]

Trawling is an important fishing method used by the fishermen in the Turkey. Bottom trawling fisheries in this part of Mediterranean are essentially multispecies. Commercial fishing vessels use 44 mm diamond shaped mesh for trawl cod-end s in the Mediterranean Coast of Turkey. The trawl nets (cod-end) of the fishery retain a lot of juvenile individuals, which has negative effects on the population of fish species. Currently fishing boats use very low selectivity gears. Because of this reason, fishing ground is predominantly overfished. Although there are many selectivity studies carried out in the Mediterranean coast of Turkey, selectivity experiments results have not used into practice for management of fisheries yet. [ABSTRACT FROM AUTHOR]

Mapping trawling pressure on the benthic habitats is needed as background to support an ecosystem approach to fisheries management. The extent and intensity of bottom trawling on the European continental shelf (0-1000 m) was analysed from logbook statistics and vessel monitoring system data for 2010-2012 at a grid cell resolution of 1 × 1 min longitude and latitude. Trawling intensity profiles with seabed impact at the surface and subsurface level are presented for 14 management areas in the North-east Atlantic, Baltic Sea and Mediterranean Sea. The footprint of the management areas ranged between 53-99% and 6-94% for the depth zone from 0 to 200 m (Shallow) and from 201 to 1000 m (Deep), respectively. The footprint was estimated as the total area of all grid cells that were trawled fully or partially. Excluding the untrawled proportions reduced the footprint estimates to 28-85% and 2-77%. Largest footprints per unit landings were observed off Portugal and in the Mediterranean Sea. Mean trawling intensity ranged between 0.5 and 8.5 times per year, but was less in the Deep zone with a maximum intensity of 6.4. Highest intensities were recorded in the Skagerrak-Kattegat, Iberian Portuguese area, Tyrrhenian Sea and Adriatic Sea. Bottom trawling was highly aggregated. For the Shallow zone the seabed area where 90% of the effort occurred comprised between 17% and 63% (median 36%) of the management area. Footprints were high over a broad range of soft sediment habitats. Using the longevity distribution of the untrawled infaunal community, the seabed integrity was estimated as the proportion of the biomass of benthic taxa where the trawling interval at the subsurface level exceeds their life span. Seabed integrity was low (<0.1) in large parts of the European continental shelfs, although smaller pockets of seabed with higher integrity values occur. The methods developed here integrate official fishing effort statistics and industry-based gear information to provide high-resolution pressure maps and indicators, which greatly improve the basis for assessing and managing benthic pressure from bottom trawling. Further they provide quantitative estimates of trawling impact on a continuous scale by which managers can steer. [ABSTRACT FROM AUTHOR]

Groundfishes are important species for commercial, recreational, and tribal fisheries along the Pacific Coast of the United States. Understanding the abundance and distribution of these fishes is necessary for successful fisheries management. Many groundfish species spend at least part of their life cycle in nearshore habitats. However, assessing groundfish species assemblages in nearshore habitats can be limited by the relatively small size of young-of-the-year and subadult life history stages, which may not be quantitatively retained with traditional survey gears. In addition, portions of the innermost nearshore (<55 m water depth) can be inaccessible to vessels employed in trawl surveys. To help improve the fishery-independent data informing the current understanding of nearshore assemblages, we compared catches resulting from two different but spatially overlapping surveys. One is the National Oceanic and Atmospheric Administration's (NOAA) West Coast Groundfish Bottom Trawl Survey (WCGBTS), which is representative of a typical groundfish survey in USA and EU continental shelf habitats. The other is an ad-hoc beam trawl survey along the Newport Hydrographic (NH) Line – an oceanographically well-monitored sampling line off the Pacific Coast. Our objectives were to evaluate the representativeness of nearshore fish communities in the WCGBTS and to assess if additional nearshore sampling would enhance the WCGBTS. For the purposes of this study, "nearshore" is defined as the continental shelf shoreward of 200 m depth. Examining fish catches and environmental variables from both surveys, we found significant differences in fish assemblages, oxygen, temperature, and salinity based on depth, season, year, and survey type. The WCGBTS is designed and well-suited for sampling subadult and adult groundfishes in trawlable habitat. However, year-round sampling of the beam trawl survey allows it to capture ephemeral environmental conditions better than the WCGBTS. The gear type and sampling location make the beam trawl survey better suited than the WCGBTS for sampling smaller individuals and species that live at shallower depths. The beam trawl survey caught 69 unique species or taxa groups within the comparative data subset, whereas the WCGBTS caught 83. The three most commonly occurring species in the beam trawl survey were Pacific sanddab (Citharichthys sordidus), English sole (Parophrys vetulus), and speckled sanddab (Citharichthys stigmaeus), while the WCGBTS most commonly caught rex sole (Glyptocephalus zachirus), Dover sole (Microstomus pacificus), and spotted ratfish (Hydrolagus colliei). Of the fish with measured lengths, the catch from the beam trawl survey had a mode standard length of 2 cm, contrasted with the mode length (total length, fork length, anal length, and natural length combined) of 22 cm for the WCGBTS. We found that there is a transition in species assemblages right where the WCGBTS ends (about 55 m). Thus, while the surveys overlap in some capabilities, this analysis shows that the beam trawl survey or a similar nearshore survey would complement the WCGBTS, providing an enhanced characterization of groundfish assemblages. • Juvenile groundfish assemblages may not be well sampled in stock assessment surveys. • Compared inner continental shelf fish assemblages: beam trawl vs. Aberdeen trawl. • There is a transition in species composition where stock assessment survey ends. • Beam trawl survey better represents young-of-the-year flatfish assemblages. • Beam trawl survey provides improved seasonal and shallow depth (< 55 m) coverage. [ABSTRACT FROM AUTHOR]

A traditional codend (40 mm diamond mesh) and an experimental codend (40 mm square mesh) made of 2.6 mm diameter knotless PA netting were tested on a commercial trawl net on a sandy-muddy bottom (~70 m depth) of the Adriatic sea in order to assess the size selectivity of European hake (Merluccius merluccius) and the reduction of the discards in a demersal multi-species trawl fishery. The catch was sorted as target species and bycatch and the selectivity with respect to European hake was investigated using the covered codend method. The square-mesh codend allowed a reduction of about 37% of the fraction discarded at sea. The mean catch obtained with the experimental codend was lower than that obtained with the traditional codend (about 14 kg per haul) but the short-term economic losses were low (~12%). The square-mesh codend was also more selective than the traditional codend, giving the juveniles of European hake a good chance of escape: the mean selection length (L50) was 7.60 cm in DM and 12.98 cm in SM. Moreover, the mesh configuration did not affect the gear’s performance. Thus, the square-mesh codend could be an easy, inexpensive and useful solution for a more sustainable management of the resources in Adriatic multi-species fishery.

In order to improve the capacity of bottom trawl fishing gears to reduce catches of young fish and discards in a highly exploited demersal trawl fisheries in the Mediterranean, the size-selection performance of a 36-mm square-mesh codend and two sorting grids with 20 and 15 mm bar spacing was assessed. Alternate hauls were used to assess the selectivity of 36-mm square-mesh codend. Selectivity of sorting grids was assessed using a double codend in which fish that escaped through the grid were captured in the lower codend while other fish were guided into the upper codend. The mean selection length (L50) for European hake was 18.5 cm and that for the Atlantic horse mackerel was 14.0 cm with the 36-mm square-mesh codend . These values are close to their current minimum landing sizes (20 cm for hake and 12 cm for horse mackerel). The sorting grid with 20-mm bar spacing showed L50 value of 13.3 cm for hake, suggesting that a larger grid-spacing would be needed to obtain sufficient sorting performance. Similarly, for Atlantic mackerel the estimated L50 of 14.3 cm indicates that larger grid spacing is required to attain an L50 that would be close to the current MLS (18 cm). For Atlantic horse mackerel and red mullet, the L50 obtained with the sorting grid with 20-mm bar spacing was close to the MLS of these species (the MLS of red mullet is 11 cm). The selectivity of the sorting grid with 15-mm bar spacing was generally very poor. Size-selection performance of sorting grids was assessed for the first time in the local fisheries. In order to effectively improve size-selection, seasonal and depth-dependent differences between target and by-catch species must be taken into account, which is a good indicator of the difficulty of implementing a single mesh size or grid spacing in the Mediterranean demersal trawl fishery.

Detecting the origin of marine benthic litter is fundamental for developing policies aimed at achieving the Good Environmental Status in European Seas by 2020, as requested by the Marine Strategy Framework Directive (MSFD). The abundance and composition of benthic litter in the Northern and Central Adriatic Sea were investigated at 67 stations with bottom trawl nets. Average density of benthic litter was 913 ± 80 items/km 2 , ranking the Adriatic as one of the most polluted basins worldwide. Plastic was dominant in terms of numbers (80%) and weight (62%), and mainly consisted in bags, sheets and mussel nets. Higher quantities of litter were found in coastal areas, especially in front river mouths, coastal cities and mussel farms. In deep waters, litter hotspots were associated with most congested shipping lanes, indicating an additional litter input to the basin. Benthic litter composition resulted to be largely driven by the vicinity to local sources, i.e. mussel farming installations and most congested shipping routes. These findings provide useful insights to set measures to manage marine litter in the Adriatic region, and possibly to minimize this anthropogenic pollution. [ABSTRACT FROM AUTHOR]

A trouser trawl was used to determine the size selectivity of three sizes of mesh opening (114, 140 and 165 mm double 5 mm twine diamond) on a commercial fishing vessel fishing off Provincetown, Massachusetts, USA. Fifty-six tows were completed in March and April 2013, catching over 42,000 kg of Acadian redfish ( Sebastes fasciatus ) and about 6000 kg of other species. Robust models for the mean L 50s and selection ranges, and confidence intervals, were developed for all three tested codends, incorporating both within and between haul variability. L 50 and selection ranges were determined for the nominal 114 mm ( L 50:22.3 cm; SR:3.3 cm), 139 mm ( L 50:29.2 cm; SR:4.4 cm), and 165 mm ( L 50:33.6 cm; SR:5.0 cm) codends. All measures of model validity were positive. These models are fully adequate to provide guidance to managers and fishermen on size retention of redfish and appropriate codend mesh size. Additionally, simulation of fishing of the three tested codends on the observed population indicated that substantial escape of redfish through codend meshes occurs (51–96%), suggesting that investigation of escape of redfish is warranted to support a sustainable fishery. The observed population also indicates that inadequate numbers of larger redfish may be available to support a higher-priced market. [ABSTRACT FROM AUTHOR]

Measuring the size selectivity of pollock, or saithe, Pollachius virens, has been challenging due to the patchy, elusive nature of the species. By using data collected opportunistically during a redfish Sebastes fasciatus selectivity study, selectivity of three sizes of mesh opening (114, 140 and 165 mm double 5 mm twine diamond) for pollock was determined using a commercial fishing vessel fishing off Provincetown, Massachusetts, USA. Fifty-six tows were completed in March and April 2013; 21 included sufficient catches of pollock to estimate size selectivity. Robust, simple models for the mean L50s (50% selection length) and SR (selection ranges), and confidence intervals, were developed for all three tested codends, incorporating both within and between haul variability. Selection parameters and selection ranges were determined for codends with nominal mesh sizes of 114 mm (L50: 34.8 cm; SR: 2.4 cm), 139 mm (L50: 45.6 cm; SR: 3.1 cm), and 165 mm (L50: 52.4 cm; SR: 3.6 cm). All measures of model validity were positive, indicating robust and reliable findings that can be used to provide guidance to fishery managers, stock assessment scientists, and fishermen on size-dependent retention of pollock by codend mesh size. [ABSTRACT FROM AUTHOR]

The new Common Fisheries Policy may exempt some species from the landing obligation if a high survival rate can be demonstrated among discards. This study focuses on the survival capacity of Nephrops norvegicus discarded from trawlers of the Bay of Biscay (France). Three sea trials were conducted on board 3 commercial trawlers and 15 fishing operations were sampled. The vitality of Nephrops was classed into three categories (healthy, moribund or dead) before release at sea and samples of healthy and moribund individuals were kept in captivity on Nephrops grounds for three days. A Generalised Linear Model was used to examine the variability in the proportion of healthy Nephrops discarded, which was significantly influenced by tow duration, duration of air exposure and temperature, as well as individual length. By combining the results on vitality before release at sea with those on survival in captivity following re-immersion, resampled by bootstrapping, it was calculated that 51% [42–60%] of discarded Nephrops would survive after three days of re-immersion. We discuss the sources of variability in survival rate, as well as the implications of a potential exemption from the landing obligation for this species. [ABSTRACT FROM AUTHOR]

We inserted a new double steel grid system consisting of a lower and an upper grid in a four-panel section to increase the cross-sectional area and improve the size selectivity in the Norwegian bottom trawl fishery. We tested its ability to size select and release typical bycatch species in the cod ( Gadus morhua ) and haddock ( Melanogrammus aeglefinnus ) directed fishery, i.e. two species of redfish ( Sebastes spp.). The redfish selectivity data were analysed using a new model that included direct quantification of the probability that fish will make contact with the grids. The results showed that the proportion of redfish escaping through the two grids did not differ significantly. The release efficiency of the first (lower) grid was, however predicted to be significantly lower than that of the second grid when accounting for the actual fraction of redfish reaching the zones of the individual grids. An estimated 80% of the redfish made contact with at least one of the two grids. However, the release efficiency and overall size selection for redfish of the new double grid system was not significantly better than obtained in former selectivity trials testing the grid systems used in the fishery today. Moreover, this comparison of results showed that the existing Sort-V single grid system releases significantly more redfish than the new double grid system. [ABSTRACT FROM AUTHOR]