Article

Global climate change, range changes and potential implications for the conservation of marine cetaceans: A review and synthesis

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Abstract

Global climate change has already resulted in an increase in oceanic water tempera- tures in some areas and is predicted to lead to further increases throughout much of the world in the foreseeable future. One possible response of cetacean species to these increases in water tempera- ture is that species' ranges may change. Here, I provide a framework for assessing which cetacean species' ranges are likely to change as a result of increases in water temperature and whether they will expand, shift poleward or contract based on their current distributions. Based on this framework, it is predicted that the ranges of 88% of cetaceans may be affected by changes in water temperature resulting from global climate change. For 47% of species, these changes are anticipated to have unfavourable implications for their conservation, and for 21% the changes may put at least one geo- graphically isolated population of the species at high risk of extinction. This framework suggests that certain characteristics put some species at greater risk from such changes than others. These include a range that is restricted to non-tropical waters (including temperate species) and a preference for shelf waters. These characteristics are shared by most porpoises and Lagenorhynchus species and by all members of the genus Cephalorhynchus. As a result, species in these taxa are potentially at par- ticular risk from changes in range in response to increasing water temperatures. However, further research is required to assess whether these predictions are, indeed, correct.

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... Cetaceans are particularly vulnerable to climate change (MacLeod, 2009) due to their crucial function as apex predators in marine ecosystems (Bowen, 1997). Climate change influences the availability of their prey and modifies the habitat, thereby impacting several (if not all) cetacean species and may even put some of them at a high risk of extinction (Learmonth et al., 2006). ...
... Climate change influences the availability of their prey and modifies the habitat, thereby impacting several (if not all) cetacean species and may even put some of them at a high risk of extinction (Learmonth et al., 2006). As a response, several cetacean species are shifting their distribution ranges to track suitable habitats or adapt locally by switching to different food resources (Lambert et al., 2011;Learmonth et al., 2006;MacLeod, 2009;Williamson et al., 2021). For example, temperate and subpolar small cetaceans like the harbor porpoises (Phocoena phocoena) are likely to show a poleward shift (Heide-Jørgensen et al., 2011;MacLeod, 2009). ...
... As a response, several cetacean species are shifting their distribution ranges to track suitable habitats or adapt locally by switching to different food resources (Lambert et al., 2011;Learmonth et al., 2006;MacLeod, 2009;Williamson et al., 2021). For example, temperate and subpolar small cetaceans like the harbor porpoises (Phocoena phocoena) are likely to show a poleward shift (Heide-Jørgensen et al., 2011;MacLeod, 2009). ...
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Impact of climate change is expected to be especially noticeable at the edges of a species' distribution, where they meet suboptimal habitat conditions. In Mauritania and Iberia, two genetically differentiated populations of harbor porpoises ( Phocoena phocoena ) form an ecotype adapted to local upwelling conditions and distinct from other ecotypes further north on the NE Atlantic continental shelf and in the Black Sea. By analyzing the evolution of mitochondrial genetic variation in the Iberian population between two temporal cohorts (1990–2002 vs. 2012–2015), we report a substantial decrease in genetic diversity. Phylogenetic analyses including neighboring populations identified two porpoises in southern Iberia carrying a divergent haplotype closely related to those from the Mauritanian population, yet forming a distinct lineage. This suggests that Iberian porpoises may not be as isolated as previously thought, indicating possible dispersion from Mauritania or an unknown population in between, but none from the northern ecotype. Demo‐genetic scenario testing by approximate Bayesian computation showed that the rapid decline in the Iberian mitochondrial diversity was not simply due to the genetic drift of a small population, but models support instead a substantial decline in effective population size, possibly resulting from environmental stochasticity, prey depletion, or acute fishery bycatches. These results illustrate the value of genetics time series to inform demographic trends and emphasize the urgent need for conservation measures to ensure the viability of this small harbor porpoise population in Iberian waters.
... While future shifts in distributions of beaked whale populations related to climate change are likely as prey ranges change (e.g., Hooker et al. 2019), little work has been done to investigate these possible shifts. Macleod (2009) included beaked whale species in their assessment of potential global changes to marine mammal distributions relative to climate change. They hypothesized that out of the 21 species considered, 6 would experience a range expansion, 8 a range shift, and 5 a range contraction, depending on if they were cold-or warm-water limited, and that 12 of these shifts would not be favorable to the species (Macleod 2009). ...
... Macleod (2009) included beaked whale species in their assessment of potential global changes to marine mammal distributions relative to climate change. They hypothesized that out of the 21 species considered, 6 would experience a range expansion, 8 a range shift, and 5 a range contraction, depending on if they were cold-or warm-water limited, and that 12 of these shifts would not be favorable to the species (Macleod 2009). ...
... Shifts in geographic distributions of prey, predator and competitor communities with climate change (Lambert et al., 2011;MacLeod, 2009) will alter trophic interactions, which in turn will influence ecological responses to climate change (Araújo & Luoto, 2007;Davis et al., 1998;Van der Putten et al., 2010). ...
... phenylalanine, lysine) are not broken during dominant metabolic pathways, thereby conserving baseline δ 15 N values throughout food webs. Referencing trophic AA δ 15 N against source AA δ 15 N values thus allows for calibration of trophic position using only consumer samples (McClelland & Montoya, 2002, Chikaraishi et al., 2007, 2009; but see Nuche-Pascual et al., 2018), bypassing requirements of dietary applications of bulk tissue SI analysis (namely, extensive sampling of the potential prey base over temporal and spatial scales integrated by the consumer tissue). Validation studies, however, have shown considerable deviations from these primary assumptions in marine mammals (Germain et al., 2013;Matthews, Ruiz-Cooley, et al., 2020), with notably showing that the δ 15 N difference between the primary trophicsource AA pairing, glutamic acid and phenylalanine, decreased with trophic position in killer whales rather than increase as predicted based on conventional CSIA-AA studies (Chikaraishi et al., 2007(Chikaraishi et al., , 2009McClelland & Montoya, 2002). ...
Article
1. Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic-endemic prey. 2. We assessed diet and distribution of ECA killer whales using bulk and compound-specific stable isotope analysis (CSIA) of amino acids (AA) of 54 skin biopsies collected from 2009 to 2020 around Baffin Island, Canada. 3. Bulk ECA killer whale skin δ 15 N and δ 13 C values did not overlap with potential Arctic prey after adjustment for trophic discrimination, and instead reflected foraging history in the North Atlantic prior to their arrival in the ECA. Adjusted killer whale stable isotope (SI) values primarily overlapped with several species of North Atlantic baleen whales or tuna. Amino acid (AA)-specific δ 15 N values indicated the ECA killer whales fed primarily on marine mammals, having similar glutamic acid δ 15 N-phenylalanine δ 15 N (δ 15 N Glx-Phe) and threonine δ 15 N (δ 15 N Thr) as mammal-eating killer whales from the eastern North Pacific (ENP) that served as a comparative framework. However, one ECA whale grouped with the fish-eating ENP ecotype based δ 15 N Thr. 4. Distinctive essential AA δ 13 C of ECA killer whale groups, along with bulk SI similarity to killer whales from different regions of the North Atlantic, indicates different populations converge in Arctic waters from a broad source area. Generalist diet and long-distance dispersal capacity favour range expansions, and integration of these insights will be critical for assessing ecological impacts of increasing killer whale predation pressure on Arctic-endemic species. K E Y W O R D S compound-specific stable isotope analysis of amino acids,
... Shifts in geographic distributions of prey, predator and competitor communities with climate change (Lambert et al., 2011;MacLeod, 2009) will alter trophic interactions, which in turn will influence ecological responses to climate change (Araújo & Luoto, 2007;Davis et al., 1998;Van der Putten et al., 2010). ...
... phenylalanine, lysine) are not broken during dominant metabolic pathways, thereby conserving baseline δ 15 N values throughout food webs. Referencing trophic AA δ 15 N against source AA δ 15 N values thus allows for calibration of trophic position using only consumer samples (McClelland & Montoya, 2002, Chikaraishi et al., 2007, 2009; but see Nuche-Pascual et al., 2018), bypassing requirements of dietary applications of bulk tissue SI analysis (namely, extensive sampling of the potential prey base over temporal and spatial scales integrated by the consumer tissue). Validation studies, however, have shown considerable deviations from these primary assumptions in marine mammals (Germain et al., 2013;Matthews, Ruiz-Cooley, et al., 2020), with notably showing that the δ 15 N difference between the primary trophicsource AA pairing, glutamic acid and phenylalanine, decreased with trophic position in killer whales rather than increase as predicted based on conventional CSIA-AA studies (Chikaraishi et al., 2007(Chikaraishi et al., , 2009McClelland & Montoya, 2002). ...
Article
Full-text available
Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic‐endemic prey. We assessed diet and distribution of ECA killer whales using bulk and compound‐specific stable isotope analysis (CSIA) of amino acids (AA) of 54 skin biopsies collected from 2009 to 2020 around Baffin Island, Canada. Bulk ECA killer whale skin δ¹⁵N and δ¹³C values did not overlap with potential Arctic prey after adjustment for trophic discrimination, and instead reflected foraging history in the North Atlantic prior to their arrival in the ECA. Adjusted killer whale stable isotope (SI) values primarily overlapped with several species of North Atlantic baleen whales or tuna. Amino acid (AA)‐specific δ¹⁵N values indicated the ECA killer whales fed primarily on marine mammals, having similar glutamic acid δ¹⁵N–phenylalanine δ¹⁵N (δ¹⁵NGlx‐Phe) and threonine δ¹⁵N (δ¹⁵NThr) as mammal‐eating killer whales from the eastern North Pacific (ENP) that served as a comparative framework. However, one ECA whale grouped with the fish‐eating ENP ecotype based δ¹⁵NThr. Distinctive essential AA δ¹³C of ECA killer whale groups, along with bulk SI similarity to killer whales from different regions of the North Atlantic, indicates different populations converge in Arctic waters from a broad source area. Generalist diet and long‐distance dispersal capacity favour range expansions, and integration of these insights will be critical for assessing ecological impacts of increasing killer whale predation pressure on Arctic‐endemic species.
... The three species studied have populations in the Pacific, Indian and both sides of the Atlantic, being absent in the polar areas. They are expanding in relation to global warming [1], two of them-Dd and Tt-towards the north [2]. It is obvious that species with a wide geographic distribution suffer significant selective pressure, especially in their more distant areas, such as the western and eastern Atlantic coasts and associated seas, even if they are offshore or near-shore populations. ...
... This suggests that pelagic, generalist prey species can significantly condition the modifications in the distribution area of the dolphinids that preferentially consume them. In this respect, in relation to climate change, the authors of [1] consider the distribution of the three species discussed here to be "expanding", which may be related to what has been argued above. ...
Article
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A review of the prey of three amphiatlantic dolphin species, Tursiops truncatus, Stenella coeruleoalba and Delphinus delphis, is carried out. The main objective of this work is to review the feeding of these species in the Atlantic in order to assess the degrees of trophic competition and speciation pressure. A total of 103 fish families, 22 cephalopod families and 19 crustacean families have been counted, from which the species identified to the genus level only included seventy-one fish, twenty cephalopods and five crustaceans, and the total species identified included three-hundred-one fish, fifty cephalopods and twenty-six crustaceans. The most consumed prey were fish, followed by cephalopods and crustaceans. The exclusive prey consumed by each of the three dolphin species, as well as those shared by all or at least two of them, have also been counted. T. truncatus is the most general; however, the western Atlantic populations exhibit high dietary specialization compared to the eastern Atlantic populations, reflecting strong speciation pressure on both sides of the Atlantic. D. delphis and S. coeruleoalba, despite their amphiatlantism, have hardly been studied in the western Atlantic, except for a few references in the southern hemisphere, so the fundamental differences between the two species and their comparison with T. truncatus have been established with records from the eastern Atlantic. All three dolphin species have been observed to be expanding, especially D. delphis. This northward expansion and that of their prey is discussed.
... Consequently, the viability of these small subpopulations was reduced due to inbreeding depression and the reduction of population fitness, compromising their ability to cope with environmental fluctuations and anthropogenic impacts (Paudel & Koprowski, 2020). The reduced capacity of small populations to respond to environmental fluctuations is a great concern with Earth's warming oceans (MacLeod, 2009). ...
... growth, an effect which is likely compounded by the low level of dispersal and gene flow around the species' range(Hamner et al., 2012).Additionally, factors including potential reductions in prey species abundance, infection with diseases such as toxoplasmosis and warming waters due to climate change are all possible explanations for a lack of observed population growth (e.g.MacLeod, 2009;Roe et al., 2013).Combining the use of visual methods and PAM provides an interesting comparison of differing indicators to quantify the risk of bycatch. Using photo-ID as a tool to estimate abundance and monitor population trends contributes to a robust understanding of the inherent vulnerability of this subpopulation to all risks due to its small size. ...
Article
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Hector's dolphin ( Cephalorhynchus hectori ) is an endangered species endemic to the coastal waters of Aotearoa New Zealand. To address the unsustainable bycatch of Hector's dolphins, restrictions on commercial gillnetting within 4 nautical miles of the coast were implemented in 2008, covering most of the South Island's east and south coasts. A small subpopulation of Hector's dolphins, estimated at 42 (95% CI: 19–92) in 2012, is located off Dunedin, on the south‐east coast of the South Island. It is known from other locations that Hector's dolphins are distributed well beyond 4 nautical miles from the coast and hence are vulnerable to ongoing gillnetting. In this study, a combination of boat‐based surveys, passive acoustic monitoring (PAM) and analysis of fishing effort were used to generate an up‐to‐date abundance estimate for Hector's dolphins off Dunedin and assess their vulnerability to commercial fishing. In the summer of 2021, abundance was estimated at 41 individuals (95% CI = 31–54), providing no evidence for population change since 2012. Analysis of visual sighting data indicated ongoing overlap between Hector's dolphins and commercial fishing effort. Using PAM, Hector's dolphins were detected on 94% of days at a location approximately 0.3 nautical miles from the coast, suggesting that shallow waters provide critical habitat for these dolphins year‐round. At an offshore mooring, approximately 4.5 nautical miles from the coast and therefore outside the area in which gillnetting is prohibited, detections were made on 35% of days, indicating potential for direct overlap with commercial fisheries. The inherent vulnerability of small populations to extinction highlights the need to take a precautionary approach to the management of Dunedin's Hector's dolphins if population recovery is to be facilitated.
... Cetaceans exhibit complex social behaviour adapting to environmental changes on local and global scales and facing many anthropogenic pressures in the Mediterranean Sea [6], [7]. In this basin they suffer for habitats fragmentation and loss [8], variations in distribution and availability of resources [9], fishing, shipping collision, noise and chemical pollution [9], [10]. ...
... Cetaceans exhibit complex social behaviour adapting to environmental changes on local and global scales and facing many anthropogenic pressures in the Mediterranean Sea [6], [7]. In this basin they suffer for habitats fragmentation and loss [8], variations in distribution and availability of resources [9], fishing, shipping collision, noise and chemical pollution [9], [10]. ...
... Microsoft Excel was used to produce data figures and tables. 1985-1986-2000Guzón-Zatarain, 2002 San Diego 369 997 1981-19891996-1997199820042009Dudzik, 1999Lang, 2002Dudzik et al., 2006 ...
... The CCE has been identified as one of the global marine "hotspots" where ocean warming is proceeding at the fastest rate (Hobday & Pecl, 2014), increasing the probability of extreme environmental conditions such as marine heatwaves attributable to anthropogenic warming (Laufkötter et al., 2020). California coastal bottlenose dolphins, like other marine taxa, can reasonably be expected to continue moving to higher latitudes (MacLeod, 2009;Pinsky et al., 2013). ...
Article
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California coastal bottlenose dolphins (Tursiops truncatus) comprise a distinct ecotype that typi-cally inhabits waters < 1 km from shore and about 10 to 30 m deep, often to the surf zone (Defran & Weller, 1999; Defran et al., 1999; Bearzi et al., 2009; Perrin et al., 2011). An offshore bottlenose dolphin ecotype is found in deeper waters of California, usually more than a few kilometers from shore to well beyond the continental shelf edge (Defran & Weller, 1999; Bearzi et al., 2009; Perrin et al., 2011; Lowther-Thieleking et al., 2014). The National Marine Fisheries Service (NMFS) manages these ecotypes as separate stocks (Carretta et al., 2017), differentiated by cranial morphology, diet, parasite load (Walker, 1981; Perrin et al., 2011), and genetics (Lowther-Thieleking et al., 2014). The two forms, however, cannot be reliably identified in the field based on external appearance (Walker, 1981; Leatherwood et al., 1982)
... Empirical and modelled studies indicate climate change will likely result in abundance and distribution shifts for marine mammals (Becker et al., 2019;Derville et al., 2019;Hamilton et al., 2019;MacLeod, 2009). However, even though modelled predictions for Guiana dolphins do not exist yet, a study is ongoing in Brazil (Rodrigo Tardin, pers. ...
Article
In 2014, a Resolution was approved by the IWC for establishing new, specific Terms of Reference to consolidate the Scientific Committee’s mandate on small cetaceans within its broader working program. This program opens the possibility of periodic reviews about the current knowledge and threats, as well as the possibility to implement Conservation Plans for Endangered Species within the scope of the IWC when appropriate. The first Conservation and Management Plan for a small cetacean was proposed for the franciscana dolphin (Pontoporia blainvillei) and endorsed by the Commission in 2016. In recent years, the Scientific Committee has worked to better understand the extent of multiple disturbances on small cetaceans - habitat degradation, incidental and intentional catches (for human consumption, bait, trade and traditional use) - to mitigate these threats. This task force resulted in a series of workshops to enable local research groups to collect, share and analyse data aiming to paint a clearer broad picture of the conservation status of these species. River and estuarine dolphins in South America have been of great concern by the Small Cetacean Sub-committee (SM). During the IWC/67b Scientific Committee Meeting, held in Bled in 2018, Slovenia, the sub-committee on small cetaceans listed the Guiana dolphin (Sotalia guianensis) as a priority species for an evaluation of its conservation status in the upcoming years (2019/20 – presented at the meeting as SC/67b/SM/WP/12). The Guiana dolphin is restricted to coastal areas, including estuaries and bays in western tropical South America, from Nicaragua in Central America to Santa Catarina state in southern Brazil (Flores and Da Silva, 2009). Due to its exclusive coastal habits, the distribution of Guiana dolphins overlaps with densely human coastal populations, raising concerns on the status of various populations (Avila et al., 2018). It is important to clarify that although the taxonomy of this genus has been controversial, some of the main questions, regarding the taxonomic identification of Sotalia dolphins in the Maracaibo Lake and in the Orinoco River, have been recently confirmed to be Sotalia guianensis (Caballero et al., 2018; Caballero et al., 2010). The Guiana dolphin was previously listed by IUCN Red List as ‘Data deficient’ (DD) because the data available on abundance, trends, and mortality levels or rates were considered inadequate for assigning it to a single Red List category at the time (Secchi, 2012). However, the current assessment classified the species as ‘Near threatened’ (NT) (Secchi et al., 2018), approaching criterion A2d+3d+4d. Regional assessments classified the species in different categories depending on the country and availability of data on each population (details in the section ‘Management and Conservation actions’). In 2006, the SM reviewed the status of the Sotalia genus, as part of a review of the small cetaceans of the Caribbean and the western tropical Atlantic. Since then, not only the taxonomy of the genus has been clarified, but also new data on the dolphin populations from the Orinoco River, French Guiana and Maracaibo Lake has been collected and analysed. While bycatch in artisanal gillnets is a major threat to Guiana dolphin populations, other threats such as intentional captures for bait, habitat loss, high contaminant load, and diseases (MeCV, herpesvirus, skin diseases of unknown aetiology), are emerging factors depleting some Guiana dolphin populations. For example, recently a high mortality event in the populations of Sepetiba and Ilha Grande bays in southeastern Brazil has been associated with morbillivirus (Groch et al., 2018). Also, deliberate capture of Guiana dolphins for human consumption has been recorded in Maracaibo Lake (Yurasi Briceño, pers. comm.; Barrios-Garrido et al. (2015) where the population is exposed to pollutants, particularly from oil spills (Espinoza-Rodríguez et al., 2019). Throughout its distribution, Guiana dolphins are facing habitat degradation and loss due to anthropogenic activities, such as high boat traffic and their high noise levels, eutrophication due to run-off and pollution from agriculture, mining and industrial activities to name but a few (Barrios-Garrido et al., 2016; Crespo et al., 2010; Secchi et al., 2018). Given these threats, an assessment of population structure and viability, temporal trends in abundance and in space use, and estimative of population connectivity are urgently needed to guide discussions by the SM sub-committee, regarding the sub-committee priority agenda focusing on riverine and estuarine dolphins from South America (IWC, 2019). A pre-assessment of the status of knowledge about Sotalia guianensis was proposed, due to the difficulty in obtaining summarised data in a timely manner during IWC annual Scientific Committee meetings, since much information is scattered in grey literature in local research groups along the wide distribution range of the species. The pre-assessment plan included holding two intersessional workshops following SC68B and probably SC69A. Dr. Camila Domit volunteered to lead the organisation of these workshops in partnership with Centro Nacional de Pesquisa e Conservação de Mamíferos Aquáticos do Instituto Chico Mendes de Conservação a Biodiversidade (CMA/ICMBio), Brazil. The first Guiana Dolphin (GD) Pre-Assessment Workshop was held in the city of Lima in October 2018, during the SOLAMAC meeting. The attendance was limited and composed mainly of researchers from south/southeastern Brazil, in addition to one researcher from Colombia. They mapped resident populations of Guiana dolphins and the ongoing research efforts, as well as they listed the research teams working with the species along its distribution that would be relevant to conduct the review. The group also delineated a participative strategy to compile the knowledge about Guiana dolphins supporting a future assessment. Because the species distribution is transboundary, covering an extensive coastal area, and there are many experts focusing on this species, the group decided to develop an online questionnaire to circulate for all institutions, research teams and individuals identified. A total of 35 experts answered the questionnaire (see Annex B for their contact details), including their opinions for prioritising locations and scientific researches in supporting improvements in conservation actions. The results are summarised in the ‘Expert elicitation’ section of this report. The Second Intersessional Workshop for Pre-Assessing the Status of Knowledge of Guiana Dolphins had two goals. The first was gathering and analysing information collected by the online questionnaire; the second, was compiling the available information on a series of population, biological and ecological parameters, as well as about threats, along the species distribution. Supported by the compiled knowledge, the participants collaborated to delineate conservation measures and research needs both in national and international contexts. The second Workshop was held in Santos, São Paulo, from 26-28 November 2019, at the Instituto Chico Mendes de Conservação da Biodiversidade/Centro Nacional de Pesquisa e Conservação de Mamíferos Aquáticos (ICMBIO/CMA). The Workshop was divided into five sessions, following the priority topics listed by the IWC for the conservation of the species: (1) population structure; (2) abundance and population trends; (3) biological parameters; (4) threats and its potential effects; and (5) management and conservation. A list of experts relevant to the aims of the Workshop from each country were identified during the SC/67b and the Guiana Dolphin Workshop held in Peru during the 2018 SOLAMAC meeting, and in consultation with the Scientific Committee (SC) Vice-Chair, and co-Chairs of SM. There were 13 experts on Guiana dolphin research from three countries (Brazil, Colombia and Venezuela) and another 20 participants to the Workshop. Information gathered from the literature review, ongoing projects and the expert elicitation via online questionnaire were used by the group of Point of Contact (POCs) and other co-authors to compile and present the best up-to-date information on the species. The participants list is given as Annex A and the Agenda is given as Annex C.
... However, the relationship between received level of vessel noise and foraging behavior for each phase of odontocete foraging and the mechanism(s) by which vessel noise interferes with foraging are unknown. Given the critical relationship between foraging, survival, and reproduction, the spectral overlap between vessel noise and echolocation sounds (Burnham et al., 2023;Veirs et al., 2016;Wladichuk et al., 2019), the positive effects of vessel quantity and speed on noise level , the growing intensity and spatiotemporal extent of vessel noise globally (Duarte et al., 2021;Kaplan & Solomon, 2016;Possenti et al., 2024), the at-risk status of many odontocetes worldwide (Chen et al., 2022;Davidson et al., 2012;IUCN, 2022;MacLeod, 2009), and their role as apex predators in their marine ecosystems, understanding vessel noise impacts on the foraging ecology of odontocetes is an urgent conservation priority (Duarte et al., 2021;. Endangered Species Act (DFO, 2017;National Marine Fisheries Service, 2016). ...
Article
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Understanding how the environment mediates an organism's ability to meet basic survival requirements is a fundamental goal of ecology. Vessel noise is a global threat to marine ecosystems and is increasing in intensity and spatiotemporal extent due to growth in shipping coupled with physical changes to ocean soundscapes from ocean warming and acidification. Odontocetes rely on biosonar to forage, yet determining the consequences of vessel noise on foraging has been limited by the challenges of observing underwater foraging outcomes and measuring noise levels received by individuals. To address these challenges, we leveraged a unique acoustic and movement dataset from 25 animal‐borne biologging tags temporarily attached to individuals from two populations of fish‐eating killer whales ( Orcinus orca ) in highly transited coastal waters to (1) test for the effects of vessel noise on foraging behaviors—searching (slow‐click echolocation), pursuit (buzzes), and capture and (2) investigate the mechanism of interference. For every 1 dB increase in maximum noise level, there was a 4% increase in the odds of searching for prey by both sexes, a 58% decrease in the odds of pursuit by females and a 12.5% decrease in the odds of prey capture by both sexes. Moreover, all but one deep (≥75 m) foraging attempt with noise ≥110 dB re 1 μPa (15–45 kHz band; n = 6 dives by n = 4 whales) resulted in failed prey capture. These responses are consistent with an auditory masking mechanism. Our findings demonstrate the effects of vessel noise across multiple phases of odontocete foraging, underscoring the importance of managing anthropogenic inputs into soundscapes to achieve conservation objectives for acoustically sensitive species. While the timescales for recovering depleted prey species may span decades, these findings suggest that complementary actions to reduce ocean noise in the short term offer a critical pathway for recovering odontocete foraging opportunities.
... A number of toothed and baleen cetacean species have shown distribution shifts northwards in the Northeast Atlantic off Ireland associated with climate change (Evans & Waggitt, 2020;MacLeod, 2009 phin Lagenorhynchus acutus (Gray 1828), have shifted more northwards to remain within cooler waters, but these movements are likely also linked to prey habitat preferences (Chosson et al., 2023;Evans & Waggitt, 2020;Levesque et al., 2023;Plint et al., 2023). Baleen whale strandings (primarily minke whales Balaenoptera acutorostrata) along the coasts of Ireland and the UK increased in northern areas between 1990 and 2020, but it was not clear whether climate change was a significant factor in this increase or whether other variables such as increased observer effort or population increase explained the increased prevalence in northern areas compared to the south (Snell et al., 2023). ...
Article
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Sperm whales spatially segregate by sex and social behavior as they mature. In the North Atlantic, male whales move to higher latitudes as far as Svalbard at 80° N, while females and young whales typically remain around lower latitudes below 40–45° N. The Azores, Madeira, and the Canary Islands constitute important nursery grounds for female and young sperm whales. Irish waters represent a midpoint for this species’ spatial segregation in the Northeast Atlantic, where the species occurs along the submarine canyon systems to the west of the country. Historically, just male whales were thought to be found in this region between 51 and 55° N, but one adult female was caught by commercial whalers in 1910, and a 5.49 m calf was found stranded in 1916. Between 1995 and 2023, 10 female sperm whales have been stranded around the coast of Ireland. Eight of these whales have been stranded since 2013, and there has been at least one stranding per year between 2019 and 2023. Four of these strandings have occurred in Donegal in the northwest of Ireland, indicating the presence of female whales along the continental shelf off this region. Two females were stranded within a day of each other and were found in similar states of decomposition in February 2022, indicating that they may have been part of the same group rather than being lone vagrant individuals. Sperm whale calves and juveniles were also sighted in Irish waters in 2001, 2004, and 2010 in the Rockall Trough, along the Porcupine Bank and Goban Spur, where between 1 and 3 individuals were observed on four occasions while one calf live stranded in 2004. These records indicate a historical presence of female and young sperm whales in this region but that an apparent increase in occurrence has taken place over the past decade.
... Environmental change has the potential to result in a range expansion for harbour porpoise (MacLeod, 2009;van Weelden et al., 2021). Changes in prey distribution associated with the change in seawater temperature is considered to be the key driver of such change. ...
Technical Report
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https://www.ascobans.org/sites/default/files/document/ascobans_mop10_doc6.1.3b_nsp-revision.pdf
... Variability in the spatiotemporal presence of marine mammals has been documented for many species, with increasing variability often observed as previously depleted populations increase in number and environmental conditions continue to change [3,58,59]. This variability introduces challenges for the effective monitoring and management of species, particularly given that an environmental impact assessment is typically only undertaken at the approvals stage of an offshore industry project or activity to inform mitigation and management over the entire project life. ...
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An understanding of the spatial and temporal range of marine mammals, and identification of habitats that support critical behaviours is fundamental for effective species management and conservation. The humpback whale ( Megaptera novaeangliae ), while considered to be recovered in Australian waters, is subject to increasing levels of anthropogenic pressure across its migratory range. Historically, the Western Australian (WA) population has been known to calf in the north-west of WA in the Kimberley region (15–18° S), with recent records of calving extending as far south as Exmouth, Western Australia (21–22° S). This paper presents recent evidence of humpback whale calves being born over 1500 km further south in southwest WA (33–34° S), along their northern migratory route, including live sightings of neonates, and strandings of deceased neonate calves. The presence of neonates outside of known calving grounds presents challenges for species conservation and management with effective mitigation and management of anthropogenic pressures contingent on a contemporary understanding of species presence and behaviour. Further, there is considerable concern for the viability of calves this far south on their migratory route where water temperatures are cooler and sheltered areas for resting are more limited.
... As our rapidly changing climate continues to affect the distribution of marine foraging habitats, it is important that researchers can predict the shifting movement patterns (MacLeod, 2009) of protected species such as Pacific white-sided dolphins who are known to interact with fisheries (Carretta et al., 2022). The two cryptic populations are currently managed as a single stock by the National Marine Fisheries Service (NMFS) as they are visually indistinguishable (Carretta et al., 2022). ...
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Aim This study investigates the biogeographic patterns of Pacific white‐sided dolphins (Lagenorhynchus obliquidens) in the Eastern North Pacific based on long‐term passive acoustic records. We aim to elucidate the ecological and behavioural significance of distinct echolocation click types and their implications for population delineation, geographic distribution, environmental adaptation and management. Location Eastern North Pacific Ocean. Time Period 2005–2021. Major Taxa Studied Pacific white‐sided dolphin. Methods Over 50 cumulative years of passive acoustic monitoring (PAM) data from 14 locations were analyzed using a deep neural network to classify two distinct Pacific white‐sided dolphin echolocation click types. The study assessed spatial, diel, seasonal and interannual patterns of the two click types, correlating them with major environmental drivers such as the El Niño Southern Oscillation and the North Pacific Gyre Oscillation, and modeling long‐term spatial‐seasonal patterns. Results Distinct spatial, diel and seasonal patterns were observed for each click type. Significant biogeographical shifts in presence were observed following the 2014–2016 marine heatwave event. Main Conclusions Distinct spatial distributions of the two click types support the hypothesis that Pacific white‐sided dolphins produce population‐specific echolocation clicks. Seasonal and diel patterns suggest spatiotemporal niche partitioning between the populations in Southern California. Interannual changes, notably initiated during the 2014–2016 marine heatwave, indicate climate‐driven range expansions and contractions related to gradual tropicalization of the Southern California Bight.
... Physical specimens from a stranding also provide an opportunity to obtain genetic material for genome sequencing. These genomes can be a pathway towards understanding past population size changes, adaptation, and vulnerability to changing climate -an aspect particularly important for the hourglass dolphin in the rapidly changing Antarctic environment (MacLeod 2009). In addition, considerable uncertainty remains around the evolutionary relationships between Lissodelphininae -the subfamily of true dolphins to which the hourglass dolphin belongs Vollmer et al. 2019;Harlin-Cognato and Honeycutt 2006;Cope 1866;McGowen 2011;Banguera-Hinestroza et al. 2014;Leduc, Perrin, and Dizon 1999). ...
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The hourglass dolphin ( Lagenorhynchus cruciger ) is a small cetacean species of the Southern Ocean, with significance to iwi Māori ( Māori tribes ) of Aotearoa New Zealand as taonga ( treasured/valued ). Due to the remoteness and difficulty of surveying Antarctic waters, it remains one of the least-studied dolphin species. A recent stranding of an hourglass dolphin represented a rare opportunity to generate a genome assembly as a resource for future study into the conservation and evolutionary biology of this species. In this study, we present a high-quality genome assembly of an hourglass dolphin individual using a single sequencing platform, Oxford Nanopore Technologies, coupled with computationally efficient assembly methods. Our assembly strategy yielded a genome of high contiguity (N50 of 8.07 Mbp) and quality (98.3% BUSCO completeness). Compared to other Delphinoidea reference genomes, this assembly has fewer missing BUSCOs than any except Orcinus orca , more single-copy complete BUSCOs than any except Phocoena sinus , and 20% fewer duplicated BUSCOs than the average Delphinoidea reference genome. This suggests that it is one of the most complete and accurate marine mammal genomes to date. This study showcases the feasibility of a cost-effective mammalian genome assembly method, allowing for genomic data generation outside the traditional confines of academia and/or resource-rich genome assembly hubs, and facilitating the ability to uphold Indigenous data sovereignty. In the future the genome assembly presented here will allow valuable insights into the past population size changes, adaptation, vulnerability to future climate change of the hourglass dolphin and related species.
... Shifts in cetacean distribution associated with climate change are increasingly evident worldwide due to altered prey resources and rising ocean temperatures [21,22]. Predictive studies indicate that beaked whales, along with other cetaceans, are likely to experience continued range shifts towards higher latitudes, resulting in reduced suitable habitats [23][24][25][26][27][28]. These changes could exacerbate other stressors faced by beaked whales and lead to new challenges, such as increased fishing pressures, altered noise exposure due to new shipping routes and heightened disease outbreaks [29][30][31]. ...
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This review comprehensively evaluates the impacts of anthropogenic threats on beaked whales (Ziphiidae)—a taxonomic group characterized by cryptic biology, deep dives and remote offshore habitat, which have challenged direct scientific observation. By synthesizing information published in peer-reviewed studies and grey literature, we identified available evidence of impacts across 14 threats for each Ziphiidae species. Threats were assessed based on their pathways of effects on individuals, revealing many gaps in scientific understanding of the risks faced by beaked whales. By applying a comprehensive taxon-level analysis, we found evidence that all beaked whale species are affected by multiple stressors, with climate change, entanglement and plastic pollution being the most common threats documented across beaked whale species. Threats assessed as having a serious impact on individuals included whaling, military sonar, entanglement, depredation, vessel strikes, plastics and oil spills. This review emphasizes the urgent need for targeted research to address a range of uncertainties, including cumulative and population-level impacts. Understanding the evidence and pathways of the effects of stressors on individuals can support future assessments, guide practical mitigation strategies and advance current understanding of anthropogenic impacts on rare and elusive marine species.
... By combining animal object detection through artificial intelligence and climate change projections from the Copernicus Climate Change Service (C3S), we can contribute both effectively and at low costs to identify and establish new high seas habitat protected areas, which may be essential in the conservation of beluga whales and other threatened species. Cetacean species with a range limited to non-tropical waters are more likely to be impacted by water temperature alterations (MacLeod, 2009). Beluga whales (Delphinapterus leucas) (Pallas, 1776) are strictly ice-dependent species that inhabit isolated Arctic Ocean waters (Suydam et al., 2001) and, thus, may comprise good bioindicators concerning how climate change can affect other icedependent Arctic species. ...
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Climate change has been shown to alter the spatial distribution of whales and other marine mammals. Fast changing ocean temperatures may also affect the spatial distribution of whales at a finer scale, namely within populations, including aggregation behaviour. Our ability to analyze the impact of climate change on whale aggregation behavior, however, has been limited by our ability to collect spatial observation data over large areas. To overcome this limitation, this study analyzed open-access satellite imagery obtained between 2007 and 2020 in Canada, Russia, and Alaska using Deep Convolutional Neural Networks (CNN) to detect 1,980 beluga whales in 11 populations and to quantify their aggregation patterns within their populations. Subsequently, we examined the relationship between sea surface temperature (SST) and the intra-population spatial patterns of beluga whales during summer seasons, when these whales normally aggregate. We detected a negative correlation between SST and the frequency of beluga whale aggregation, suggesting that warming temperatures may impact beluga whale spatio-behavioral dynamics. Considering that the relative abundance of beluga whales is declining and the future SST projections in these Arctic Ocean locations, climate change may pose yet another threat to beluga whales and other ice-dependent species.
... Generally, climate change may have a lower impact on certain cetacean species (particularly those that are more resilient and mobile), while other species will be placed under extreme pressure by effects that may be largely indirect, and mediated via ecosystem and biodiversity changes, including changes in prey availability (Simmonds and Elliot, 2009;Sousa et al., 2019;van Weelden et al., 2021). Cetacean communities may reorganise in response to ocean warming, with shifts in distribution and losses of resilience Learmonth et al., 2006;Whitehead et al., 2008;MacLeod, 2009). ...
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The Adriatic Sea is one of the Mediterranean areas most exposed to cumulative human stressors. This semi-enclosed and largely shallow basin has been subjected to intensive exploitation and destructive fishing practices for decades, resulting in biodiversity decline and poor ecosystem health. Diversity of cetaceans is lower than in other parts of the Mediterranean, and the extant dolphins and whales have been facing threats that include the combined effects of habitat loss and degradation, prey depletion, incidental mortality and injury caused by fisheries, anthropogenic noise, chemical contamination and climate change. Here, we report information for the nine cetacean species known to occur in the basin (classified as either regular, visitor or vagrant), plus three species characterized by a single record. For these species, we review evidence from field research and other studies-with a bias towards the common bottlenose dolphin *Tursiops truncatus* (by far the most intensively-studied cetacean in this area). We also describe and characterize the main threats to cetaceans in the Adriatic, relying on recent literature as well as historical information that helps frame the present status of cetaceans in the context of past human impacts (particularly the extensive killing campaigns conducted until the 1960s). Finally, we provide management recommendations to inform and guide the action that must be taken in compliance with extant legislation, marine conservation directives and international commitments to protect marine biodiversity.
... The patterns of occurrence and distribution of species are influenced by a variety of physical, biological, and environmental parameters operating at different spatial and temporal scales (e.g., Hillebrand, 2004;Whitehead et al., 2008;Tittensor et al., 2010;Torreblanca et al., 2022), as well as by the variability of these parameters due to natural fluctuations and human induced changes (e.g., MacLeod, 2009;Lu et al., 2023;Snell et al., 2023). ...
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The ACCOBAMS Survey Initiative (ASI) is the first synoptic large-scale survey of the entire ACCOBAMS Area and as such it plays a key role in filling the current gaps in our biological and ecological knowledge of large vertebrate species occurring in the region. Data gathered during the ASI were analyzed in a distance sampling surface-modelling framework to assess the summer distribution, densities and patterns, as well as to investigate the correlates of these parameters, for large vertebrate species and taxa in the Mediterranean Basin. Static and dynamic explanatory variables, including water depth (m), distance to depth contours (km), distance to canyons and seabed slope (km), sea surface temperature (°C), mixed layer depth (m) and levels of chlorophyll-a (mg/l), were considered to predict density and compute its variance spatially at a resolution of 10x10 km. A strong longitudinal gradient from low densities in the east to high densities in the west is shared by most taxa. In addition, several taxa also showed a less marked latitudinal gradient varying in direction according to species, and finally, a few of them exhibited patchy distributions.
... Projections of future habitat for whales and temperate dolphins in this study show overall habitat loss in response to environmental conditions in agreement with previous work (MacLeod, 2009;Pecl et al., 2017;Pinsky et al., 2021). For example, projections suggest a constraint of habitat along the California coast and a shift poleward of 100 km for humpback whales (Appendices S6 and S14). ...
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Aim Marine biodiversity faces unprecedented threats from anthropogenic climate change. Ecosystem responses to climate change have exhibited substantial variability in the direction and magnitude of redistribution, posing challenges for developing effective climate‐adaptive marine management strategies. Location The California Current Ecosystem (CCE), USA. Methods We project suitable habitat for 10 highly migratory species in the California Current System using an ensemble of three high‐resolution (~10 km) downscaled ocean projections under the Representative Concentration Pathway 8.5 (RCP8.5). Spanning the period from 1980 to 2100, our analysis focuses on assessing the direction and distance of distributional shifts, as well as changes in core habitat area for each species. Results Our findings reveal a divergent response among species to climate impacts. Specifically, four species were projected to undergo significant poleward shifts exceeding 100 km, and gain habitat (~7%–60%) in response to climate change. Conversely, six species were projected to shift towards the coast, resulting in a loss of habitat ranging from 10% to 66% by the end of the century. These divergent responses could typically be characterized by the mode of thermoregulation (i.e. ectotherm vs. endotherm) and species' affiliations with cool and productive upwelled waters that are characteristic of the region. Furthermore, our study highlights an increase in niche overlap between protected species and those targeted by fisheries, which may lead to increased human interaction events under climate change. Main Conclusions By providing valuable species distribution projections, our research contributes to the understanding of climate change effects on marine biodiversity and offers critical insight and support for developing climate‐ready management of protected and fished species.
... In the western waters of Scotland, for instance, the relative strandings of white-beaked dolphins (a cold-water species) and common dolphins (a warm-water species) respond differently to variations in water temperature [111]. The majority of cetaceans recorded in this study are warm-water species, and as water temperatures rise, they are likely to migrate to polar regions, except for some particular species with high-site fidelity [112], thereby reducing their activity range. Therefore, if cetaceans migrate northward in years with higher temperatures, the abundance in the study area decreases, resulting in fewer strandings. ...
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The frequency of cetacean strandings is increasing, with multiple causes identified. We examined temporal and spatial trends in stranding numbers along the coastal areas of the East China Sea from 1990 to 2021. Using structural equation models, we analyzed the relationships between strandings and climate, oceanic properties, and human activities. Our findings revealed time-dependent interannual variability in strandings but no linear trend, indicating relative stability in cetacean strandings. Seasonal patterns were observed only in narrow-ridged finless porpoises (Neophocaena asiaeorientalis), with significant spring increases (March to May). Clustering of strandings occurred in central Fujian and northern/southern Taiwan, according to spatial analysis. The impact of variables on cetacean strandings varied across time periods. Storm surges, coastal fishing, and the Pacific decadal oscillation were associated with stranding events from 1990 to 2006. However, from 2006 to 2021, the influence of storm surges weakened, while the climate index only indirectly affected strandings through sea surface temperature and salinity, with an increased intensity in the effects of winter sea surface temperature and salinity. Structural equation models unveiled the cascading effects of environmental changes on strandings. This study reports changing trends in cetacean strandings and identifies relevant variables. Although not exhaustive, understanding the reasons behind strandings enhances our comprehension of cetacean responses to environmental changes, supporting targeted conservation and management efforts.
... In addition, water temperatures in the GOM are experiencing faster warming than any other ocean ecosystem (Pershing et al., 2015 ). Warming waters are expected to have marked impacts on the distribution and life history of cetaceans (MacLeod, 2009, Chambault et al., 2022, Wild et al., 2019, either directly through thermoregulation requirements or indirectly through impacts on productivity and prey availability (Martin et al., 2023 ). Continued and expanded monitoring of porpoises and their behaviour in this region will be a critical component in future conservation efforts. ...
Article
Offshore wind energy is set to develop rapidly in waters off the east coast of the United States. There is considerable overlap between areas proposed for offshore wind development and harbour porpoise habitats in the Gulf of Maine (GOM) and Southern New England waters. Baseline data on the occurrence and foraging activity of porpoises was collected using 10 echolocation-click detectors (F-PODs) from 2020 to 2022. Porpoises were present year-round in the GOM with peak detections in the summer and fall. In line with previous reported distribution patterns, porpoise occurrence in Southern New England was high in fall, winter and spring, but porpoises were largely absent in the summer. One site in the GOM, Mount Desert Rock (MDR), was an anomaly as porpoise detections here were highest in the winter. On average, foraging was identified in 29% of all porpoise detections, with the most foraging occurring at MDR (53%). Results from generalized additive models suggest that time of year, hour of day, lunar illumination, and temperature are significant contributors to porpoise presence and/or foraging effort. European studies show that harbour porpoises exhibit behavioural changes, disruption of foraging and displacement due to wind energy development. Therefore, early identification of areas of importance, mitigating impacts, and monitoring changes is essential for the protection of this species in US waters.
... Climate change is likely to have both direct and indirect effects on common dolphins in European waters. Increasing sea surface temperatures will cause shifts in the distribution of suitable habitat, causing expansion of the range towards the poles and a contraction away from the tropics, associated with an overall contraction or expansion of the range if the area of habitat lost is not matched by the area gained (MacLeod 2009;Lambert et al. 2011;Cañadas and Vázquez 2017). In the Alborán Sea, Cañadas and Vázquez (2017) concluded that common dolphins will experience a reduction of suitable habitat due to warming waters. ...
... Thus, in our study, this stranding event in the Gulf of Thailand provides evidence of an extralimital range of distribution not documented previously for this species. The extension of the living range south into the Gulf of Thailand may be due to a reduction in the distribution range of their main prey (krill) or to competition with other baleen species for this food source, perhaps due to changing water temperatures as a result of climate change [43][44][45]. Thus, it is possible they are seeking alternative feeding habitats outside the normal range. ...
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On 5 September 2022, a dead baleen whale was found stranded at Laem Phak Bia, Phetchaburi, the Gulf of Thailand, Thailand but could not be identified because it was in an advanced stage of decomposition. It was first suspected to be Omura’s whale (Balaenoptera Omurai), as that is a common species in the Gulf of Thailand. However, the cranium morphology was different from B. omurai and more similar to the common minke whale (Balaenoptera acutorostrata) from the North Pacific Ocean, which has never been reported in Thai territorial waters. The mitochondrial DNA control region (D-loop) was then used to identify the species through the Basic Local Alignment Search Tool (BLAST) available at the National Center for Biotechnology Information (NCBI) GenBank, which resulted in a high percent identity, 96.49 to 98.84, with B. acutorostrata. A Bayesian phylogenetic tree was further used to confirm the species, which grouped with B. acutorostrata from the North Pacific Ocean. This study provides evidence of the first stranding event of B. acutorostrata in the Gulf of Thailand. It is new information that extends previous knowledge on the distribution of the common minke whale and raises the need for more active surveys of cetaceans in the South China Sea going forward.
... The anthropogenically driven increase in ocean temperature has been predicted to result in changes in cetacean reproductive success, abundance, and distribution (MacLeod, 2009;Tynan & Demaster, 1997;Whitehead et al., 2008). Humpback whales in both hemispheres now arrive at breeding grounds earlier than in previous years, presumably as a response to processes set forth by rising temperatures that affect the timing of ice-sheet breakage, which causes a decline in feeding resources (Avila et al., 2020;Ramp et al., 2015). ...
Article
Humpback whale (Megaptera novaeangliae) winter distribution and core habitats in relation to El Niño Southern Oscillation and depth in coastal and oceanic waters off Ecuador ABSTRACT Southern Pacific Humpback whales (Megaptera novaeangliae) breed in subtropical and tropical waters off Perú in the south to Nicaragua in the north. The effect of warming oceans on humpback whale distribution in breeding areas remains unclear. We modelled the spatial distribution of humpback whales off the coast of Ecuador in relation to environmental variables. We analyzed the temporal variability in humpback whale sighting rates (animals/h) in a subtropical (Manabí, 1996 – 1999) and tropical (Esmeraldas, 2001 – 2019) breeding ground. At the regional scale, we found humpback whale presence was more likely in shallow waters over the continental shelf. Esmeraldas and Manabí breeding grounds are core wintering habitats with most humpback whale sightings along Ecuador. Within breeding grounds, individual sighting rates varied between and within years and in relation to local sea surface temperature anomalies (SSTa). More animals were sighted in years with cooler waters in the Esmeraldas breeding ground, while the opposite was true in Manabí. Our findings suggest that during ENSO conditions, humpback whales may reach their temperature niche limit in the warm tropical waters near Esmeraldas, while during La Niña conditions, cooler areas such as Peru and Manabi become less suitable, and whales move further North. Keywords: humpback whale, Megaptera novaeangliae, distribution, habitat, sighting rates, Sea Surface Temperature, ENSO, climate change.
... The Arctic is drastically changing due to global warming and anthropogenic activities 1 . Current alterations are influencing the temporal and spatial habitat suitability, forcing species to rapidly adapt to modifications of the environment and the food web 2,3 . Marine mammals are sentinels of these changes because their presence, behaviour, and fitness are tightly linked to ecosystem conditions 4 . ...
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The Arctic marine environment is highly affected by global warming with notable changes in habitat conditions, which have great consequences on migrating species. For example, the timing of their migration can be altered leading to changes in their occurrence in suitable areas, which are critical for their survival. In this study, seven years of acoustic data were analysed in Svalbard Islands from 2014 to 2020, revealing that the occurrence of fin whales (Balaenoptera physalus) happened all year-round. The sea surface temperature recorded reveals conditions which could be favorable for these species to persist until the Polar Night. The occurrence of songs indicated that certain individuals did not undertake the migratory journey through the southern breeding grounds, possibly using the area for mating purposes. The analyses of the Inter-Note-Interval (INI) demonstrated that over the years songs with different patterns were found. This suggests that either the fin whales are able to switch their INI patterns or that populations with different INIs are visiting during the Winter. Therefore, this study unveils the undertaking of an alternative strategy to migration movements, and the possible potential origin of the fin whales overwintering in Svalbard.
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This paper aims to review and evaluate published literature on the impact of climate change on marine mammals. A systematic method was utilized to access research works of literature on "Impact of Climate Change on Marine Mammals". A total of eighty-two (82) research papers published between the years 1976 to 2024 were accumulated and used for this review. A subjective approach was used to select the topics: impact of climate change and marine mammals. In this paper, nine (9) direct and indirect effects of climate change and environmental factors affecting marine mammals were assessed in this paper. Further, six (6) detrimental impacts of climate change on marine mammals were evaluated and presented. In addition, an integrated checklist of one hundred twenty-seven (127) marine mammal species were presented along with their current IUCN Red List status categories. Subsequently, a total of eighty-three (83) cetaceans (whales, dolphins and porpoises), thirty-four (34) pinnipeds (seals, sea lions and walruses), six (6) sirenians (manatees and dugongs) and four (4) fissipeds (polar bears and sea otters) were presented on the integrated checklist. In addition, this paper assessed some marine mammal species that are endangered and threatened with extinction such as Monachus monachus and Phocoena sinus. Legislation, conservation and implications for the management and preservation to address marine mammals and combat the effect of climate change was also presented in this review. The published works of literature established that the global marine mammal population dynamics, ecology, reproduction, abundance and distribution are all affected by the threats of climate change. The availability of prey impacts the distribution, abundance and movement of marine mammals as well as their community structure, vulnerability to toxins and disease, success of their reproduction, and, ultimately, their survival. Additionally, marine mammals are particularly vulnerable to the possible effects and repercussions of changes in salinity, pH, and CO2. This review highlights that more extensive studies on the impact of climate change on marine mammals should be done in neotropical countries since there are gaps of such information on research and published data in these biodiversity-rich regions.
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An understanding of the spatial and temporal range of marine mammals, and identification of habitats that support critical behaviours is fundamental for effective species management and conservation. The humpback whale, while considered to be recovered within Australian waters, is subject to increasing levels of anthropogenic pressure across its migratory range. Increasing population size, in concert with long term climatic change, is likely to lead to intra and inter-species competition for food resources and habitat. Historically, humpback whales have been known to calf in the Kimberley region, with recent records of calving extending into the Pilbara as far south as Ningaloo Reef, off Exmouth Western Australia. This paper presents empirical evidence of significant numbers of humpback whale calves being born over 1500 km further south in Ngari Marine Park, southwest Western Australia, along their northern migratory route, including live sightings of neonates, deceased strandings of neonate calves and evidence of killer whale predation events. The presence of calving behaviour outside of known calving grounds presents challenges for species conservation and management with effective mitigation and management of anthropogenic pressures contingent on a contemporary understanding of species presence and behaviour. Further, there is considerable concern for the viability of calves this far south on their migratory route where water temperatures are cooler and sheltered areas for resting are more limited.
Article
The data of accompanying observations of the spatial distribution, species composition and abundance of cetaceans in the southern part of the Atlantic and Indian oceans and in the coastal waters of Antarctica in the southern autumn of 2021 are presented. In total, 3 species of whales (82 sightings–136 individuals), 1 species of beaked (1 sighting–4 individuals) and 6 species of dolphins (15 sightings–324 individuals) were registered in the research area. In total, cetacean were observed 98 times, 464 individuals were registered. As in previous years, humpback whales Megaptera novaeangliae predominated (58.82%), they are successfully restoring their quantity, although they suffered greatly during whaling in the XVIII–XX centuries. Antarctic minke whales Balaenoptera bonaerensis made up 21.32%, and fin whales Balaenoptera physalus made up 19.85% of all whales. Southern right whale dolphins (83.33%) prevailed among all dolphins.
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A quarter of marine mammals are at risk of extinction, with disease and poor habitat quality contributing to population decline. Investigation of the Major Histocompatibility Complex (MHC) provides insight into species’ capacity to respond to immune and environmental challenges. The eighteen available cetacean chromosome level genomes were used to annotate MHC Class I loci, and to reconstruct the phylogenetic relationship of the described loci. The highest number of loci was observed in the striped dolphin (Stenella coeruleoalba), while the least was observed in the pygmy sperm whale (Kogia breviceps) and rough toothed dolphin (Steno bredanensis). Of the species studied, Mysticetes had the most pseudogenes. Evolutionarily, MHC Class I diverged before the speciation of cetaceans. Yet, locus one was genomically and phylogenetically similar in many species, persisting over evolutionary time. This characterisation of MHC Class I in cetaceans lays the groundwork for future population genetics and MHC expression studies.
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The Ojo de Liebre Lagoon is the largest wintering and calving area on the Baja California Peninsula for the north Pacific stock of gray whales (Eschrictius robustus), where up to 2721 individuals have been counted in a single season (January-April). This study describes the effects of spatial (zones), temporal (months), and environmental factors at the local (temperature and chlorophyll-a) and large-scale levels (Pacific Decadal Oscillation, PDO) on the abundance of gray whales in this lagoon using generalized additive models. Results suggest that larger populations are expected at temperatures below 15 ◦C and Chl-a values above 1 mg m􀀀 3 during the neutral (0􀀀 1) and positive (>1) phases of the PDO, in February and March, and around the mouth of the lagoon (zone 6). Findings highlight the importance of environmental variability on the abundance of this species at the local and large-scale levels. According to our models, the abundance of the gray whales that arrive in the Ojo de Liebre Lagoon is affected by local and large-scale environmental variability. The latter factor was evaluated by an index that integrated atmospheric and oceanic variations in the northeast and tropical Pacific Ocean. In spatial terms, the physical characteristics inside the lagoon may be the main factors that impact the distribution of whales. Management and conservation measures can use these results to improve strategies, considering the variability of the population in both local and long-term perspectives.
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Information on marine mammals and marine birds in US Pacific Northwest waters is limited but necessary to assess potential impacts from proposed and planned human activity (for example, cable installation, energy and port development) as required by regulatory permitting processes, particularly relative to recent plans for offshore wind development. We conducted daily opportunistic, non-systematic observations of marine mammals and marine birds in autumn 2014 and of marine mammals in summer 2015 to meet mitigation and monitoring requirements associated with a geophysical site characterization survey for a proposed offshore wind floating platform demonstration project off Coos Bay, Oregon. Two biologists completed observations during daylight with the naked eye and reticle binoculars from a 17-m vessel between Coos Bay and the proposed platform site 30 km offshore. In 2014, 1058 h (3244 km) of observation occurred during 3 October through 4 November, with 1182 h (4367 km) observations conducted from 10 July through 28 August 2015. In total, 543 groups (approximately 1389 individuals) representing at least 14 marine mammal species and 7444 groups (approximately 18322 individuals) representing at least 22 marine bird species were observed. Sighting rates (number of individuals observed per 100 km of observation) were higher for nearly every species of marine mammal in summer 2015 than autumn 2014. An extralimital sighting of 25 Bottlenose Dolphins (Tursiops truncatus) and 5 sightings of rare transient Killer Whales (Orcinus orca) were documented. Results address a gap in site-specific marine mammal and marine bird baseline occurrence data and information required to assess effects of proposed offshore wind development and other human-related activities near Coos Bay, Oregon, as well as climate and oceanographic changes.
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Although habitat temperature is an important determinant of species distributions, its measurement is difficult in mobile marine organisms. Chemical tracers such as alkenones constitute an alternative tool for gauging marine habitat temperature, something particularly relevant in the current scenario of global warming. The unsaturation index of alkenones, the Uk’37 index, can be used to estimate sea surface temperature (SST) in living organisms. Here, we analyse alkenone concentrations in a predator species, the fin whale, and its prey, the northern krill, both sampled in 2 areas with different SSTs: SW Iceland and NW Spain. In NW Spain (but not in SW Iceland), alkenone concentrations were higher in krill than in fin whale blubber, suggesting that they may biodilute along the trophic transfer. Consistently with local SST, the Uk’37 index was lower in the Icelandic samples of both fin whales and krill than in those from NW Spain, confirming the ability of this index to distinguish populations that are thermally separated. Whales are migratory animals; thus, the alkenones present in their blubber are a mix of those ingested locally and in recently visited regions. Consistently, the Uk’37 index showed a higher correlation with the local SST in krill than in fin whales. Alkenone turnover rates should be considered when using this proxy to assess the thermal range of the feeding habitat of a species. We conclude that the Uk’37 index is a potentially efficient tool to study the behaviour of whales, thus providing an alternative perspective to other chemical tracers.
Article
Social behaviours can allow individuals to flexibly respond to environmental change, potentially buffering adverse effects. However, individuals may respond differently to the same environmental stimulus, complicating predictions for population-level response to environmental change. Here, we show that bottlenose dolphins (Tursiops truncatus) alter their social behaviour at yearly and monthly scales in response to a proxy for food availability (salmon abundance) but do not respond to variation in a proxy for climate (the North Atlantic Oscillation index). There was also individual variation in plasticity for gregariousness and connectedness to distant parts of the social network, although these traits showed limited repeatability. By contrast, individuals showed consistent differences in clustering with their immediate social environment at the yearly scale but no individual variation in plasticity for this trait at either timescale. These results indicate that social behaviour in free-ranging cetaceans can be highly resource dependent with individuals increasing their connectedness over short timescales but possibly reducing their wider range of connection at longer timescales. Some social traits showed more individual variation in plasticity or mean behaviour than others, highlighting how predictions for the responses of populations to environmental variation must consider the type of individual variation present in the population.
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Climate change and climate variability are affecting marine mammal species and these impacts are projected to continue in the coming decades. Vulnerability assessments provide a framework for evaluating climate impacts over a broad range of species using currently available information. We conducted a trait-based climate vulnerability assessment using expert elicitation for 108 marine mammal stocks and stock groups in the western North Atlantic, Gulf of Mexico, and Caribbean Sea. Our approach combined the exposure (projected change in environmental conditions) and sensitivity (ability to tolerate and adapt to changing conditions) of marine mammal stocks to estimate vulnerability to climate change, and categorize stocks with a vulnerability index. The climate vulnerability score was very high for 44% (n = 47) of these stocks, high for 29% (n = 31), moderate for 20% (n = 22), and low for 7% (n = 8). The majority of stocks (n = 78; 72%) scored very high exposure, whereas 24% (n = 26) scored high, and 4% (n = 4) scored moderate. The sensitivity score was very high for 33% (n = 36) of these stocks, high for 18% (n = 19), moderate for 34% (n = 37), and low for 15% (n = 16). Vulnerability results were summarized for stocks in five taxonomic groups: pinnipeds (n = 4; 25% high, 75% moderate), mysticetes (n = 7; 29% very high, 57% high, 14% moderate), ziphiids (n = 8; 13% very high, 50% high, 38% moderate), delphinids (n = 84; 52% very high, 23% high, 15% moderate, 10% low), and other odontocetes (n = 5; 60% high, 40% moderate). Factors including temperature, ocean pH, and dissolved oxygen were the primary drivers of high climate exposure, with effects mediated through prey and habitat parameters. We quantified sources of uncertainty by bootstrapping vulnerability scores, conducting leave-one-out analyses of individual attributes and individual scorers, and through scoring data quality for each attribute. These results provide information for researchers, managers, and the public on marine mammal responses to climate change to enhance the development of more effective marine mammal management, restoration, and conservation activities that address current and future environmental variation and biological responses due to climate change.
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Sperm whale: Physeter macrocephalus Lin-naeus Handbook of marine mammals, Vol 4: river dolphins and the larger toothed whales Marine mammals of the world: systematics and distribution. Spec Publ No Extinction risk in the sea
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Mar Mamm Sci 12:301–307 Rice DW (1989) Sperm whale: Physeter macrocephalus Lin-naeus, 1758. In: Ridgway SH, Harrison RJ (eds) Handbook of marine mammals, Vol 4: river dolphins and the larger toothed whales. Academic Press, Cambridge, p 177–234 Rice DW (1998) Marine mammals of the world: systematics and distribution. Spec Publ No. 4, Society of Marine Mam-malogy, Beaufort, NC Roberts CM, Hawkins JP (1999) Extinction risk in the sea