17 urn:lsid:arphahub.com:pub:8E638694-B4E0-570A-856A-746FF325BF6B urn:lsid:zoobank.org:pub:FEF66878-15EE-4F8B-B369-7652D735020E Research Ideas and Outcomes RIO 2367-7163 Pensoft Publishers 10.3897/rio.11.e171663 171663 29010 Methods Aquaculture & Fisheries Environmental economics & policies Environmental impact assessment Environmental protection 14.c Conservation & sustainable use of ocean resources Life below water Mitigation measures, fishing practices and technologies to reduce interactions between Endangered, Threatened, and Protected (ETP) species and drifting longline fisheries (LLD) targeting large pelagics: a global scoping review protocol Anastasopoulou Iro iroanastasopoulou9@gmail.com 1 Kavakakis Konstantinos 1 Asimogiorgou Vasiliki 1 Iatrou Foteini https://orcid.org/0009-0008-6272-5564 1 Petza Dimitra 2 Carbonara Pierluigi 3 Tserpes George 4 Alemany Francisco 5 Kalogirou Stefanos stefanos.kalogirou@aua.gr https://orcid.org/0000-0002-3064-9236 1 Agricultural University of Athens, Athens, Greece Agricultural University of Athens Athens Greece University of the Aegean, Mytilene, Greece University of the Aegean Mytilene Greece Fondazione COISPA ETS, Bari, Italy Fondazione COISPA ETS Bari Italy Hellenic Centre for Marine Research, Heraklion, Greece Hellenic Centre for Marine Research Heraklion Greece International Commission for the Conservation of Atlantic Tunas, Madrid, Spain International Commission for the Conservation of Atlantic Tunas Madrid Spain

Corresponding authors: Iro Anastasopoulou (iroanastasopoulou9@gmail.com), Stefanos Kalogirou (stefanos.kalogirou@aua.gr).

Academic editor: Editorial Secretary

 2025 23 12 2025 11 e171663 93AA396C-6CC9-5155-BDD0-F73F74A7594E 18052024 10 09 2025 17 12 2025 Iro Anastasopoulou, Konstantinos Kavakakis, Vasiliki Asimogiorgou, Foteini Iatrou, Dimitra Petza, Pierluigi Carbonara, George Tserpes, Francisco Alemany, Stefanos Kalogirou This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Objective: The objective of this scoping review is to map and synthesize evidence on mitigation measures, fishing practices, and technologies to reduce endangered, threatened, and protected (ETP) species bycatch in drifting longline fisheries targeting large pelagics, summarize key concepts and findings across disciplines, and identify knowledge gaps to inform policy and research at a global scale.

Introduction: Drifting longline fisheries targeting large pelagic species continue to pose a significant conservation and management challenge for ETP species. Although various types of mitigation measures, fishing practices, and technologies have been developed and utilized globally to reduce ETP bycatch, the scope and nature of field-tested evidence remain diverse and scattered.

Inclusion criteria: Studies about regional measures adopted, and fishing practices and technologies tested in the field aimed at reducing ETP species in drifting longlines (LLD) for large pelagics. Both peer-reviewed and grey literature will be included. Studies published in English, Swedish, Norwegian, Greek, Spanish and Italian language and between the years 1990 and 2024 will be included. Studies related to other types of fishing gear, those that do not mention ETP species, or any type of evidence synthesis will be excluded.

Methods: This scoping review will be guided by the Joanna Briggs Institute (JBI) methodology. Scopus and Web of Science databases will be used and complemented with grey literature sources, i.e. organisational websites and a web-based search engine. A team of four reviewers will conduct the screening and the data extraction processes. EndNote software, Covidence software, Microsoft Excel and Flourish platform will be used for data management, screening, extraction and presentation of the outputs. The results will be presented both graphically and in tabular form.

 Bycatch reduction devices Fisheries policy Fisheries management Fishing gear innovation Marine biodiversity Funding program

This scoping review is supported by Marine Stewardship Council (MSC) Ocean Stewardship Fund (OSF) for students, Grant number 2024-1321. The funders had no role in the design, conduct, or reporting of the review. The co-authors would like to thank the MSC for their generous support. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect those of the authors’ affiliated institutions.

 Introduction

Drifting longline (LLD) fisheries primarily targetting commercially important large pelagics, such as tuna and tuna-like species frequently report bycatch of non-target species. Bycatch includes incidental catch (species with commercial value) and discarded species (species with no economic value). Discarded species are often protected, and when released back to the sea, can frequently sustain significant injuries that lead to mortality (Santos et al. 2023). Of particular concern are vulnerable species affected by the LLD fishery, primarily elasmobranchs (especially pelagic sharks), sea turtles, seabirds, and marine mammals (Clarke et al. 2014). In marine fisheries, these species are collectively referred to as endangered, threatened, and protected (ETP) species. While there is a lack of a universally accepted and agreed-upon definition of ETP species, these are typically defined through multi-level legal and policy frameworks for conservation (Gray and Kennelly 2018). For this scoping review, ETP species will be identified using the IUCN Red List (IUCN 2012), CITES Appendix II (Convention on International Trade in Endangered Species of Wild Fauna and Flora 2023) and CMS Appendix II (Convention on the Conservation of Migratory Species of Wild Animals 2024).

ETP species primarily interact with LLD fisheries through hooking (attracted to bait) or entanglement (Santos et al. 2023). These interactions not only threaten species’ survival but also cause economic losses for fishers due to depredation (consumption of fish or bait from the gear) (Fader et al. 2021).

Pelagic LLD fisheries affect negatively several marine taxa, including seabirds, elasmobranchs, marine mammals, and sea turtles as discards (Carpentieri et al. 2021). Some elasmobranchs, including frequently captured species in LLD such as Prionace glauca (Linnaeus, 1758), Isurus oxyrinchus Rafinesque, 1810, Pseudocarcharias kamoharai (Matsubara, 1936), Alopias superciliosus Lowe, 1841, Galeorhinus galeus (Linnaeus, 1758) and Carcharodon carcharias (Linnaeus, 1758), are due to their biological traits (such as low reproductive potential, slow growth and late maturity) and highly migratory patterns sensitive to overfishing (Coelho et al. 2012, Cortés et al. 2009, Gallagher et al. 2014, Jordaan et al. 2020, Peristeraki et al. 2008). Seabirds, especially long-lived albatrosses and petrels, suffer annual mortalities of up to 160,000-320,000 individuals from longline interactions (Anderson et al. 2011, Jiménez et al. 2019, Lewison and Crowder 2003). Sea turtles, particularly leatherbacks Dermochelys coriacea (Vandelli, 1761) and loggerheads Caretta caretta (Linnaeus, 1758), face similar threats (Lewison and Crowder 2007). In addition, odontocete cetaceans including false killer whales Pseudorca crassidens (Owen, 1846), short-finned pilot whales Globicephala macrorhynchus Gray, 1846, and Risso's dolphins Grampus griseus (G. Cuvier, 1812) are also affected across various regions (Fader et al. 2021, Hamer et al. 2012, Macías López et al. 2012).

The LLD fishery has in recent years developed positively towards reducing the interactions with ETP species through the adoption of measures driven by technological innovations and modifications in fishing practices (Jordaan et al. 2020). Among these innovations are various fishing technologies such as, bycatch reduction devices (BRDs) and gear modifications (Suuronen and Browman 2022). These innovations include bait modifications (e.g., blue dyed bait), hook designs (e.g., circle hooks), leader materials (e.g., nylon/monofilament alternatives) and deterrent systems (e.g., magnetic/acoustic devices, scaring lines) (Gilman et al. 2005, Gilman 2011, Gilman et al. 2016, Lucas and Berggren 2022). Some of these approaches can substantially decrease by-catch with low-cost investment, some of which with increased capture efficiency of target species (e.g. circle hook and albacore tuna) while in others, with decreased capture efficiency (e.g. circle hooks and swordfish) (Santos et al. 2023).

Measures to reduce the interaction between ETP species and LLD fisheries are typically adopted through regulatory frameworks, time-area closures and standardized fishing practices (Sacchi 2021). These measures are adopted through specific management actions coordinated by Regional Fisheries Management Organizations (RFMOs). Contracting parties such as the European Union (EU) has integrated several of these measures in its legislation. In addition, LLD fisheries, encompass fishing practices with critical operational decisions including bait selection, numbers of hooks, soak time, operational time (including moon phase considerations), and LLD depth setting (Ward and Hindmarsh 2007).

This scoping review aims to:

map and summarize global data and evidence from real-life settings of mitigation measures adopted, and fishing practices and technologies tested, that reduce the interaction between ETP species and LLD fisheries targeting large pelagics.

identify key concepts and summarize key findings

identify the main gaps in the literature

A preliminary search in Scopus and Web of Science revealed no existing systematic or scoping reviews that comprehensively address mitigation measures, fishing practices, and technologies for ETP species in LLD. While several relevant reviews exist, they are limited in scope, focusing either on single ETP species (Avery et al. 2017, Gilman et al. 2006, Gilman and Huang 2016, Godin et al. 2012, Hamer et al. 2012, Løkkeborg 2003, Lucchetti and Sala 2010, Read 2007, Werner et al. 2015) or individual mitigation approaches such as circle hooks, bait modifications, or sensory deterrents (Graves et al. 2012, Kumar et al. 2016, Southwood et al. 2008, Yokota et al. 2012). Notably, one review in Japanese (Kiyota and Yokota 2010) could not be fully studied due to linguistic limitations, while another review examined post-capture handling practices across pelagic LLD and several ETP species (Zollett and Swimmer 2019). A recent meta-analysis evaluated gear modifications (hooks, bait, leaders) for teleosts, elasmobranchs, and sea turtles (Santos et al. 2023), but its narrow focus on specific technologies and species, differs from the broader objectives of this scoping review. The most comparable review (Swimmer et al. 2020) covers multiple ETP species (cetaceans, sea turtles, seabirds, sharks, and billfishes) but includes comparisons between purse seine fisheries and pelagic longlines.

To cover the broad scope and nature of this study, including various measures, fishing practices, and technological solutions, we will use the JBI as a fit-for-purpose approach to systematically examine evidence, identify research gaps and provide direction for future research (Aromataris et al. 2024). The available evidence includes information from many locations and disciplines across the globe and includes studies on operational fishing practices (Melvin et al. 2014, Jiménez et al. 2020), gear modifications (Lima et al. 2023, Santos et al. 2019, Ward et al. 2008, Gilman et al. 2021) and innovative technologies (Sullivan et al. 2017). These studies collectively form the evidentiary foundation for a global scoping review on ETP species bycatch mitigation in LLD fisheries.

The findings of this scoping review will bridge the fields of fisheries, environmental sciences, and policy, highlighting the need for effective bycatch management to protect ETP species while ensuring sustainable and capture-efficient fisheries.

 Review question

The main question to be addressed by this scoping review is: What mitigation measures have been adopted, and what fishing practices and technologies have globally been tested in real-life fisheries settings to reduce the interactions between ETP species in drifting longline fisheries targeting large pelagics? Additional sub-questions that the review seeks to answer are:

Which country/countries have mostly contributed to this research, and in which marine FAO fishing areas and fisheries has the science driven policy adoption?

Which ETP species are most frequently reported from LLD fisheries in the literature?

Which gear modifications in fishing practices and technologies have been mostly tested per ETP taxa?

Inclusion criteria Participants

The participants of this scoping review (ScR) are the ETP species. Within the framework of this review, ETP species are considered the species included in the IUCN Red List of Threatened Species (IUCN 2012), species listed in the Convention on International Trade in Endangered Species of wild fauna and flora appendices (CITES) (Convention on International Trade in Endangered Species of Wild Fauna and Flora 2023) and species listed in the appendices of the Convention on the Conservation of Migratory Species of wild animals (CMS) (Convention on the Conservation of Migratory Species of Wild Animals 2024). More specifically, the IUCN Red List include three categories of species, collectively referred to as "threatened" species, classified i.e. critically endangered (CR), endangered (EN) and vulnerable (VU) (IUCN 2012). Additionally, species listed in Appendix I and II of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora 2023) and in Appendix II of CMS (Convention on the Conservation of Migratory Species of Wild Animals 2024), are all considered as ETP species for this ScR. Studies on measures, practices and/or technologies on target species capture efficiency and other associated factors (e.g. yield) that do not specifically mention an ETP species will be excluded.

 Concept

All types of management measures, including fishing practices and technologies, that aim to reduce the interaction of ETP species with LLD fisheries constitute the concept of this ScR. Mitigation measures adopted by tuna RFMOs (Commission for the Conservation of Southern Bluefin Tuna, CCSBT; Indian Ocean Tuna Commission IOTC; International Commission for the Conservation of Atlantic Tunas ICCAT; The Inter-American Tropical Tuna Commission IATTC; and Western and Central Pacific Fisheries Commission WCPFC) to reduce ETP species bycatch in LLD will be included, while national measures will be excluded. Examples of such measures are international regulations, agreements, time-area closures, quotas and gear restrictions adopted by tuna RFMOs e.g., ICCAT etc. Finally, only in-force/active measures will be considered to ensure the findings are updated and scientifically justified to current management practices and policy decisions.

For fishing practices, this ScR will include studies that contribute to the reduction of the interaction with ETP species and LLD fisheries, such as changes in fishing operations (e.g., set time, depth setting, bait type, soak time, haul-back time, handling and release practices, post-capture handling of ETP species, etc.).

For fishing technologies, this ScR will include studies designed to reduce ETP species interaction with LLD fisheries, such as hook modifications (circle hooks, magnetic hooks), bait alternatives (artificial bait, coloured bait), gear modifications (weighted lines, bird-scaring lines), and acoustic, visual, or electronic deterrents (LED lights, pingers).

For both fishing practices and fishing technologies, only field-tested studies will be included. Finally, studies focusing on other gear types such as bottom longlines, gillnets, trammel nets, purse seiners, or trawls will be excluded. Additionally, research from recreational, or sports fisheries will not be included.

 Context

This ScR will include studies in marine environments where LLD fisheries operate. The ScR will focus on LLD fisheries targeting large pelagics, including swordfish Xiphias gladius Linnaeus, 1758, tunas e.g., albacore Thunnus alalunga (Bonnaterre, 1788), bluefin tuna Thunnus thynnus (Linnaeus, 1758), yellowfin tuna Thunnus albacares (Bonnaterre, 1788), bigeye tuna Thunnus obesus (Lowe, 1839), and marlins. Studies from any geographic location worldwide will be considered.

 Types of sources

This ScR considers research studies published in peer-reviewed journals (e.g. research articles, field studies, experimental studies, etc) and grey literature (e.g. organisational websites, technical reports, guidelines, documents, etc.). All forms of secondary research, such as review articles and evidence syntheses (e.g. systematic reviews, scoping reviews, rapid reviews, meta-analyses, umbrella reviews, literature reviews, etc.) will be excluded to prevent duplication of evidence. Chronologically, the literature search will cover the years between 1990 and 2024, to ensure the review captures most recent developments in bycatch mitigations since bycatch issues started to appear in the scientific literature (Soykan et al. 2008). No search limitations will be applied regarding subject area, publication stage, document type or source type. Studies in languages other than English, Swedish, Norwegian, Greek, Spanish and Italian will be excluded to meet authors’ language competence, a limitation which may affect outcomes from the grey literature.

 Methods

The proposed scoping review will be conducted in accordance with the JBI methodology for scoping reviews (Aromataris et al. 2024). The preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews, PRISMA-ScR (Tricco et al. 2018) will be used to improve the transparency and completeness of this ScR. The JBI SUMARI (Joanna Briggs Institute System for the Unified Management, Assessment and Review of Information) software (JBI SUMARI 2004) will be used to develop the protocol. To ensure transparency, any deviations from the protocol will be detailed in the final ScR report.

Search strategy

The search strategy will aim to identify both peer-reviewed and grey literature. A three-step search strategy will be applied in this review. Firstly, an initial limited search in Scopus will be undertaken to identify articles on the topic, keywords and index terms. Secondly, the text words contained in the titles and abstracts of relevant articles, and the index terms used to describe the articles, will be used to develop a full search strategy for Scopus (see Suppl. material 1). This full search strategy will form the basis for developing search strategies for other databases and/or information sources. Thirdly, the reference lists of all included sources of evidence will also be screened to identify additional studies that aligns with the inclusion and exclusion criteria of this ScR.

The scientific databases to be searched include Scopus and Web of Science Core Collection. Sources of unpublished studies and grey literature include the web-based search engine Google Search and organisational websites (e.g. ICCAT, FAOLEX, FAO Knowledge Repository BETA). For web-based search, a screening limit of the first five pages will be set and will include keyword combinations that match the aim of this study. This approach is expected to substantially improve the efficiency in management of both time and volume of grey literature, as also recommended by the JBI methodology (Aromataris et al. 2024). The full three-step search strategy will be presented in the final review article.

 Study/Source of evidence selection

Following the search strategy, all identified citations will be collated and uploaded into EndNote 20.6 (Clarivate Analytics) (Clarivate 2023) and duplicates will be removed. Four reviewers will take part in the screening process of this ScR. Prior to the screening process, a pilot test of the sources for evidence selection will be conducted, the framework of which is recommended by the JBI methodology (Aromataris et al. 2024). The pilot testing includes 20 random samples of titles/abstracts and screened by each of the four reviewers, following eligibility criteria set in this protocol. This process will enable reviewers to consider any necessary modifications needed in the eligibility criteria. The screening will commence after the reviewers have reached an agreement of >75%. Once an agreement has been reached, the four reviewers will proceed for a full screening process of all articles, including titles and abstracts which will be assessed against the final inclusion criteria (see section Inclusion Criteria; Table 1). The four reviewers will be divided into groups of two to facilitate the screening process. All sources that meet the inclusion criteria, together with their full reference, will be imported into the Covidence Systematic Review Software (Covidence 2025). As a next step, the full text will be assessed in detail against the inclusion criteria by each of the reviewers. Reasons for excluding sources of evidence at full text not meeting the inclusion criteria will be recorded and reported in the scoping review paper. Any disagreements that arise between the reviewers during the selection process, will be resolved through discussion, or by inviting an additional independent reviewer. The results of the search strategy and the inclusion/exclusion process will be presented in the final scoping review as a preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews (PRISMA-ScR) flow diagram (Tricco et al. 2018).

 Data extraction

Data will be extracted from documents included in the scoping review by four independent reviewers using a data extraction tool, such as a charting table (Suppl. material 2). The data extracted will include specific details about the participants, concept, context, study methods and key findings relevant to the review question.

To promote consistency and support collaboration and communication among reviewers, the data extraction tool will be incorporated into the Covidence systematic review management software (Covidence 2025). The extraction mode of Covidence will be used by four reviewers, i.e. two reviewers will extract relevant data based on our data extraction tool for each study. Any disagreements that arise between the reviewers will be resolved through discussion, or with an additional reviewer/s. The data extraction tool may be modified during the data extraction process if additional information is considered crucial for the scope of this study and detailed in the scoping review. If necessary, authors of papers will be contacted to request missing or additional data.

 Data analysis and presentation

The evidence presented in the final review paper will directly respond to the review objective and questions. The data will be presented graphically and in tabular form. Features of Microsoft Excel (Microsoft Corporation 2025) and Flourish (Flourish, Canva UK Operations Ltd. 2025) will be used to visualize and present the data. A narrative summary will accompany the tabulated and/or charted results, describing how the results relate to the review's objective and review question. We aim to use parametric and non-parametric tests to statistically justify outcomes.

 Acknowledgements

The authors would like to thank Antigoni Foutsi from MSC for informing us for the possibility of submitting proposals to the Ocean Stewardship Fund (OSF) of MSC.

 Author contributions

IA led the writing, editing and reviewing process, acquired funding, designed the search strategy and data extraction tool. KK, VA, FI contributed to writing, editing, reviewing. DP provided supervision, contributed to writing, editing, reviewing. PC, GT, and FA contributed to writing. SK conceived the study, provided supervision, acquired funding, contributed to writing, editing, reviewing. All authors contributed equally to the approval of the final protocol.

 Conflicts of interest

No conflict of interest to declare

Disclaimer: This article is (co-)authored by any of the Editors-in-Chief, Managing Editors or their deputies in this journal.

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Silva‐Costa Augusto Sant'Ana Rodrigo Gianuca Dimas Yates Oliver Marques Caio Neves Tatiana 2019 Improved line weighting reduces seabird bycatch without affecting fish catch in the Brazilian pelagic longline fishery Aquatic Conservation: Marine and Freshwater Ecosystems 29 3 442 449 10.1002/aqc.3002 Southwood A Fritsches K Brill R Swimmer Y 2008 REVIEW: Sound, chemical, and light detection in sea turtles and pelagic fishes: sensory-based approaches to bycatch reduction in longline fisheries Endangered Species Research 5 225 238 10.3354/esr00097 Soykan CU Moore JE Zydelis R Crowder LB Safina C Lewison RL 2008 Why study bycatch? An introduction to the Theme Section on fisheries bycatch Endangered Species Research 5 91 102 10.3354/esr00175 Sullivan B. J. Kibel B. Kibel P. Yates O. Potts J. M. Ingham B. Domingo A. Gianuca D. Jiménez S. Lebepe B. Maree B. A. Neves T. Peppes F. Rasehlomi T. Silva‐Costa A. Wanless R. 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Inclusion and exclusion criteria for the Scoping Review based on the "Participants, Concept and Context, PCC" mnemonic.

Inclusion criteria Exclusion criteria
PARTICIPANTS Endangered, Threatened, and Protected (ETP) species as defined by:- IUCN Red List (CR, EN, VU)- CITES Appendix II- CMS Appendix IIIf a species meets one or more of these, it is considered ETP - Studies focusing on ETP species - Studies on measures, practices, or technologies that do not include ETP species
CONCEPT Regional mitigation measures, fishing practices, and technologies aimed at reducing ETP species interaction with LLD on a global scale - Mitigation measures adopted by tuna RFMOs to reduce ETP species bycatch in LLD- Only in-force/active measures- Fishing practices that reduce ETP interaction (e.g., set time, depth setting, bait type, soak time, haulback time, handling and release, post-capture handling)- Technologies specifically designed for ETP species reduction in LLD (e.g., hook modifications, bait alternatives, gear modifications, deterrents)- Only field-tested practices and technologies included - Measures, practices, or technologies related to other types of longline fisheries (such as bottom longlines) or other gear types (gillnets, trammel nets, purse seiners, trawls)- National measures- Non-field-tested (theoretical, conceptual, or lab-based) practices/technologies- Studies about recreational, or sports fisheries
CONTEXT Drifting longline fisheries (LLD) targeting large pelagic species - Studies conducted in marine environments where LLD fisheries operate- Evidence about large pelagic species (e.g., swordfish, tuna, billfishes)- Studies from any geographic location
EVIDENCE TYPES & SOURCES - Peer-reviewed research studies (articles, field studies, experimental studies) from literature databases- Selected grey literature (organizational websites, technical reports, guidelines, etc.)- Literature from 1990 to 2024- Studies published in English, Swedish, Norwegian, Greek, Spanish and Italian- No limitations on subject area, publication stage, document or source type - Theoretical, conceptual, or laboratory-only studies- Secondary research, review articles, systematic or scoping or rapid or meta or umbrella or literature reviews- Studies before 1990 or after 2024
C11E70C6-ECD1-5A90-86E4-1E59BF16B513 10.3897/rio.11.e171663.suppl1 18052152

Search strategy

Search strategy

The entire search strategy (query string) applied in Scopus at 21 July 2025 and search results (number of articles retrieved).

File: oo_1401675.docx

https://binary.pensoft.net/file/1401675 Iro Anastasopoulou, Konstantinos Kavakakis, Vasiliki Asimogiorgou, Foteini Iatrou, Dimitra Petza, Pierluigi Carbonara, George Tserpes, Francisco Alemany, Stefanos Kalogirou D05CD2EF-7416-5A2A-A2B9-369D9D7E3617 10.3897/rio.11.e171663.suppl2 18052154

Data extraction instrument

Data extraction tool

A charting table aligned to the objective and the questions of the ScR, including specific details about the participants, concept, context, relevant to the review objective.

File: oo_1401677.xlsx

https://binary.pensoft.net/file/1401677 Iro Anastasopoulou, Konstantinos Kavakakis, Vasiliki Asimogiorgou, Foteini Iatrou, Dimitra Petza, Pierluigi Carbonara, George Tserpes, Francisco Alemany, Stefanos Kalogirou