Area-based Management Tools Research Articles

Potential Contributions of IMO Area-Based Shipping Management and Port State Jurisdiction to the Regulation of Ship-Borne Tourism in Antarctica

Given the rapid growth of ship-borne tourism in Antarctica, the International Maritime Organization (IMO) area-based management tools (ABMTs) could be a timely and effective contribution to mitigate some of the associated risks. Utilization of IMO ABMTs in Antarctic waters, which constitute high seas, raises several legal and practical issues. The central challenge is how to ensure compliance with IMO measures on the high seas, given the lack of generally accepted coastal state jurisdiction in Antarctica and shortcomings in flag state control. This article addresses these questions and analyzes port state jurisdiction as a potential mechanism to enforce IMO ABMTs in the Antarctic. The article concludes that Antarctic port states have sufficient legal arguments to justify the exercise of jurisdiction in relation to IMO ABMTs, and that significant constraints lie in the economic and political dimensions of regulation rather than in regulation itself.

Beyond equilibrium thinking: dynamic area-based management tools in a changing ocean

Area-based management tools (ABMTs), including marine protected areas (MPAs) are often static and fail to reflect the dynamic realities of marine ecosystems. Marine ecosystems are characterized by their embodiment of constant change, which is further amplified by anthropogenic stressors, particularly climate change. ABMTs and MPAs are, however, premised on an implicit assumption of environmental equilibrium as their boundaries and management framework are often fixed and difficult to adjust. This article seeks to lay bare the tension between static conservation strategies and the deeply and inherently dynamic nature of marine ecosystems. It further seeks to advance the notion of dynamic ABMTs, proposing an integrated conceptualization of ABMT governance, one that is more apt to respond to the type of challenges that the dynamism of complex marine ecosystems presents. Dynamism, in this context, is broadly construed as encompassing three dimensions: spatial, with fluid and adjustable conservation measures; normative, denoting a volatile and adaptive management framework that utilizes ecological and management thresholds as an initiator for adaptive, timely, and prospective approaches to enhance management outcomes; and institutional, i.e., sufficiently flexible and dynamic institutional machinery overseeing ABMT implementation. Following a comprehensive conceptualization of dynamic ABMTs, the article addresses the question whether the legal frameworks governing the ocean can sustain such a dynamic mode of ocean governance.

An ecological coherence assessment of the Wider Caribbean Region marine protected area network

Marine protected areas (MPA) are area-based management tools that serve as the cornerstone for marine conservation and sustainable use. There has been a recent shift from establishing MPAs on an individual basis to establishing networks of connected MPAs to better reflect the transient dynamics of marine species and to ensure they are acting synergistically to deliver their intended outcomes in a coherent manner. This study employs innovative geospatial analysis to assess the ecological coherence of the MPA network comprising 846 sites within the Wider Caribbean Region, a global hotspot of marine biodiversity. Evaluating four main criteria widely used in policy—representativity, replicability, connectivity, and adequacy—through 14 tests, our findings indicate that the current MPA network is unlikely to have achieved ecological coherence across all criteria. To improve ecological coherence, regional management could focus on expanding coverage of ecologically important areas, encompassing a broader range of biogeographic zones, and protecting the full spectrum of marine habitats in the region. Efforts should also be directed towards establishing larger MPAs and increasing the number of MPAs with no-take zones, while ensuring the protection of indigenous and local communities' rights to sustainable marine resource use.

Highly structured populations of copepods at risk to deep-sea mining: Integration of genomic data with demogenetic and biophysical modelling.

Copepoda is the most abundant taxon in deep-sea hydrothermal vents, where hard substrate is available. Despite the increasing interest in seafloor massive sulphides exploitation, there have been no population genomic studies conducted on vent meiofauna, which are known to contribute over 50% to metazoan biodiversity at vents. To bridge this knowledge gap, restriction-site-associated DNA sequencing, specifically 2b-RADseq, was used to retrieve thousands of genome-wide single-nucleotide polymorphisms (SNPs) from abundant populations of the vent-obligate copepod Stygiopontius lauensis from the Lau Basin. SNPs were used to investigate population structure, demographic histories and genotype-environment associations at a basin scale. Genetic analyses also helped to evaluate the suitability of tailored larval dispersal models and the parameterization of life-history traits that better fit the population patterns observed in the genomic dataset for the target organism. Highly structured populations were observed on both spatial and temporal scales, with divergence of populations between the north, mid, and south of the basin estimated to have occurred after the creation of the major transform fault dividing the Australian and the Niuafo'ou tectonic plate (350 kya), with relatively recent secondary contact events (<20 kya). Larval dispersal models were able to predict the high levels of structure and the highly asymmetric northward low-level gene flow observed in the genomic data. These results differ from most studies conducted on megafauna in the region, elucidating the need to incorporate smaller size when considering site prospecting for deep-sea exploitation of seafloor massive sulphides, and the creation of area-based management tools to protect areas at risk of local extinction, should mining occur.

Designating Particularly Sensitive Sea Areas in Areas Beyond National Jurisdiction

While the International Maritime Organization’s (IMO) Particularly Sensitive Sea Area (PSSA) concept has been operational for over 30 years, no state has ever brought forward a proposal for a high seas PSSA. This is despite the fact that shipping demonstrably poses a threat to high seas biodiversity. The adoption, by the United Nations, of a new implementing agreement for the conservation and sustainable use of biodiversity in areas beyond national jurisdiction (BBNJ Agreement) opens a new chapter in the governance of the high seas, and creates, for the first time, a legal mechanism, agreed at the global level, for the establishment of area-based management tools (ABMTs). This new agreement strengthens the arguments for utilizing the PSSA regime in the high seas and, as a consequence, has implications for the IMO, and how its member states consider the potential application of PSSAs in areas beyond national jurisdiction (ABNJ). Drawing on recent discussions concerning the potential to designate two specific high seas areas as PSSAs, namely, the Sargasso Sea and the Costa Rica Thermal Dome, this article examines the practical issues to be addressed when applying the PSSA concept to the high seas and considers the opportunities for advancing PSSA proposals through enhanced cooperation between the IMO and the parties to the BBNJ Agreement.

After the Dust Settles: Selected Considerations about the New Treaty on Marine Biodiversity in Areas beyond National Jurisdiction with Respect to ABMTs and MPAs

The recent adoption of a new agreement on the conservation and sustainable use of marine biodiversity in areas beyond national jurisdiction has been welcomed as a historic achievement that will herald a new era of marine conservation and global ocean governance. This article aims to raise and discuss some questions, as the dust settles, and to analyze selected aspects of the text of the new Agreement, with particular respect to Part III of the BBNJ agreement, dedicated to area-based management tools (ABMTs), including marine protected areas (MPAs), which are arguably crucial for the operationalization of the Agreement but remain ambiguous or underarticulated, and may thus reduce its effectiveness and ambition. These questions concern the relationship with other relevant instruments, frameworks, and bodies (IFBs); relatedly, the issue of recognition of area-based measures adopted under other IFBs; and the so-called opt-out question, that is, the right to make objections to an ABMT and/or MPA adopted under the BBNJ agreement.

The area-based management tools coordination between IMO and BBNJ agreement regimes and its implications on vessel pollution control

The International Maritime Organization (IMO), as a specialized agency of the United Nations responsible for the safety and security of international shipping and the prevention of pollution from ships, has applied two main area-based management tools (ABMTs): the “Special Areas” established under the MARPOL 73/78; and the “Particularly Sensitive Sea Areas” (PSSAs) established under the IMO resolutions. The new Agreement under the United Nations Convention on the Law of the Sea on the Conservation and Sustainable Use of Marine Biological Diversity of Areas beyond National Jurisdiction (BBNJ agreement) stipulates the establishment of a comprehensive system of ABMTs to conserve and sustainably use areas beyond national jurisdiction. Strengthening coordination in the use of ABMTs established by the IMO and the BBNJ Agreement is important for vessel pollution control in the high seas. The IMO is a stakeholder for relevant proposals and consultations on proposals regarding the establishment of ABMTs in the BBNJ Agreements, and can provide information on the implementation of them. The Conference of the Parties (COPs) to the BBNJ Agreement can also make recommendations to the IMO and its parties to promote the adoption of special areas and PSSAs. This article respectively elaborates on the practices and effect of ABMTs of the IMO and explores the relevant rules of the BBNJ agreement and their enforcement. Then this article discusses the possible approaches for the ABMTs coordination between the IMO and the BBNJ agreement regimes and their implications on vessel pollution Control in the high seas. Overall, relevant rules of the BBNJ agreement shall be interpreted and applied in a manner that does not undermine relevant legal instruments of the IMO. Meanwhile, it is necessary to promote cooperation and coordination between the COPs to the BBNJ Agreement and the IMO under the idea of conserving ecosystem integrity, gradually forming a normal cooperation and information exchange mechanism.

The Advent of the 2023 “BBNJ” Agreement: A Preliminary Legal Analysis

On 4 March 2023, the Member States of the United Nations agreed in New York on the text of a new treaty on biodiversity in areas beyond national jurisdiction (BBNJ or ABNJ) –in international maritime areas. It took marathon process spread over more than ten years of informal discussions, four years of formal negotiations and the final session of almost 36 hours. Rena Lee, the President of the intergovernmental conference, announced to the applause of the delegates that the ship had finally “reached the shore”. This new BBNJ Agreement, now signed by more than 80 countries, is a historic step for the conservation and sustainable use of marine biodiversity of areas beyond national jurisdiction. It is also in consonance with the objectives of the global Kunming-Montreal Biodiversity Framework adopted at CBD COP15 in December 2022. This article aims to provide a preliminary analysis of the environmental (preamble, principles and approaches, area-based management tools and environmental impact assessments) and economic (marine genetic resources, capacity building and transfer of marine technologies) content of the 2023 BBNJ Agreement, which are both the result of important compromises. It also seeks to underline the numerous remaining uncertainties and potential difficulties it raises, especially in terms of implementation and articulation with existing instruments and frameworks.

The quantifying, mapping, and risk analysis of human-related stressors in the high seas.

Objectives: Marine biodiversity and ecosystem services in the high seas are threatened by numerous stress factors caused by human activities, including global shipping, high-sea fishing, marine plastic pollution, and anthropogenic climate change. Socioeconomic factors are one of the criteria for the establishment of area-based management tools in the high seas for marine biodiversity conservation beyond national jurisdiction. The aim of the work is to propose a spatiotemporal approach to identify risks from marine human activities and recommendations for high seas governance. Methods: Data related to human activities from 2014 to 2022 were used to calculate the distribution and changes of human-related stressors, and the risk to marine biodiversity in the high seas caused by human activities. Results: The North Atlantic, Philippine Sea, Arabian Sea, Bay of Bengal, and East Central Atlantic show high and increasing intensities of human-related stressors, and are therefore particularly at need for the protection and conservation of marine biodiversity. Risks from human activities vary within the marine areas that are prioritized for biodiversity protection. The study recommends that the designation of high seas protected areas should take into account the types of risks to which the different marine areas are exposed, and that the high seas protected areas should be established gradually. At the same time, appropriate management measures should be formulated according to the intensity of human activities in the different marine areas. Conclusions: Quantifying and classifying the risk from human-related stressors could help identify solution for the protection and conservation and facilitate the marine spatial planning, establishment area based management tools, including marine protected areas in the high seas.

Area‐based management tools under the BBNJ Agreement: Ambition or illusion?

AbstractThis article intends to answer the question of whether and to what extent the arrangements for area‐based management tools (ABMTs) under the Agreement on the conservation and sustainable use of marine biological diversity of areas beyond national jurisdiction (BBNJ Agreement) can contribute to the comprehensiveness, coherence and consistency of the international legal regime relating to ABMTs. To answer this question, the article analyses and evaluates the key aspects of the arrangements for ABMTs of the BBNJ Agreement, including consistency with the United Nations Convention on the Law of the Sea (UNCLOS), the interpretation of ‘not undermining’, decision making and the implementation mechanism. It concludes that the arrangements for ABMTs of the BBNJ Agreement are consistent with the UNCLOS and may contribute to the comprehensiveness, coherence and consistency of the international legal regime relating to ABMTs to a large extent. The article further notes that the arrangements for ABMTs of the BBNJ Agreement are ambitious, but lots of work needs to be done to ensure the ambition does not become an illusion.

Decisive conservation action in areas beyond national jurisdiction is urgently required for seabird recovery in the face of global change

AbstractAreas beyond national jurisdiction, or the high seas, are vital to life on Earth. However, the conservation of these areas, for example, through area‐based management tools (ABMTs), is challenging, particularly when accounting for global change. Using decision science, integrated population models, and a Critically Endangered seabird (Kuaka; Pelecanoides whenuahouensis) as a case study, we evaluated potential ABMTs in the high seas under global change and different governance structures, while accounting for uncertainty and imperfect compliance. Our study highlighted that global change in these areas will likely cause population declines of ∼60% by 2050. However, decisive conservation action could cost‐effectively address predicted declines, particularly when implemented as soon as possible and under the Biodiversity Beyond National Jurisdiction Treaty. We illustrate how decision science can transparently navigate a complex seascape of management decisions and we advocate for its wider integration in the management of the largest sections of our planet, the high seas.

Highly structured populations of deep-sea copepods associated with hydrothermal vents across the Southwest Pacific, despite contrasting life history traits

Hydrothermal vents are extreme environments, where abundant communities of copepods with contrasting life history traits co-exist along hydrothermal gradients. Here, we discuss how these traits may contribute to the observed differences in molecular diversity and population genetic structure. Samples were collected from vent locations across the globe including active ridges and back-arc basins and compared to existing deep-sea hydrothermal vent and shallow water data, covering a total of 22 vents and 3 non-vent sites. A total of 806 sequences of mtDNA from the Cox1 gene were used to reconstruct the phylogeny, haplotypic relationship and demography within vent endemic copepods (Dirivultidae, Stygiopontius spp.) and non-vent-endemic copepods (Ameiridae, Miraciidae and Laophontidae). A species complex within Stygiopontius lauensis was studied across five pacific back-arc basins at eight hydrothermal vent fields, with cryptic species being restricted to the basins they were sampled from. Copepod populations from the Lau, North Fiji and Woodlark basins are undergoing demographic expansion, possibly linked to an increase in hydrothermal activity in the last 10 kya. Highly structured populations of Amphiascus aff. varians 2 were also observed from the Lau to the Woodlark basins with populations also undergoing expansion. Less abundant harpacticoids exhibit little to no population structure and stable populations. This study suggests that similarities in genetic structure and demography may arise in vent-associated copepods despite having different life history traits. As structured meta-populations may be at risk of local extinction should major anthropogenic impacts, such as deep-sea mining, occur, we highlight the importance of incorporating a trait-based approach to investigate patterns of genetic connectivity and demography, particularly regarding area-based management tools and environmental management plans.

Effects of management objectives and rules on marine conservation outcomes.

Understanding the relative effectiveness and enabling conditions of different area-based management tools is essential for supporting efforts that achieve positive biodiversity outcomes as area-based conservation coverage increases to meet newly set international targets. We used data from a coastal social-ecological monitoring program in 6 Indo-Pacific countries to analyze whether social, ecological, and economic objectives and specific management rules (temporal closures, fishing gear-specific, species-specific restrictions) were associated with coral reef fish biomass above sustainable yield levels across different types of area-based management tools (i.e., comparing those designated as marine protected areas [MPAs] with other types of area-based management). All categories of objectives, multiple combinations of rules, and all types of area-based management had some sites that were able to sustain high levels of reef fish biomass-a key measure for coral reef functioning-compared with reference sites with no area-based management. Yet, the same management types also had sites with low biomass. As governments advance their commitments to the Kunming-Montreal Global Biodiversity Framework and the target to conserve 30% of the planet's land and oceans by 2030, we found that although different types of management can be effective, most of the managed areas in our study regions did not meet criteria for effectiveness. These findings underscore the importance of strong management and governance of managed areas and the need to measure the ecological impact of area-based management rather than counting areas because of their designation.

Dynamic Ocean Management in Areas Beyond National Jurisdiction

Law and space are intimately connected. In the ocean, the natural environment is divided into maritime zones. Such a division neglects the interconnected nature of the ocean and its inhabitants. Since this zonal approach relies on geographically stable boundaries, it also limits the opportunities to manage a fluid ocean. Area-based management tools, including marine protected areas (MPAs), address some of the limitations of zonal management. However, MPAs are also static from a geographical point of view. The deteriorating state of many marine species and ecosystems indicates a failure of traditional management approaches and puts a renewed emphasis on adapting legal scales to “natural scales,” such as ecosystems. In this article, we argue that there are positive trends and new tools that could be developed within the current legal order to face the challenges that nature is facing in the Anthropocene. One such tool is dynamic ocean management, which moves away from the static rationale of traditional ocean management illustrated here by MPAs, toward a management system focused on the temporal and spatial dynamism of the marine environment. In order to understand how such a management tool could be developed and used within the current legal system, we show how traditional ocean management rests on the notion of delimited and static boundaries and temporarily fixed measures. We discuss this in terms of fixity and simplification. Then we analyze dynamic ocean management and its potential to capture more of the complexity of the marine environment. This analysis is followed by an overview of MPAs and networks of MPAs in areas beyond national jurisdiction (ABNJ), where we discuss the impact of the Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction (BBNJ Treaty) in the development of dynamic ocean management. This overview provides information about both the possibilities and challenges of area-based management in ABNJ. We argue that MPA networks and large marine ecosystems (LMEs), coupled with the establishment of coordination mechanisms between existing institutional structures, are necessary first steps to secure dynamic ocean management.

Systematic evaluation of a spatially explicit ecosystem model to inform area-based management in the deep-sea

The long-term provision of ecosystem goods and services depends on the operationalisation of ecosystem-based management approaches that ensure effective conservation and sustainable use of marine resources. This management challenge is addressed internationally through two United Nations instruments: Sustainable Development Goal (SDG) 14 - Life Below Water, and the Convention on the Law of the Sea (UNCLOS) for the Conservation and Sustainable Use of Marine Biological Diversity in Areas Beyond National Jurisdiction (BBNJ Agreement). To achieve sustainability and conservation goals as described in SDG 14 and the BBNJ Agreement, a combination of management tools, including area-based management tools (ABMTs), is necessary. Spatially explicit ecosystem models can inform policy frameworks by enabling ecosystem-wide assessments of ABMTs with indicators that track their management performance. However, the operational use of these complex models depends on the confidence and uncertainty of their predictions. Here, we present a framework to systematically evaluate the performance of a spatially explicit ecosystem model for deep-sea and open-ocean environments, using the ecosystem model for the EEZ of the Azores (NE Atlantic, Portugal) as a case study. The systematic approach aimed to determine the model's suitability as a tool to inform area-based management in the deep-sea. The framework was applied to Ecospace, the spatial-temporal module of the ecological modelling suite Ecopath with Ecosim. It consisted of a stepwise approach for model development and assessment through key parameterisation steps. The steps served for calibration of model parameter values and formal evaluation of temporal and spatial results against the best available reference data. Overall, this approach proved useful in identifying key model sensitivities and sources of uncertainty that arise when considering spatial variability in trophodynamics in the ecosystem model. Moreover, we concluded the model i) effectively predicted the observed inter-annual variability of benthic fish stocks in response to fisheries, trophic interactions, and environmental factors and ii) showed good and moderate spatial goodness-of-fit in replicating reference spatial distribution patterns of stocks and fishing activities. Despite its strengths, the spatial model has limitations related to uncertainties in model parameterisation and the spatial variability of trophodynamics. The systematic assessments presented in this study provide a framework for future model applications to predict the ecosystem-wide impacts of alternative spatial management measures in the deep-sea.

Negotiations to implement area-based management tools beyond national jurisdiction: the scientific community’s view

A new international legally-binding instrument, under the United Nations Convention on the Law of the Seas (UNCLOS), for the conservation and sustainable use of marine biodiversity in areas beyond national jurisdiction has recently been agreed on– the BBNJ agreement. Area-based management tools (ABMTs), including marine protected areas (MPAs) have an important role in maintaining biodiversity and ecosystem services in the current context of multiple threats to the ocean and are one of central elements of new instrument. In this work, we assessed the perspective of the scientific community, throughout the period of negotiations, on the potential of the BBNJ treaty to promote the creation of new area-based management tools, including MPAs, and fulfil acknowledged gaps in ocean governance. A systematic literature review was conducted, resulting in 80 publications then analysed in detail. From these, a total of 608 key messages were retrieved and classified into: 1) Strengths (S), Weaknesses (W), Opportunities (O) or Threats (T) for a SWOT analysis and 2) one of six categories that cover crucial aspects for the successful implementation of the ABMTs in areas beyond national jurisdiction. A Sentiment Analysis (SA) to these key messages shows that the instrument has been perceived by the scientific community as an opportunity for conserving and achieving sustainable use of biodiversity. However, the scientific community also feels that agreement needs stronger provisions to ensure effective measures, which is reflected by the small number of identified strengths. An overall decrease in sentiment score over the negotiations period, i.e. a growing pessimism, was also observed, which is supported by an increase of weaknesses and threats identified in the final stages of the negotiations. Our results suggest that despite its potential to promote conservation in areas beyond national jurisdiction, the instrument should include a unified definition of MPA, address fishing activities and clarify conflicting terms in its provisions, such as the term “not undermine”. Further, we show that sentiment analysis is a useful tool to evaluate opinion trends and facilitate the integration of different and subjective perspectives into final provisions of complex social-political-environmental agreements, identifying positive and negative attitudes that can enable better solutions to address existing governance challenges in international waters.

Data about marine area-based management tools to assess their contribution to the UN Sustainable Development Goals

Data about marine area-based management tools to assess their contribution to the UN Sustainable Development Goals

A metric-based framework for climate-smart conservation planning.

Climate change is already having profound effects on biodiversity, but climate change adaptation has yet to be fully incorporated into area-based management tools used to conserve biodiversity, such as protected areas. One main obstacle is the lack of consensus regarding how impacts of climate change can be included in spatial conservation plans. We propose a climate-smart framework that prioritizes the protection of climate refugia-areas of low climate exposure and high biodiversity retention-using climate metrics. We explore four aspects of climate-smart conservation planning: (1) climate model ensembles; (2) multiple emission scenarios; (3) climate metrics; and (4) approaches to identifying climate refugia. We illustrate this framework in the Western Pacific Ocean, but it is equally applicable to terrestrial systems. We found that all aspects of climate-smart conservation planning considered affected the configuration of spatial plans. The choice of climate metrics and approaches to identifying refugia have large effects in the resulting climate-smart spatial plans, whereas the choice of climate models and emission scenarios have smaller effects. As the configuration of spatial plans depended on climate metrics used, a spatial plan based on a single measure of climate change (e.g., warming) will not necessarily be robust against other measures of climate change (e.g., ocean acidification). We therefore recommend using climate metrics most relevant for the biodiversity and region considered based on a single or multiple climate drivers. To include the uncertainty associated with different climate futures, we recommend using multiple climate models (i.e., an ensemble) and emission scenarios. Finally, we show that the approaches we used to identify climate refugia feature trade-offs between: (1) the degree to which they are climate-smart, and (2) their efficiency in meeting conservation targets. Hence, the choice of approach will depend on the relative value that stakeholders place on climate adaptation. By using this framework, protected areas can be designed with improved longevity and thus safeguard biodiversity against current and future climate change. We hope that the proposed climate-smart framework helps transition conservation planning toward climate-smart approaches.

China’s choice on the participation in establishing marine protected areas in areas beyond national jurisdiction

Currently, the issue of marine biodiversity in areas beyond national jurisdiction (ABNJ) has made a lot of significant progress in both international legislative process and national practices. As a State Party to UNCLOS, China has actively participated in the negotiations of the BBNJ agreement, in which the marine protected areas (MPAs) as one of the area-based management tools have been an issue of great concern. It is considered to be a feasible and direct conservation tool. In order to evaluate the possibility of China’s participation in the establishment of MPAs in the future, this paper analyzes the drivers for and limits on China’s involvement in the construction of MPAs in the context of the current Chinese situation. And it also puts forward possible countermeasures on how to deal with the challenges brought by the MPAs in ABNJ to China. It is concluded that there is a great possibility that China will eventually choose to participate in the establishment of MPAs in ABNJ as China advocates the concept of a maritime community with a shared future.

A decade of humpback whale abundance estimates at Bermuda, an oceanic migratory stopover site

We constructed annual abundance of a migratory baleen whale at an oceanic stopover site to elucidate temporal changes in Bermuda, an area with increasing anthropogenic activity. The annual abundance of North Atlantic humpback whales visiting Bermuda between 2011 and 2020 was estimated using photo-identification capture-recapture data for 1,204 whales, collected between December 2009 and May 2020. Owing to a sparse data set, we combined a Cormack-Jolly-Seber (CJS) model, fit through maximum likelihood estimation, with a Horvitz-Thompson estimator to calculate abundance and used stratified bootstrap resampling to derive 95% confidence intervals (CI). We accounted for temporal heterogeneity in detection and sighting ratesviaa catch-effort model and, guided by goodness-of-fit testing, considered models that accounted for transience. A model incorporating modified sighting effort and time-varying transience was selected using (corrected) Akaike’s Information Criterion (AICc). The survival probability of non-transient animals was 0.97 (95% CI 0.91-0.98), which is comparable with other studies. The rate of transience increased gradually from 2011 to 2018, before a large drop in 2019. Abundance varied from 786 individuals (95% CI 593-964) in 2016 to 1,434 (95% CI 924-1,908) in 2020, with a non-significant linear increase across the period and interannual fluctuations. These abundance estimates confirm the importance of Bermuda for migrating North Atlantic humpback whales and should encourage a review of cetacean conservation measures in Bermudian waters, including area-based management tools. Moreover, in line with the time series presented here, regional abundance estimates should be updated across the North Atlantic to facilitate population monitoring over the entire migratory range.