Shrimp Trawl Research Articles

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.

Using historical catch flexibility and fishing ground mobility as measures of the adaptive capacity of fishing communities to future ocean change

Abstract Changing ocean characteristics, moving species, and competing ocean uses challenge fishing communities reliant on marine resources. Many communities have diversified what they catch, or where they fish to cope with variation in availability of fish. However, we often lack understanding of the frequency of these adaptation strategies in response to historical variability. Here, we quantitatively evaluate catch flexibility, catch switching, and fishing ground mobility of Communities at Sea (CaS) in the Northeast USA. CaS capacity to change catch composition or shift fishing grounds differed by gear type and with regional drivers. Dredge was highly mobile but species selective, and groundfish trawl either altered their catch or shifted fishing grounds. Lobster and shrimp trawl CaS were largely unable to take advantage of either strategy, while fleets using other pots and traps did both. Differences within gear types often reflected distinct regional strategies in dealing with the loss of target species from historical fishing grounds. Overall, adaptive capacity for a port reflects its portfolio of fleets as well as shared constraints and opportunities of their home port. Understanding the degree to which fishing communities have adapted to historical variability can help prioritize efforts to enhance adaptive capacity for future ocean change.

Legal perspectives on unintended and unsanctioned humpback whale entanglement in the South Atlantic trawl fishery

Whale interactions with fishing gear pose a major anthropogenic threat, yet entanglements in South Atlantic trawl fisheries remain underreported, with no published records. This lack of data extends to reports of whales found stranded with amputated tails, despite documented cases of survival even without a fluke. This study presents a novel case: a video recorded in May 2020 captured a shrimp trawler in Santa Catarina, Brazil, entangled with a humpback whale (Megaptera novaeangliae). Vocalizing and bleeding, the whale had recently lost its fluke and remained caught in the vessel's gear. Following the video's public outcry, authorities identified and apprehended the responsible vessel, conducting a thorough investigation. Although initial sanctions were issued, and evidence confirmed illegal fishing practices and neglect towards the whale, subsequent legal proceedings deemed the act unintentional and acquitted the involved parties. This report seeks to not only document this unprecedented case but also to analyze why such infractions against cetacean often receive minimal legal consequences. Examining this case within the context of broader policy and enforcement frameworks, we discuss potential explanations for the perceived low legal severity of such incidents and argue for the need for enhanced legal accountability to effectively protect marine mammals in the South Atlantic.

Fishers' perception and activity shifts in a dolphin bycatch mitigation context

Fishing exclusion zones aim to reduce cetacean bycatch, but often neglect social and ecological side effects, exacerbating social injustices and reshaping fishing practices. We present a case study of an endangered population of Lahille's bottlenose dolphins (Tursiops truncatus gephyreus) in a Brazilian coastal lagoon, known for its unique cooperation with net-casting fishers. However, the local small-scale fisheries (SSF) also employ other fishing gears that contribute to dolphin bycatch, prompting the enforcement of a fishing ban in the area. We investigated fishers' socioeconomic conditions, evidence of social disparities, perceptions on dolphin bycatch, and projected changes on fisheries activities to understand the repercussions of the ban. We categorized 128 surveyed fishers into five groups based on socioeconomic factors and their reliance on dolphin-cooperative and gillnet fisheries. Our findings revealed significant disparities in social capital among fishers and their different attitudes towards dolphin bycatch, highlighting unforeseen consequences. To investigate how fishers would likely shift fishing practices, we considered two management scenarios: 1) should dolphin-fishing cease due to unsuccessful bycatch mitigation, fishing efforts would shift towards shrimp trawling, seine nets, and gillnet effort; 2) if gillnet-fishing is successfully banned as a bycatch mitigation measure, a shift to shrimp trawling and cast net effort. Both scenarios would intensify pressure on shrimp stocks, which are already heavily exploited in this socioecological system. Our research underscores the importance of contemplating alternatives to achieve sustainable outcomes when designing bycatch mitigation measure. Furthermore, our results point to the importance of a participatory governance approach, grounded in the socioeconomic context, to safeguard the livelihoods of small-scale fishers and foster broader conservation efforts beyond species-specific concerns.

Quantitative Assessment and Temporal Fluctuation of a Multiday Shrimp Trawl Bycatch off Digha Coast, West Bengal, India

Quantitative Assessment and Temporal Fluctuation of a Multiday Shrimp Trawl Bycatch off Digha Coast, West Bengal, India

Length-Weight Relationships of Eight Fish Species Collected as Bycatch from Deep-Sea Shrimp Trawls Operated in the Arabian Sea

Length-Weight Relationships of Eight Fish Species Collected as Bycatch from Deep-Sea Shrimp Trawls Operated in the Arabian Sea

Population structure and reproductive aspects of Callinectes ornatus (Decapoda: Brachyura) present in the bycatch of shrimp fisheries in northeastern Brazil

AbstractThis study aimed at analysing the population structure and reproductive aspects of Callinectes ornatus present in the bycatch of shrimp fisheries off Sergipe (northeastern Brazil), and at comparing the findings with other regions. Samples were obtained monthly from shrimp trawlers based in the Pirambu municipality (11°S–37°W) from May/2015 to May/2016. Each specimen of C. ornatus was separated, identified and weighed (TW, total weight, g). Carapace length (CL, mm) and width (CW, not including lateral spines, mm) were measured, and the sex and stage of morphological maturity were identified. A total of 403 females and 427 males of C. ornatus were found and analysed. The overall sex ratio did not differ from 1:1. Males were larger and heavier than females. Biometric relations (CL‐CW and TW‐CW) were different between sexes. The size at first morphological maturity (CWm) was 38.20 mm for females and 44.00 mm for males. The reproductive and recruitment periods were continuous, with some peaks throughout the year. Despite C. ornatus being a frequent species in shrimp bycatch, its exploitation status is still unknown.

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.

Network Analysis Reveals Species-Specific Organization of Microbial Communities in Four Co-Occurring Elasmobranch Species along the Georgia Coast

Comparing co-occurring species may provide insights into how aspects of ecology may play a role in influencing their microbial communities. During the 2019 commercial shrimp trawl season off coastal Georgia, swabs of skin, gills, cloaca, and gut were taken for three species of batoids (Butterfly Ray, Bluntnose Stingray, and Atlantic Stingray) and one shark species (Atlantic Sharpnose) for high-throughput sequencing of the V4 region of the bacterial 16S rRNA gene. White muscle was analyzed for stable isotopes (δ13C and δ15N) to evaluate potential niche overlap in these four sympatric mesopredators. Significant differences were found in both δ13C and δ15N signatures across species, suggesting a degree of resource partitioning. When examined within tissue type, the host species had a weak effect on β-diversity for cloaca and skin, with no differences found for gill and gut samples. However, network analysis metrics demonstrated a stronger species-specific effect and distinct microbial community relationships were apparent between the shark and batoids, with the former having tighter networks for both internally- and externally-influenced tissues (gut/cloaca and skin/gills, respectively). Despite overlapping habitat use, species’ microbiomes differed in their organizational structuring that paralleled differences in stable isotope results, suggesting a mediating role of species-specific ecology on bacterial microbiomes.

Squids caught by shrimp trawlers off the coast of Sergipe, northeastern Brazil

Squids caught by shrimp trawlers off the coast of Sergipe, northeastern Brazil

Spatial patterns of beta diversity in marine benthic assemblages from coastal areas of southern Brazil and their implications for conservation

Beta diversity helps to understand changes in species composition over space and time, with two key components: nestedness (hierarchical pattern in richer sites) and turnover (species replacement due to niche or dispersal differences). It measures the loss or gain of species (nestedness) and species replacement (turnover) when comparing two or more spatial/temporal/environmental units. As both components require different species conservation strategies, assessing which of them the communities are organized is an important tool for this purpose. Our study aimed to evaluate which two components of beta diversity (nestedness or turnover) are responsible for structuring invertebrate and fish assemblages on the southern coast of Brazil. This region is historically recognized as a shrimp trawling area, a type of fishing with negative impacts on marine biota, such as the removal of species and habitat destruction. Our results suggest that the overall beta diversity values demonstrated a high environmental heterogeneity among the sampled areas. The most significant fraction of the general beta diversity for both assemblages is explained by the spatial turnover component. As depth increased, there was a significant rise in overall beta diversity and species turnover for fish and invertebrate assemblages. In contrast, there were no significant correlations among the nestedness component, the geographical distance and depth. In water mass conditions, fish assemblage decreased with rising chlorophyll and decreasing temperature. Elevated marine phosphate and thick sediments adversely impacted invertebrate composition. Additionally, invertebrate richness showed a positive correlation with fine sand grains. The research conducted along the southern coast of Brazil suggests the utmost importance of these regions in terms of species conservation. Here, the dominant influence of the turnover component shapes the organization of subtropical marine benthic assemblages. Furthermore, these areas receive frequent visits from migratory species, further accentuating their ecological significance.

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.

Artisanal fisher knowledge on the impacts of destructive and illegal practices on the Southern Coast of Bahia, Brazil

Destructive fishing practices (DFP) and illegal, unreported, and unregulated (IUU) activities result in significant marine ecosystem effects, such as habitat destruction, biomass reduction, bycatch, and waste of resources. They also generate socioeconomic impacts on artisanal fisher coastal populations. Both DFP and IUU are linked to fisheries management system failures and the impossibility of marine surveillance. In this context, from an Ethnoecological approach, the aim of this study was to analyze the local ecological knowledge of fishers from Ilhéus (Bahia), Northeastern Brazil, regarding DFP and IUU fisheries. A total of 59 interviewees pointed to decreased resource catches in recent years, citing increasing fishing efforts and certain types of gear as the main reasons. They also claim that local fishers and fishers from other Brazilian regions have been using banned equipment, such as compressors and lobster nets. In turn, although permitted by law, shrimp trawling and gillnet fishing were reported as being excessively applied and identified as destructive fisheries. Surprisingly, longline fishing was one of the most reported as responsible for excessive catches and for causing decreases in Common dolphinfish catches. This study reinforces the importance of including the knowledge of local fishers and their participation to contribute to fisheries management and resource conservation. In this context, some recommendations are highlighted to reduce the impacts of harmful practices and improve regional fisheries management, summarized as: (i) policy improvement; (ii) fishing monitoring; (iii) incentives; and (iv) enforcement.

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.

Fine-scale spatial variation of northern shrimp and Atlantic cod across three Norwegian fjord systems and implications for management

The spatial complexity of coastal ecosystems represents a challenge for the management of inshore resources. Here we compared two large fjord systems in northern Norway that have been closed for all bottom trawling for 50 years to a fjord with continuous shrimp fishery with bottom trawls. No significant differences were found between fjords with and without commercial trawling in population density and stock composition of northern shrimp (Pandalus borealis) and their main predator, Atlantic cod (Gadus morhua). Shrimp density was instead linked with bottom depth, while shrimp size and stage composition as well as cod density were explained by seasonal effects and shrimp density. For shrimp, a large degree of the observed variation was captured by spatial correlation that could not be explained by other covariates. The results underline the complex ecology in heavily structured coastal habitats and indicate that coastal shrimp dynamics are shaped by an interplay of multiple ecological and environmental drivers, possibly in concert with local genetic adaptations. The substantial fine-scale spatial variation adds to the challenges of assessing and managing fisheries resources in these fjord ecosystems. Because shrimp are an important forage species, notably as prey for cod, there are potential management conflicts between rebuilding cod stocks and reopening closed shrimp trawling areas.

New record of Trichopeltarion dextrum (Rathbun, 1898) (Brachyura: Trichopeltariidae) from Brazil.

Trichopeltarion dextrum (Rathbun, 1898) is herein reported from the first time from Northern Brazil. The specimens were captured using the shrimp trawls during the REVIZEE-Score Program. Six specimens, being two males and four females, were examined. The material fits well with diagnostic characters of T. dextrum, but the males have the carapace almost as long as wide, while in the type material, is slightly longer the wide. This is the second species of the genus Trichopeltarion reported from Brazilian waters.

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