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a, A trawler in operation. b, A bottom trawl net and its parts.

a, A trawler in operation. b, A bottom trawl net and its parts.

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Trawling remains a controversial method of fishing due to the perceived lack of selectivity of the trawl net and the resultant capture of a huge quantity and diversity of non-target species, including endangered species such as sea turtles, coupled with its effect on the marine ecosystem. The impacts of trawling on the physical, chemical and biolog...

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... large trawlers performing 'stay-in fishing', the target species are stored in refrigerated fish holds, and non-target species are thrown back into the sea. Some of these trawlers bring back the last day's by-catch to the landing centre to be used as food, manure and animal feed (Figure 1). Larger, economically valuable fish and shell fish in the by-catch are marketed fresh. ...

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Cryptic, not readily detectable, components of fishing mortality are not routinely accounted for in fisheries management because of a lack of adequate data, and for some components, a lack of accurate estimation methods. Cryptic fishing mortalities can cause adverse ecological effects, are a source of wastage, reduce the sustainability of fishery r...

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... The intensity of fishing by trawlers in coastal zones depicts the highly vulnerable grounds, continuation of effort in such areas may lead to depletion of residence resources and stability of ecosystems. Demarcation of high intensity fishing grounds to designate as protection zone or refugia will sustain the overexploited resources and conserve the depleting stocks (Kumar and Deepthi, 2006). The countries like India, which are signatories to the Convention on Biological Diversity, need to designate 10% of their coastal and marine areas as 'equitably and effectively' managed within protected areas by 2020 (CBD, 2011). ...
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Trawlers are the key fishing fleet, which is contributing significantly to the global marine fish catches because of the harvest efficiency and mechanization techniques. The trawl fleet comprises multi-day trawlers, MDTN, and mechanized trawlers, MTN in the region. The passive georeferencing technique (using haversine function) was attempted to locate possible fishing grounds using distance and bearing data. The mean distance traveled by MDTN and MTN fleets was 97.41 ± 77.33 km and 17.65 ± 9.64 km, respectively. Distinct variations in depth of operation were observed for MDTN and MTN at 71.56 ± 41.04 m and 26.48 ± 9.96 m, respectively. The depth and distance of fishing by MDTN were much greater than the MTN fleet in the region because of the duration of fishing, target resources, and fishing craft durability. The catch rates were higher in the case of MTN (Mean ± SD, 62.77 ± 39.82 kg/hr) than the MDTN (Mean ± SD, 32.57 ± 16.95 kg/hr). The research deliverable from the current work gives a comprehensive understanding of trawl fishery, range of operation, abundance and fishing intensity zones, and temporal preferences, etc. The results could be taken as decision tools in fishery management plans, inter-sector conflicts, declaration of MPA’s, and Marine Spatial Planning (MSP) in the region.
... In the case of shrimp fishery on the ACS, the dimension related to ecological factors is closely related to the nature of the activity. Trawling carries unsustainability elements due to the low selectivity of this fishing practice, which is a threat to marine biodiversity, affecting the complex ecological processes in the oceans (Kumar and Deepthi, 2006;Worm et al., 2009), the biota and the ecosystem (Jørgensen et al., 2016;Mazor et al., 2020;Behera et al., 2021). ...
... Trawl nets harvest at least 201 species as by-catch, especially teleost fishes (Marceniuk et al., 2019) and over 200 invertebrate species (Nóbrega, 2019). There is also the risk of by-catch of species that are deemed vulnerable or endangered, as is the case of some shark and marine turtle species (Kumar and Deepthi, 2006;Lewison et al., 2014;Marceniuk et al., 2019;Peixoto, 2020). These factors reduced the score of ecological metrics. ...
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Brown shrimp (Penaeus subtilis) trawling in the northern coastal waters of Brazil is an industrial fishing activity with a share in the international market and an important resource in the fishery market. Due to the scarcity of updated information on this practice and owing to its complexity, it is difficult to have a measurement of all dimensions of the development of this fishery, whether they are ecological, economic, or social-institutional. The present paper uses an assessment tool focused on data-poor fishery systems, the Fishery Performance Indicators (FPIs), to assess the multidimensional conditions of this fishery. The indicators were assessed between 2019 and 2020, and the metrics were based on public official data, scientific publications, in loco consultations with production agents, and databases of research projects. Results showed that the critical points of this activity are primarily related to the ecological indicator (1.75), which obtained a lower score compared to other fisheries assessed using the same methodology. This is due to its low selectivity, which results in high by-catch volumes and discards. The limited participation of productive chain actors also restrains the efficacy of management measures, which hampers successful resource management. This issue maximizes other setbacks throughout the productive chain, such as economic and social factors.
... Though the studies on trawler bycatch were attempted by various researchers in India (Boopendranath, 2009;George et al., 1981;Gibinkumar and Boopendranath, 2008;Gordon, 1991;Kumar and Deepthi, 2006;Kurup et al., 2003;Pravin and Manohardoss, 1996;Rao, 1998;Sujatha, 1995Sujatha, , 1996Sujatha, and 2005, studies on the trawler bycatch diversity in Tamil Nadu, particularly in Nagapattinam coastal area is very limited. In this context, the paper attempted to provide information on the diversity of trawl finfish bycatch along the Nagapattinam coast. ...
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Background: The present study was undertaken to analyse the monthly and seasonal finfish bycatch diversity of trawler fishery of Nagapattinam coast situated in the state of Tamil Nadu, South India from January 2017 to August 2019. Methods: Samples of finfish bycatch were collected fortnightly from the commercial shrimp trawlers operating in the coastal waters off Nagapattinam. The collected bycatch of finfish species was identified and month-wise and season-wise trawl finfish bycatch occurrence data collected were subjected to univariate and multivariate analysis using PRIMER Version 6.1.7. software. Result: In this study, the annual average total landing was estimated at 15,414.41 tonnes with an annual average fishing effort of 9327 boat days. Of this total landing, commercial catch constituted 70.75% (10,905.78 tonnes), whereas finfish bycatch formed 21.12% (3,256.14 tonnes) and rest by other groups. The peak fishing effort was observed in every March during the study period. A total of 210 finfish species belonging to 15 orders, 79 families and 153 genera were recorded, in which the order, Perciformes alone shared 53.81% of the total number of species. The monthly univariate analysis revealed that bycatch diversity was the highest in every September and the lowest in every June during the study period, while the season-wise analysis revealed the highest diversity during monsoon seasons. Likewise, the month-wise multivariate analysis performed through cluster analysis divulged the highest similarity between September’17 and September’18, while the season-wise analysis revealed the highest similarity between postmonsoon’17 and postmonsoon’18. Further, the K dominance plot divulged that the highest density of finfish species was in every September and in monsoon seasons during the study period.
... Hake species, croakers, catfishes and elasmobranchs, mainly as adults, are important fishery resources on the Brazilian coastline (MPA, 2011), but the high amount of juveniles captured can negatively affect the recruitment process (Biju Kumar and Deepthi, 2006). Given their life history characteristics (large maximum size, late maturity, slow growth rate and low intrinsic population growth rate), elasmobranchs are less resilient to fishing impacts than other groups (García et al., 2008;Hutchings et al., 2012;Duffy and Griffiths, 2019). ...
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The overall aim of this thesis is to assess the current framework and potential future impact of fishing and environmental changes under the scope of Ecosystem Approach to Fishery (EAF) on the Sirinhaém coastal as a case study for small-scale shrimp trawling in Northeastern Brazil, contributing to the reflection on the implementation of possible management measures. In our case study and without accounting the environmental changes, not adopting effort control measures for the current trawling conditions do not appear to cause major losses for target species. A high effort reductions or size/gear limitations did not appear to be necessary measures, considering that, according to the traditional stock assessment, the target species are being exploited at accepted levels. However, the controlled decrease trawling efforts up to 10% were promising than the closed season which did not present significant improvements in terms of ecosystem functioning. In addition, given the fishing area extension, spatial management maybe not very effective in a possible fisheries management. The non-target species often not considered in management measures, given the socio-economic importance in the region, they need to be better assessed under the EAF taking into the effect in whole trophic dynamic and the bycatch sustainability, essential for the food security. Bycatch Reduction Devices may be one alternative, but its viability needs better evaluate, mainly in terms of socio-economic. Regardless the measures that may be applied, we identified that the cumulative effect of environmental changes and fishing, threaten the sustainability of the ecosystem. Hence, should be considered in any eventual measures.
... India is one of the leading elasmobranchfishing countries [5], with catch data showing a continuous decline in landing over the last two decades [8]. When trawl fishing is well-known for its lack of selectivity [9], a significant portion of rays was captured from trawl nets, gill nets and long lines [10]. Bengal whipray (Brevitrygon imbricate) is a common commercial ray fish in the south coast, especially in Tamil Nadu. ...
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India is one of the leading elasmobranch-fishing countries, with catch data exhibiting a continuous decline in landing over the last two decades. Elasmobranch research is limited in India despite its rich diversity, long history, and huge fishery. The present study was carried out for a period of 18 months from November 2019 to April 2021 in four landing centres of Pondicherry coastal waters. Totally seven rays were recorded, belongs two order and four families. Due lack of data on diversity of rays and taxonomy, the present research work was carried out.
... Climate change is the latest addition affecting fish stocks, necessitating an extensive study on the underwater ecological impacts (Das et al. 2020). Nevertheless, the most significant impact, according to Kumar and Deepthi (2006), is the marine ecological hazards posed by fishing trawlers. Apart from target-specific fishing carried out, many non-target species also get caught in the process affecting the marine food web and in the underwater biodiversity, thereby damaging the benthic habitation. ...
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Purpose Being a primary product for a multitude of processed seafood, the ecological impacts of surimi have been less noted, despite its global supply dominance, especially in India. Life cycle assessment (LCA) evaluates the environmental sustainability of existing supply chain by comparing it with two other supply chain alternatives. The ecologically understudied and fragmented nature of the existing Indian surimi supply chain necessitates the authors to highlight the significance of supply chain localizations and the reductions obtained in ecological impacts. The current study will show the direction for developing strategy(s) to improve the environmental sustainability in Indian stance. Methods A cradle-gate approach of LCA is adopted right from fishing to an export market. Different supply chain alternatives such as the current state and two different states with different localizations and downstream alternatives (i.e., Scenario 1 with partial localizations and Scenario 2 with complete localizations) are analyzed to study the impacts. An economic analysis of these scenarios is also carried out to check the competency of the proposed alternatives for economic sustainability. Results and discussion Eleven environmental impacts considered for analysis under the existing supply chain scenario denote that the process of fishing has an average environmental impact of 74%. However, the inclusion of downstream operations such as distribution in the LCA analysis reveals a significant share of environmental impact averaging 53% from fishing and 34% from distribution for the 11 environmental indicators considered. A detailed assessment of the various alternatives considered reveals vital improvements for both Scenario 1 and Scenario 2 in human carcinogenic toxicity (8% and 16%), fossil resource scarcity (8% and 20%), and global warming potential (GWP) (6% and 16%), respectively, in comparison to the current state. A carbon footprint assessment of the complete surimi supply chain to an export market (considered in this study) via ship freight denotes reduction in footprint values from 4.67 kg CO2 equivalent/kg (existing state) to 4.43 kg CO2 equivalent/kg (Scenario 1) and 4.06 kg CO2 equivalent/kg (Scenario 2), respectively. The economic analysis reveals maximum fiscal gains of 9.83% and 13.31% in Scenario 1 and Scenario 2 respectively. Conclusion Results highlight that the introduction of supply chain localizations in the Indian surimi scenario can reduce environmental impacts and improve economic savings. Among the assessed alternatives, Scenario 2 is found to be the best sustainable alternative with reduced environmental impacts and improved savings.
... Banning the catch and trade of seahorses will serve no purpose for their conservation if non-selective fisheries are not managed (Lawson et al. 2017). India's trawl fisheriesmany of which involve large boats with large engines, greater than permissible under the state Marine Fisheries Regulation Acts (MFRAs)-are exerting unsustainable impacts on marine life and ecosystems (Gupta et al. 2019;Kumar and Deepthi 2006;Mohamed et al. 2010), and must be managed. Although the ecological benefits of absolute trawl bans remain poorly documented, McConnaughey et al. (2020) predicted a complete recovery of seabeds in the absence of trawling over time. ...
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Implementing a ban on fishing specific taxa is difficult enough without the added complexity of the taxa being primarily obtained as incidental catch. Most measures for restricting capture and trade to sustainable levels are directed towards targeted species, while overlooking the needs of incidentally caught species. Our study investigates the exploitation and conservation of seahorses (Hippocampus spp.) in India, which have been primarily obtained in bycatch globally, in the context of a ban on their catch and trade. We found that seahorse extraction continues, with annual catches of around 13 million seahorses, based on estimates from the locations we surveyed along the coast of mainland India. Most of these animals were perceivably obtained by non-selective fishing gear operating along the sea bottom, close to the shore, at lower latitudes and shallower depths, particularly in biogenic habitats. We found that the state with the highest catch and trade of seahorses was also the state where the largest number of fishers provided unprompted comments about the national ban. Our work indicates the serious limitations of extraction and trade bans on species that are taken incidental to other extractive activities, a message that should also apply to terrestrial and freshwater species.
... Diamond mesh shape trawl cod end of sizes 10 to 25 mm is being used rampantly in India, despite the regulation of 35 mm size (Panicker and Sivan 1965;Rajeswari et al. 2013). As a result, smallsized species as well as juveniles of larger species are caught along with the target species, and moreover, it also alters the bottom habitat and thus affects the entire benthic ecosystem (Biju and Deepthi 2006;Thomas et al. 2006). The quantity and quality of juveniles and sub adults in the by-catch depends upon the type of trawl net used and methods of operation. ...
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A study was carried out to assess the economic value of juveniles of commercially important species of finfish and shellfish caught as by-catch by multiday commercial trawlers operated off the coast of Visakhapatnam, north Andhra Pradesh from January 2014 to December 2015. Juveniles of twenty species (four species of cephalopods and sixteen species of finfish) were found to dominate the trawl by-catch. The landed juveniles of these 20 species formed 12,757.16 t and 286.86 million numbers per year and their contribution to the total landings of these species in trawl by-catch were 55.30% by weight and 57.03% by numbers. The highest percentage of quantities of juveniles (biomass) was found in trawl by-catch in the months of August and July in, 2014 and 2015 respectively. Among the juveniles, ribbonfish (Trichiurus lepturus) and goatfish (Upeneus vittatus) dominated, contributing together, on an average 11.60% by weight and 33.68% by numbers respectively. Using the bio-economic model, it was estimated that if the juveniles were allowed to grow up to length at first maturity; total annual economic gain would have been Rs. 273.21 crores (42.03 million USD) with biomass gain of 44,493.02 t per annum. The estimated total annual biomass would have increased 3.46 times with an increase in revenue by 4.20 times. Annual average loss due to fishing of juveniles was estimated to be Rs. 209.62 crores (32.25 million USD). The results of the present study suggested that sustainable harvest of these resources would have yielded maximum economic return to the fishers. With the help of stakeholders using a participatory approach, management measures such as increase of cod end mesh size of trawl to 40 mm from the present mesh size of 10–12 mm, use of square mesh for trawl cod ends, fishing effort restriction and awareness campaign on the detrimental impacts of catching juveniles needs to be implemented at the earliest for avoiding growth overfishing.
... Therefore, considering their high abundance in the by-catch indicates that estuarine mouth benthic environment serves as an important habitat for the juveniles by providing ample food. By-catch related mortality of juvenile of marine species arises across the world oceans, as well as in Indian seas is a serious concern (Bijukumar, Deepthi, 2006;Lobo, 2012). A large quantity of by-catch and discard due to trawling and unregulated use of small meshed net causes loss of marine life including endangered species like sea turtle, sea horses and elasmobranchs (Shankar et al., 2004;Salin et al., 2005;Tiralongo et al., 2018). ...
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Hydrophis schistosus (Daudin, 1803) commonly known as beaked sea snake occurs in shallow marine and estuarine habitats of India. The population of H. schistosus has been frequently noted in the shore-seine net as By-catch. Only a few studies are available about By-catch of sea snakes in Indian coasts. Being a top predator, their mortality and ecological consequences are largely unknown. The present study was conducted along the Caranzalem-Miramar coast of Caranzalem bay, Goa during monsoon (August-September, 2017 and 2018) to focus on the by-catch mortality of H. schistosus and their feeding preferences. Observations indicated that the fishing activities, particularly during every shore-seine operation, results in a significant by-catch of sea snakes where approximately 20–60 individuals get entangled in the fishing net. The study indicated a large number (90%) of juveniles being caught in the shore-seine. Gut content analysis of H. schistosus revealed that 80% of snakes preferred catfish Arius jella as the desired prey species. Sea snakes being top predator play a vital role in checking the local catfish population. Hence, in concern to save H. schistosus population and sea snakes, in general, the fishing methods, as well as awareness towards conservation of sea snakes among fishermen, should be raised.
... India is one of the leading elasmobranch-fishing countries , with catch data exhibiting a continuous decline in landing over the last two decades (CMFRI, 2000(CMFRI, -2018. When trawl fishing is well-known for its lack of selectivity (Kumar and Deepthi, 2006), a significant portion of rays was bycaught from trawl nets, gill nets and long lines (Akhilesh et al., 2011). However, species-specific data is not available for these species in the bycatch. ...
... Gupta et al. (2020) proposed participatory monitoring for holistic bycatch assessment, spatio-temporal closures and gear restriction measures, bycatch reduction devices (BRDs), and live onboard release as measures towards mitigation of elasmobranch bycatch of trawlers in Indian coast. The reduction in fishing pressure would also become an unattainable target, as the closed fishing season applies only to trawling in India (Kumar and Deepthi, 2006), and the catch quota system and monitoring of exploited fish populations have not been attempted systematically. Though the mainstreaming of FAO Code of Conduct for Responsible Fisheries into marine fisheries regulation has been successfully implemented to achieve many targets, there has been a failure in adopting policies related to bycatch reduction in India, not to speak of effective strategies for building awareness among the fisherman on conservation paradigms required for the sustainable management of fishery resources. ...
Article
Bycatch of trawl fishery is a global concern and batoid fishes, including skates, rays and guitar fishes, are caught frequently as non-targeted species in commercial trawl fishery of India. While the commercial batoid species are documented separately in fishery data, a large number of non-commercial species do not form part of fishery data, even though many such species are listed as ‘Data Deficient’ in IUCN red list. A survey was conducted from July 2018 to June 2019 in the major harbours and landing centers of the south coasts of India to monitor the non-commercial batoid species in the trawl bycatch. Massive landings of non-commercial batoid species such as Torpedo sinuspersici, Narcine cf maculata, Orbiraja powelli Acroteriobatus variegatus and the occasional occurrence of Dipturus johannisdavisi, Benthobatis moresbyi, Narcine timlei and Plesiobatis daviesi have been recorded, besides the juveniles, sub-adults and few adults of commercial species Rhinobatos annandalei, Brevitrygon imbricata and Neotrygon indica from south India. The non-commercial batoids mainly inhabit continental shelf and slope regions of Indian coast where fishing pressure and efforts are high. When these k-selected species live in fishing zones with intense fishing pressure, data deficient species of batoids should be considered as threatened, and this paper discuss challenges in the sector, and forwards strategies for conserving non-targeted batoids.