Shrimp Trawl Fishery Research Articles

Distribution and Population Structure of Discarded Parastichopus regalis (Holothuroidea) from the Shrimp Trawling Fishery in the Sea of Marmara

Royal sea cucumber Parastichopus regalis is frequently caught as a bycatch in shrimp fishery with beam trawl in the Sea of Marmara (SoM). This study presents the first assessment of the distribution patterns and population structure of the royal sea cucumber in the SoM. The dataset was obtained based on the area scanning method with underwater visual counting techniques (<50 m) and beam trawling (≥50 m). A total of 1,377 royal sea cucumbers were sampled off the Kapıdağ Peninsula and Marmara Islands between May 2022 and April 2023 at monthly intervals. The gutted lengths of the samples ranged from 6.65 to 30.70 cm. No gonads were found from October to March according to macroscopic examinations; thus, the gonadal cycle starts in April, peaks in July where there gonadosomatic index gain its maxima for both sexes, and completes in September. The mean annual biomass was calculated as 30.5 kg·km−2, and the highest value obtained in a fishery operation reached 100.8 kg·km−2. The distribution patterns of royal sea cucumber seasonally varied however further studies on the relationships between food availability, social interaction, and biotic factors are needed to understand relevant spatiotemporal patterns.

Unraveling migratory corridors of loggerhead and green turtles from the Yucatán Peninsula and its overlap with bycatch zones of the Northwest Atlantic.

Bycatch represents a conservation problem when endangered species are affected. Sea turtles are highly vulnerable to this threat as their critical habitats overlap with fishing zones in all regions of the world. We used sequences of the mitochondrial DNA control region obtained from loggerhead (Caretta caretta) and green (Chelonia mydas) turtles to determine the migratory routes between nesting habitats in the Yucatán Peninsula and their critical marine habitats in the Northwest Atlantic. Mixed Stock Analysis revealed that loggerheads from Quintana Roo migrated to foraging areas in the northwestern Atlantic. Migratory routes used by green turtles are determined by their natal nesting colony: (1) green turtles from the Gulf of Mexico migrate to foraging aggregations in Texas and the northern Gulf of Mexico, (2) Mexican Caribbean turtles travel to foraging grounds in Florida, and (3) a smaller proportion of individuals born in the Yucatán Peninsula display a local connectivity pattern. Our results suggest that the migratory corridors used by Mexican loggerheads overlap with longline fisheries in the mid-Atlantic where sea turtle bycatch is comprised predominantly of immature individuals. Green turtles from the Yucatán Peninsula migrate to critical habitats that overlap with shrimp trawl fisheries within the Gulf of Mexico. Bycatch data and the identification of migratory corridors used by loggerheads and green turtles suggests that shrimp trawl fisheries on the east coast of the U.S. and the Gulf of Mexico pose a serious threat to the conservation and recovery of Mexican sea turtle populations.

Toward Sustainable Fisheries: Assessing Catch per Unit Effort, Retained Bycatch, and Discard Ratios in the Red Sea Shrimp Trawl Fishery of the Kingdom of Saudi Arabia

Shrimp trawl fishery is of significant importance in Saudi Arabia’s marine capture fishery sector. Al Qunfudhah and Jizan are the only ports along the southern Saudi Arabian coast of the Red Sea dedicated to shrimp fishing. This study evaluates the catch per unit effort (CPUE) of targeted shrimp species along with the associated retained bycatch and discard ratios across these two trawling locations. Using daily catch data from commercial shrimp trawlers specific to each port’s vessel type, this research provides the first comprehensive analysis of CPUE dynamics and fishing practices in these fishing grounds. The CPUE of target shrimps exhibited a wide range (0.01 kg h−1 to 13.08 kg h−1) with an overall mean of 1.37 ± 0.143 kg h−1. Penaeus semisulcatus emerged as the predominant species (mean CPUE: 3.77 ± 0.28 kg h−1), followed by Metapenaeus monoceros (mean CPUE: 0.1 ± 0.02 kg h−1). Significant differences in CPUE were observed among species, including P. semisulcatus, Penaeus hathor, and Penaeus pulchricaudatus, although CPUE differences between the two fishing grounds were minor, likely due to their proximity and similar environmental conditions. The bycatch analysis identified a total of 72 species across 28 families, with significant variation in the relative ratios. Sepiidae species constituted 31.8% of the total bycatch, followed by Portunidae species (24.8%). Discard patterns also varied, with Gerres oyena being the most commonly discarded species (mean discard ratio: 11.37% ± 1.89%), followed by Equulites klunzingeri (mean discard ratio: 8.76% ± 2.00%). While CPUE differences between Al Qunfudhah and Jizan were modest, this study highlights the need for expanded spatial and temporal coverage to enhance future analyses. These findings underscore the importance of integrated data for a comprehensive understanding of fishing effort and bycatch dynamics, supporting sustainable fisheries management in the Red Sea. By addressing bycatch and discard practices, this research contributes to efforts to mitigate ecological impacts and promote sustainable resource use in Saudi Arabia’s fisheries sector.

Assessing Codend Mesh Selectivity: Comparing Diamond and Square Mesh Codend in the Red Sea Shrimp Trawl Fishery of Saudi Arabia

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.

Learning from the history of red shrimp fisheries in the Mediterranean to improve sustainability of deep-water bottom trawling

Abstract As deep-water red shrimp (DWRS) trawl fisheries gain importance in the Mediterranean, their impact on fragile deep-sea ecosystems requires careful management. We reviewed the historical development of DWRS fisheries in the Mediterranean to propose a harvest strategy that would enhance fishery sustainability, while preserving habitat and community integrity. We considered two representative typologies of DWRS fisheries: a domestic fleet operating within the Italian territorial waters of the Ligurian Sea, and a distant fleet operating mostly in international waters of the central-eastern Mediterranean and sharing shrimp stocks with non-European countries. Our proposed management approach is based on three main harvesting measures: (i) preventing the uncontrolled growth in number of trawlers, (ii) adopting a catch control regime, and (iii) identifying a network of deep-water areas designated alternately for fishing and conservation purposes. As with fisheries in other regions, new fishing grounds should be explored using “encounter protocols” to avoid areas hosting species indicators of Vulnerable Marine Ecosystems. Additionally, empirical indicators such as catch rate thresholds derived from fishers’ experience, could be used to move from one fishing ground to another to avoid local depletion of DWRS abundance and a decrease in fishery profitability.

Size at sexual maturity, seasonal variation by maturity stages, and fecundity of the spotted round ray (Urobatis maculatus) and the thorny stingray (Urotrygon rogersi) from the northern tropical eastern Pacific.

Round rays (family: Urotrygonidae) are commonly caught as by-catch by shrimp trawl fisheries in the tropical eastern Pacific (TEP). However, little information on their life history and catch species composition exists for most round ray species, preventing the evaluation of the impact of fishing on their populations. The mean size at sexual maturity (DW50), seasonal variation by maturity stages, and fecundity for two round ray species caught during shrimp trawl research cruises in the south-eastern Gulf of California (northern TEP) were estimated using a multi-model approach and inference for the first time, to determine the part of the population of each species that is being affected by shrimp trawling. Disc width (DW) ranged from 7.0 to 30.9 cm for the spotted round ray (Urobatis maculatus), and 7.2-33.5 cm for the thorny stingray (Urotrygon rogersi), with females reaching larger sizes than males in both species. The DW50 was estimated at 12.8 and 11.8 cm DW for the males and females of U. maculatus, respectively, whereas for U.rogersi, it was 15.0 and 18.4 cm DW for males and females, respectively. Embryos were found in females ≥14.5 cm DW in both species. The maximum fecundity was five embryos for U. maculatus (mean = 3.1 ± 0.2 S.E., mode = 4), and six embryos for U. rogersi (mean = 3.0 ± 0.3 S.E., mode = 2). Fecundity and embryo size did not vary with maternal size. Male and female immature and mature individuals for both species, including pregnant females, were found in the catches in all seasons of the year. Our results can help determine the vulnerability of the studied species populations to fishing pressure from shrimp trawling in the northern TEP and guide the development of future monitoring strategies and conservation actions for these species, if necessary.

Improving the size selectivity and exploitation pattern of cocktail shrimp (Trachypenaeus curvirostris) in shrimp trawl fishery of the South China Sea.

In order to improve the size selectivity and exploitation pattern for cocktail shrimp (Trachypenaeus curvirostris) in shrimp trawl fishery of the South China Sea (SCS), selective properties of four codends were tested and compared. These experimental codends involved two mesh sizes, 30 and 35 mm, and two mesh shapes, diamond-mesh (T0) and diamond-mesh turned by 90 degree (T90), respectively. Our results demonstrated that increasing the mesh sizes in T0 codends or/and applying T90 codends would improve the selective properties for cocktail shrimp in the SCS. By comparing selectivity parameters, delta selectivity and exploitation pattern indicators, the T90 codend with 35-mm mesh size (T90_35) presented the best selective properties for cocktail shrimp in the studied areas. It will be a potential choice to substitute the currently legal codend in fisheries management to mitigate the bycatch of undersized cocktail shrimp in shrimp trawl fisheries of the SCS.

Trouble in the trawls: Is bycatch in trawl fisheries preventing the recovery of sawfish? A case study using the US population of smalltooth sawfish, Pristis pectinata

All five species of sawfish (Family Pristidae), are among the most threatened families of elasmobranchs, and face significant threats from fishing, in particular trawl fisheries, and habitat loss. Unfortunately, there is little data on the level of sawfish taken in trawl fisheries outside Australia and the United States and case studies from these areas can provide a “risk analysis” for populations elsewhere. In the United States, bycatch risk for smalltooth sawfish is significantly higher for the southeast shrimp trawl fishery than all other fisheries assessed. Using new estimates of life history and population size, an updated population viability model was developed and trajectories using different scenarios of initial population sizes, fishery catches and post-release mortality were projected for 100 years. The simulated population trajectories for the assumed initial population sizes and fishing mortality ranged between population extinction, quasi-extinction, to a slight reduction in population size and in some cases the population continuing to recover. The most pessimistic scenarios were when the initial population was lowest and post-release mortality in the shrimp trawl fishery was highest. Quasi-extinction for some scenarios was between 6.9 and 22.8 years. While some scenarios suggest that smalltooth sawfish still can recover despite the potential for shrimp trawl fishing mortality, key input variables for these optimistic scenarios is the initial population size and the true level of fishing mortality. This uncertainty highlights the importance of improving our understanding of sawfish life history, captures in fisheries and their associated post-release mortality.

To ignore or mitigate – Economic implications of an illegal artisanal trawl fishery in northern Peru

An artisanal shrimp trawl fishery operating illegally in northern Peru has high levels of bycatch and three main commercial species. Here we provide the first characterisation of the socio-economic contribution of this fishery. Estimates have been generated for the capital values, operational and maintenance costs, as well as net profits at point of landing and across the value chain. This fleet sector in northern Peru is estimated at 105 vessels, generating an annual gross income of U$D 4.8 million with 315 direct jobs. Vessel owners could potentially have a net income of over ∼$12,000 per year, and crew are likely to be earning 45 % above the living wage for similar land-based rural employment, including other fishing activities operating in the same areas. With an appropriate multiplier for the seafood supply chain, the gross economic value of the fishery from landings up to the retail level is estimated at U$D 35 million with 915 jobs. Recommendations for improving the sustainability of the fishery and possible mitigations are discussed to address the gulf between policy and regulatory intent and reality, where enforcement is lacking or absent.

Amino Acid and Fatty Acid Profile of Whole-dried and Minced-dried Fish Discards (<em>Leiognathus</em> sp.) from Shrimp Trawl Fishery in Jaffna, Sri Lanka

The by-catch and discards from shrimp trawl fishery have increased during the last few years. Leiognathus sp. is one of the most discarded fish species in the shrimp trawling fishery in Jaffna, Sri Lanka. Lack of information was found regarding the nutrient composition of Leiognathus sp. and therefore the present study was carried out to assess the presence of amino acids and fatty acids in whole-dried and mince-dried fish which are beneficial for human health. The total sum of amino acids was estimated to be 229.8 and 174.4 mg/g raw protein percentages in whole-dried fish and minced-dried fish, respectively. The protein content of fish is mainly explained by the sum of the total amino acids identified. The total lipid was 5.5% and 7.3% in whole-dried fish and minced-dried fish, respectively. Proline and glycine were found to be the abundant amino acids in both whole-dried and minced-dried fish. A total of 13 fatty acids in whole-dried fish and 14 fatty acids in minced-dried fish were identified in the present study. The n-3 polyunsaturated fatty acids were found to be one of the highly abundant compounds in this fish and docosahexaenoic acid is also considerably higher in amount. In the sense of higher availability of protein, storage of whole-dried fish will be a better option than minced-dried fish. Drying is one of the best and easiest methods to preserve this fish and dried fish products could be supplied to the local population at a low cost to overcome the nutrient deficiency among them. Alternatively, utilizing these bycatch fish is an effective method to reduce marine pollution as well.

Elasmobranch bycatch of the shrimp trawl fishery along the Pacific coast of Guatemala

Elasmobranch bycatch of the shrimp trawl fishery along the Pacific coast of Guatemala

Integrating research and fishing extension approaches to engage small-scale fishers in the participatory evaluation and voluntary use of bycatch reduction devices

The main strategy for reducing discards in shrimp trawl fisheries has been the development and use of bycatch reduction devices (BRDs). Research has focused on the performance of BRD in biological and technological terms, undermining the importance of the human dimensions, such as fishers’ perceptions. On the other hand, a better comprehension of which methodological approach enables fishers volunteer adoption of BRDs is required. This paper analyzed the performance of BRD through a combination of interaction activities and conventional scientific experiments. Four interaction activities were conducted with shrimp trawlers from 12 fishing sites at the coast of Paraná, South Brazil. Adapted from previous research and after fishers’ suggestion in the interaction activities, a Nordmore grid was tested against a control net to evaluate differences in shrimp (Xiphopenaeus kroyeri) and bycatch weight, and total length of X. Kroyeri. Interaction activities stressed the importance of dialogue and participation and showed that fishers perceived a high diversity of parameters, expanding the understanding of BRD performance. Also, the methodological approach provided room for collective learning and fishers’ engagement, with reports of voluntary initiatives to reduce bycatch. The results showed that the dialog is improved with diversification and integration of communication methods, as well as timing is crucial for fishers to process information and to build knowledge. An analysis of the methodological approach used in this paper provide insights on how to increase voluntary BRD adoption as well as to engage fishers more consistently in being stewards for the responsible fishing.

Vulnerability assessment of species caught by the shrimp trawl fishery in northeastern Brazil

In Brazil, there are no official fisheries statistics to quantitatively assess the status of target and bycatch species. Since food security is at stake, appropriate tools are needed to maintain fisheries sustainability. One widely used “data-poor” method, despite the critics of its subjectivity, is Productivity and Susceptibility Analysis (PSA). In this study, we use PSA to assess the impact of a northeastern Brazil shrimp fishery which is socioeconomically relevant for the local population but is known to have adverse ecological impacts. The vulnerability status (high, medium, or low) of 30 species were determined by the PSA and compared with two other semi-quantitative approaches that assess stock or extinction risk. The results obtained from the PSA and other methods were partially convergent, highlighting six bycatch and one target species for which management measures or data collection should be prioritised. This study showed that PSA, when compared with other semi-quantitative methods, can constitute a valuable preliminary assessment for assessing data-poor fisheries. The integrated use of various methods is advisable in diagnosing fishery resources. However, it is essential to understand the peculiarities of each technique to appreciate its applicability and feasibility.

Age and Growth of the Threatened Smalleye Round Ray, Urotrygon microphthalmum, Delsman, 1941, from Northeastern Brazil

The age and growth of Urotrygon microphthalmum were studied using specimens captured between March 2010 and March 2012 as by-catch in the shrimp trawl fishery off the coast of the state of Pernambuco, Brazil. A total of 347 vertebrae were read, 161 from males (81.6–249.55 mm) and 186 from females (86.15–298.1 mm). The estimated average percentage index (IAPE) ranged from 0.71% to 4.33% (mean = 2.5%) in vertebrae from specimens with 1 and 6 band pairs, respectively. In the present study, the different approaches to validation produced variable results (partially valid growth zones). We then decided to discuss the growth of the species considering the formation of an annual ring. There were statistically significant differences in growth between the sexes. The best model to describe male growth was the von Bertalanffy growth model for two phases (VBGM TP) with growth parameters L∞ (maximum theoretical length) = 230.35 mm, k (growth constant) = 1.00, t0 (theoretical age of size zero) = −0.76 years and for females it was the von Bertalanffy with birth size (VBGM L0) model with parameters L∞ = 282.55 mm, k = 0.37. The age of maturity for males and females was 1.52 and 2.02 years, respectively, and the maximum age observed was 5.5 and 8.5 years, respectively. Despite being a fast-growing species, Urotrygon microphthalmum is threatened, probably due to the high mortality levels from shrimp trawling in a very narrow range of the shelf where all the life stages are captured.

Investigating an Unknown Biodiversity: Evidence of Distinct Lineages of the Endemic Chola Guitarfish Pseudobatos percellens Walbaum, 1792 in the Western Atlantic Ocean

Anthropogenic actions have affected marine species for a long time, through overexploitation of natural stocks and habitat degradation, influencing the life strategies of several taxa, especially rays and sharks, which have suffered significant population declines in recent years. Therefore, conservation actions and stock management have become paramount. In this regard, chola guitarfish, Pseudobatos percellens, distributed throughout the Brazilian coast, is often commercially fished by local artisanal fleets or as by-catch in shrimp trawl fisheries. Therefore, this study aimed to understand the genetic diversity of P. percellens throughout the Brazilian coast, using single nucleotide polymorphisms (SNPs). Genetic analyses employing 3329 SNPs revealed a hidden biodiversity within P. percellens, with at least one lineage occurring in the Northern and Northeastern regions and another distributed in the Southeastern/Southern Brazilian coast, with high genetic differentiation between them. However, the Discriminant Analysis of Principal Components (DAPC) indicated the presence of in fact three lineages distributed in these regions that must still be better investigated. Therefore, to ensure adequate conservation of chola guitarfish biodiversity, populations must be managed separately along the Brazilian coast. Furthermore, the need for a taxonomic review for this group is noted.

A characterisation of common bottlenose dolphin (Tursiops truncatus) interactions with the commercial shrimp trawl fishery of South Carolina, USA

In the United States, interactions between the shrimp trawl fishery and bottlenose dolphins are known to exist; however, the level of mortality is largely unknown, and has not been studied in South Carolina, USA. The current study attempted to determine if interactions between bottlenose dolphins and the South Carolina commercial shrimp trawl fishery pose a significant threat to dolphin populations and if fishery related mortality is underreported. Onboard observations were made during a 25 day (August–December 2010) field study. No dolphin takes occurred during the observational period. These observations focused on direct physical interactions with the gear and depredation behaviours. Additionally, a subsample of the shrimp fishery in South Carolina was asked to participate in a mailed survey. The survey included questions related to gear, dolphin observations, and the status of the shrimp fishery. This paper also examines historical dolphin stranding data from the NOAA/CCEHBR MMIS database for signs of shrimp fishery interactions. A three-tiered flow diagram was developed to characterise each stranding case according to the likelihood that mortality resulted from trawler interaction. Field results point to significant dolphin presence around commercial trawlers (x2 = 23.406, p < 0.001). Survey results showed 12 unreported incidents of shrimp trawl fishery mortality of dolphins. Finally, stranding records revealed several more cases with signs of possible trawler interaction. The current US National Marine Fisheries Service (NOAA) designation of the fishery as a Category II fishery is correct. Increased observer coverage and improved communication with the fishery on the importance of reporting takes is warranted.

Minimising discards while taking revenue into account: Spatio-temporal assessment of catches in an artisanal shrimp trawl fishery in Peru

Around 4.2 million tonnes of fish and other species, some of which are of conservation concern, are discarded every year in bottom trawl fisheries. This study focusses on a small-scale shrimp trawl fishery located in northern Peru that operates with high level of discards which causes conflict with other local fishers. Despite trawling being an illegal activity within the 5NM off the coast, this fishery has been operating in these inshore areas for over 40 years because it sustains the well-being of hundreds of fishers. This study aimed to identify the factors that affect the spatio-temporal variation in catches in order to propose recommendations that can be adopted by fishers to minimise their impact on the ecosystem while still providing economic opportunities. The spatial distributions of shrimp, main commercial species and discards were modelled over time using hierarchical generalised additive models. Strong spatio-temporal variation was observed for all catch components and moon phase affected commercial species and discards differently. The results show that, to reduce the environmental impacts of this fishery in the short-term, the fishing area could be divided into north and south and that fishing activities should be limited to the southern area in the autumn. Other recommendations rely on temporal closures during the week of the first quarter of the moon phase. Finally, considering the institutional weaknesses in monitoring, control and surveillance, we suggest that the only realistic approach to reduce the fishery's environmental impacts in the short-term is to foster the willingness of fishers to adopt responsible fishing practices. Yet, long-term solutions will require comprehensive co-management efforts.

Turtles, TEDs, tuna, dolphins, and diffusion of innovations: key drivers of adoption of bycatch reduction devices

AbstractFisheries extension programmes frequently fail to secure mandatory or voluntary adoption of bycatch reduction devices and techniques. Approaches for improving the outcomes of extension programmes are often based on ad hoc assessments and do not consider human behaviour or change theories. This paper offers an in-depth analysis of extension activities that led to various adoption outcomes in two prominent bycatch case studies in the United States: turtle excluder devices in shrimp trawl fisheries and dolphin bycatch in the tuna purse seine fishery. Using a grounded theory approach to text analysis of interviews and documents, I examine five periods of voluntary or mandatory adoption efforts. I explain the outcomes through the lens of diffusion of innovation theory. The most effective extension programme involved informative and persuasive efforts, enforced regulations, and commercially practical bycatch reduction devices. Voluntary adoption occurred under exceptional circumstances of public and political pressure and a device that offered substantial benefits to the adopter. The two periods of successful adoption applied the most core principles of diffusion theory. This paper concludes with recommendations for how change agents can apply diffusion theory to future fisheries extension programmes to improve the adoption of bycatch reduction devices.

T90 Codends Improve the Size Selectivity and Catch Efficiency of Shrimp Trawl Fisheries for Southern Velvet Shrimp (Metapenaeopsis palmensis) in the South China Sea

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.

Effect of codend mesh sizes on the size selectivity and exploitation pattern of cocktail shrimp (Trachypenaeus curvirostris) in shrimp trawl fishery of the South China Sea

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.