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The New York Bight is an ecologically and economically important marine region along the U.S. Atlantic Coast. Extensive assessments have characterized the habitats and biota in this ecosystem; however, most have focused on fishes, benthic habitats, and human impacts. To investigate the spatial and temporal occurrence of whales in this region, we conducted a three-year passive acoustic monitoring survey that documented the acoustic presence of five baleen whale species that occur within the New York Bight and are of conservation concern: North Atlantic right whales (Eubalaena glacialis), humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus), sei whales (Balaenoptera borealis), and blue whales (Balaenoptera musculus). Data were recorded with 14 bottom-mounted acoustic sensors across the continental shelf between 2017 and 2020. Right whales were detected across all seasons, with most detections in autumn closer to New York Harbor and spring detections at sites closer to the continental shelf edge. Humpbacks were detected during all months of the year with varying distribution of detections across the shelf. The year-round presence of right and humpback whales challenges previous hypotheses that this region is primarily a stopover location along their migration paths. Fin whales were detected at all sites on most days. Sei whales were detected primarily during the spring at offshore sites. Blue whales were detected in the winter at sites closer to the continental shelf edge, but were rare. These data improve our understanding of baleen whale seasonal occurrences in the New York Bight and can inform monitoring and mitigation efforts associated with the management and conservation of these species. [ABSTRACT FROM AUTHOR]

Pacific fin whales (Balaenoptera physalus velifera), once the most abundant cetacean species in British Columbia (BC), were also one of the most heavily targeted by commercial whaling. Much of what we know about their phenology and ecology is from catch records, but their current status has not yet been summarized in Canadian waters. Here, we collated evidence from dedicated surveys, opportunistic sightings, and passive acoustic records that had not been reported before and reviewed them in the context of past data. This was to add new findings to what is known, and to establish if the population was showing signs of recovery. This is particularly relevant considering discussions of downlisting their population status in Canada from endangered to threatened. We then asked if this rebounding was consistent with what is known about pre-whaling presence and movement patterns, or if changes in whale distribution reflected altered oceanic regimes, prey availability, or increased anthropogenic pressures. The evidence suggested that fin whale populations in the northeast Pacific Ocean are repopulating areas along the BC coast recognized as part of their historic range. However, they are recovering in a different ocean than they were removed from, which makes them increasingly vulnerable to new anthropogenic threats. The sightings data suggested that, at least for the west coast of Vancouver Island, this repopulation has occurred over a relatively short period, with fin whales still absent from regular surveys as recent as the early 2000's. The recent acoustic recordings suggested their presence is not transitory, but that fin whales may be using locales along the BC coast for feeding and breeding activities. [ABSTRACT FROM AUTHOR]

The blue whale is an endangered and globally distributed species of baleen whale with multiple described subspecies, including the morphologically and genetically distinct pygmy blue whale. North Atlantic and North Pacific populations, however, are currently regarded as a single subspecies despite being separated by continental land masses and acoustic call differences. To determine the degree of isolation among the Northern Hemisphere populations, 14 North Pacific and 6 Western Australian blue whale nuclear and mitochondrial genomes were sequenced and analysed together with 11 publicly available North Atlantic blue whale genomes. Population genomic analyses revealed distinctly differentiated clusters and limited genetic exchange among all three populations, indicating a high degree of isolation between the Northern Hemisphere populations. Nevertheless, the genomic and mitogenomic distances between all blue whale populations, including the Western Australian pygmy blue whale, are low when compared to other inter‐subspecies distances in cetaceans. Given that the Western Australian pygmy blue whale is an already recognised subspecies and further supported by previously reported acoustic differences, a proposal is made to treat the two Northern Hemisphere populations as separate subspecies, namely Balaenoptera musculus musculus (North Atlantic blue whale) and Balaenoptera musculus sulfureus (North Pacific blue whale). Furthermore, a first molecular viability assessment of all three populations not only found a generally high genomic diversity among blue whales but also a lack of alleles at low frequency, non‐neutral evolution and increased effects of inbreeding. This suggests a substantial anthropogenic impact on the genotypes of blue whales and calls for careful monitoring in future conservation plans. [ABSTRACT FROM AUTHOR]

Baleen whales are among the largest marine megafauna, and while mostly well-protected from direct exploitation, they are increasingly affected by vessel traffic, interactions with fisheries, and climate change. Adverse interactions, notably vessel strikes and fishing gear entanglement, often result in distress, injury, or death for these animals. In Atlantic Canadian waters, such negative interactions or 'incidents' are consistently reported to marine animal response organizations but have not yet been analyzed relative to the spatial distribution of whales and vessels. Using a database of 483,003 whale sightings, 1,110 incident reports, and 82 million hours of maritime vessel activity, we conducted a spatiotemporal vulnerability analysis for all six baleen whale species occurring in the Northwest Atlantic Ocean by developing an ensemble of habitat-suitability models. The relative spatial risk of vessel-induced incidents was assessed for present (1985–2015) and projected near-future (2035–2055) distributions of baleen whales. Areas of high habitat suitability for multiple baleen whale species were intrinsically linked to sea surface temperature and salinity, with multispecies hotspots identified in the Bay of Fundy, Scotian Shelf, Laurentian Channel, Flemish Cap, and Gulf of St. Lawrence. Present-day model projections were independently evaluated using a separate database of acoustic detections and found to align well. Regions of high relative incident risk were projected close to densely inhabited regions, principal maritime routes, and major fishing grounds, in general coinciding with reported incident hotspots. While some high-risk regions already benefit from mitigation strategies aimed at protecting North Atlantic Right Whales, our analysis highlights the importance of considering risks to multiple species, both in the present day and under continued environmental change. [ABSTRACT FROM AUTHOR]

The editorial from Molecular Ecology Resources highlights the journal's continued leadership in providing resources for the molecular ecology community. Despite a slight decrease in the impact factor, other metrics like the 5-year IF and Scopus CiteScore show consistency. The journal aims to maintain high publication standards and support its contributors and readers. Top articles from the past year cover various topics such as landscape genetics, genotype-environment associations, and species delimitation. The editorial also acknowledges the contributions of editors, reviewers, and board members to the journal's success. [Extracted from the article]

Traditional methods for quantifying the internal temperature of marine mammals require handling live animals, which is not practical for free-swimming baleen whales. Developing a less invasive, more repeatable method would significantly improve our understanding of whale health and thermal physiology. Infrared thermography (IRT) devices compatible with remotely piloted aircraft systems (RPAS) have facilitated qualitative assessments of heat signatures from marine mammals at sea, but absolute temperatures derived using this approach are rare. The goal of this study was to develop a precise empirical method for estimating intranasal temperatures of baleen whales using RPAS-based IRT. We conducted controlled field experiments and flights over North Atlantic right whales (Eubalaena glacialis, NARWs) to develop and test the methodology. Two approaches were evaluated to estimate intranasal temperatures from IRT sensor intensities: a three-point empirical line regression calibrated per flight using known-temperature objects and a generalized linear model incorporating environmental variables. Controlled field experiments demonstrated that the former approach had a median bias of −0.6°C (interquartile range: 1.5ºC), while the latter approach had unexplained negative proportional bias with increasing true temperature of the target object. After accounting for bias, the former approach yielded an average intranasal temperature of 26.9 ± 1.7°C for 21 unique NARWs. The anatomy of the mysticete upper respiratory tract and physiological heat conservation strategies may explain why estimates were low compared to internal temperatures measured from baleen whales using other techniques (30–39ºC). Variability within whales was less than ± 2°C, supporting the use of these methods to monitor the health of individuals over time. However, variability among whales was greater (up to 7ºC). Improvements in our understanding of whale physiology and respiratory mechanics and advancements in RPAS-based IRT calibrations could make this technology more reliable for assessing individual body temperatures and monitoring populations in the future. [ABSTRACT FROM AUTHOR]

Stable isotope analysis (SIA) is a useful tool to assess the health and foraging habits of large marine predators, metabolic stress, pregnancy, and migration patterns. This study provides baseline SIA data for four Gulf of Maine mysticete species and serves as a benchmark for future assessments. SIA was conducted on skin biopsies collected in two time periods: 1988 to 1992 (n = 15) and 1999 to 2005 (n = 187). Samples were collected from humpback whales (Megaptera novaeangliae; n = 116), fin whales (Balaenoptera physalus; n = 74), minke whales (Balaenoptera acutorostrata; n = 6), and North Atlantic right whales (Eubalaena glacialis; n = 6). There were statistically significant differences in isotopic value among species, years, and regions sampled. By species, North Atlantic right whale δ13C and δ15N levels were significantly different than the other species analyzed. Additionally, humpback whales had a δ15N value that was significantly higher than the value found in fin whales. By date, humpback whales showed significant difference in δ13C in 2002 from the two previous years. For fin whales, 2002 showed significant difference in δ13C for all other years' samples (2000 to 2003). By region, two regions that were the greatest distance apart (Bay of Fundy and Great South Channel) showed significant differences in d13C for humpback whales. Demographic analyses for humpback and fin whales found a significant difference between calves versus other age classes, presumably due to nursing. A decadal comparison of humpback whales at one site (Stellwagen Bank) found no significant difference between decades. This dataset provides a benchmark for stable isotope measurements in large baleen whales for this regional ecosystem. [ABSTRACT FROM AUTHOR]

Most research on cetacean swimming has been conducted on captive dolphins due to limited accessibility to wild cetaceans. Epibiotic barnacles have been used as indirect evidence of cetacean hydrodynamics, given their lifelong association with cetaceans and dependence on water flow. Previous studies suggested that the spatial distribution of the barnacle Xenobalanus globicipitis on the tail flukes of striped dolphins (i.e., higher load in the center and dorsal side) sheds light on dolphin hydrodynamics. The present study investigates whether these spatial patterns are shared among 13 cetacean species: 1 species of baleen whale (N=33), 3 beaked whales (N=11), and delphinids: 3 globicephalines (N=21) and 6 smaller dolphins (N=118). We found higher barnacle densities on the dorsal side of the flukes of delphinids, particularly in the smaller species (mostly subfamily Delphininae); whereas both fluke sides of the whales were equally colonized. The center of the flukes was generally a preferred settlement location for X. globicipitis, although it became less predictable in the ventral side of dolphins. Our findings conform to evidence on cetacean morphokinematics: while large odontocetes and whales have greater mobility in their torso during swimming, dolphins rely mostly on asymmetric fluke oscillation, likely favoring a set of more favorable conditions for barnacle settlement on the dorsal fluke side of dolphins (i.e., higher cyprid advection and lower shear stress). Also, the interaction of the dorsal fin vortices with the flow at the flukes could be more pronounced in dolphins. An additional effect of dolphin aerial behavior cannot be ruled out. This study provides novel indirect evidence on cetacean swimming performance, highlighting possible nuances between ecomorphological groups, and underlines that epibionts are a cost-effective tool for studying wild cetaceans. [ABSTRACT FROM AUTHOR]

The article in Marine Mammal Science discusses the sequences of a possible distress call of a juvenile gray whale found in a shallow lagoon within the Gulf of California. Gray whales use sound to communicate, with various sounds associated with different activities. The study reports a new tonal call type, S10, possibly produced by a juvenile gray whale, which was detected in sequences along with known S1 calls. The authors speculate that the distress calls or mixed sequences could serve as contact or distress calls, especially in the context of whales visiting shallow areas where they could potentially strand. [Extracted from the article]

The article in Marine Mammal Science discusses the southbound migration of satellite-tagged pygmy blue whales from the Savu Sea in Indonesia to subantarctic waters. The study tracked two pygmy blue whales, showing their movements from Indonesia to Australian waters and the subantarctic region. The research highlights the extended habitat range of Australian pygmy blue whales and suggests the need for more satellite tagging to confirm migratory routes. The study also acknowledges the support of various individuals and organizations in conducting the research. [Extracted from the article]

We consider how the ongoing recovery of baleen whale populations requires improved understanding when managing the largest commercial fishery in the Southern Ocean, the fishery for Antarctic krill. Baleen whales already represent one of the major consumers of krill, and as such compete with the fishery. However, they are not explicitly included either in the monitoring programme or the krill fisheries management approach of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Individual baleen whales are at direct mortality risk from ship strike, entanglement, or by-catch. In addition, sub-lethal impacts on individuals, albeit with population-level consequences, via decreased body condition and reproductive rates, may arise from local depletion of prey and prey-field disturbance that increases whale energetic costs. Mitigating these risks requires that baleen whales, including those species not yet recovered, are fully integrated into management procedures. A vital issue will be to facilitate the ongoing recovery of blue, fin and sei whales, populations of which are still heavily depleted relative to their pre-whaling abundance. Part of the answer to this will be how CCAMLR resolves outstanding issues related to its newly emerging revised krill fishery management framework. Management of the krill fishery is data-poor, with much of the scientific support reliant upon data that are now decades old. The decision rules for determining sustainable yields need careful re-evaluation, given they were negotiated at a time when baleen whales were rarely observed, and krill fishery catches were low in relation to the estimated available krill biomass. The Antarctic marine ecosystem is spatially and temporally dynamic, and is changing, yet CCAMLR still assumes a static system. An explicit commitment to collect up-to-date monitoring data about krill and baleen whales is vital to help inform the revised management framework. Precaution argues that catch levels should not increase until adequate data are available for effective management. Knowledge about the status of baleen whales will inevitably require close collaboration with the International Whaling Commission. [ABSTRACT FROM AUTHOR]

Abstract Passive acoustic monitoring (PAM) is commonly used to obtain year‐round continuous data on marine soundscapes harboring valuable information on species distributions or ecosystem dynamics. This continuously increasing amount of data requires highly efficient automated analysis techniques in order to exploit the full potential of the available data. Here, we propose a benchmark, which consists of a public dataset, a well‐defined task and evaluation procedure to develop and test automated analysis techniques. This benchmark focuses on the special case of detecting animal vocalizations in a real‐world dataset from the marine realm. We believe that such a benchmark is necessary to monitor the progress in the development of new detection algorithms in the field of marine bioacoustics. We ultimately use the proposed benchmark to test three detection approaches, namely ANIMAL‐SPOT, Koogu and a simple custom sequential convolutional neural network (CNN), and report performances. We report the performance of the three detection approaches in a blocked cross‐validation fashion with 11 site‐year blocks for a multi‐species detection scenario in a large marine passive acoustic dataset. Performance was measured with three simple metrics (i.e., true classification rate, noise misclassification rate and call misclassification rate) and one combined fitness metric, which allocates more weight to the minimization of false positives created by noise. Overall, ANIMAL‐SPOT performed the best with an average F metric of 0.83, followed by the custom CNN with an average fitness metric of 0.79 and finally Koogu with an average fitness metric of 0.59. The presented benchmark is an important step to advance in the automatic processing of the continuously growing amount of PAM data that are collected throughout the world's oceans. To ultimately achieve usability of developed algorithms, the focus of future work should be laid on the reduction of the false positives created by noise.

We fit ongoing 40+-year mark-recapture databases from the thriving southern right whale (SRW), Eubalaena australis, and highly endangered North Atlantic right whale (NARW), Eubalaena glacialis, to candidate survival models to estimate their life spans. Median life span for SRW was 73.4 years, with 10% of individuals surviving past 131.8 years. NARW life spans were likely anthropogenically shortened, with a median life span of just 22.3 years, and 10% of individuals living past 47.2 years. In the context of extreme longevity recently documented in other whale species, we suggest that all balaenid and perhaps most great whales have an unrecognized potential for great longevity that has been masked by the demographic disruptions of industrial whaling. This unrecognized longevity has profound implication for basic biology and conservation of whales. [ABSTRACT FROM AUTHOR]

Baleen whale calves vocalize, but the behavioural context and role of their social calls in mother–calf interactions are yet to be documented further. We investigated the context of call production in humpback whale (Megaptera novaeangliae) calves using camera-equipped animal-borne multi-sensor tags. Behavioural states, including suckling sessions, were identified using accelerometer, depth and video data. Call types were categorized through clustering techniques. We found that call types and rates predict the occurrence of a given state. Milling, resting and travelling were associated with a median call rate of 0 calls min−1, while surface play, tagging responses and suckling were associated with higher call rates, averaging up to a median of 0.5 calls min−1 for suckling. Suckling sessions were mainly associated with two sets of low-frequency calls corresponding to previously described burping, barking and snorting sounds. Surface play sessions featured mid-frequency calls with whoop-like sounds and other call types. These results address the significance of vocal signalling in mother–calf communication and the calf's development, including the first identification of potential begging calls. Overall, this study offers new insights into baleen whale behaviour, underscores the importance of social calls in mother–calf interactions and enhances our understanding of communication systems in aquatic mammalian mother–young pairs. [ABSTRACT FROM AUTHOR]

Key points Improving our understanding of energy allocation in reproduction is key for accurately parameterizing bioenergetic models to assess population responses to environmental perturbations and anthropogenic disturbance. We quantified the energetic cost of gestation in humpback whales (Megaptera novaeangliae) using historical whaling records, non‐invasive unoccupied aerial system (UAS) photogrammetry and post mortem tissue samples. First, we estimated relative birth size using body length measurements of 678 mother–fetus pairs from historical whaling records and 987 mother–calf pairs measured in situ using UAS‐photogrammetry. The total energetic cost of gestation includes fetal growth (FG), heat increment of gestation and placental tissue development. FG was modelled from conception to birth, with fetal volume and mass estimated using the volume‐to‐length relationship of perinatal calves and published humpback whale tissue composition estimates. Tissue‐specific energy content was quantified using post mortem bone, muscle, viscera and blubber samples from a neonatal humpback whale. Placental tissue development was estimated using humpback whale placental tissue and published equations. Relative birth length was found to be 33.75% (95% CI: 32.10–34.61) of maternal length. FG rates and absolute birth size increased with maternal length, with exponential growth in fetal length, volume and mass resulting in minimal energetic costs over the first two quadmesters (0.01–1.08%) before increasing significantly in the final quadmester (98.92%). Gestational heat constituted the greatest energetic cost (90.42–94.95%), followed by fetal (4.58–7.76%) and placental (0.37–1.83%) tissue growth. Our findings highlight the energetic costs endured by capital breeding females preceding parturition, with the most substantial energetic costs of gestation coinciding with migration and fasting. We quantified the energetic cost of gestation using body length measurements of mother–fetus pairs from historical whaling records, length estimates of mother–calf pairs measured in situ using aerial photogrammetry and post mortem tissue samples. Fetal growth rates and birth size increased with maternal length, with fetal length, volume and mass increasing exponentially over gestation. Energetic costs over the first two quadmesters were negligible (0.01–1.08%) before increasing significantly in the final quadmester (98.92%). Though larger females incur nearly twice the energetic cost of smaller females, they are likely buffered by greater absolute energy reserves, suggesting smaller females may be less resilient to perturbations in energy balance. We demonstrate the significant energetic costs incurred by pregnant humpback whales, with most of the energetic expenditure occurring over the final 100 days of gestation. Late‐pregnant females are, therefore, particularly vulnerable to disruptions in energy balance, given periods of greatest energetic stress coincide with fasting and migration. [ABSTRACT FROM AUTHOR]

Blue (Balaenoptera musculus) and fin (B. physalus) whales are prominent species in the California Current Ecosystem (CCE) using the area for migration and foraging. Blue whales migrate between tropical wintering grounds and higher latitude foraging grounds in the CCE, whereas fin whales may remain there year-round. We used Argos tracks of 182 blue (mean duration: 78 days) and 98 fin (mean duration: 35 days) whales tagged from 1994-2018 along the U.S. West Coast to examine residence time and occupancy in U.S. Navy training and testing areas. Bayesian hierarchical switching state-space model locations calculated from Argos tracks were used to provide residence time and proportion of tracking duration within each Navy area. We also calculated relative occupancy isopleths from the state space models, for both directed and non-directed movement, to assess spatial use of Navy areas. We then used generalized linear mixed models and beta regression to examine relationships between Navy area use and covariates, including six climate indices. Point Mugu Sea Range (PMSR) was the most heavily used Navy area by both species in terms of whale numbers, followed by the Southern California Range Complex (SOCAL). Residence time was longest in PMSR for blue whales and in the Northwest Training and Testing Study Area (NWTT) for fin whales. Blue whale use in PMSR was greater in summer versus autumn and for whales tagged in Southern versus Central California. Proportion of tracking duration decreased in all areas with increasing values of the Oceanic Niño Index (ONI), and in PMSR, with increasing values of the North Pacific Gyre Oscillation. Fin whale residence time was longer in PMSR during summer than winter or spring and decreased with increasing values of Habitat Compression Index and ONI. Proportion of tracking duration for fin whales was greatest in summer in PMSR and in winter in SOCAL and NWTT. Overlap of directed and non-directed movement was greatest in PMSR for both species. This assessment of blue and fin whale residence time and occupancy in Navy areas improves our understanding of potential threats these animals face, not only from military activities in Navy areas, but throughout the CCE. [ABSTRACT FROM AUTHOR]

Subarctic baleen whales, including humpback (Megaptera novaeangliae), fin (Balaenoptera physalus), and gray whales (Eschrichtius robustus), migrate through the Bering Strait every summer to feed in the Chukchi Sea. When and where the whales are found in the region likely reflects environmental conditions. Using recordings collected between 2009 and 2018 from a hydrophone ~ 35 km north of the strait, we identified whale calls during the open-water season (May–December), examined migration timing, and investigated potential drivers of whale presence. The acoustic presence of fin and humpback whales varied across the years, while gray whales were consistently detected each year. We compared detection rates for October and November since these months had recordings each year. We observed the highest proportion of recordings with humpback whale calls for October–November in 2009, 2017, and 2018 (66–80% of recordings); the highest proportion of recordings with fin whale calls in 2015, 2017, and 2018 (75–79% of recordings); and the highest proportion of recordings with gray whale calls in 2013 and 2015 (46 and 51% of recordings, respectively). Fin and humpback whales departed the Bering Strait ~ 3 and 2 days later per year over the study period (p < 0.04). Both fin and humpback whales delayed their southward migration in years with warmer water temperatures (Pearson r ≥ 0.73, p < 0.02). Generalized additive models of location, shape, and scale identified day of the year, water temperatures, and the lagged presence of a thermal front the previous month as drivers of acoustic presence for all three species during the open-water season. [ABSTRACT FROM AUTHOR]

Major evolutionary transitions, such as the shift of cetaceans from terrestrial to marine life, can put pressure on sensory systems to adapt to a new set of relevant stimuli. Relatively little is known about the role of smell in the evolution of mysticetes (baleen whales). While their toothed cousins, the odontocetes, lack the anatomical features to smell, it is less clear whether baleen whales have retained this sense, and if so, when the pressure on olfaction diverged in the cetacean evolutionary lineage. We examined eight genes encoding olfactory signal transduction pathway components and key chaperones for signs of inactivating mutations and selective pressures. All of the genes we examined were intact in all eight mysticete genomes examined, despite inactivating mutations in odontocete homologs in multiple genes. We also tested several models representing various hypotheses regarding the evolutionary history of olfaction in cetaceans. Our results support a model where olfactory ability is specifically reduced in the odontocete lineage following their split from stem cetaceans and serve to clarify the evolutionary history of olfaction in cetaceans. [ABSTRACT FROM AUTHOR]

Anthropogenic stressors threaten large whales globally. Effective management requires an understanding of where, when, and why threats are occurring. Strandings data provide key information on geographic hotspots of risk and the relative importance of various threats. There is currently considerable public interest in the increased frequency of large whale strandings occurring along the US East Coast of the United States since 2016. Interest is accentuated due to a purported link with offshore wind energy development. We reviewed spatiotemporal patterns of strandings, mortalities, and serious injuries of humpback whales (Megaptera novaeangliae), the species most frequently involved, for which the US government has declared an "unusual mortality event" (UME). Our analysis highlights the role of vessel strikes, exacerbated by recent changes in humpback whale distribution and vessel traffic. Humpback whales have expanded into new foraging grounds in recent years. Mortalities due to vessel strikes have increased significantly in these newly occupied regions, which show high vessel traffic that also increased markedly during the UME. Surface feeding and feeding in shallow waters may have been contributing factors. We found no evidence that offshore wind development contributed to strandings or mortalities. This work highlights the need to consider behavioral, ecological, and anthropogenic factors to determine the drivers of mortality and serious injury in large whales and to provide informed guidance to decision‐makers. [ABSTRACT FROM AUTHOR]

Simple Summary: The welfare of free-ranging cetaceans is being impacted around the world due to human activities like commercial fishing and marine traffic. Here, we validate a non-invasive physical indicator of welfare for humpback and fin whales found in the Gulf of St-Lawrence, Canada. Multi-scale measurement of welfare showed that most humpback whales were in a good welfare state, whereas most fin whales were in a moderate state. For both species, welfare was mainly affected by prolonged effects of physical trauma (entanglement in fishing gear and boat collisions) on body condition, specifically whales being thinner. Other factors impacting welfare included degradation of the marine environment (e.g., oxygen levels, water temperatures and salinity levels). Anthropogenic activities impacting marine environments are internationally recognized as welfare issues for wild cetaceans. This study validates a first evidence-based physical indicator for the welfare assessment protocol of humpback (n = 50) and fin whales (n = 50) living in a highly anthropized environment. Visual assessments of body condition, skin health, prevalence of injuries and parasite/epibiont loads were performed using a species-specific multi-scale measuring tool. A total of 6403 images were analyzed (fin, n = 3152; humpback, n = 3251) and results were validated through reliability and positive discrimination statistical tests. Based on physical measures, welfare assessment results showed that 60% of humpback whales were considered in a good welfare state compared to only 46% of fin whales. Significant relationships were observed in both species, between environmental parameters like dissolved oxygen levels, and prevalence of cutaneous lesions like pale skin patch syndrome. Furthermore, animals with injuries due to anthropogenic activities were more likely to be in poorer body condition, suggesting chronic stress affecting welfare. [ABSTRACT FROM AUTHOR]

Simple Summary: The tongues of vertebrates reflect their adaptations to various feeding strategies, the types of food they consume, and the environments they inhabit. In cetacean, the macro- and microanatomical aspects of the tongues of few species have been studied. Here, we analyzed, for the first time, the morphology of the tongues of two porpoise species (Spectacled and Burmeister's Porpoises; juvenile and adults), whose biology is little known. We describe a range of novel aspects related to ontogenetic morphological differences and document the finding of thermoregulatory structures and components of the immune system. Differences between juvenile and adult individuals of the same species, as well as between juveniles and adults of both species, may be related to their feeding types and/or geographical distribution. Additionally, we found a lingual vascular system, which has only been mentioned for baleen whales and the sperm whale (but never for smaller-toothed cetaceans), that may participate in the thermoregulation of these individuals. Both species have marginal papillae, but only in Burmeister's Porpoise were small taste buds, possibly vestigial, found. A better understanding of the biology of these two porpoise species will help to develop useful strategies that contribute to their protection in the near future. Vertebrates' tongues reflect part of their adaptations to diverse feeding strategies, the types of food items they eat, and the environments where they live. Our contribution was to analyze the macro- and microscopic morphology of the tongues of two porpoise species (Phocoena dioptrica and Phocoena spinipinnis; juveniles and adults), whose biology is little known. Macroscopic and microscopic studies (conventional histology, scanning electron microscopy, immunohistochemistry, and morphometry) were performed. Differences between juvenile and adult individuals of the same species, as well as between juveniles and adults of both species, were found, probably related to their feeding and/or geographical distribution. In addition, novel aspects related to ontogenetic morphological differences, thermoregulation, and immune system components were described. We found a lingual countercurrent vascular system (periarterial venous retia), only mentioned for mysticetes and Physeter macrocephalus (never for smaller odontocetes). In addition, we identified mechanoreceptors (lamellar corpuscles). Both species showed marginal papillae, but only in P. spinipinnis were small (probably vestigial) taste buds observed. Finally, lingual lymphoid aggregates were found. [ABSTRACT FROM AUTHOR]

Previous studies have described two distinct vascular systems in cetacean fins. However, these studies have been limited to Delphinoidea species, with little information on their three‐dimensional structures. In this study, the anatomical analysis of the caudal and dorsal fins of a dwarf sperm whale was conducted using X‐ray computed tomography and gross dissection with staining, providing the first confirmation of the two vascular systems in the fins of the family Kogiidae. This finding suggested that these vascular systems are common across Odontoceti species. In addition, we observed unique three‐dimensional structures in the superficial veins, which formed a reticulate pattern in both fins and converged at the centerline at the base of the dorsal fin, potentially influencing individual's heat reduction capabilities. [ABSTRACT FROM AUTHOR]

Understanding the causes of mortality for a declining species is essential for developing effective conservation and management strategies, particularly when anthropogenic activities are the primary threat. Using a competing hazards framework allows for robust estimation of the cause‐specific variation in risk that may exist across multiple dimensions, such as time and individual. Here, we estimated cause‐specific rates of severe injury and mortality for North Atlantic right whales (Eubalaena glacialis), a critically endangered species that is currently in peril due to human‐caused interactions. We developed a multistate capture–recapture model that leveraged 30 years of intensive survey effort yielding sightings of individuals with injury assessments and necropsies of carcass recoveries. We examined variation in the hazard rates of severe injury and mortality due to entanglements in fishing gear and vessel strikes as explained by temporal patterns and the age and reproductive status of the individual. We found strong evidence for increased rates of severe entanglement injuries after 2013 and for females with calves, with consequently higher marginal mortality. The model results also suggested that despite vessel strikes causing a lower average rate of severe injuries, the higher mortality rate conditional on injury results in significant total mortality risk, particularly for females resting from a recent calving event. Large uncertainty in the estimation of carcass recovery rate for vessel strike deaths permeated into the apportionment of mortality causes. The increased rates of North Atlantic right whale mortality in the last decade, particularly for reproducing females, has been responsible for the severe decline in the species. By apportioning the human‐caused threats using a quantitative approach with estimation of relevant uncertainty, this work can guide development of conservation and management strategies to facilitate species recovery. Our approach is relevant to other monitored populations where cause‐specific injuries from multiple threats can be observed in live and dead individuals. [ABSTRACT FROM AUTHOR]

Climate change-induced habitat alterations in the Arctic Ocean are expected to affect spatial and temporal occurrence patterns of seasonally migrating baleen whale species, leading to poleward range shifts and prolonged stays in Arctic waters. The aim of this study was to investigate occurrence patterns of blue (Balaenoptera musculus musculus) and fin (B. physalus) whales in Fram Strait, a summering habitat and historic whaling ground for both species. Passive acoustic monitoring data were collected between 2012 and 2021 at eight different mooring positions in eastern and central Fram Strait. These data were initially analyzed for the acoustic presence of blue and fin whales. Afterwards, the environmental impact on acoustic occurrences and the potential temporal expansion of acoustic presence periods were investigated. Blue whale acoustic presence showed a clear seasonality, with most calls being detected from July to October. Additionally, sporadic blue whale calls were detected in winter in three years on one or a few consecutive days. Fin whale acoustic presence varied between years, with peak presence from mid-summer through autumn, moderate presence in winter, and sporadic presence in spring. Random forest models suggested that zooplankton mass content, sea surface temperature and day of the year influenced blue whale acoustic presence, while fin whale acoustic presence was impacted by day of the year. For both species, no temporal trend in the onset and offset of acoustic presence periods was found. Our findings highlight eastern Fram Strait as key marine mammal habitat, probably serving as a feeding ground. Occasional (blue whales) and regular (fin whales) acoustic presence during the winter months further supports the hypothesis of complex migration behaviors in both species. [ABSTRACT FROM AUTHOR]

Predicting and mitigating the impacts of anthropogenic ocean noise on marine animals is hindered by a lack of information on hearing in these species. We established a catch-and-release program to temporarily hold adolescent minke whales (Balaenoptera acutorostrata) for hearing tests during their summer migration. In 2023, two minke whales provided measures of the auditory brainstem response and data on the frequency range of their hearing. Results show that minke whales are sensitive to sound frequencies as high as 45 to 90 kilohertz. These tests provide information on the types of anthropogenic noise that could affect minke whales and potentially, other related baleen whale species. [ABSTRACT FROM AUTHOR]

In coastal British Columbia, Canada, marine megafauna such as humpback whales (Megaptera novaeangliae) and fin whales (Balaenoptera physalus velifera) have been subject to a history of exploitation and near extirpation. While their populations have been in recovery, significant threats are posed to these vulnerable species by proposed natural resource ventures in this region, in addition to the compounding effects of anthropogenic climate change. Genetic tools play a vital role in informing conservation efforts, but the associated collection of tissue biopsy samples can be challenging for the investigators and disruptive to the ongoing behaviour of the targeted whales. Here, we evaluate a minimally intrusive approach based on collecting exhaled breath condensate, or respiratory 'blow' samples, from baleen whales using an unoccupied aerial system (UAS), within Gitga'at First Nation territory for conservation genetics. Minimal behavioural responses to the sampling technique were observed, with no response detected 87% of the time (of 112 UAS deployments). DNA from whale blow (n = 88 samples) was extracted, and DNA profiles consisting of 10 nuclear microsatellite loci, sex identification and mitochondrial (mt) DNA haplotypes were constructed. An average of 7.5 microsatellite loci per individual were successfully genotyped. The success rates for mtDNA and sex assignment were 80% and 89% respectively. Thus, this minimally intrusive sampling method can be used to describe genetic diversity and generate genetic profiles for individual identification. The results of this research demonstrate the potential of UAS‐collected whale blow for conservation genetics from a remote location. see also the Perspective by Elena Valsecchi. [ABSTRACT FROM AUTHOR]

A growing and increasingly globalised human population, requiring the movement of goods and commodities, is placing increasing demands on the maritime industry, resulting in a concurrent increase in global shipping activities. This has consequences for the marine environment, particularly for species vulnerable to the impacts of vessel traffic. For example, vessel collisions can result in sub‐lethal or fatal injuries for marine mammals, whilst vessel noise can cause acoustic masking that effectively reduces an animal's listening space, potentially impacting their communication, navigation and foraging capacity.While a number of parallel approaches to mapping collision risk to large whales have arisen, these methods vary in their focus, usually on either co‐occurrence, collision probability, or probability of mortality. However, little attention has been given to the implications of methodological choice and data selection on subsequent risk predictions.To assess differences between these approaches, we used a standardised input dataset comprised of telemetry‐point data from tagged bowhead whales, and satellite‐based Automated Identification System (AIS) data of spatial vessel movements covering the Davis‐Baffin Arctic Marine Area. We applied this data to eight different, previously published analyses for deriving areas of vessel risk.We found that the choice of risk mapping approach affected the location, and total area, identified as 'high risk', and that more computationally complex approaches did not necessarily equate to different predictions. There was considerable variation in the total area of 'high risk' predicted within each map (range = 20–42,246 km2).Synthesis and Applications. The results underscore the importance of methodological transparency, informed data selection and careful interpretation when predicting collision risk. We provide practical recommendations for enhancing transparency when predicting risk, and discuss choice of approach suitable for different situations or management applications. It is critical that managers and policy makers are aware of the implications of applying different approaches when interpreting risk evaluation outputs. [ABSTRACT FROM AUTHOR]

Phylogenomics has the power to uncover complex phylogenetic scenarios across the genome. In most cases, no single topology is reflected across the entire genome as the phylogenetic signal differs among genomic regions due to processes, such as introgression and incomplete lineage sorting. Baleen whales are among the largest vertebrates on Earth with a high dispersal potential in a relatively unrestricted habitat, the oceans. The fin whale (Balaenoptera physalus) is one of the most enigmatic baleen whale species, currently divided into four subspecies. It has been a matter of debate whether phylogeographic patterns explain taxonomic variation in fin whales. Here we present a chromosome-level whole genome analysis of the phylogenetic relationships among fin whales from multiple ocean basins. First, we estimated concatenated and consensus phylogenies for both the mitochondrial and nuclear genomes. The consensus phylogenies based upon the autosomal genome uncovered monophyletic clades associated with each ocean basin, aligning with the current understanding of subspecies division. Nevertheless, discordances were detected in the phylogenies based on the Y chromosome, mitochondrial genome, autosomal genome and X chromosome. Furthermore, we detected signs of introgression and pervasive phylogenetic discordance across the autosomal genome. This complex phylogenetic scenario could be explained by a puzzle of introgressive events, not yet documented in fin whales. Similarly, incomplete lineage sorting and low phylogenetic signal could lead to such phylogenetic discordances. Our study reinforces the pitfalls of relying on concatenated or single locus phylogenies to determine taxonomic relationships below the species level by illustrating the underlying nuances that some phylogenetic approaches may fail to capture. We emphasize the significance of accurate taxonomic delineation in fin whales by exploring crucial information revealed through genome-wide assessments. [ABSTRACT FROM AUTHOR]

Simple Summary: The Omura's whale was first described in 2003 and is currently listed as 'Data Deficient' on the IUCN Red List. Distributed globally in tropical waters, there remains an absence of knowledge on the species' behaviour and ecology, especially in Australian waters. This study utilised historic acoustic data to provide the first wide-scale investigation into Omura's whale distribution and seasonality around Australia, including any potential migratory movements they undertake. We identified the species' acoustic presence on the east coast of Australia for the first time and its seasonal presence on the west coast. Unlike most baleen whales which migrate between the poles and the equator annually with separated feeding and breeding grounds, the Omura's whale inhabits certain regions around Australia for all months of the year. Currently, the Omura's whale is not listed in any management or conservation policies in Australia so the description of when and where they are inhabiting will provide the first steps in developing these policies for the species in Australia, which is particularly important given that the identified distribution of the species crosses over with a lot of offshore industry operations. The Omura's whale (Balaenoptera omurai) is one of the most recently described species of baleen whale. Initially known only from stranding and whaling specimens, it has now been identified in all ocean basins excluding the central and eastern Pacific. Unlike most baleen whales that migrate between the poles and the equator seasonally, the Omura's whale is known to inhabit tropical to sub-tropical waters year-round. In Australian waters, there remain fewer than 30 confirmed visual sightings over the past decade. However, based on acoustic records, the Omura's whale has been detected off areas of the northwest coast of Australia year-round. This study utilises passive acoustic recordings from 41 locations around Australia from 2005 to 2023 to assess the distribution and seasonality of the Omura's whale. The seasonal presence of Omura's whale vocalisations varied by location, with higher presence at lower latitudes. Vocalisations were detected year-round in the Joseph Bonaparte Gulf in the Timor Sea, and near Browse Island and Scott Reef, in the Kimberley region. In the Pilbara region, acoustic presence mostly peaked from February to April and no acoustic presence was consistently observed from July to September across all sites. The most southerly occurrence of Omura's whale vocalisations was recorded off the North West Cape in the Gascoyne region. Vocalisations similar but not identical to those of the Omura's whale were detected in the Great Barrier Reef. The identified seasonal distribution provides valuable information to assess environmental and anthropogenic pressures on the Omura's whale and to aid in creating management and conservation policies for the species in Australia. [ABSTRACT FROM AUTHOR]

In 2014, a novel call was discovered in autonomous acoustic recordings from the Mariana Archipelago and designated a "Biotwang". It was assumed to be produced by a baleen whale, but without visual verification it was impossible to assign a species. Using a combination of visual and acoustic survey data collected in the Mariana Archipelago, we determined that Biotwangs are produced by Bryde's whales. Bryde's whales occur worldwide in tropical and warm temperate waters, but their population structure and movements are not well understood. Genetic and morphological data recognize two populations in the western North Pacific (WNP), separate from those elsewhere in the Pacific. We used a combination of manual and machine learning annotation methods to detect Biotwangs in our extensive historical passive acoustic monitoring datasets collected across the central and western North Pacific. We identified a consistent seasonal presence of Biotwangs in the Mariana Archipelago and to the east at Wake Island, with occasional occurrence as far away as the Northwestern Hawaiian Islands and near the equator (Howland Island). The seasonal occurrence of Biotwangs is consistent with Bryde's whales migrating between low and mid-latitudes, with a small peak in calling between February and April and a larger peak between August and November as the whales travel past the recording sites. Our results provide evidence for a pelagic WNP population of Bryde's whales with broad distribution, but with seasonal and inter-annual variation in occurrence that imply a complex range most likely linked to changing oceanographic conditions in this region. [ABSTRACT FROM AUTHOR]

Blue whales (Balaenoptera musculus) are the largest living animal and, like other baleen whales, became endangered due to whaling. Here, we used population genomics to infer the number, distribution and other characteristics of subspecies and populations. We used the largest DNA dataset in blue whales, both in terms of genomic markers (16,661 SNPs and mtDNA) and geographic coverage (n = 276 for SNPs; n = 531 for mtDNA). We found greatest divergence among the eastern Pacific, Indo‐western Pacific and Antarctic blue whales. There were indications that natural selection in different environments promoted divergence among these groupings. Within these regions, there was divergence between the eastern North and eastern South Pacific, and among the eastern Indian Ocean, the western South Pacific and the northern Indian Ocean. There was no divergence within the Antarctic. These findings are consistent with the current classification of Antarctic and Indo‐western Pacific blue whales in the Southern Hemisphere as different subspecies but call into question the subspecies taxonomy of eastern Pacific blue whales. The study shows that opposite breeding seasons on either side of the equator do not necessarily inhibit connectivity across the equator, and reinforces that population structure needs to be well understood to conserve the diversity within species. [ABSTRACT FROM AUTHOR]

Ocean noise produced by seismic exploration has been implicated in causing changes in baleen whale hearing, physiology, feeding, breeding, and migratory behaviours. Here, we observed changes in the mating tactics of humpback whales (Megaptera novaeangliae) during a one-hour exposure to nearby seismic air guns. Males employ a conditional mating strategy where they switch between singing and non-singing tactics. Singing is presumably an advertisement signal, while non-singing behaviours include seeking out and joining with females as well as forming competitive groups. During periods of active air guns, the number of male singing whales increased, and singers were more likely to be observed joining females. Conversely, non-singing males were less likely to engage in joining interactions suggesting that active air guns caused a switch in male breeding tactics. Though we cannot translate these effects into changes in breeding success, this indicates that seismic exploration has the potential to alter breeding behaviours in baleen whales. Male humpback whales respond to seismic air gun activity by increasing singing and breeding activity. [ABSTRACT FROM AUTHOR]

Dichromatic color vision is mediated by two cone visual pigments in many eutherian mammals. After reentry into the sea, early cetaceans lost their violet-sensitive visual pigment (short wavelength-sensitive 1) independently in the baleen and toothed whale ancestors and thus obtained only monochromatic cone vision. Subsequently, losses of the middle/long wavelength-sensitive (M/LWS) pigment have also been reported in multiple whale lineages, leading to rhodopsin (RH1)-mediated rod monochromatic vision. To further elucidate the phenotypic evolution of whale visual pigments, we assessed the spectral tuning of both M/LWS and RH1 from representative cetacean taxa. Interestingly, although the coding sequences for M/LWS are intact in both the pygmy right whale and the Baird's beaked whale, no spectral sensitivity was detected in vitro. Pseudogenization of other cone vision-related genes is observed in the pygmy right whale, suggesting a loss of cone-mediated vision. After ancestral sequence reconstructions, ancient M/LWS pigments from cetacean ancestors were resurrected and functionally measured. Spectral tuning of M/LWS from the baleen whale ancestor shows that it is green sensitive, with a 40-nm shift in sensitivity to a shorter wavelength. For the ancestor of sperm whales, although no spectral sensitivity could be recorded for its M/LWS pigment, a substantial sensitivity shift (20 to 30 nm) to a shorter wavelength may have also occurred before its functional inactivation. The parallel phenotypic evolution of M/LWS to shorter wavelength sensitivity might be visual adaptations in whales allowing more frequent deep-sea activities, although additional ecological differentiations may have led to their subsequent losses. [ABSTRACT FROM AUTHOR]

The earliest Miocene (Aquitanian, 23–20 Ma) remains a critically under-sampled 'dark age' in cetacean evolution. This is especially true of baleen whales (mysticetes), Aquitanian specimens of which remain almost entirely unknown. Across the globe, the nature of the cetacean fossil record radically shifts at the Oligocene-Miocene boundary, with mysticetes and some archaic odontocete lineages suddenly disappearing despite the availability of cetacean-bearing rock units. New Zealand is the only place worldwide where this change is not readily apparent, with baleen whales apparently persisting into the earliest Miocene. Whether this is a genuine pattern has so far remained obscured by a lack of biostratigraphic resolution associated with the Oligo-Miocene boundary. Here, we report 23 new strontium (87Sr/86Sr) dates from Lentipecten shells associated with 16 mysticete and seven odontocete specimens, respectively. Of these, eight fall within the Early Miocene and seven – including five mysticetes – specifically within the Aquitanian. Our findings confirm the unique nature and global importance of the cetacean fossil record from New Zealand, and provide a foundation for investigations into the causes and effects of the Early Miocene cetacean 'dark age'. [ABSTRACT FROM AUTHOR]

Eomysticetidae are a clade of early diverging functionally toothless, longirostrine and likely baleen-bearing stem mysticete whales. Eomysticetid fossils are rare but known worldwide from Oligocene strata. The richest assemblage of eomysticetids has been uncovered in New Zealand from the Kokoamu Greensand and Otekaike Limestone (North Otago and South Canterbury regions, South Island). This includes some of the largest known eomysticetids, Tokarahia kauaeroa and Tokarahia lophocephalus, some older and more archaic forms such as Matapanui waihao, the fragmentary Tohoraata raekohao and Tohoraata waitakiensis, and the well-known Waharoa ruwhenua represented by several well-preserved skulls and mandibles of adults and juveniles. Studies of these New Zealand fossils strongly indicates monophyly of Eomysticetidae and suggest possible skim feeding behaviour, possession of non-functional teeth and baleen, extreme rostral lengthening during growth and peramorphic evolution, rostral kinesis, use of Zealandia as a calving ground, and probable extinction at or near the Oligo-Miocene boundary. [ABSTRACT FROM AUTHOR]

Recent research on mysticete fossils from the Late Eocene and Oligocene has revolutionised our understanding of the diversity and evolutionary scenarios for early baleen whales. For example, aetiocetids are a possible, though controversial, lineage that bridges the gap between the toothed and baleen-bearing mysticetes, and eomysticetids show a further transitional step towards the baleen-bearing status, with the presence of non-functional dentition in adults. However, information about the origin of crown mysticetes, including the most recent common ancestor of all extant lineages and its descendants, is critical to further understanding the evolution of baleen whales. The phylogenetic positions of the Oligocene Toipahautea, Whakakai, Horopeta, and Mauicetus from New Zealand remain unresolved and problematic, but all four genera show a close relationship with crown mysticetes. The original and subsequent cladistic analyses have consistently revealed a sister relationship between the Toipahautea-to-Mauicetus grade and crown mysticetes, and Horopeta has been placed close to the cetotheriids within the crown group. This review aims to stimulate more research on this topic by elucidating the origin of crown mysticetes, which likely experienced a poorly known radiation event during the Oligocene that established the modern lineages. [ABSTRACT FROM AUTHOR]

Passive acoustic monitoring (PAM) is commonly used to obtain year‐round continuous data on marine soundscapes harboring valuable information on species distributions or ecosystem dynamics. This continuously increasing amount of data requires highly efficient automated analysis techniques in order to exploit the full potential of the available data. Here, we propose a benchmark, which consists of a public dataset, a well‐defined task and evaluation procedure to develop and test automated analysis techniques. This benchmark focuses on the special case of detecting animal vocalizations in a real‐world dataset from the marine realm. We believe that such a benchmark is necessary to monitor the progress in the development of new detection algorithms in the field of marine bioacoustics. We ultimately use the proposed benchmark to test three detection approaches, namely ANIMAL‐SPOT, Koogu and a simple custom sequential convolutional neural network (CNN), and report performances. We report the performance of the three detection approaches in a blocked cross‐validation fashion with 11 site‐year blocks for a multi‐species detection scenario in a large marine passive acoustic dataset. Performance was measured with three simple metrics (i.e., true classification rate, noise misclassification rate and call misclassification rate) and one combined fitness metric, which allocates more weight to the minimization of false positives created by noise. Overall, ANIMAL‐SPOT performed the best with an average F metric of 0.83, followed by the custom CNN with an average fitness metric of 0.79 and finally Koogu with an average fitness metric of 0.59. The presented benchmark is an important step to advance in the automatic processing of the continuously growing amount of PAM data that are collected throughout the world's oceans. To ultimately achieve usability of developed algorithms, the focus of future work should be laid on the reduction of the false positives created by noise. [ABSTRACT FROM AUTHOR]

After the worldwide moratorium on whaling, humpback whale populations began to recover, reoccupying former areas of use, as also observed on the Brazilian coast. Abrolhos Bank represents the area of greatest humpback whale concentration but the number of individuals to the north has increased, as has happened in the region of Serra Grande. To compare relative abundance, habitat use, and movement patterns between a well‐established breeding and a reoccupation area, visual monitoring from land‐based stations was performed: 160 days in the Abrolhos Archipelago located on the Abrolhos Bank and 133 days in Serra Grande in 2014, 2015, 2018, and 2019. While relative abundance varied annually in the Abrolhos Archipelago, it gradually increased in Serra Grande, surpassing the number registered in Abrolhos in 2019. Group composition frequency was similar between areas except for mother and calf accompanied by one or more escorts, which were more frequent in Abrolhos. Despite similar movement speed and linearity values, whales in Serra Grande had a higher reorientation rate. Monitoring different areas occupied by this population supports decisions about spatial management of the Brazilian coast in relation to the implementation of anthropogenic activities, especially in areas where whales have recently returned to occupy. [ABSTRACT FROM AUTHOR]

We explore the utility of estimating the density of calls of baleen whales for better understanding acoustic trends over time. We consider as a case study stereotyped 'song' calls of Antarctic blue whales (Balaenoptera musculus intermedia) on their Antarctic feeding grounds over the course of a year-long, continuous recording from 2014. The recording was made in the Southern Ocean from a deep-water autonomous hydrophone moored near the seafloor in the Eastern Indian sector of the Antarctic. We estimated call density seasonally via a Monte-Carlo simulation based on the passive sonar equation, and compared our estimates to seasonal estimates of detection rate, which are commonly reported in acoustic studies of Antarctic blue whales. The resulting seasonal call densities at our Antarctic sitewere strongly influenced by seasonally varying noise levels, which in turn yielded seasonal differences in detection range. Incorporating the seasonal estimates of detection area into our analysis revealed a pattern of call densities in accord with historic (nonacoustic) knowledge of Antarctic blue whale seasonal distribution and migrations, a pattern that differed from seasonal detection rates. Furthermore, our methods for estimating call densities produced results that were more statistically robust for comparison across sites and time and more meaningful for interpretation of biological trends compared to detection rates alone. These advantages came at the cost of a more complex analysis that accounts for the large variability in detection range of different sounds that occur in Antarctic waters, and also accounts for the performance and biases introduced by automated algorithms to detect sounds. Despite the additional analytical complexities, broader usage of call densities, instead of detection rates, has the potential to yield a standardized, statistically robust, biologically informative, global investigation of acoustic trends in baleen whale sounds recorded on single hydrophones, especially in the remote and difficult to access Antarctic. [ABSTRACT FROM AUTHOR]

The relative importance of various sensory modalities can shift in response to evolutionary transitions, resulting in changes to underlying gene families encoding their reception systems. The rapid birth‐and‐death process underlying the evolution of the large olfactory receptor (OR) gene family has accelerated genomic‐level change for the sense of smell in particular. The transition from the land to sea in marine mammals is an attractive model for understanding the influence of habitat shifts on sensory systems, with the retained OR repertoire of baleen whales contrasting with its loss in toothed whales. In this study, we examine to what extent the transition from a terrestrial to a marine environment has influenced the evolution of baleen whale OR repertoires. We developed Gene Mining Pipeline (GMPipe) (https://github.com/AprilJauhal/GMPipe), which can accurately identify large numbers of candidate OR genes. GMPipe identified 707 OR sequences from eight baleen whale species. These repertoires exhibited distinct family count distributions compared to terrestrial mammals, including signs of relative expansion in families OR10, OR11 and OR13. While many receptors have been lost or show signs of random drift in baleen whales, others exhibit signs of evolving under purifying or positive selection. Over 85% of OR genes could be sorted into orthologous groups of sequences containing at least four homologous sequences. Many of these groups, particularly from family OR10, presented signs of relative expansion and purifying selective pressure. Overall, our results suggest that the relatively small size of baleen whale OR repertoires result from specialisation to novel olfactory landscapes, as opposed to random drift. [ABSTRACT FROM AUTHOR]

The Southern Ocean ecosystem has undergone extensive changes in the past two centuries driven by industrial sealing and whaling, climate change and commercial fishing. However, following the end of commercial whaling, some populations of whales in this region are recovering. Baleen whales are reliant on Antarctic krill, which is also the largest Southern Ocean fishery. Since 1993, krill catch has increased fourfold, buoyed by nutritional supplement and aquaculture industries. In this Perspective, we approximate baleen whale consumption of Antarctic krill before and after whaling to examine if the ecosystem can support both humans and whales as krill predators. Our back-of-the-envelope calculations suggest that current krill biomass cannot support both an expanding krill fishery and the recovery of whale populations to pre-whaling sizes, highlighting an emerging human-wildlife conflict. We then provide recommendations for enhancing sustainability in this region by reducing encounters with whales and bolstering the krill population. The Southern Ocean ecosystem is recovering from 20th-century industrial whaling, while the krill fishery in this region has grown rapidly and may expand further, driven by demand for supplements and aquaculture feed. This Perspective discusses how current krill biomass is unlikely to support both a growing krill fishery and rebounding whale populations in the Southern Ocean. [ABSTRACT FROM AUTHOR]

A new fossil gray whale genus and species, Glaucobalaena inopinata, is established based on craniomandibular remains from the Pliocene Sabbie d'Asti Formation, Piedmont, northwestern Italy. The holotype (MGPT-PU 19512) consists of two cranial fragments corresponding to the posterolateral corners of the skull, including both partial periotics, and in the posterior portion of the right mandibular ramus preserving the condyle and angular process. The new taxon is characterized by gray whale (eschrichtiid) synapomorphies in the posterior portion of the mandible (dorsally raised mandibular condyle with articular surface faced dorsoposteriorly, well-developed and robust angular process of the mandible) and in the earbone (massive transverse elongation of the pars cochlearis, indistinct flange of the ventrolateral tuberosity, and triangular and short anterior process of the periotic). A CT scan of the cranial fragments allowed us to reconstruct tridimensional renderings of the periotic, revealing the dorsal morphology of this bone. A phylogenetic analysis confirmed the inclusion of Glaucobalaena inopinata within Eschrichtiidae (the family to whom gray whales are included) and showed that it is monophyletic with Gricetoides aurorae; our phylogenetic results show that Eschrichtioides gastaldii is the sister group of the genus Eschrichtius. Our work lends further support to the idea that Eschrichtiidae is a separate family of baleen whales, characterized by specialized ecomorphological characters evident in both skull and mandibular architecture. [ABSTRACT FROM AUTHOR]

Most baleen whale populations are increasing after the end of industrial whaling, but their recovery patterns challenge long‐standing assumptions about density dependence.It has long been assumed that population growth rates will decline with recovery, until reaching equilibrium ('carrying capacity', K). Indeed, the International Whaling Commission assumes that growth rates will slow long before K is reached, with maximum productivity at 0.6K. This 0.6K population level is used as an international benchmark that forms the basis of whaling regulations and decisions about whether baleen whale populations are declared depleted.We fit models to four long‐term data sets for baleen whales with multiple abundance estimates that span the range from low to high abundance, finding strong evidence that increase rates remain at near‐maximal levels across a wide range of abundance levels, and only decline as the population nears K. As a result, maximum productivity occurs at 0.69–0.87 of K across these populations, which predicts more rapid recovery for baleen whale populations than currently assumed. The overall mean of these values (0.8K) would be a more sensible default choice than the 0.6K currently assumed.Synthesis and applications. Estimated recovery rates imply that management thresholds currently used are lower than actual maximum productivity and that populations can increase rapidly even at high abundance. However, if population models continue to assume that maximum productivity is at 0.6K, they will estimate abundance relative to K to be lower than it is, providing conservative assessment results. Our results should stimulate further discussion about the role of maximum sustainable yield as a fundamental concept in fisheries and wildlife management. [ABSTRACT FROM AUTHOR]

Coastal marine and fluvial deposits, exposed at Cerro El Divisadero near Rancho La Palma, Baja California Sur, Mexico, contain a fossil record of cetaceans (baleen whales). U-Pb zircon dating of a tuff horizon collected near the base of Cerro El Divisadero yields a 206Pb/238U age of 27.95 ± 0.16 Ma. This suggests that the marine and fluvial beds at the Rancho La Palma locality are late Rupelian in age and not lower Miocene as previously reported. Therefore, the marine deposits from the Cerro El Divisadero section can be correlated with the Oligocene El Cien Formation at San Juan de La Costa and are contemporaneous with the middle part of its San Juan Member, representing a marginal facies of this unit. Our results constrain the age of the baleen whales found at the Cerro El Divisadero section, providing clues for Oligocene cetacean evolution in the North Pacific. [ABSTRACT FROM AUTHOR]