Eighteen years of visual survey and strandings data were used to describe baleen whale occurrence along the continental shelf of Virginia and North Carolina, U.S.A. This region experiences heavy anthropogenic use, which poses risks for mortality and injury to baleen whales. Between 2001 and 2019, six species of baleen whales were recorded, and whales occurred year-round. The total number of (on- and off-effort) sightings and strandings amounted to 838 whales, including humpback (Megaptera novaeangliae, n = 503), fin (Balaenoptera physalus, n = 197), North Atlantic right (Eubalaena glacialis, NARW, n = 76), common minke (B. acutorostrata, n = 51), sei (B. borealis, n = 10), and blue (B. musculus, n = 1) whales. Spatial modeling and abundance estimates indicated whale density and distribution changed seasonally. The highest densities of all whales combined occurred in winter and spring. Across seasons, average densities were highest in the northern portion of the study area. Ninety percent of NARW sightings were outside the designated Seasonal Management Areas in place for their protection. The stranding record offered a complementary view of species richness and seasonality. This study provides a baseline of baleen whale occurrence in an area experiencing increasing anthropogenic pressures (e.g., ship traffic and offshore wind-energy development).

The complex population structure of Tamanend's bottlenose dolphins (Tursiops erebennus) along the U.S. Mid-Atlantic coast complicates assessment of their bycatch. To improve our understanding of the stock identity of individual dolphins taken as bycatch in this region, we compared images of the dorsal fins of bottlenose dolphins that stranded with evidence of fishery interactions (FI+) to the Mid-Atlantic Bottlenose Dolphin Catalog (MABDC). We obtained stranding data from NOAA Fisheries for 715 FI+ bottlenose dolphins from Virginia (VA), North Carolina (NC), and South Carolina (SC) from 1996 to 2019; approximately two thirds of these records included dorsal fin images. For records for which images were available, we applied restrictive criteria for image quality and dorsal fin distinctiveness and compared the remaining 145 distinctive FI+ individuals to the MABDC. We matched 18 dolphins to regional catalogs and assigned stock identity to 13 of the matches; two were from migratory coastal stocks and 11 were from small estuarine stocks in NC and SC. Our analysis demonstrates how the risk of bycatch varies across bottlenose dolphin stocks along the Mid-Atlantic coast, provides an important feedback information loop to stranding responders and researchers studying dolphins in the field, and informs conservation efforts to address bycatch of bottlenose dolphins in this region.

The pygmy sperm whale (Kogia breviceps) possesses an exocrine gland associated with its false gill slit pigmentation pattern. The cervical gill slit gland is a compound tubuloalveolar gland that produces a holocrine secretion and displays maturational changes in size and secretory histology. While the morphology of the cervical gill slit gland has been described in detail, to date, the chemical composition of its secretion remains uncharacterized. This study used histochemical staining techniques and quantitative lipid analysis to identify and characterize the constituents expressed in the secretory cells and secretion of the cervical gill slit gland. Results demonstrate that the secretion, like those of terrestrial artiodactyls that function in chemical communication, includes a complex mixture of carbohydrates, proteins, and lipids. Differences in staining intensity across germinal and secretory epithelial layers demonstrate differential expression, or maturation, of mucins and proteins. Additionally, a highly unusual and primary constituent of the secretion is uric acid. Uric acid was identified within the secretion using histochemical stains and polarized light imaging, and chemically verified using scanning electron microscopy with energy dispersive spectrometry. While uric acid is not a common constituent of mammalian exocrine glands, urate-based compounds are abundant in the secretions of marine organisms used in chemical communication. Thus, uric acid may contribute to the chemical message produced by K. breviceps in its marine environment. We hypothesize that the chemical signals produced by the gill slit gland may be shared at close-range by conspecifics, and that the mode of sensory reception is likely gustation.

The glymphatic system, an analog of the peripheral lymphatic system in the brain, and the meningeal lymphatic system are critical to central nervous system health. The glymphatic system functions to distribute cerebrospinal fluid and important compounds throughout the brain and to remove metabolic waste. The flow of cerebrospinal fluid through this system is affected by changes in cerebral blood flow, intracranial pressure, and vascular tone. Cetaceans experience profound cardiorespiratory alterations while diving that can directly affect cerebrospinal fluid and blood flow and, thus, glymphatic function. Our goal was to investigate glymphatic and lymphatic system structures, including perivascular spaces, aquaporin-4 water channels, meningeal lymphatic, and dural venous sinus vessels in the common dolphin (Delphinus delphis), using immunofluorescent labeling, histochemical staining, and postmortem computed tomography (CT) angiography. We highlight perivascular spaces and aquaporin-4 water channels surrounding blood vessels in the parenchyma and demonstrate evidence of meningeal lymphatic vessels and associated dural venous sinuses. These results demonstrate that common dolphins possess the key anatomical structures required for functional glymphatic and meningeal lymphatic systems. Future studies can build upon these anatomical discoveries to study the function and role of these systems in brain health in this species.

In humans and mice, the glymphatic system, critical for central nervous system (CNS) health, relies on cardiorespiratory coupling, but has not yet been investigated in a diving mammal that routinely experiences apnea, bradycardia, and peripheral vasoconstriction. The glymphatic and meningeal lymphatic systems maintain CNS homeostasis by distributing nutrients and clearing metabolic waste via cerebrospinal fluid. We investigated meningeal lymphatic and glymphatic structures in stranded bottlenose dolphins (Tursiops truncatus; n = 9) using immunofluorescence microscopy, histochemical staining, and CT angiography. Results demonstrate that the bottlenose dolphin possesses prominent perivascular spaces and aquaporin-4 astroglial water channels required for glymphatic function, as well as meningeal lymphatic vessels in close anatomic proximity to dural venous sinuses, required for a functional meningeal lymphatic system. Notably, we also identified arachnoid granulations involved in cerebrospinal fluid resorption, marking the first such observation in this species. This study provides evidence of both glymphatic and meningeal lymphatic systems in the most well-studied cetacean, the bottlenose dolphin.

The Critically Endangered North Atlantic right whale Eubalaena glacialis entered a population decline around 2011. To save this species without closing the ocean to human activities requires detailed information about its intra-annual density patterns that can be used to assess and mitigate human-caused risks. Using 2.9 million km of visual line-transect survey effort from the US Atlantic and Canadian Maritimes conducted in 2003-2020 by 11 institutions, we modeled the absolute density (ind. km-2) of the species using spatial, temporal, and environmental covariates at a monthly time step. We accounted for detectability differences between survey platforms, teams, and conditions, and corrected all data for perception and availability biases, accounting for platform differences, whale dive behavior, group composition, and group size. We produced maps of predicted density and evaluated our results using independently collected passive acoustic monitoring (PAM) data. Densities correlated positively (r = 0.46, ρ = 0.58, τ = 0.46) with acoustic detection rates obtained at 492 stationary PAM recorders deployed across the study area (mean recorder duration = 138 d). This is the first study to quantify the concurrence of visual and acoustic observations of the species in US waters. We summarized predictions into mean monthly density and uncertainty maps for the 2003-2009 and 2010-2020 eras, based on the significant changes in the species’ spatial distribution that began around 2010. The results quantify the striking distribution shifts and provide effort- and bias-corrected density surfaces to inform risk assessments, estimations of take, and marine spatial planning.

On November 1, 2023, the American Ornithological Society (AOS), announced it would "change all English bird names currently named after people within its geographic jurisdiction" (AOS, 2023). The AOS President, Dr. Colleen Handel, noted that "there is power in a name, and some English bird names have associations with the past that continue to be exclusionary and harmful today" (AOS, 2023). Common names are important because they are used to identify and communicate effectively about species amongst the scientific and broader community. As noted by Dr. Handel, these names also carry a legacy that can reinforce exclusivity. In this letter, we urge the marine mammal science community to discard the use of the English common name "Cuvier's beaked whale" for Ziphius cavirostris. Instead, we recommend adoption of the alternative English common name for this species, the goose-beaked whale. We make this request because of Georges Cuvier's foundational role in creating and disseminating scientific racism and his misogynistic beliefs. We also ask that marine mammal scientists address the history associated with other eponymous common names and the impact of this history on members of our community. Georges Cuvier erroneously described Ziphius cavirostris as an extinct species of whale in Recherches sur les ossements, after the specimen was excavated and donated to him by a "peasant" in Cuvier's words (Cuvier, 1823). His name is often associated with the species, as a result. However, many modern scientists may not be familiar with Cuvier's role in creating and disseminating scientific racism and how his racist beliefs were foundational in his research practices and theories, which we will describe briefly here. During his career, Cuvier was a vocal critic of theories of evolution (Cuvier & Latreille, 1829; Jackson & Weidman, 2006) and, in 1829, published Le Règne Animal, in which he ranked three "human races" and proclaimed Caucasians as the original and superior race (Jackson & Weidman, 2006). He "correlated cranial and facial measurements with perceived moral and mental capabilities," which he claimed was "divinely created and unchangeable," following his belief in monogenism (Cuvier & Latreille, 1829; Jackson & Weidman, 2006). Cuvier's work was foundational to scientific racism. He also had many students who promoted monogenism and elaborated eugenic theories, including Sir William Lawrence, who believed that "sexual selection has improved the beauty of advanced races and governing classes" (Darlington, 1961; Hartocollis, 2019; Jackson & Weidman, 2006). As part of his scientific work, Georges Cuvier exploited a woman called Saartjie "Sara" Baartman, a Khoisan woman from the Eastern Cape in South Africa (Johnson & Rolls, 2023). The name Saartjie Baartman was given to her by Dutch colonizers, and her true given name is unknown. In 1810, she was taken to London to be exhibited for white Europeans using the stage name "Hottentot Venus." She was displayed as an animal, a freak of nature "exhibited like a wild beast; being obliged to walk, stand, or sit as [her keeper] ordered her" due to her physical features as a Black woman (Schiebinger, 2013). She was later sold and taken to France to again be put on public display before she died in 1815 at the age of 26 (Johnson & Rolls, 2023). Before Baartman's death, Cuvier subjected her to countless examinations which she opposed, as he noted in his report "Extract of Observations Made on the Corpse of a Woman Known… under the name of Venus Hottentot." After Baartman's death, Cuvier took over three days to dissect her corpse (Johnson & Rolls, 2023). In his report, Cuvier suggested that Baartman, as well as people who looked like her, were not to be mistaken as equals, labeling them as "almost entirely savage" and those that "infest certain parts of the Cape colony" (Johnson & Rolls, 2023). Much of the content presented in the autopsy characterized Baartman as a specimen whose humanity was not worth acknowledging or honoring (Jackson & Weidman, 2006). Cuvier considered Baartman and other people of African descent as inhuman, inferior, and unworthy of the same respect as white Europeans (Cuvier & Latreille, 1829; Jackson & Weidman, 2006). There are many other quotations from the report that are too horrific and demeaning to include in this letter, but we refer readers to the analysis of Johnson & Rolls (2023) for a full account. Cuvier preserved parts of her body, including her brain and genitalia, and they were displayed in the Musée de l'Homme in Paris until the 1970s. Her remains were returned to South Africa in 2002, where they were finally buried (Daley, 2002). Considering Cuvier's horrific history of racism and sexism, we believe that the continued use of his name perpetuates the harm that he inflicted on Sara Baartman and continues to harm Black women, people who identify as women, and the Black community in general. The Society for Marine Mammalogy Diversity and Inclusion Statement recognizes that "the field of marine mammal science is only strengthened by the participation of people representing all ages, career stages, professional status, races, national, cultural, and socio-economic backgrounds, genders, gender identities, sexual orientations, and physical abilities." To act on this statement, we request that the marine mammal science community discontinue the use of Cuvier's name to refer to Ziphius cavirostris and, more broadly, follow the AOS and reconsider all eponymous names of marine mammal species. We encourage marine mammal scientists to read the AOS committee report and other readings listed below. Finally, we urge our colleagues around the world to engage with diverse scholars from varying backgrounds to generate common names that reflect the attributes of each species, including their distribution, morphology, and behavior. We want the field of marine mammal science to be an inclusive space for everyone, especially those who have been historically marginalized. To do so, we must work to address the history of scientific racism and do our part in acknowledging and rectifying the harm that this history carries. Ashley D. Rogers: Conceptualization; writing – original draft; writing – review and editing. Andrew Read: Conceptualization; writing – review and editing. Arona Bender: Writing – review and editing. Anna Borroni: Writing – review and editing. William R. Cioffi: Writing – review and editing. Brianna Elliott: Writing – review and editing. Craig Harms: Writing – review and editing. Anne E. Harshbarger: Writing – review and editing. Ann-Marie Jacoby: Writing – review and editing. Aileen Lavelle: Conceptualization; writing – original draft; writing – review and editing. Kathyrn Lienhard: Conceptualization; writing – review and editing. Sydney Mantell: Conceptualization; writing – review and editing. William A. McLellan: Writing – review and editing. Greg Merrill: Writing – review and editing. D. Ann Pabst: Writing – review and editing. Keith A. Rittmaster: Writing – review and editing. Massimiliano Rosso: Writing – review and editing. Greg Schorr: Writing – review and editing. Brandon L. Southall: Writing – review and editing. Zach T. Swaim: Writing – review and editing. Paola Tepsich: Writing – review and editing. Vicky G. Thayer: Writing – review and editing. Kim W. Urian: Writing – review and editing. Danielle M. Waples: Writing – review and editing. Daniel L. Webster: Writing – review and editing. Jillian Wisse: Writing – review and editing. Dana L. Wright: Writing – review and editing. We thank Dr. Heather Vermeulen, the Mary Derrickson McCurdy Visiting Scholar at the Duke University Marine Laboratory, for opening our eyes to the horrific legacy of Georges Cuvier and for inspiring this call for change.

Oceans are increasingly crowded by anthropogenic activities yet the impact on Outer Continental Shelf (OCS) marine life remains largely unquantified. The MAPS (Marine Mammal Acoustic and Spatial Ecology) study of 2019 included passive acoustic and visual vessel surveys over the Mid-Atlantic OCS of the USA to address data gaps in winter/spring for deep-diving cetaceans, including sperm whales. Echolocation clicks were used to derive slant ranges to sperm whales for design- and model-based density estimates. Although more survey effort was realised in the spring, high densities of whales were identified in both winter and spring (10.46 and 8.89 per 1000 km2 respectively). The spring model-based abundance estimate of 1587 whales (CI 946-2663) was considered the most representative figure, in part due to lower coefficients of variation. Modelling suggested that high densities of whales were associated with warm core rings, eddies and edges. As OCS waters provide an important foraging habitat for North Atlantic sperm whales, appropriate mitigation is required to ensure commercial pressures to develop offshore energy do not negatively affect this endangered species.

Increasing amounts of noise have been introduced into the marine environment by commercial, military and recreational activities over recent decades. Ziphiids (beaked whales in the Family Ziphiidae) are particularly sensitive to anthropogenic noise, which can lead to behavioural and physiological changes that may cause death in extreme cases. Despite these concerns, there are significant gaps in our knowledge of ziphiid distribution and density in areas exposed to noise. This study presents data from acoustic and visual vessel surveys conducted across the Outer Continental Shelf of North and South Carolina and southern Virginia in the USA (NOAA permits 14,809-03 and 16,473) with the aim of addressing data gaps for this region in spring and winter. Echolocation click trains were attributed to either Cuvier's (Ziphius cavirostris) or Gervais' (Mesoplodon europaeus) beaked whales based on peak frequency, 3 dB and 10 dB bandwidths, and inter-click interval. Estimates of click depth were used to correct estimates of perpendicular distance and improve detection functions used in Multiple Covariate Distance Sampling. Availability bias was quantified using tag data from other regions modified with local dive data. Swell height and sea surface temperature were found to affect the detection function and were therefore included in the final model. Incorporating cruise identity (winter vs. spring), candidate species (Cuvier's vs. Gervais' beaked whale) and/or cluster size did not improve model fit, suggesting there was no discernible seasonal effect, variation in detectability by species or increased probability of detection for larger groups. Design-based estimates of global beaked whale density (1.64 individuals per 100 km2: CI 0.88-3.03) and abundance (2963: CI 1597-5497) were then made incorporating a g(0) estimate of 0.43. These represent the first abundance estimates made for ziphiids using a towed hydrophone array off the USA's eastern seaboard. A Density Surface Model suggested slope and Sea Surface Temperature may influence ziphiid density in the region. This study provides seasonal data on deep diving beaked whales that can be used to inform management decisions regarding anthropogenic activities in this region.

Toothed whales utilize specialized nasal structures such as the lipid-rich melon to produce sound and propagate it into the aquatic environment. Very little nasal morphology of mesoplodont beaked whales has been described in the literature, and the anatomy of the melon and associated musculature of Gervais' beaked whale (Mesoplodon europaeus) remains undescribed. Heads of three (n = 3) Gervais' beaked whales were examined in detail via dissection as well as computed tomography (CT) and magnetic resonance imaging (MRI). Two additional Gervais' beaked whale individuals (n = 2) were studied via archived CT and MRI scans. Representative transverse dissection sections of the melon were processed for polarized light imaging to verify the presence of tendons inserting into the melon tissue. Three-dimensional (3D) CT reconstructions of the melon, rostral muscles, and associated structures were performed to assess morphology and spatial relationships. In all individuals, the melon's main body demonstrated a bilaterally asymmetrical, curvilinear geometry. This curvilinear shape was defined by a pattern of alternating asymmetry in the medial rostral muscles that projected into the melon's tissue. In transverse polarized light imaging, a network of tendons originating from these asymmetrical rostral muscle projections was observed permeating the melon's lipid tissue. This curvilinear melon morphology and associated asymmetrical musculature suggest a means of lengthening the lipid pathway within a relatively short dimensional footprint. In addition, the species-specific arrangement of muscular projections suggests complex fine-tuning of the melon's geometry during echolocation. Further studies may lend additional insight into the function of this unusual melon morphology.

In the US mid-Atlantic, multi-disciplinary studies are underway to elucidate the complex stock structure of coastal bottlenose dolphins (Tursiops truncatus), as well as the degree of overlap between coastal and offshore ecotypes. In this study we use geo-referenced data, collected during aerial surveys in 2000-2002, to describe the distribution and relative abundance of bottlenose dolphins along the US midAtlantic coast. Two aerial survey designs were used: (1) onshore/offshore surveys out to 35 n.miles during winter from Georgia to Virginia; and (2) coastal surveys throughout the year along North Carolina (NC). The winter onshore/offshore surveys demonstrated that significantly more bottlenose dolphins occur in Raleigh Bay (between Cape Hatteras and Cape Lookout, NC), than in all other regions. Additionally, in winter most bottlenose dolphins occur in the coastal waters of NC; nearly half of all sightings occurred between the shoreline and 3km from shore. The year-round, coastal surveys demonstrated that this winter distribution pattern is the result of a distinct seasonal increase in the number of dolphins within the coastal waters of NC. Circular statistical analyses demonstrated a strong influence of season on dolphin abundance. Relatively few bottlenose dolphins were observed in late spring, summer, and early autumn, with increased numbers observed during winter. In all seasons but summer, dolphin numbers were highest in Raleigh Bay. Thus, the results of both surveys indicate the importance of the habitat surrounding Cape Hatteras to bottlenose dolphins. Dolphins may preferentially use these waters in response to changes in prey distribution and/or abiotic factors such as water temperature. These results reveal an overall seasonal movement pattern along the US Atlantic coast, which appears to be correlated, at least in part, to water temperature gradients and prey availability. Although the stock identity of dolphins sighted during these aerial surveys could not be ascertained, focused photo-identification efforts, together with enhanced genetic sampling, would provide insights into the movement patterns, and, thus, stock identity, of dolphins in this region.

Adaptive approaches are needed to effectively manage dynamic marine systems, and ecological forecasts can help managers anticipate when and where conservation issues are likely to arise in the future. The recent development of subseasonal global environmental forecasts provides an opportunity to inform management by forecasting species distributions in advance over operational timeframes. We demonstrate the utility of environmental forecasts for managing marine mammals by integrating species distribution models with subseasonal forecasts to predict the arrival of migratory humpback whales (Megaptera novaeangliae) at foraging grounds in the Northeast US. Environmental forecasts showed high model skill at lead times of up to 2 weeks and resulting humpback whale models performed well in predicting humpback arrival. Forecasts of whale distribution can shape management efforts to minimize both impacts on whales and economic costs. Applying subseasonal forecasts to anticipate future risk presents a powerful tool for the dynamic management of marine mammals. Front Ecol Environ 2022;

Gut microbiomes are important determinants of animal health. In sentinel marine mammals where animal and ocean health are connected, microbiome impacts can scale to ecosystem-level importance. Mass mortality events affect cetacean populations worldwide, yet little is known about the contributory role of their gut bacterial communities to disease susceptibility and progression. Here, we characterized bacterial communities from fecal samples of common bottlenose dolphins, Tursiops truncatus, across an unusual mortality event (UME) caused by dolphin Morbillivirus (DMV). 16S rRNA gene sequence analysis revealed similar diversity and structure of bacterial communities in individuals stranding before, during, and after the 2013-2015 Mid-Atlantic Bottlenose Dolphin UME and these trends held in a subset of dolphins tested by PCR for DMV infection. Fine-scale shifts related to the UME were not common (10 of 968 bacterial taxa) though potential biomarkers for health monitoring were identified within the complex bacterial communities. Accordingly, acute DMV infection was not associated with a distinct gut bacterial community signature in T. truncatus. However, temporal stratification of DMV-positive dolphins did reveal changes in bacterial community composition between early and late outbreak periods, suggesting that gut community disruptions may be amplified by the indirect effects of accumulating health burdens associated with chronic morbidity.

Between June 1987 and March 1988, bottlenose dolphins (Tursiops truncatus Montagu 1821) along the US Atlantic coast experienced an epizootic. Monthly interquartile ranges of strandings during the epizootic were used to propose the Coastal Migratory Stock (CMS) of bottlenose dolphins (Scott et al., 1988). To date, the hypothesised CMS remains poorly understood. The goal of this study was to use a 25-year database to compare stranding patterns during the epizootic to those before (1972-1986) and after (1989-1997) the event. These comparisons reveal that monthly interquartile ranges during the epizootic are dissimilar to those before and after the event. The frequency distribution of total monthly strandings during the epizootic is also significantly different from those observed outside the event. Seasonal stranding patterns from 1989-1997 suggest more complex movements of dolphins along the US Atlantic coast than those of a single group ranging seasonally from Florida to New Jersey. In winter, for example, when the current model for the CMS predicts dolphin distributions concentrated in central Florida, the highest number of strandings occurred in North Carolina. Thus, these comparative analyses suggest that the pattern observed during the epizootic was anomalous, and not representative of stranding distributions for any other time period of the study. During the 15 years before the epizootic, and the nine years following, there was no clear picture of ‘migration’ of mortality along the coast. This study demonstrates how long-term, systematic collection of strandings data can be useful in testing hypotheses regarding the complex stock structure of coastal bottlenose dolphins. This knowledge will greatly enhance the ability to conserve and manage these animals as they recover from historic (i.e. directed takes and epizootic) and current sources of mortality.

Carbon monoxide (CO) is known as “The Silent Killer” due to its toxic effect at high concentrations, leading to an impairment in oxygen storage, delivery, and use. The cytotoxicity of CO is due to its high affinity for transition metals, such as iron, where CO outcompetes oxygen for the heme binding sites on hemoproteins in the body. CO is made in vivo in most organisms as a byproduct of heme degradation via heme oxygenase enzymes. Certain species of deep-diving marine mammals with high quantities of hemoproteins in blood and skeletal muscle have naturally elevated concentrations of CO in these tissues. To date, there exist few data on extravascular tissue CO content in wild animals. This study aims to characterize CO concentrations in nine different tissues from stranded Atlantic bottlenose dolphins ( Tursiops truncatus ). We found three tissues (liver, skeletal muscle, and spleen) have higher CO concentrations than other tissues. In a subset of samples from animals that tested positive for dolphin morbillivirus, the CO content in their kidney and liver was lower when compared to animals that tested negative. The mean CO concentration found in every tissue from dolphins was higher than those previously reported in healthy rodents. However, the skeletal muscle CO concentrations in dolphins from this study were much lower than those of deep-diving elephant seals. These results highlight the diversity and pattern of CO found in different tissues from bottlenose dolphins and continues to show that the heme oxygenase/carbon monoxide pathway appears to be critical for air-breathing divers.

In this paper the occurrence, distribution and abundance of cetaceans in offshore waters of Onslow Bay, North Carolina, USA is described. Between June 2007 and June 2010 monthly aerial and shipboard line-transect surveys were conducted along ten 74km transects placed perpendicular to the shelf break. In total 42,676km of aerial trackline (218 sightings) and 5,209km of vessel trackline (100 sightings) were observed. Seven species of cetaceans were observed, but the fauna was dominated strongly by common bottlenose and Atlantic spotted dolphins. Both species were present year-round in the study area. Using photo-identification techniques, five bottlenose dolphins and one spotted dolphin were resighted during the three-year period. In general, the abundance of cetaceans in Onslow Bay was low and too few sightings were made to estimate monthly abundances for species other than bottlenose and spotted dolphins. Maximum monthly abundances of bottlenose and spotted dolphins were 4,100 (95% CI: 1,300–9,400) in May 2010 and 6,000 (95% CI: 2,500–17,400) in March 2009, respectively. Bottlenose dolphins were found throughout the study area, although they were encountered most frequently just off the shelf break. In contrast, spotted dolphins exhibited a strong preference for waters over the continental shelf and were not encountered beyond the shelf break.

In recent years, humpback whales (Megaptera novaeangliae) have been observed in the waters of the US mid-Atlantic states (USMA; New Jersey to North Carolina), notably in winter. The level of the mortality in this area (52 recorded deaths from 1990-2000), makes it important to understand the nature and population identity of this aggregation. Of the approximately 100 humpback whales documented in this study, photographs of 41 (live or dead) were of sufficient quality to be compared to catalogues from the Gulf of Maine (GOM, the closest feeding ground) and elsewhere in the North Atlantic. Of 22 live whales, 10 (45.5%) matched to the GOM, 5 (22.7%) to Newfoundland and 1 (4.5%) to the Gulf of St Lawrence (GSL). Of 19 dead whales, 6 (31.6%) were known GOM whales. Although the population composition of the USMA is dominated by GOM whales, lack of recent photographic effort in Newfoundland makes it likely that the observed match rates under represent the true presence of Canadian whales in the region. Length data from 48 stranded whales (18 females, 22 males and 8 of unknown sex) suggest that 39 (81.2%) were first-year animals, 7 (14.6%) were immature and 2 (4.2%) were adults. However, sighting histories of five of the dead whales indicate that some were small for their age and histories of live whales further indicate that the population contains a greater percentage of mature animals than is suggested by the stranded sample. The authors suggest that the study area primarily represents a supplemental winter feeding ground that is used by humpbacks for more than one purpose. From a management perspective, although the only successful matches of mortalities to date have been to the GOM, the observed mixing of live whales from different summer stocks might suggest that the high numbers of mortalities occurring there may not be impacting this single stock alone. Although further data are required before conclusions can be drawn, the mortality rate may be significant for the GOM population and this warrants further investigation.

Odontocetes are breath-hold divers with a suite of physiological, anatomical, and behavioral adaptations that are highly derived and vastly different from those of their terrestrial counterparts. Because of these adaptations for diving, odontocetes were originally thought to be exempt from the harms of nitrogen gas embolism while diving. However, recent studies have shown that these mammals may alter their dive behavior in response to anthropogenic sound, leading to the potential for nitrogen supersaturation and bubble formation which may cause decompression sickness in the central nervous system (CNS). We examined the degree of interface between blood, gases, and neural tissues in the spinal cord by quantifying its microvascular characteristics in five species of odontocetes ( Tursiops truncatus, Delphinus delphis, Grampus griseus, Kogia breviceps, and Mesoplodon europaeus ) and a model terrestrial species (the pig- Sus scrofa domesticus ) for comparison. This approach allowed us to compare microvascular characteristics (microvascular density, branching, and diameter) at several positions (cervical, thoracic, and lumbar) along the spinal cord from odontocetes that are known to be either deep or shallow divers. We found no significant differences ( p < 0.05 for all comparisons) in microvessel density (9.30–11.18%), microvessel branching (1.60–2.12 branches/vessel), or microvessel diameter (11.83–16.079 µm) between odontocetes and the pig, or between deep and shallow diving odontocete species. This similarity of spinal cord microvasculature anatomy in several species of odontocetes as compared to the terrestrial mammal is in contrast to the wide array of remarkable physio-anatomical adaptations marine mammals have evolved within their circulatory system to cope with the physiological demands of diving. These results, and other studies on CNS lipids, indicate that the spinal cords of odontocetes do not have specialized features that might serve to protect them from Type II DCS.

Compared with terrestrial mammals, marine mammals possess increased muscle myoglobin concentrations (Mb concentration, g Mb · 100g−1 muscle), enhancing their onboard oxygen (O2) stores and their aerobic dive limit. Although myoglobin is not homogeneously distributed, cetacean muscle O2 stores have been often determined by measuring Mb concentration from a single muscle sample (longissimus dorsi) and multiplying that value by the animal’s locomotor muscle or total muscle mass. This study serves to determine the accuracy of previous cetacean muscle O2 stores calculations. For that, body muscles from three delphinid species: Delphinus delphis, Stenella coeruleoalba, and Stenella frontalis, were dissected and weighed. Mb concentration was calculated from six muscles/muscle groups (epaxial, hypaxial and rectus abdominis; mastohumeralis; sternohyoideus; and dorsal scalenus), each representative of different functional groups (locomotion powering swimming, pectoral fin movement, feeding and respiration, respectively). Results demonstrated that the Mb concentration was heterogeneously distributed, being significantly higher in locomotor muscles. Locomotor muscles were the major contributors to total muscle O2 stores (mean 92.8%) due to their high Mb concentration and large muscle masses. Compared to this method, previous studies assuming homogenous Mb concentration distribution likely underestimated total muscle O2 stores by 10% when only considering locomotor muscles and overestimated them by 13% when total muscle mass was considered.