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Sea trials to test size selectivity equipment in trawls are often limited in time because they are costly, and the results can be influenced by multiple factors that are often overlooked. In the Barents Sea gadoid trawl fishery, the use of a size sorting grid in front of the codend is compulsory. The flexigrid, a netting section containing two flexible grids, is the most widely used grid section in this fishery. However, earlier selectivity studies with this device have shown inconclusive results. It has been speculated that the differences observed resulted from the difference in age and usage of the grid sections in the studies compared. To reveal whether potential changes in the device construction over time can lead to differences in size selection properties, we performed comparative fishing trials where we compared a brand new flexigrid section and a well-used flexigrid section used continuously by a commercial trawler for approximately four years. The results showed that the new flexigrid released significantly more cod below ~60 cm than the used flexigrid. However, when the grids were fished with a subsequent diamond mesh codend, there was no difference in the overall selectivity of the two gears, meaning that the size selectivity in the codend compensates for the potential reduction in selectivity performance of the grids. This study shows the importance of considering the age and earlier use of size selection devices like sorting grids before they are compared with other devices, as their size selection properties can change significantly over time and with use. [ABSTRACT FROM AUTHOR]

This study assessed catch composition, size selectivity, and fishing efficiency of demersal trawls targeting penaeid shrimp species in the Red Sea. It first compared the currently used diamond mesh codends in two fishing areas, Al Qunfudhah and Jazan, and then compared alternative square mesh codends to diamond mesh codends in Jazan. A total of 33 valid hauls were conducted in 2023, yielding 10,869 kg of total catch. The results showed that the square mesh codend significantly improved size selectivity, particularly for Penaeus semisulcatus and Metapenaeus monoceros, with L50 (50% retention length) values closer to their size at first maturity. The fishing efficiency indicators revealed a reduced retention probability for undersized individuals with square mesh codends. Additionally, bycatch discard rates decreased, indicating potential benefits for ecosystem conservation. This study suggests incorporating square mesh codends into fishery management regulations to enhance size selectivity and reduce bycatch during Red Sea shrimp trawling. Establishing a legal minimum landing size requirement is recommended to complement these efforts and promote sustainable fishing practices. [ABSTRACT FROM AUTHOR]

Sea trials to test size selectivity equipment in trawls are often limited in time because they are costly, and the results can be influenced by multiple factors that are often overlooked. In the Barents Sea gadoid trawl fishery, the use of a size sorting grid in front of the codend is compulsory. The flexigrid, a netting section containing two flexible grids, is the most widely used grid section in this fishery. However, earlier selectivity studies with this device have shown inconclusive results. It has been speculated that the differences observed resulted from the difference in age and usage of the grid sections in the studies compared. To reveal whether potential changes in the device construction over time can lead to differences in size selection properties, we performed comparative fishing trials where we compared a brand new flexigrid section and a well-used flexigrid section used continuously by a commercial trawler for approximately four years. The results showed that the new flexigrid released significantly more cod below ∼60 cm than the used flexigrid. However, when the grids were fished with a subsequent diamond mesh codend, there was no difference in the overall selectivity of the two gears, meaning that the size selectivity in the codend compensates for the potential reduction in selectivity performance of the grids. This study shows the importance of considering the age and earlier use of size selection devices like sorting grids before they are compared with other devices, as their size selection properties can change significantly over time and with use.

In the single‐species literature, it is widely acknowledged that conserving young fish for future harvesting is beneficial. This finding holds great significance in fisheries economics and has garnered substantial attention over the years. In this study, a full‐blown age‐structured predator–prey model is developed and used to demonstrate that multispecies considerations may shift the optimal selection of predators towards smaller individuals, providing valuable counteractive insights. These new results offer a fresh perspective highly relevant to regulation and choice of selectivity patterns. Recommendations for Resource Managers: Single‐species analyses often suggest that it is optimal to design gear restrictions to spare young fish for future harvest. However, this study reveals that the dynamics of predator–prey interactions may challenge this notion. Specifically, our findings demonstrate that targeting only large predators can result in disadvantages, including increased prey mortality, decreased utilization of growth potential, and lower catch per unit effort for the prey. As a result, managers should exercise caution when contemplating changes in gear restrictions for predator species that are integral to a predator–prey system involving high‐value prey. [ABSTRACT FROM AUTHOR]

This study assessed catch composition, size selectivity, and fishing efficiency of demersal trawls targeting penaeid shrimp species in the Red Sea. It first compared the currently used diamond mesh codends in two fishing areas, Al Qunfudhah and Jazan, and then compared alternative square mesh codends to diamond mesh codends in Jazan. A total of 33 valid hauls were conducted in 2023, yielding 10,869 kg of total catch. The results showed that the square mesh codend significantly improved size selectivity, particularly for Penaeus semisulcatus and Metapenaeus monoceros, with L50 (50% retention length) values closer to their size at first maturity. The fishing efficiency indicators revealed a reduced retention probability for undersized individuals with square mesh codends. Additionally, bycatch discard rates decreased, indicating potential benefits for ecosystem conservation. This study suggests incorporating square mesh codends into fishery management regulations to enhance size selectivity and reduce bycatch during Red Sea shrimp trawling. Establishing a legal minimum landing size requirement is recommended to complement these efforts and promote sustainable fishing practices.

Fisheries-independent surveys are a critical tool for monitoring marine populations and communities. However, considerations must be made to account for variable-size-based catchability. The size-specific catchability function is therefore key for estimating size distributions, but often requires extensive data sets or specialized field experiments to determine. We develop a Bayesian model capable of simultaneously estimating both a size-based catchability curve and species-specific size spectrum parameters from trawl data by assuming that individual species size spectra follow a theoretically derived parametric size spectrum model. The resulting model provides a means of estimating catchability and size spectra within an adaptive framework capable of accommodating confounding factors such as vessel power and fish density, potentially allowing for improved biomass and productivity estimates. We demonstrate the application of this model using 15 years of Greenland Halibut (Reinhardtius hippoglossoides) survey data from Nunavut to determine size-specific catchabilities and assess whether the size spectrum of Greenland Halibut has changed across the time series. While size spectrum parameters for this stock were not found to vary, we did find evidence of time-varying catchability parameters across the study period. [ABSTRACT FROM AUTHOR]

The offshore Northern shrimp (Pandalus borealis) bottom trawl fishery in eastern Canada currently uses 22 and 28 mm bar spacing Nordmøre grids to limit bycatch from using small mesh codends. However, a recent rebound of juvenile redfish (Sebastes spp.), that can pass through the grids, has greatly increased bycatch. To address this concern, this study investigated the effectiveness of 17 and 15 mm bar spacing Nordmøre grids in a twin-trawl (paired) configuration against the traditional 22 mm bar spacing grid. Size selectivity analyses showed that the 17 and 15 mm grids resulted in no significant reduction in shrimp catch across all length classes. The 17 mm grid significantly reduced redfish bycatch for all length classes and the 15 mm grid significantly reduced redfish bycatch for individuals larger than 95 mm total length. Less redfish entered the codend with the experimental grids, however, the overlap in width between redfish and Northern shrimp limits the overall sorting efficiency of the grids, leaving some redfish still vulnerable to capture.

The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study. A 34 m high opening trawl was used, which is a common design used by fishermen operating along the northwest coast of India, and the cover codend method was employed to determine codend selectivity. Along with the changes in the length at 50% retention rate for Trichiurus lepturus with the usage of the square and diamond mesh codends, indicators to understand the exploitation pattern of this species in the fishery were assessed based on the total number of individuals and on total weight of the catch. The mean selection length increased and discard fraction is reduced when 40 mm square mesh codends are used in place of diamond meshes, however, it is observed that individuals at commercial length are also lost. The results demonstrate that mandatory use of legal mesh sizes alone will be insufficient to aid in the sustainable harvest of this species, given its estimated length at first sexual maturity of 61.2 cm. This is the first study to compare the size selection of this species in 40 mm diamond and square mesh codends along Northwest coast of India. Results of the study will help as a baseline for gear-based regulations in the region.

The offshore Northern shrimp (Pandalus borealis) bottom trawl fishery in eastern Canada currently uses 22 and 28 mm bar spacing Nordmøre grids to limit bycatch from using small mesh codends. However, a recent rebound of juvenile redfish (Sebastes spp.), that can pass through the grids, has greatly increased bycatch. To address this concern, this study investigated the effectiveness of 17 and 15 mm bar spacing Nordmøre grids in a twin-trawl (paired) configuration against the traditional 22 mm bar spacing grid. Size selectivity analyses showed that the 17 and 15 mm grids resulted in no significant reduction in shrimp catch across all length classes. The 17 mm grid significantly reduced redfish bycatch for all length classes and the 15 mm grid significantly reduced redfish bycatch for individuals larger than 95 mm total length. Less redfish entered the codend with the experimental grids, however, the overlap in width between redfish and Northern shrimp limits the overall sorting efficiency of the grids, leaving some redfish still vulnerable to capture. [ABSTRACT FROM AUTHOR]

The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study. A 34 m high opening trawl was used, which is a common design used by fishermen operating along the northwest coast of India, and the cover codend method was employed to determine codend selectivity. Along with the changes in the length at 50% retention rate for Trichiurus lepturus with the usage of the square and diamond mesh codends, indicators to understand the exploitation pattern of this species in the fishery were assessed based on the total number of individuals and on total weight of the catch. The mean selection length increased and discard fraction is reduced when 40 mm square mesh codends are used in place of diamond meshes, however, it is observed that individuals at commercial length are also lost. The results demonstrate that mandatory use of legal mesh sizes alone will be insufficient to aid in the sustainable harvest of this species, given its estimated length at first sexual maturity of 61.2 cm. This is the first study to compare the size selection of this species in 40 mm diamond and square mesh codends along Northwest coast of India. Results of the study will help as a baseline for gear-based regulations in the region. [ABSTRACT FROM AUTHOR]

Experiments were conducted to assess the selectivity of diamond mesh codends in capturing largehead hairtail (Trichiurus lepturus) in the demersal trawl fishery of the Beibu Gulf, located in the South China Sea. The selectivity experiments involved four codends with different mesh sizes (30, 35, 40, and 45 mm), and the covered codend method was employed. Catch data were analyzed using the maximum likelihood method, with both Logistic and Richards curves fitted to the data, and the abundance–biomass comparison (ABC) curve method was used to analyze the impact of codend on fishery resources. Model deviance was compared with the degree of freedom to choose the best fit curve. The Logistic curves gave a better fit for the codends with 30 and 40 mm mesh sizes, while the Richards curves had a better fit for the codends with 35 and 45 mm mesh sizes, respectively. The 50% retention lengths (L50) and selection ranges (SR) were determined for 30 mm (L50: 11.40 cm; SR: 3.81 cm), 35 mm (L50: 11.65 cm; SR: 3.98 cm), 40 mm (L50: 12.92 cm; SR: 5.30 cm), and 45 mm (L50: 13.28 cm; SR: 4.14 cm) mesh codends. The results indicated that the present minimum mesh size, 40 mm diamond mesh, did not match with minimum landing size of largerhead hairtail, 190 mm anal. length. Based on the observed linear relationship between L50 and mesh opening, it was determined that the diamond mesh codend should be adjusted to a larger mesh opening of approximately 72.47 mm in order to achieve an L50 value of 190 mm. The ABC curve characteristics indicate that the fish community structure in the Beibu Gulf in the South China Sea is in a severely disturbed state. This study suggests that the square mesh codend and T90 codend (diamond mesh netting turned by 90 degrees) should be tested and compared with the diamond mesh codend, to obtain the optimal configuration and mesh size of the codend for demersal trawl fishery in the Beibu Gulf in the South China Sea. [ABSTRACT FROM AUTHOR]

In order to optimize the size selectivity of demersal trawl targeting Banded Scad, Alepes djedaba, in the South China Sea (SCS), we tested and compared the selective properties of four experimental codends. These codends included two diamond-mesh codends (T0 codends) with different mesh openings (30 and 35 mm), and two T90 codends (the netting was turned by 90 degrees) with the relatively same mesh opening. The results demonstrated that the T0_30 codend (diamond-mesh codend with 30-mm mesh opening) presented the best size selectivity and is a potential choice to harvest Banded Scad in the studied area among the codends tested. Although applying the T0_35 or T90_30 codend might obtain a little improvement in size selectivity, the loss of marketable-size individuals could be a compromise. Considering the results in our study and those of previous studies, we recommend that the T0_30 codend should be mandated in the fisheries management regulation of trawl fisheries targeting Banded Scad in the SCS. [ABSTRACT FROM AUTHOR]

A synthetic approach has been developed to prepare silica gel monoliths that embed well separated silver or gold spherical nanoparticles (NP), with diameters of 8, 18 and 115 nm. Fe3+, O2/cysteine and HNO3 were all successfully used to oxidize and remove silver NP from silica, while aqua regia was necessary for gold NP. In all cases, NP-imprinted silica gel materials were obtained, with spherical voids of the same dimensions of the dissolved particles. By grinding the monoliths, we prepared NP-imprinted silica powders that were able to efficiently reuptake silver ultrafine NP (Ag-ufNP, d = 8 nm) from aqueous solutions. Moreover, the NP-imprinted silica powders showed a remarkable size selectivity, based on the best match between NP radius and the curvature radius of the cavities, driven by the optimization of attractive Van der Waals forces between SiO2 and NP. Ag-ufNP are increasingly used in products, goods, medical devices, disinfectants, and their consequent diffusion in the environment is of rising concern. Although limited here to a proof-of-concept level, the materials and methods described in this paper may be an efficient solution for capturing Ag-ufNP from environmental waters and to safely dispose them. [ABSTRACT FROM AUTHOR]

To address the issue of minimum mesh size regulations of the stow net fishery for croaker species, we tested and compared the size selectivity and exploitation pattern for diamond- and square-mesh codends with mesh sizes 35, 45 and 55 mm for little yellow croaker (Larimichthys polyactis), silver croaker (Pennahia argentata), and flower croaker (Nibea albiflora) in the Yellow Sea, China. Our results showed that the legal codend (35 mm diamond-mesh) was inadequate to protect the juvenile croaker species because more than 75% of undersized individuals were retained, and the discard ratios were as high as approximately 60%. Irrespective of mesh shape, increasing the codend mesh sizes could significantly improve the size selectivity and exploitation pattern of croaker species. Between codends with the same mesh size, the square-mesh codends had higher size selectivity than diamond-mesh codends. Based on results, the 55 mm square-mesh codend was recommended for rational exploitation of croaker stocks. This study can provide feasibility and insight for the enforcement and reform of management strategies for sustainable fishing in Chinese stow net fisheries. [ABSTRACT FROM AUTHOR]

Two decades of use of the compulsory selectivity gear configuration in the Northeast Atlantic bottom trawl fishery, which consists of a rigid sorting grid followed by a diamond mesh codend, have revealed problems with performance and efficiency. Size selectivity gear alternatives to this configuration are being pursued, and recent studies of codends with shortened lastridges have reported promising results. In this study, we compared the size selectivity and catch efficiency for cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) caught using a sorting grid with 55 mm bar spacing followed by a 130 mm knotted diamond mesh codend (i.e. the compulsory gear) that same configuration but considering only the catch in the 130 mm diamond mesh codend (regular codend), and an alternative knotless codend with shortened lastridge ropes and a thinner twine. We also addressed the question of whether size-selective gear is even needed to avoid exceeding the bycatch limits of the fishery. Our results demonstrated that the alternative codend improved size selectivity by reducing the loss of fish above minimum legal size (MLS), with a minor increase in the retention of fish below MLS , compared to the compulsory combined grid and codend configuration. The regular codend also reduced the loss of fish above MLS , but the retention of haddock below MLS approached the legal limit of 15% by number. Our results also showed that the abundance of cod below MLS in the fishing area during the trials was low. They also suggested that spatial and seasonal closures in combination with a flexible choice of selection device and modern monitoring tools could be an alternative to rigid enforcement of the use of selective fishing gear. [ABSTRACT FROM AUTHOR]

In order to obtain gear-based management instruments of shrimp trawl fishery for southern velvet shrimp in the South China Sea (SCS), the size selectivity and catch efficiency of four codends were tested and compared. These codends included two mesh sizes, 30 and 35 mm, and two mesh shapes, T0 (diamond-mesh) and T90 (diamond-mesh turned by 90°), respectively. Our results demonstrated that increasing the mesh-sizes of the T0 codends or/and applying the T90 codends would statistically and significantly improve the size selectivity and catch efficiency. Comparing the size selectivity and catch efficiency of four codends tested, and accounting for the results of the previous study, we conclude that the T0 codend with a mesh size of 35 mm (T0_35) or T90 codend with a mesh size of 30 mm (T90_30) would be potential choices for mitigating the bycatch issue of undersized individuals for southern velvet shrimp (Metapenaeopsis palmensis) in the SCS. We recommend that they are applied as the compulsory gears in the fishery management regulation. Our study will be beneficial for the decision-making regarding gear-based management for sustainable fishing in the specific shrimp trawl fishery of the SCS. [ABSTRACT FROM AUTHOR]

In order to optimize the size selectivity of demersal trawl targeting Banded Scad, Alepes djedaba, in the South China Sea (SCS), we tested and compared the selective properties of four experimental codends. These codends included two diamond-mesh codends (T0 codends) with different mesh openings (30 and 35 mm), and two T90 codends (the netting was turned by 90 degrees) with the relatively same mesh opening. The results demonstrated that the T0_30 codend (diamond-mesh codend with 30-mm mesh opening) presented the best size selectivity and is a potential choice to harvest Banded Scad in the studied area among the codends tested. Although applying the T0_35 or T90_30 codend might obtain a little improvement in size selectivity, the loss of marketable-size individuals could be a compromise. Considering the results in our study and those of previous studies, we recommend that the T0_30 codend should be mandated in the fisheries management regulation of trawl fisheries targeting Banded Scad in the SCS.

Experiments were conducted to assess the selectivity of diamond mesh codends in capturing largehead hairtail (Trichiurus lepturus) in the demersal trawl fishery of the Beibu Gulf, located in the South China Sea. The selectivity experiments involved four codends with different mesh sizes (30, 35, 40, and 45 mm), and the covered codend method was employed. Catch data were analyzed using the maximum likelihood method, with both Logistic and Richards curves fitted to the data, and the abundance–biomass comparison (ABC) curve method was used to analyze the impact of codend on fishery resources. Model deviance was compared with the degree of freedom to choose the best fit curve. The Logistic curves gave a better fit for the codends with 30 and 40 mm mesh sizes, while the Richards curves had a better fit for the codends with 35 and 45 mm mesh sizes, respectively. The 50% retention lengths (L50) and selection ranges (SR) were determined for 30 mm (L50: 11.40 cm; SR: 3.81 cm), 35 mm (L50: 11.65 cm; SR: 3.98 cm), 40 mm (L50: 12.92 cm; SR: 5.30 cm), and 45 mm (L50: 13.28 cm; SR: 4.14 cm) mesh codends. The results indicated that the present minimum mesh size, 40 mm diamond mesh, did not match with minimum landing size of largerhead hairtail, 190 mm anal. length. Based on the observed linear relationship between L50 and mesh opening, it was determined that the diamond mesh codend should be adjusted to a larger mesh opening of approximately 72.47 mm in order to achieve an L50 value of 190 mm. The ABC curve characteristics indicate that the fish community structure in the Beibu Gulf in the South China Sea is in a severely disturbed state. This study suggests that the square mesh codend and T90 codend (diamond mesh netting turned by 90 degrees) should be tested and compared with the diamond mesh codend, to obtain the optimal configuration and mesh size of the codend for demersal trawl fishery in the Beibu Gulf in the South China Sea.

The small-scale whelk (Rapana venosa) and Asian paddle crab (Charybdis japonica) pot fishery are of great socio-economic importance to coastal communities of the Yellow Sea, China. However, the conventional pot with a regulated mesh size of 25 mm is unfavorable to the sustainability of these two species due to its poor selectivity. In this study, we intend to improve the size selectivity of pots by configuring escape vents. Three different escape vent sizes (diameter of 45 mm, 50 mm, and 55 mm) were tested using a catch comparison method. Our results demonstrated that escape vents significantly improved the size selectivity of pots for whelk and crab. The escape vent with a diameter of 55 mm released the maximum number of undersized whelk and meanwhile maintained the catch efficiency of individuals above the Market Reference Size (MRS; 45 mm) compared with the conventional (control) pots. The escape vent with a diameter of 50 mm significantly reduced the retention of undersized crab to 21% and increased the catch rates of individuals above the Minimum Landing Size (MLS; 50 mm) to 112%. Although hard to achieve "perfect selectivity" for morphologically different species in mixed fisheries, we recommend a compromise escape vent size of 52 mm in comprehensive consideration of resources' sustainability and fishermen's profits. The promising results of this study can provide feasibility and insight to develop management strategies for small-scale pot fishery. [ABSTRACT FROM AUTHOR]

The size selectivity and usability of three codends were quantified and compared for the first time in the inshore Northern shrimp (Pandalus borealis) trawl fishery of Iceland using the covered codend method: a conventional diamond-mesh codend (T0), conventional square-mesh codend (T45), and a 90° turned mesh codend (T90) constructed of four panels and with shortened lastridge ropes. Fishers, wanting to increase the average-individual size of captured shrimp, had requested the T90 codend to be compared with conventional codends for consideration in the fishery. Results showed that, on average, the T45 and T90 codends had better size selectivity than the T0 codend in terms of releasing individuals smaller than 13 mm carapace length (Minimum References Size; MRS). The T90 codend retained significantly less Northern shrimps between 9 and 19 mm than the T0 codend and between 15 and 19 mm than the T45 codend. No significant difference of size selectivity between T45 and T0 codends was observed. All three codends presented high retention ratios of Northern shrimps above MRS (>63%) for the population encountered. However, the T0 codend was not effective at sorting out small Northern shrimps; at least 86% of Northern shrimps smaller than 13 mm were retained in the T0 codend if encountered. Catches from T45 and T90 codends had a lower proportion of shrimp below MRS. Since discarding of undersized Northern shrimps is prohibited in Iceland and fishers wanted to catch on average larger shrimp, using the novel T90 codend would enable fishers to use their quotas more efficiently.

This study aims at improving fishery management by testing and comparing the size selectivity and exploitation pattern of diamond-mesh codends, with mesh sizes ranging from 25 to 54 mm, for cocktail shrimp (Trachypenaeus curvirostris) in the South China Sea (SCS). Beginning from 25 mm, the minimum mesh size regulated by the shrimp trawl fishery industry, we investigated how the mesh sizes of the codends would affect the size selectivity and exploitation pattern in reference to the minimum conservation reference size (MCRS, 7.0 cm total length) of cocktail shrimp in the SCS. According to our results, the selective properties of the codend mesh sized at 25 mm in line with the regulation failed to protect the undersized individuals of cocktail shrimp because of its 50% retention length of 5.85 cm (confidence interval, CI: 5.16–6.18 cm), far less than the MCRS of cocktail shrimp. As the retention probability of a shrimp with a MCRS length was as high as 97.45 % (CI: 86.86–100.00%), more than 40% of the undersized shrimp was retained. It was proved that increasing the codend mesh size did not significantly improve the size selectivity and exploitation pattern which might be improved by other gear modifications.

A synthetic approach has been developed to prepare silica gel monoliths that embed well separated silver or gold spherical nanoparticles (NP), with diameters of 8, 18 and 115 nm. Fe3+, O2/cysteine and HNO3 were all successfully used to oxidize and remove silver NP from silica, while aqua regia was necessary for gold NP. In all cases, NP-imprinted silica gel materials were obtained, with spherical voids of the same dimensions of the dissolved particles. By grinding the monoliths, we prepared NP-imprinted silica powders that were able to efficiently reuptake silver ultrafine NP (Ag-ufNP, d = 8 nm) from aqueous solutions. Moreover, the NP-imprinted silica powders showed a remarkable size selectivity, based on the best match between NP radius and the curvature radius of the cavities, driven by the optimization of attractive Van der Waals forces between SiO2 and NP. Ag-ufNP are increasingly used in products, goods, medical devices, disinfectants, and their consequent diffusion in the environment is of rising concern. Although limited here to a proof-of-concept level, the materials and methods described in this paper may be an efficient solution for capturing Ag-ufNP from environmental waters and to safely dispose them.

The catch composition of bottom trawls is commonly refined and improved through changes in codend design. Measures like reducing the number of meshes in codend circumference or turning diamond netting by 90 degrees are well known to improve the size selectivity of fish species with rounded cross-sectional shape. Based on this we speculated whether the same measures, if applied in other parts of a bottom trawl, would provide similar benefits as in the codend. Therefore, experiments were carried out by deploying these changes to the trawl extension piece in a Mediterranean bottom trawl fishery. However, for European hake and monkfish, results showed no indication of improved selectivity or catch pattern compared to the standard extension piece in the trawl. Contrary, for red mullet, one of the most important species in this fishery, reducing the number of meshes in the circumference of the extension piece jeopardized the size selection obtained in the trawl with a standard extension piece. The lesson learnt from this study was that the design changes that work for the codend do not necessarily work for other parts of the trawl. In fact, they can even have negative effects.

The narrow-clawed crayfish (Pontastacus leptodactylus) is one of the most ecologically and economically important freshwater species in Turkey. However, the harvest of this species has declined from 7937 t in 1984 to 696 t in 2019. One of primary reasons for this decrease in stock is the use of fishing gears with poor size selectivity. In this study, new codend designs were investigated to improve the size selectivity of fyke nets for P. leptodactylus. Seven codends of three different designs were tested: (1) a commercially used standard codend with 34 mm mesh size (Com34); (2) sorting grids with 20 (SG20), 25 (SG25) and 30 mm (SG30) bar spacing attached to the last circle of the net; and (3) a stiff rigged net, the last part of the fyke nets (codend) with 34 (SRN34), 42 (SRN42) and 50 mm (SRN50) mesh size. The average length at 50% retention probability (L50) and selection range (SR) (L75–L25) values of Com34 were 9.4 cm and 3.1 cm, respectively. For the SG20, SG25 and SG30 grids, the L50 values were 11.3 cm, 11.6 cm and 12.0 cm, while the SR values were 1.4 cm, 1.3 cm and 0.6 cm, respectively. For the SRN34, SRN42 and SRN50 codends, the L50 values were 10.9 cm, 11.6 cm and 11.6 cm, while the SR values were 2.1 cm, 2.1cm and 1.1 cm, respectively. Overall, the commercial codend resulted in lower L50 values when the minimum conservation reference length of 10 cm was considered. However, all tested new codend designs showed improved selectivity compared with the standard, with optimum results obtained with SG20. SG20 grid decreased discarding by 15.7% compared to the classic commercial fyke net; thus, this is a very important result for the sustainability of natural P. leptodactylus stocks. [ABSTRACT FROM AUTHOR]

Size selectivity of the trammel net for Pomadasys stridens and Gerres oyena in Suez Bay, Gulf of Suez, Red sea, was estimated by comparing three mesh sizes 34, 37 and 40 mm for the inner layer of the trammel net. The SELECT model was used to estimate the selectivity curve. Length frequency data were fitted by five models: normal scale, gamma distribution model, normal location, lognormal distributions model, and bi-normal model. The results revealed that the best fit model of selectivity curve of the trammel nets data for Gerres oyena was obtained by the and bi-normal model, whilst the Log-normal model gave the best fit for Pomadasys stridens. The length-weight relationship equations were estimated to be W = 0.027 × L2.735 with r2 = 0.97 for Pomadasys stridens and W = 0.050 × L2.470, r2 = 0.93 for Gerres oyena. The study concluded that the mesh size of the trammel nets used in Suez Bay fishery should not be less than 40 mm especially for Pomadasys stridens and Gerres oyena to protect their stocks from overfishing.

In this study, size selectivity and exploitation pattern of six diamond-mesh codends with different mesh sizes, ranging from 25 to 54 mm, for Southern velvet shrimp (Metapenaeopsis palmensis) were tested and compared in a shrimp trawl fishery of the South China Sea (SCS). We used a codend with a mesh size of 25 mm (D25) as a starting point, which is the minimum mesh size (MMS) currently regulated in the studied area. Four different fishing population scenarios were applied to quantify and compare how mesh sizes of codends used would impact the size selectivity and exploitation pattern for the target shrimp species. The results demonstrated that the D25 codend was not proper for protecting juvenile shrimp at the studied area. By applying this legal codend, L50 (50% retention length) of the target shrimp species was below its minimum conservation reference size (MCRS, 7.0 cm total length), the retention probability of shrimp with a length of MCRS was above 95% CI [91–99] and more than 43% of undersized shrimp was retained. To mitigate the bycatch issue of undersized shrimp, increasing the mesh size in the diamond mesh codend is a simple and effective option. However, the loss of catch efficiency for marketable shrimp is a major concern while increasing the mesh size. A good compromise between releasing undersized shrimp and maintaining the legal individuals is manifested by using the codend with 35 mm mesh size (D35). Our study will be beneficial for the management of shrimp trawl fisheries in the SCS. [ABSTRACT FROM AUTHOR]

Sustainable development of the important economic species, Asian paddle crab (Charybdis japonica), has attracted attention in the coastal waters of the Yellow Sea, China. The commonly used round pots are almost nonselective, resulting in severe bycatch of juveniles. In this study, we explored a method to improve the size selectivity for C. japonica by mounting escape vents on the side panels of each pot. The selectivity of pots with escape vent sizes of 70 mm × 20 mm, 70 mm × 25 mm, 70 mm × 30 mm, and 70 mm × 35 mm was tested using a catch comparison method. The estimated minimum landing size (MLS) of carapace height (27 mm), according to the regulated MLS of carapace length (50 mm), was used as a reference point to explain the results. Significant increases in the size of crabs caught by pots were found with the enlargement of escape vent size (Kruskal-Wallis test, P < 0.01). The pots with 70 mm × 20 mm, 70 mm × 25 mm and 70 mm × 30 mm escape vents released nearly 50%, 75% and 95% of undersized individuals, respectively, and these three types of pots retained approximately 90% of legal-sized individuals compared with the control pots without escape vents. The pots with 70 mm × 35 mm escape vents released nearly all undersized individuals, but they also released most legal-sized individuals. Pots with an escape vent size of 70 mm × 30 mm were recommended for the sustainable development of C. japonica in the Yellow Sea of China. The results of this study reiterate the importance of carapace height for determining the size selectivity, which can serve as a reference to formulate management regulations in the coastal waters of the Yellow Sea, China. [ABSTRACT FROM AUTHOR]

In this study, we have developed a mild and effective method to prepare a metal-organic framework (MOF)-based microcapsule by the self-assembly of pre-synthesized zeolite imidazolate framework-8 (ZIF-8) nanoparticles at the oil-water interface combined with deposition of a dense ZIF-8 coating outside the capsule. By introducing the enzyme Candida antarctica lipase B (CalB) directly into the stabilizer ZIF-8 or the water phase of Pickering emulsion during the preparation process, we achieved that the enzyme was immobilized within the shell (CalB@ZIF-8@cap) or in the cavity (ZIF-8@cap-CalB) of the microcapsules, respectively. The resulting CalB-loaded microcapsules were robust and had a core-shell structure proved by scanning electron microscopy. Meanwhile, Fourier transform infrared spectroscopy was conducted to confirm the encapsulation of enzymes in the microcapsules and their position in the microcapsules was confirmed by fluorescence microscopy. Furthermore, through the comparison of transesterification reactions between a pair of small substrates and a pair of larger ones, the two types of CalB-loaded microcapsules showed great catalytic activity, stability and size selectivity, and the catalytic activity of CalB@ZIF-8@cap was slightly higher than that of ZIF-8@cap-CalB. Importantly, due to the large size of the microcapsules, the catalyst could be separated from the reaction system by sedimentation, thereby reducing the energy consumption for separation. These kinds of multifunctional MOF-enzyme composites may open up new opportunities for the biocatalysis and microreactor.

Abstract Most fishing is inherently size‐selective, in that fishers preferentially select a subset of the population for harvest based on economic incentives associated with different‐sized fish. Size‐selective fishing influences the targeted population and fishery performance in multiple ways, including changing the reproductive capacity of the target population and altering fishery yield. Understanding how social–ecological variability, including size selectivity, affects target species populations is critical for fisheries management to optimize the benefits of fisheries and the ecological impacts on target populations. In this study, we used yield per recruit, spawning stock biomass per recruit, and length‐based spawning potential ratio models to explore how a range of size selectivity scenarios affect fishery and population productivity for Mexican chocolate clams, Megapitaria squalida, in Loreto, Baja California Sur, Mexico. We found that alternate slot limits result in trade‐offs between fishery yield and reproductive productivity of the target population. A more restrictive slot limit reduced the proportion of the population available to harvest, resulting in higher reproductive capacity of the population, compared to a less restrictive slot limit, conditional on the rate of fishing mortality. In the long run, a more restrictive slot limit will likely lead to a higher number of recruits, larger stock size, and higher long‐term fishery yield relative to a less restrictive scenario. Our findings highlight that how people fish matters, perhaps as much as the quantity of fish harvested; size‐selective fishing that aligns with the life history of target populations and stakeholders’ goals is critical to sustaining fisheries and the valuable food and livelihoods they provide.

European hake (Merluccius merluccius) is an important commercial species for several European bottom trawl fisheries. Therefore, understanding the influence of codend mesh size and shape on the size selection of European hake is critical for defining technical measures for fisheries targeting this species. Based on morphology data collected on European hake, the influence of mesh size and shape on bottom trawl codend size selectivity was investigated by simulation using the FISHSELECT methodology successfully applied previously for other species. The predicted size selection for European hake was found to agree well with previous experimental results for a wide range of mesh sizes if it was assumed that the codend meshes had a relatively small opening angle, between 20° and 40°, during trawling. This study enables detailed prediction of size selectivity for European hake and offers a potential explanation for previous experimental size selectivity results.

Size selectivity of the trammel net for Pomadasys stridens and Gerres oyena in Suez Bay, Gulf of Suez, Red sea, was estimated by comparing three mesh sizes 34, 37 and 40 mm for the inner layer of the trammel net. The SELECT model was used to estimate the selectivity curve. Length frequency data were fitted by five models: normal scale, gamma distribution model, normal location, lognormal distributions model, and bi-normal model. The results revealed that the best fit model of selectivity curve of the trammel nets data for Gerres oyena was obtained by the and bi-normal model, whilst the Log-normal model gave the best fit for Pomadasys stridens. The length-weight relationship equations were estimated to be W = 0.027 × L2.735 with r2 = 0.97 for Pomadasys stridens and W = 0.050 × L2.470, r2 = 0.93 for Gerres oyena. The study concluded that the mesh size of the trammel nets used in Suez Bay fishery should not be less than 40 mm especially for Pomadasys stridens and Gerres oyena to protect their stocks from overfishing. [ABSTRACT FROM AUTHOR]

The size selectivity of crayfish traps (fyke-nets) with 34, 38 or 42 mm mesh size and with diamond-shaped (D) or hexagonal-shaped (Hex) mesh was compared for narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823 in the Eğirdir Lake, Turkey. The SELECT model was used to fit the logistic selection curves and to calculate selectivity parameters. The selectivity curves and parameters were calculated by comparing the size frequencies of the crayfish retained in the traps, including the 34 mm diamond (D) trap control. The 50%-selectivity length (l50) and selection range (SR) of fyke-net traps with diamond mesh were 8.70 cm and 3.16 cm for 38 mm (38 D) and 8.69 cm and 1.99 cm for 42 mm (42 D) bar length. The l50 and SR values of hexagonal mesh traps were 8.06 cm and 3.42 cm for 34 mm (34 Hex), 10.23 cm and 2.80 cm for 38 mm (38 Hex) and 11.00 cm and 2.62 cm for 42 mm (42 Hex) bar length, respectively. [ABSTRACT FROM AUTHOR]

Most fishing is inherently size-selective, in that fishers preferentially select a subset of the population for harvest based on economic incentives associated with different-sized fish. Size-selective fishing influences the targeted population and fishery performance in multiple ways, including changing the reproductive capacity of the target population and altering fishery yield. Understanding how social-- ecological variability, including size selectivity, affects target species populations is critical for fisheries management to optimize the benefits of fisheries and the ecological impacts on target populations. In this study, we used yield per recruit, spawning stock biomass per recruit, and length-based spawning potential ratio models to explore how a range of size selectivity scenarios affect fishery and population productivity for Mexican chocolate clams, Megapitaria squalida, in Loreto, Baja California Sur, Mexico. We found that alternate slot limits result in trade-offs between fishery yield and reproductive productivity of the target population. A more restrictive slot limit reduced the proportion of the population available to harvest, resulting in higher reproductive capacity of the population, compared to a less restrictive slot limit, conditional on the rate of fishing mortality. In the long run, a more restrictive slot limit will likely lead to a higher number of recruits, larger stock size, and higher long-term fishery yield relative to a less restrictive scenario. Our findings highlight that how people fish matters, perhaps as much as the quantity of fish harvested; size-selective fishing that aligns with the life history of target populations and stakeholders' goals is critical to sustaining fisheries and the valuable food and livelihoods they provide. [ABSTRACT FROM AUTHOR]

• A Pt(II) photocatalyst has been supported onto mesoporous silica-based materials. • The Pt-containing materials have been characterized by different methods. • The photocatalytic activity has been tested in debromination reactions. • The heterogeneous catalysts have a high robustness, versatility and recyclability. • Catalytic selectivity by size exclusion due to silica features was observed. • The materials have also high catalytic activity in α-alkylation of aldehydes. The grafting of a Pt(II) photocatalyst into three different mesoporous silica-based materials with different particle sizes and pore sizes was easily achieved through an amide bond formation. The analysis and results of the different characterization techniques showed that the catalyst is immobilized inside the pores of the materials and the photophysical properties of the catalyst are preserved after the covalent anchoring. The photocatalytic material catalyzed efficiently the debromination reaction of different substrates and is reused without detriment in its catalytic activity. In addition, the incorporation of the catalyst into mesoporous silica materials with different pore size allows the selective debromination of substrates by size discrimination. [ABSTRACT FROM AUTHOR]

In order to explore how cucurbituril hosts accommodate an N-phenyl-pyridinium derivative guest, the complexation of the solvatochromic dye, 4-(4-(dimethylamino)styryl)-1-phenylpyridinium iodide (PhSt) with α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (Me4CB6) and cucurbit[7]uril (CB7) was investigated by absorption spectroscopic, fluorescence and NMR experiments. In aqueous solutions, PhSt forms 1:1 complexes with both cucurbiturils, the complex with CB7 has a higher stability constant (Ka = 6.0 × 106 M−1) than the complex with Me4CB6 (Ka = 1.1 × 106 M−1). As revealed by NMR experiments and confirmed by theoretical calculations, CB7 encapsulates the whole phenylpyridinium entity of the PhSt cation guest, whereas the cavity of Me4CB6 includes only the phenyl ring, the pyridinium ring is bound to the carbonyl rim of the host. The binding of PhSt to cucurbiturils is accompanied by a strong enhancement of the fluorescence quantum yield due to the blocking of the deactivation through a twisted intramolecular charge transfer (TICT) state. The TICT mechanism in PhSt was characterized by fluorescence experiments in polyethylene glycol (PEG) solvents of different viscosities. The PhSt-CB7 system was tested as a fluorescence indicator displacement (FID) assay, and it recognized trimethyl-lysine selectively over other lysine derivatives.

This study investigates the effects of trap selectivity of various mesh size on escape success of the blue crab (Callinectes sapidus). The study was carried out Çamlık Lagoon of Yumurtalık Gulf in the Mediterranean Sea and total of 1051 blue crabs were caught by rectangular baited trap. Using traps constructed with 30, 35, 40, 45 and 50 mm square mesh the proportion of crabs escaping through each mesh size was measured for each half centimetre carapace width (CW) class. A logistic model was fitted to the size frequency data of the retained and escaped blue crabs for each mesh size in the experiment. L50 and selection range (SR) for the 30, 35, 40, 45 and 50 mm (bar length) square meshes tested in this study was 8.47 cm and 0.85 cm; 9.31 cm and 0.39 cm; 10.40 cm and 0.31 cm; 11.72 cm and 1.17 cm; 13.17 cm and 0.89 cm respectively. The 50 mm square mesh of the trap showed relatively better selectivity considering the size at 50% sexual maturity of blue crab Callinectes sapidus, and the high rate of immature escapers

We describe an unbiased length-based, age-structured mark-recapture (LAMR) model for estimating length-based abundance and recruitment of fish populations. Many mark-recapture studies employ capture gear that is size-selective, leading to a larger and faster growing marked sub-population with a different capture probability than the unmarked sub-population, resulting in a basic violation of assumptions for many mark-recapture models. Persistent differences in marked and unmarked individuals are estimated in our model using growth-type group accounting. Simulation-evaluation results indicate that the model produces largely unbiased estimates of recruitment and abundance across a range of sampling scenarios and population life-history types, and is robust to growth parameter misspecification. However, in older, slow growing populations, the model is prone to ‘smearing’ of recruitment estimates across early year-classes. The LAMR model is applied to data from multiple wild populations of rainbow trout to estimate recruitment and abundance. Overall, results indicate that the LAMR model addresses shortcomings associated with using size-selective gear in mark-recapture studies to produce reliable estimates of recruitment and size-based abundance. [ABSTRACT FROM AUTHOR]

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]

Characterizing sediment selectivity during transport will improve understanding of soil erosion processes, but few studies have focused on steep slopes and soil with loose, coarse material. This study examined colluvial deposits, which contain loose materials with large amounts of coarse particles. These soils were subjected to simulated rainfall in a 5 m2 (5 m by 1 m) box at heavy rainfall intensities (1, 1.33, 1.67, 2, and 2.33 mm min–1) and on five steep slopes (20°, 25°, 30°, 35°, and 40°). During the experiments, the particle size of the eroded material gradually coarsened, then stabilized and often showed short-term fluctuations as the rainfall progressed. During interrill erosion processes, the sediment became enriched with finer particles because of the low runoff energy of interrill flow; the dominant transport mechanism was the suspension-saltation transport of sediment with a grain size finer than 0.537 mm. However, the sediment was coarser after rill development than before, and increased stream power meant that bed-load transport by rolling of the larger sediment grains (coarser than 0.957 mm) became an increasingly important mechanism; bed-load transport also increased with rainfall intensity, so the particle-size distribution for high-intensity rainfall resembled that of the original soil. Finally, during rill erosion processes, rill bank collapse occured and the original soil contained coarse, heavy particles that could more easily be rolled on steep slopes. These factors could increase the relative importance of bed-load transport. The results of this study have important implications for assessment and modeling of erosion processes in disturbed soils with large amounts of coarse particles. [ABSTRACT FROM AUTHOR]

In the deep sea trawl fishery targeting shrimp (Pandalus borealis) and other cold-water shrimp species, fishers often use a Nordmöre sorting grid ahead of a small mesh codend to avoid bycatch. However, small fish can pass through the grid and are subsequently retained in the codend. This makes shrimp size selection complex and the size-dependent curve for both the shrimp and the bycatch species often exhibits a bell-shaped signature. In this study we developed a new model and method to estimate size selection in this fishery, conducted fishing trials in the Northeast Barents Sea, and applied the new method to quantify the individual and combined size selection of the Nordmöre grid and codend for deep water shrimp and two bycatch species. The size selectivity for both bycatch species showed the expected bell-shaped signature with low retention probability of very small and larger fish. The Nordmöre grid had high passage probability for all sizes, although it decreased slightly for the largest shrimps. The smallest shrimps were released by the codend. [ABSTRACT FROM AUTHOR]