Lagenorhynchus Albirostris Research Articles

A review of small cetacean hunts in Greenland

Seven odontocete species are targeted by hunters in Greenland. Beluga (Delphinapterus leucas) and narwhal (Monodon monoceros) are hunted under annual quotas. Atlantic white-sided dolphin (Lagenorhynchus acutus), white beaked dolphin (Lagenorhynchus albirostris), harbour porpoise (Phocoena phocoena), killer whale (Orcinus orca) and long-finned pilot whale (Globicephala melas) are hunted without quotas. From 1993–2023, 109, 645 small cetaceans have been recorded in the North Atlantic Marine Mammal Commission (NAMMCO) catch database as hunted in Greenland. The hunt follows the scientific advice in 3 out of 25 populations considered: the hunt is higher than the advice for 12 and there has been no assessment or advice for 10. Population trends are unknown for 14 populations, while numbers are stable or increasing in 6 and decreasing in 4. One population has been extirpated by hunting. Catches of all small cetaceans have increased since data records are available, including for narwhal and beluga since quotas have been in place. In some cases, insufficient monitoring and inaccurate reporting occur and there is a lack of data to assess struck and lost rates and times to death. Narwhals are experiencing significant declines in abundance due to hunting, particularly in East Greenland, where recovery may be compromised. To ensure the protection of small cetaceans in Greenland, management is required for all hunts, consistent with international conservation management recommendations. Measures should ensure sustainability, include stuck and lost and additional anthropogenic threats, be precautionary, based upon up-to-date knowledge of population status and trends and consider welfare aspects and recovery rates.

Features of the distribution and habitat conditions of cetaceans in the Barents Sea in the summer-autumn period 2004–2021

The aim of the paper is to identify the features of distribution of cetaceans in ice-free areas of the Barents Sea and adjacent waters in August-November and to characterize their habitat conditions (abiotic factors, distribution relative to mass fish species and macroplankton).The material of the study was the data collected by the Polar branch of VNIRO during the joint RussianNorwegian ecosystem surveys.Methods: geoprocessing and mapping of the studied parameters, comparative and statistical (principal component and correlation) analysis of the data.Results: Cetaceans were mainly observed in the western Barents Sea and distributed in waters with depths of from 23 to 2294 m, at temperatures of –1.9…10.7 °C and salinities of 33.0–35.2, the weighted averages of these parameters were 265 m, 3.1 °C and 34.7 respectively. Minke whales, fin whales, humpback whales, whitebeaked dolphins, killer whales, and porpoises were observed in waters with wide ranges of temperature and salinity, while blue whales and sperm whales were observed in waters with narrow ranges of these parameters. The lowest weighted average water temperature (0.3 °C) and salinity (34.4) were typical of humpback whale. Minke whale, fin whale, humpback whale and white-beaked dolphin had the largest overlap in their distribution with that of possible preys. Statistical analysis showed that priority preys for these cetaceans could be capelin and polar cod for the studied period. In addition, one of the possible preys for baleen whales was also macroplankton, and for the white-beaked dolphin — cod, blue whiting and redfishes.Practical significance: The results of this study can be used in studying the ecology of cetaceans in the Barents Sea, in assessing their impact on stocks of commercial fish species, as well as in ecosystem modeling.

Further Evidence for Breeding White-Beaked Dolphin (Lagenorhynchus albirostris) in Inner Danish Waters

The white-beaked dolphin (Lagenorhynchus albirostris) is the second most frequently stranded cetacean species along the Danish coastline. The northern North Sea, the Skagerrak, the Kattegat and the Danish straits are part of the species distributional range. Here, we present eight incidents of breeding activity for the white-beaked dolphin in the inner Danish waters, reviewed from yearly reports made by the National Contingency Plan concerning strandings of marine mammals in Denmark from 2009 to 2023, Danish Wildlife Diseases Surveillance reports from 2014 to 2023 and the citizen science database Naturbasen in the period 2002 to 2023. Three pregnant females, three lactating females and one calf were found stranded in the inner Danish waters. Besides this, there have been live sightings of a female with a newborn calf. We conclude that the white-beaked dolphin is breeding in the inner Danish waters.

Cetacean fauna of the southern part of the Barents Sea in winter 2019–2023 under changing climate conditions

Biophysical changes occurring in Arctic marine ecosystems under the influence of climatic factors may affect cetaceans staying here. For this reason, the urgent task is to conduct regular monitoring of marine mammals in order to assess the state of their populations and preserve the biodiversity of species. We analyzed the results of ship-based surveys of marine mammals carried out by the Polar branch of VNIRO in January–March 2019–2023 in the south of the Barents Sea and compared them with the observation data of earlier years. As the studies have shown, the winter cetacean fauna is currently represented by six species of baleen Mysticeti and toothed Odontoceti whales. White-beaked dolphin Lagenorhynchus albirostris Gray, 1846 was the most abundant and widespread species among all cetaceans; however, since 2022 we have seen a decrease in both the number of observations and abundance of this species. Fin whale Balaenoptera physalus Linnaeus, 1758 and killer whale Orcinus orca Linnaeus, 1758 were regularly registered in the study area, while sightings of harbor porpoise Phocoena phocoena Linnaeus, 1758 and humpback whale Megaptera novaeangliae Borowski, 1781 were single. Comparative analysis of the obtained data with the materials of 2012–2013 revealed some changes in the cetacean fauna that occurred during the last decade. In the waters of the southern part of the Barents Sea, there began met species that had not been previously recorded in our surveys, first of all, minke whale Balaenoptera acutorostrata Lacépède, 1804 and humpback whale. The materials we collected expanded our understanding of cetaceans staying in the western sector of the Russian Arctic during the winter.

Environmental drivers of odontocete occurrence in a nearshore temperate habitat

Nearshore coastal waters off Northumberland, UK, are important habitats for marine megafauna including marine mammals and seabirds. The area also features extensive anthropogenic activities including shipping, marine renewables development, fisheries, and tourism. Meanwhile there is lack of baseline data on odontocete occurrence to allow assessment of the potential impact from human disturbance. A recent increase in the number of sightings of common bottlenose dolphins (Tursiops truncatus) in the area has provided impetus for new data to inform conservation managers and policy makers. To provide this information, acoustic data were collected using broadband passive acoustic recorders at three sites (Druridge Bay, Newbiggin-by-the-Sea, and St Mary's Island) off the Northumberland coast and analyzed to identify species-specific click trains of common bottlenose dolphin, white-beaked dolphin (Lagenorhynchus albirostris) and harbor porpoise (Phocoena phocoena). Detection data were modelled for each species as detection-positive hours (DPH) using Generalized Additive Models with Generalized Estimating Equations (GAM-GEE) to investigate the effects of environmental covariates, including day of year, diel phase, lunar phase, salinity, year, month and sea surface temperature, and their interaction with location. A total of 20,845 h were recorded during the study resulting in a total of 1660, 71, and 1111 DPH identified for bottlenose dolphin, white-beaked dolphin and porpoise, respectively. The final model for bottlenose dolphins retained all covariates except tidal index and an interaction between location and day of year after model selection and all covariates in the final model were significant. The final model for white-beaked dolphin retained month, year, location, diel index, temperature, lunar index and interactions between location and diel index and all covariates except lunar index were significant. The final model for porpoise retained all covariates and interactions between location and diel phase, day of year, lunar index, and salinity, however, salinity and the interaction between location and lunar index were not significant. Bottlenose dolphin clicks were detected in the area year-round but with two peak periods in occurrence coinciding with May and late September; white-beaked dolphin clicks were detected predominantly in July and August; and porpoise clicks were present year-round but with much greater probability of detection at the Druridge Bay site, where there were peaks in winter and in September. The results of this study provide important information for conservation and management actions that may be needed to reduce anthropogenic pressures on odontocetes in UK waters.

Population genomics of the white-beaked dolphin (Lagenorhynchus albirostris): Implications for conservation amid climate-driven range shifts

Climate change is rapidly affecting species distributions across the globe, particularly in the North Atlantic. For highly mobile and elusive cetaceans, the genetic data needed to understand population dynamics are often scarce. Cold-water obligate species such as the white-beaked dolphin (Lagenorhynchus albirostris) face pressures from habitat shifts due to rising sea surface temperatures in addition to other direct anthropogenic threats. Unravelling the genetic connectivity between white-beaked dolphins across their range is needed to understand the extent to which climate change and anthropogenic pressures may impact species-wide genetic diversity and identify ways to protect remaining habitat. We address this by performing a population genomic assessment of white-beaked dolphins using samples from much of their contemporary range. We show that the species displays significant population structure across the North Atlantic at multiple scales. Analysis of contemporary migration rates suggests a remarkably high connectivity between populations in the western North Atlantic, Iceland and the Barents Sea, while two regional populations in the North Sea and adjacent UK and Irish waters are highly differentiated from all other clades. Our results have important implications for the conservation of white-beaked dolphins by providing guidance for the delineation of more appropriate management units and highlighting the risk that local extirpation may have on species-wide genetic diversity. In a broader context, this study highlights the importance of understanding genetic structure of all species threatened with climate change-driven range shifts to assess the risk of loss of species-wide genetic diversity.

Closing the Organofluorine Mass Balance in Marine Mammals Using Suspect Screening and Machine Learning-Based Quantification.

High-resolution mass spectrometry (HRMS)-based suspect and nontarget screening has identified a growing number of novel per- and polyfluoroalkyl substances (PFASs) in the environment. However, without analytical standards, the fraction of overall PFAS exposure accounted for by these suspects remains ambiguous. Fortunately, recent developments in ionization efficiency (IE) prediction using machine learning offer the possibility to quantify suspects lacking analytical standards. In the present work, a gradient boosted tree-based model for predicting log IE in negative mode was trained and then validated using 33 PFAS standards. The root-mean-square errors were 0.79 (for the entire test set) and 0.29 (for the 7 PFASs in the test set) log IE units. Thereafter, the model was applied to samples of liver from pilot whales (n = 5; East Greenland) and white beaked dolphins (n = 5, West Greenland; n = 3, Sweden) which contained a significant fraction (up to 70%) of unidentified organofluorine and 35 unquantified suspect PFASs (confidence level 2-4). IE-based quantification reduced the fraction of unidentified extractable organofluorine to 0-27%, demonstrating the utility of the method for closing the fluorine mass balance in the absence of analytical standards.

Phthalate contamination in marine mammals off the Norwegian coast

Phthalates are used in plastics, found throughout the marine environment and have the potential to cause adverse health effects. In the present study, we quantified blubber concentrations of 11 phthalates in 16 samples from stranded and/or free-living marine mammals from the Norwegian coast: the killer whale (Orcinus orca), sperm whale (Physeter macrocephalus), long-finned pilot whale (Globicephala melas), white-beaked dolphin (Lagenorhynchus albirostris), harbour porpoise (Phocoena phocoena), and harbour seal (Phoca vitulina). Five compounds were detected across all samples: benzyl butyl phthalate (BBP; in 50 % of samples), bis(2-ethylhexyl) phthalate (DEHP; 33 %), diisononyl phthalate (DiNP; 33 %), diisobutyl phthalate (DiBP; 19 %), and dioctyl phthalate (DOP; 13 %). Overall, the most contaminated individual was the white-beaked dolphin, whilst the lowest concentrations were measured in the killer whale, sperm whale and long-finned pilot whale. We found no phthalates in the neonate killer whale. The present study is important for future monitoring and management of these toxic compounds.

Spatiotemporal Trends Spanning Three Decades Show Toxic Levels of Chemical Contaminants in Marine Mammals.

Despite their ban and restriction under the 2001 Stockholm Convention, persistent organic pollutants (POPs) are still widespread and pervasive in the environment. Releases of these toxic and bioaccumulative chemicals are ongoing, and their contribution to population declines of marine mammals is of global concern. To safeguard their survival, it is of paramount importance to understand the effectiveness of mitigation measures. Using one of the world's largest marine mammals strandings data sets, we combine published and unpublished data to examine pollutant concentrations in 11 species that stranded along the coast of Great Britain to quantify spatiotemporal trends over three decades and identify species and regions where pollutants pose the greatest threat. We find that although levels of pollutants have decreased overall, there is significant spatial and taxonomic heterogeneity such that pollutants remain a threat to biodiversity in several species and regions. Of individuals sampled within the most recent five years (2014-2018), 48% of individuals exhibited a concentration known to exceed toxic thresholds. Notably, pollutant concentrations are highest in long-lived, apex odontocetes (e.g., killer whales (Orcinus orca), bottlenose dolphins (Tursiops truncatus), and white-beaked dolphins (Lagenorhynchus albirostris)) and were significantly higher in animals that stranded on more industrialized coastlines. At the present concentrations, POPs are likely to be significantly impacting marine mammal health. We conclude that more effective international elimination and mitigation strategies are urgently needed to address this critical issue for the global ocean health.

Improving Marine Megafauna Knowledge with eDNA: A French Story

In the current context of large-scale biodiversity loss (Díaz et al. 2019), it is urgent to carry out biodiversity inventories in order to investigate spatial and temporal variations. Among the available methods, environmental DNA (eDNA) (Taberlet et al. 2018) combined with molecular metabarcoding (Valentini et al. 2009) bring new insights in drafting inventories of taxa present in an environment. Approaches based on eDNA facilitate the study of remote ecosystems and the detection of rare, cryptic or invasive species in a non-invasive way (Bohmann et al. 2014). In the marine realm, the study of mobile fauna, including mammals particularly, can greatly benefit from these new techniques. Here, we present a case study carried out in the northeast and northwest Atlantic, within the boundaries of marine protected areas. The Iroise Natural Marine Park*1 was the first French marine natural park created in France in 2007 (Fig. 1). The first campaign in the Iroise Natural Marine Park successfully detected several species of cetacean (e.g., Lagenorhynchus albirostris, Lagenorhynchus obliquidens) and four species of elasmobranchs (e.g., Scyliorhinus canicula, Torpedo marmorata, Raja undulata and Mustelus asterias). This study was extended to the Martinique Natural Marine Park*2, where similar analyses identified three cetacean species (Stenella attenuata, Lagenodelphis hosei and Tursiops truncatus) and 193 teleost taxa (Riou 2022), representing more than half of the species expected in Martinique. The analyses carried out in Martinique highlighted several remarkable sites for fish biodiversity. In Guadeloupe, in the heart of the Agoa Marine Mammals Sanctuary*3 (corresponding to the French Antilles exclusive economic zone), the taxonomic composition of different eDNA samples made in 2021 and 2022 was compared. The samples were analyzed using different primer sets, specific to vertebrates, teleosts and mammals. Comparison of the results obtained with vertebrate-specific primers and those specific to teleosts showed complementary results. For cetaceans, the analyses distinguished ten distinct cetacean taxonomic units and at least 3 distinct species from four samples. In addition, the eDNA samples were used to discriminate between the two recently recognised bottlenose dolphin ecotypes, based on the observation of a fixed nucleotide difference on the barcode targeted by the mammal-specific primers. New primers are currently being developed to make it easier to distinguish species of Delphinidae, which are still complex to identify. Environmental DNA and metabarcoding offer new possibilities for the inventories of marine megafauna and support adequate conservation decision-making processes. It is a major step towards better monitoring of marine mammal populations of the Atlantic Ocean. Moreover, our datasets will be freely available through open platforms following the FAIR (Findable, Accessible, Interoperable, and Reusable) principles.

Stable isotope ecology and interspecific dietary overlap among dolphins in the Northeast Atlantic

Dolphins are mobile apex marine predators. Over the past three decades, warm-water adapted dolphin species (short-beaked common and striped) have expanded their ranges northward and become increasingly abundant in British waters. Meanwhile, cold-water adapted dolphins (white-beaked and Atlantic white-sided) abundance trends are decreasing, with evidence of the distribution of white-beaked dolphins shifting from southern to northern British waters. These trends are particularly evident in Scottish waters and ocean warming may be a contributing factor. This mobility increases the likelihood of interspecific dietary overlap for prey among dolphin species previously separated by latitude and thermal gradients. Foraging success is critical to both individual animal health and overall population resilience. However, the degree of dietary overlap and plasticity among these species in the Northeast Atlantic is unknown. Here, we characterise recent (2015-2021) interspecific isotopic niche and niche overlap among six small and medium-sized delphinid species co-occurring in Scottish waters, using skin stable isotope composition (δ13C and δ15N), combined with stomach content records and prey δ13C and δ15N compiled from the literature. Cold-water adapted white-beaked dolphin have a smaller core isotopic niche and lower dietary plasticity than the generalist short-beaked common dolphin. Striped dolphin isotopic niche displayed no interspecific overlap, however short-beaked common dolphin isotopic niche overlapped with white-beaked dolphin by 30% and Atlantic white-sided dolphin by 7%. Increasing abundance of short-beaked common dolphin in British waters could create competition for cold-water adapted dolphin species as a significant portion of their diets comprise the same size Gadiformes and high energy density pelagic schooling fish. These priority prey species are also a valuable component of the local and global fishing industry. Competition for prey from both ecological and anthropogenic sources should be considered when assessing cumulative stressors acting on cold-water adapted dolphin populations with projected decline in available habitat as ocean temperatures continue to rise.

Offshore construction using gravity-base foundations indicates no long-term impacts on dolphins and harbour porpoise

There are concerns about the short- and long-term effects on cetaceans from offshore construction using pile-driving. Gravity-base foundations and anchored floating turbines are alternative installation methods that may have less impact on cetaceans. In this study, we investigated the response of dolphins (Tursiops truncatus and Lagenorhynchus albirostris) and harbour porpoise (Phocoena phocoena) to the construction of wind turbines using gravity-base foundations off Blyth, Northumberland, United Kingdom using cetacean echolocation recorders (C-PODs). Data were collected at nine sites across 3 years (2016–2018) before, during and after construction. Generalised additive mixed models were used to investigate temporal, environmental, and anthropogenic drivers of dolphin and porpoise occurrence from 143,215 h (5967 days) of C-POD data. The models explained 27% and 30% of the deviance in dolphin and porpoise occurrence, respectively. Overall, the results showed no long-term effect on the dolphin occurrence from the construction of the gravity-base wind turbine array. In contrast, porpoise occurrence increased by 32% and 75%, respectively, in the years during and after construction, compared to the before-construction year. Other predictors of dolphin and porpoise occurrence included month, hour of day, tidal currents and vessel sonar activity. Our findings indicate that wind turbine installation using gravity-base foundations had no long-term effects on the occurrence of dolphins or porpoise and may represent an offshore construction methodology that is less impactful to dolphins and harbour porpoise than impact pile-driven turbine installation methods. These results are important for future offshore energy developments; however, further studies are recommended to investigate potential species and location variations.

Of dolphins, humans, other long-lived animals and Alzheimer's disease (Commentary on Vacher et al.).

Of dolphins, humans, other long-lived animals and Alzheimer's disease (Commentary on Vacher et al.).

Observations of movement and site fidelity of white-beaked dolphins (Lagenorhynchus albirostris) in Icelandic coastal waters using photo-identification

The white-beaked dolphin (Lagenorhynchus albirostris) is the most commonly sighted delphinid species in Icelandic coastal waters. However, little is known about the species’ abundance, site fidelity and movements throughout its range. Photo-identification studies were conducted from April– October (2002–10) during whalewatching operations in Faxaflói and Skjálfandi bays on the southwest and northeast coasts of Iceland, respectively. Minimum abundance, annual site fidelity and movement between bays were calculated. A total of 154 and 52 individuals were identified in Faxaflói and Skjálfandi bays, respectively. The annual re-sighting rate was 21.4% in Faxaflói bay while only one individual was re-sighted in Skjálfandi bay (1.7%). A total of five dolphins (2.3%) were matched between Faxaflói and Skjálfandi bays with the period between re-sightings ranging from 272 to 821 days (mean 28.16 days, SD = 5.94). Low site fidelity rates observed likely signify a much larger home range than the present study area, into either other coastal or offshore zones, or alternatively may be explained by a large natural population size and/or the opportunistic nature of sampling during this study. Therefore, expansion of the study area is required. The matches between bays suggest that white-beaked dolphins inhabit a largescale coastal range of the Icelandic coast and can be considered highly mobile and transient possibly due to scarce and patchy resources. Alternatively it could be due to a large population size.

Evaluating the Use of Diazepam in Stranded Dolphins and Porpoises for Husbandry and Veterinary Purposes

We evaluated the use of diazepam (Valium®) during the rehabilitation of odontocetes (dolphins and porpoises) to facilitate husbandry and for veterinary purposes, by analyzing detailed records from a period of 14 years of the treatment of 16 stranded individuals: harbor porpoises (Phocoena phocoena), white-beaked dolphins (Lagenorhynchus albirostris), a common dolphin (Delphinus delphis), and a striped dolphin (Stenella coeruleoalba). Diazepam was used occasionally (once per case or for a few days at a time) to facilitate husbandry, including for managing stressful and transitional circumstances and during transport. It was also used occasionally (once per case) for veterinary purposes, such as to reduce stress or to facilitate x-ray scanning, gastroscopy, blood sampling, or wound treatment. Diazepam was found to be effective as an anti-anxiety drug, to cause drowsiness (i.e., reduce activity levels), as a muscle relaxant, and as an appetite stimulant. The doses used were similar for husbandry and veterinary purposes (0.03 to 0.44 mg/kg body weight), and the drug was administered almost exclusively orally (via fish) or via intramuscular injection.

Cetacean spatial trends from 2005 to 2019 in Svalbard, Norway

This study uses cetacean sighting data, acquired via a citizen science programme, to update distributions and spatial trends of whales and dolphins in waters around the Svalbard Archipelago during the period 2005–2019. Distributions, based on kernel density estimates, from an early period (2005–2019) and a recent period (2015–19) were compared to identify potential shifts in distribution in this area, which is experiencing rapid warming and concomitant sea-ice losses. Among the three Arctic endemic cetaceans, white whales (Delphinapterus leucas, also known as beluga) had a stable, coastal distribution throughout the study, whereas narwhals (Monodon monoceros) and bowhead whales (Balaena mysticetus) were observed only north of the archipelago, but with increasing frequency during the recent period. White-beaked dolphins (Lagenorhynchus albirostris) had a stable distribution along the continental shelf break, west and south of Svalbard. Sperm whale observations shifted from west of Bjørnøya during the early period to being concentrated around the north end of Prins Karls Forland, west of Spitsbergen during the recent period. The four summer-resident baleen whales—blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae) and minke whales (Balaenoptera acutorostrata)—have shifted their distributions from the continental shelf break west of Spitsbergen during the early period into fjords and coastal areas during the recent period. These changes coincide with increased inflows of Atlantic Water into the fjords along the west coast of Spitsbergen and across the north of the archipelago.

White-Beaked Dolphins (Lagenorhynchus albirostris) Cooperating with Humans and Showing Altruism Toward Harbor Porpoises (Phocoena phocoena)

In an odontocete rehabilitation center in the Netherlands, repeated observations were made over several days of interspecific cooperative behavior initiated by three white-beaked dolphins (Lagenorhynchus albirostris)—that is, mutually beneficial cooperation with humans and altruism toward three harbor porpoises (Phocoena phocoena). In the first observation (mutually beneficial cooperation), a white-beaked dolphin cooperated on her own initiative with humans to herd a harbor porpoise toward a veterinary treatment/feeding area in the pool. In the second observation (altruism), two recently recovered white-beaked dolphins assisted newly arrived harbor porpoises with swimming. These first recorded examples of interspecific mutually beneficial cooperation and altruism initiated by white-beaked dolphins will help to elucidate the motivation behind such behavior and the potential fitness benefits resulting from it.

Vertebral morphology in extant porpoises: Radiation and functional implications.

Vertebral morphology has profound biomechanical implications and plays an important role in adaptation to different habitats and foraging strategies for cetaceans. Extant porpoise species (Phocoenidae) display analogous evolutionary patterns in both hemispheres associated with convergent evolution to coastal versus oceanic environments. We employed 3D geometric morphometrics to study vertebral morphology in five porpoise species with contrasting habitats: the coastal Indo-Pacific finless porpoise (Neophocaena phocaenoides); the mostly coastal harbor porpoise (Phocoena phocoena) and Burmeister's porpoise (Phocoena spinipinnis); and the oceanic spectacled porpoise (Phocoena dioptrica) and Dall's porpoise (Phocoenoides dalli). We evaluated the radiation of vertebral morphology, both in size and shape, using multivariate statistics. We supplemented data with samples of an early-radiating delphinoid species, the narwhal (Monodon monoceros); and an early-radiating delphinid species, the white-beaked dolphin (Lagenorhynchus albirostris). Principal component analyses were used to map shape variation onto phylogenies, and phylogenetic constraints were investigated through permutation tests. We established links between vertebral morphology and movement patterns through biomechanical inferences from morphological presentations. We evidenced divergence in size between species with contrasting habitats, with coastal species tending to decrease in size from their estimated ancestral state, and oceanic species tending to increase in size. Regarding vertebral shape, coastal species had longer centra and shorter neural processes, but longer transverse processes, while oceanic species tended to have disk-shaped vertebrae with longer neural processes. Within Phocoenidae, the absence of phylogenetic constraints in vertebral morphology suggests a high level of evolutionary lability. Overall, our results are in accordance with the hypothesis of speciation within the family from a coastal ancestor, through adaptation to particular habitats. Variation in vertebral morphology in this group of small odontocetes highlights the importance of environmental complexity and particular selective pressures for the speciation process through the development of adaptations that minimize energetic costs during locomotion and prey capture.

Insights into the trophic ecology of white-beaked dolphins Lagenorhynchus albirostris and harbour porpoises Phocoena phocoena in Iceland

Sympatric organisms can avoid competition by occupying different ecological niches, a mechanism known as niche partitioning. In Iceland, white-beaked dolphinsLagenorhynchus albirostrisand harbour porpoisesPhocoena phocoenaare the most common small cetaceans observed but their trophic ecology remains understudied, including the potential for resource competition. In this study, we measured δ15N and δ13C values from white-beaked dolphin (n = 28) and harbour porpoise (n = 29) muscle samples collected over a 33 yr period (1987-2019) to compare isotopic niche width and overlap of both species, as well as diet composition. We also tested for within-species effects of sex, age class, body length, year of sampling and origin (bycatch vs. stranding) on the δ13C and δ15N values. Intra-species variations included differences between stranded and bycaught white-beaked dolphins and ontogenetic variations in both species, but further studies are necessary to investigate the factors that might explain these results. Inter-species comparisons showed that harbour porpoises and white-beaked dolphins had non-overlapping isotopic niches, with harbour porpoises exhibiting smaller niche widths (corrected standard ellipse area, SEAc: 1.25 vs. 2.13‰2). While white-beaked dolphins had a broader diet, composed primarily of gadoids but with contributions of other fish species, harbour porpoises fed almost exclusively on capelinMallotus villosus, suggesting niche segregation and width is largely maintained by targeting different prey resources. Both species also showed no long-term changes in trophic ecology, despite recent ecosystem changes in this region, possibly a result of adapting to spatial changes in prey distribution or shifts to other prey at similar trophic levels.

Китообразные Баренцева моря: фауна и состояние популяций в начале XXI века

Комплексные научно-исследовательские работы, ежегодно проводимые Полярным филиалом ВНИРО (ПИНРО имени Н. М. Книповича) в Баренцевом море, позволяют получать актуальную информацию о распределении и встречаемости морских млекопитающих, в частности китообразных, которые являются важнейшим звеном в экосистеме Мирового океана. В последние годы необходимость проведения мониторинга морских млекопитающих приобретает всё бόльшую актуальность в связи с изменением климата и повышением температуры морей и океанов, что может привести к смещению ареалов и даже к возможному исчезновению тех или иных видов. В настоящей работе обобщены результаты судовых учётов китообразных, выполненных Полярным филиалом ВНИРО в Баренцевом море в 2010–2019 гг., а также приведены ретроспективные данные по фауне усатых (Mysticeti) и зубатых (Odontoceti) китов. На основе материалов судовых исследований и с учётом сведений из литературных источников определён современный состав китообразных Баренцева моря, который в начале XXI века может быть представлен 16 видами китообразных из 7 семейств. Анализ материалов судовых учётов позволил определить статус пребывания морских млекопитающих в акватории моря и выявить частоту их встречаемости. Приведена численность популяций большинства видов усатых и зубатых китов, указаны наиболее вероятные места их встреч. По данным исследований, самым массовым, часто и круглогодично встречающимся видом определён беломордый дельфин Lagenorhynchus albirostris: на его долю приходится более 80 % от общего количества учтённых морских млекопитающих и около 50 % от всех встреченных китообразных. К постоянно присутствующим в акватории моря видам также отнесены белуха Delphinapterus leucas и обыкновенная морская свинья Phocoena phocoena, местá локализации которых приурочены преимущественно к прибрежной зоне Кольского полуострова. С мая по октябрь в акватории Баренцева моря регулярно встречаются виды, прибывающие сюда для нагула из других районов Атлантики, — малый полосатик Balaenoptera acutorostrata, финвал Balaenoptera physalus и горбач Megaptera novaeangliae. Крайне редко в западном секторе Российской Арктики можно увидеть нарвала Monodon monoceros и высоколобого бутылконоса Hyperoodon ampullatus.