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Understanding the drivers of population abundance and distribution is fundamental to ecology and key to informing conservation actions, particularly in endangered species like blue whales (Balaenoptera musculus). Historically, some Eastern North Pacific blue whales have aggregated in the Gulf of California (GoC) each winter. Using photo‐identification data collected around Loreto Bay from 1984 to 2020, we analyzed 453 sightings histories using mark‐recapture models. Estimated apparent survival (including permanent emigration) decreased from 0.991, 95% CI [0.977, 0.997] in 1985 to 0.889, 95% CI [0.807, 0.939] in 2019. The estimated number of whales using the study area declined from 96 whales, 95% CI [50, 254] in 2012 to 13 whales, 95% CIs [12, 23 and 12, 28] in 2018 and 2019. Abundance of the whole Eastern North Pacific population is slowly increasing, so our results likely reflect declining usage of the GoC. Linear models found a relationship between the number of whales in the GoC and the difference in sea surface temperature between the study area and the Costa Rica Dome wintering area, suggesting that environmental variation could explain variation in blue whale numbers in the GoC. These results highlight the importance of tracking population dynamics as changing environmental conditions affect the range and distribution of populations. [ABSTRACT FROM AUTHOR]

Monitoring the presence of blue whale (Balaenoptera musculus ssp.) stereotyped calls has been a widely used method to assess the different populations' distribution worldwide. All blue whale populations also produce nonstereotyped vocalizations, or D‐calls. Here, we monitored the presence of D‐calls in long‐term records from a large hydrophone array located in the open southern Indian Ocean, using an automated detection method and manual validation of the detections. D‐calls were detected at all sites of the array, which extends from 24°S to 56°S, but the majority of them were detected at the two southernmost sites. We observed a latitudinal shift in their seasonal occurrence, with more D‐calls in the north during austral autumn and winter and more in the south during austral spring. The geographical occurrence of D‐calls compared to that of songs indicates that blue whale acoustic behavior switches from a song‐intensive and sparse‐D‐call emission in the north to song‐moderate and more intensive D‐call emissions in the south. These findings support the hypothesis that both call types are used for different purposes, as D‐calls are mainly detected around foraging grounds and songs in wintering grounds. Monitoring both call types might therefore be a relevant acoustic indicator of blue whale behavior. [ABSTRACT FROM AUTHOR]

BACKGROUND: Species distribution models have shown that blue whales (Balaenoptera musculus) occur seasonally in high densities in the most biologically productive regions of the California Current Ecosystem (CCE). Satellite telemetry studies have additionally shown that blue whales in the CCE regularly switch between behavioral states consistent with area-restricted searching (ARS) and transiting, indicative of foraging in and moving among prey patches, respectively. However, the relationship between the environmental correlates that serve as a proxy of prey relative to blue whale movement behavior has not been quantitatively assessed. METHODS: We investigated the association between blue whale behavioral state and environmental predictors in the coastal environments of the CCE using a long-term satellite tracking data set (72 tagged whales; summer-fall months 1998-2008), and predicted the likelihood of ARS behavior at tracked locations using nonparametric multiplicative regression models. The models were built using data from years of cool, productive conditions and validated against years of warm, low-productivity conditions. RESULTS: The best model contained four predictors: chlorophyll-a, sea surface temperature, and seafloor aspect and depth. This model estimated highest ARS likelihood (> 0.8) in areas with high chlorophyll-a levels (> 0.65 mg/m3), intermediate sea surface temperatures (11.6-17.5 °C), and shallow depths (

Despite holding the accolade as the largest animal ever to live on planet earth and ubiquitously inhabiting the world's major oceans, an acute paucity of information surrounds the geographical distribution and migration phenology of the endangered blue whale (Balaenoptera musculus) in the northeast Atlantic. Current migration and distribution information derived from robust scientific studies is required to ensure the formulation and implementation of successful conservation measures with a vision to support the ongoing recovery of the northeast Atlantic population. At 10:21 (UTC) on the 9th of November 2020, two blue whales were observed at position 55°13.99′N, 01°13.62′W, 18 km off the coast of the UK in the central North Sea just north of Newcastle at a water depth of 76 m. This is the first paper that has confirmed an account of live blue whales frequenting shallow waters of the central North Sea and represents a new area of occurrence within the accepted range of the northeast Atlantic population, an area in which sightings are extremely rare and may provide insight into the intricacies of migration routes and behaviour. [ABSTRACT FROM AUTHOR]

Acoustic communication is an important aspect of reproductive, foraging and social behaviours for many marine species. Northeast Pacific blue whales (Balaenoptera musculus) produce three different call types-A, B and D calls. All may be produced as singular calls, but A and B calls also occur in phrases to form songs. To evaluate the behavioural context of singular call and phrase production in blue whales, the acoustic and dive profile data from tags deployed on individuals off southern California were assessed using generalized estimating equations. Only 22% of all deployments contained sounds attributed to the tagged animal. A larger proportion of tagged animals were female (47%) than male (13%), with 40% of unknown sex. Fifty per cent of tags deployed on males contained sounds attributed to the tagged whale, while only a few (5%) deployed on females did. Most calls were produced at shallow depths (less than 30 m). Repetitive phrasing (singing) and production of singular calls were most common during shallow, non-lunging dives, with the latter also common during surface behaviour. Higher sound production rates occurred during autumn than summer and they varied with time-of-day: singular call rates were higher at dawn and dusk, while phrase production rates were highest at dusk and night.

Blue whales Balaenoptera musculus are the most abundant and widely distributed cetacean species in Sri Lankan waters. A vessel-based opportunistic line transect survey focusing on marine mammals was conducted in Sri Lankan waters between 24 June to 12 July 2018, while an ecosystem survey was performed by the R/V Dr. Fridtjof Nansen. The entire transect length was 2090 km within an area of 3895 km2. Overall, 72% (n = 57) of blue whale observations were group assemblages ranging between 1 and 5 individuals out of a total of 79 sightings. The largest aggregations of blue whales were recorded at the intersection of the submarine canyon off the coastline of Mirissa and busy shipping lanes between Dondra Head and Galle, where previous ship strikes were recorded. Overall, the average observed group size was 2.64 (CV, 12.34%; 95% CI, 2.07–3.38), the average group density was 0.0029 km−2 (CV, 35.96%; 95% CI, 0.00145–0.00610), and the total blue whale abundance within the survey area was 513 individuals (CV, 38.02%; 95% CI, 243–1083). These survey results fill vital knowledge gaps regarding the abundance and distribution of blue whales in Sri Lanka, which is essential for the establishment of management and conservation strategies. [ABSTRACT FROM AUTHOR]

The Southeast Pacific (SEP) or Chilean blue whale population is largely distributed between Northern Chilean Patagonia and the Eastern Tropical Pacific. Off South Georgia (SG), the majority of blue whales caught were Antarctic blue whales, but recent genetic and acoustic records indicate the possible presence of SEP individuals. To assess the presence of SEP blue whales off SG, we carried out new analyses of acoustic data previously reported as containing pygmy blue whale song and analyzed the length frequencies from 20th century catch data. The month of acoustic data reported to contain the presumed pygmy blue whale song was examined (August 2006), and 13 days were found to have songs which visually and quantitatively matched SEP2 songs from Northern Chilean Patagonia. The fundamental frequency of SEP2 song off SG, however, was not in line with the predicted frequency shift trend of the SEP2 songs in the SEP. A mixture analysis of lengths in historic whaling catches indicated that 3.3% of the catches from SG could be SEP blue whales, although this declined to 0.6%, 95% CI [0.0, 2.6] when fit to nonrounded lengths. Our results suggest that any SEP blue whales off SG are likely rare vagrants, at the edge of an endangered population. [ABSTRACT FROM AUTHOR]

Climate impacts affect marine ecosystems worldwide with island nations such as New Zealand being extremely vulnerable because of their socio-economic and cultural dependence on the marine and costal environment. Cetaceans are ideal indicator species of ecosystem change and ocean health given their extended life span and cosmopolitan distribution, but limited data availability prevents anticipating change in distribution under future climate changes. We projected the range shifts of a key odontocete and mysticete species (Physeter macrocephalus and Balaenoptera musculus) in 2100 relative to present day in New Zealand waters, using an ensemble modelling approach, under three climate change scenarios of different severity.The results show a latitudinal shift in suitable habitat for both whale species, increasing in magnitude with severity of sea surface temperature warming. The most severe climate change scenario tested generated 56% and 42% loss and decrease of currently suitable habitat for sperm and blue whales, respectively, mostly in New Zealand’s northern waters. These predicted changes will have a strong impact on the ecosystem functioning and services in New Zealand’s northern waters but also in coastal areas (critical for the species’ foraging and survival). Not only do these simulated range shifts help to identify future potential climate refugia to mitigate a global warming, they also generate a range of socioeconomic consequences for island nations relying on wildlife tourism, industry, and environmental protection.

The distribution of marine mammal species in many areas remains poorly understood, especially as observations for some taxa are rare and large-scale surveys are time consuming and extremely costly. Here, we present 36 records of 7 cetacean species (Balaenoptera brydei, B. musculus subspp., Delphinus delphis, Globicephala sp., Grampus griseus, Physeter macrocephalus, Pseudorca crassidens) in the New Caledonia Basin, Tasman Sea, along with their associated biological and environmental data. Data were derived from a platform of opportunity during a seismic survey that ran between December 2015 and March 2016, inclusively. The two most frequently encountered species were sperm whales (Physeter macrocephalus, 13 sightings, 5 acoustic detections) and blue whales (Balaenoptera musculus subspp., 8 visual detections). All encountered species are known to occur in New Zealand waters at least occasionally, based on historical sightings and stranding records. However, data presented here are the first cetacean records for this specific area and demonstrate that seismic vessels can act as a platform of opportunity for studying cetacean distribution in poorly accessible areas. Such data will aid future research efforts including species distribution models on cetaceans in the South Pacific. [ABSTRACT FROM AUTHOR]

Blue whales Balaenoptera musculus are the most abundant and widely distributed cetacean species in Sri Lankan waters. A vessel-based opportunistic line transect survey focusing on marine mammals was conducted in Sri Lankan waters between 24 June to 12 July 2018, while an ecosystem survey was performed by the R/V Dr. Fridtjof Nansen. The entire transect length was 2090 km within an area of 3895 km2. Overall, 72% (n = 57) of blue whale observations were group assemblages ranging between 1 and 5 individuals out of a total of 79 sightings. The largest aggregations of blue whales were recorded at the intersection of the submarine canyon off the coastline of Mirissa and busy shipping lanes between Dondra Head and Galle, where previous ship strikes were recorded. Overall, the average observed group size was 2.64 (CV, 12.34%; 95% CI, 2.07–3.38), the average group density was 0.0029 km−2 (CV, 35.96%; 95% CI, 0.00145–0.00610), and the total blue whale abundance within the survey area was 513 individuals (CV, 38.02%; 95% CI, 243–1083). These survey results fill vital knowledge gaps regarding the abundance and distribution of blue whales in Sri Lanka, which is essential for the establishment of management and conservation strategies.

Deviations from equal sex ratios in mammals can reveal insights into sex‐specific growth, survival, movements, and behavior. We assessed blue whale (Balaenoptera musculus) sex ratios based on 21,542 fetal and 311,901 whaling records, finding that males were slightly but significantly more common than females (51.3% fetal, 52.1% postnatal). Antarctic catches shifted from 52.4% male before 1951 to 48.0% male thereafter, even though larger females were preferentially targeted by whalers and should have declined. The southernmost land stations caught more males than those in southern Africa, and at land stations, sex ratios shifted subtly over the course of a year. Pelagic catches demonstrated spatial structure in sex ratios, including more males being caught in the Ross Sea. In utero, the smallest females were often misidentified as males, and there was some evidence for higher prenatal male mortality. Once born, medium‐sized blue whales within each region were more often male, while the longest were nearly all female; explained entirely by females growing faster and reaching longer sizes. Overall, though, sex ratios are remarkably close to equality across time, space, and length; with any deviations best explained by faster female growth and size‐selective whaling. [ABSTRACT FROM AUTHOR]

We report on two sightings of individual blue whales (Balaenoptera musculus) off the coast of Virginia during marine mammal surveys. On 11 April 2018, during a vessel survey off the coast of Virginia, a single blue whale was observed approximately 100 km east-northeast of Virginia Beach. On 10 February 2019, another single blue whale was recorded during an aerial survey approximately 135 km east-southeast of Virginia Beach. These observations mark the first time this endangered species has been documented with photographs off the coast of Virginia, and represent the southernmost confirmed sightings in waters of the United States Atlantic Exclusive Economic Zone (EEZ). At the time of the vessel observation, numerous fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae), and North Atlantic right whales (Eubalaena glacialis), were observed within the same approximately 8 km2 area as the blue whale. For the aerial sighting, the blue whale was seen feeding among at least 15 fin whales in an area approximately 4 km2. These sightings contribute to the small body of information existing for the late winter/early spring distribution of blue whales in waters of the western North Atlantic. [ABSTRACT FROM AUTHOR]

Hormonal biomarkers are useful indicators of mammalian reproductive and metabolic states. The present study validated and applied the use of progesterone and cortisol blubber assays for studies of blue whales from the Gulf of California, Mexico. In a validation study for pregnancy detection, blubber progesterone concentrations were correlated with pregnancy status for four female blue whales: three resighted with a calf the year following sampling and the fourth stranded with a fetus. The progesterone concentrations were significantly higher than those measured in juvenile whales (n = 3). In the application study, blubber samples from blue whales (51 noncalf females, 2 female calves, 48 noncalf males, and 1 male calf) with known sighting histories were analyzed. Putative pregnant females had elevated progesterone concentrations. Cortisol concentrations did not differ between male and female blue whales, or among females in different reproductive classes. After correcting for uncertain ages, hence maturity status, the pregnancy rate of noncalf females was 33.4% (95% CI 32.2%–34.3%). Although interpretation of hormone biomarkers must consider all physiological states that may influence progesterone concentrations, these results demonstrate the utility of pairing hormone biomarkers with sighting histories to help assess environmental or anthropogenic impacts on reproduction in blue whales. [ABSTRACT FROM AUTHOR]

Knowing the migratory movements and behaviour of baleen whales is fundamental to understanding their ecology. We compared δ15N and δ13C values in the skin of blue (Balaenoptera musculus), fin (Balaenoptera physalus) and sei (Balaenoptera borealis) whales sighted in the Azores in spring with the values of potential prey from different regions within the North Atlantic using Bayesian mixing models to investigate their trophic ecology and migration patterns. Fin whale δ15N values were higher than those recorded in blue and sei whales, reflecting feeding at higher trophic levels. Whales' skin δ15N and δ13C values did not reflect prey from high-latitude summer foraging grounds; instead mixing models identified tropical or subtropical regions as the most likely feeding areas for all species during winter and spring. Yet, differences in δ13C values among whale species suggest use of different regions within this range. Blue and sei whales primarily used resources from the Northwest African upwelling and pelagic tropical/subtropical regions, while fin whales fed off Iberia. However, determining feeding habitats from stable isotope values remains difficult. In conclusion, winter feeding appears common among North Atlantic blue, fin and sei whales, and may play a crucial role in determining their winter distribution. A better understanding of winter feeding behaviour is therefore fundamental for the effective conservation of these species.

Introduction: This is the first worldwide systematic and quantitative study to count and identify helminth parasites from 100 blue and 44 fin whale fecal samples collected in the Gulf of California during winter (1993–2014). Results: Blue and fin whale feces had similar prevalence of adult acanthocephalans (Bolbosoma sp.) in feces (18.2% and 14.6%, respectively), but blue whales had significantly higher helminth egg prevalence in feces (100%) and mean intensity (443 ± 318 eggs/g) compared to fin whales (61%, 252 ± 327 eggs/g). Diphyllobothrium sp. eggs were identified in blue whale feces and Diphyllobothridae, Ogmogaster sp. and Crassicauda sp. eggs were identified in fin whale feces. We tested the hypothesis that egg intensity in blue whale's feces varies as a function of age class, reproductive status, sex, preservation and sampling years using a Generalized Linear Model. This model explained 61% of the variance in the helminth egg intensity, but it was not significant. Eighteen blue whale individuals were resampled over time without significant difference between consecutive samples. Conclusions: Thus, all individual blue whales that migrate to the Gulf of California during winter are permanently parasitized with helminths, while the resident fin whales showed lower prevalence and intensity. This helminth load difference is likely due to their different diets duringsummer–fall, when blue whales feed on other krill species in the California Current System and fin whales shift to school fish prey types in the Gulf of California. [ABSTRACT FROM AUTHOR]

Melanin is a widespread pigment of the animal tegument. Two variants of melanin exist: (1) eumelanin, a dark brown pigment, and (2) pheomelanin, penreddish-orange pigment. While eumelanin is photo-protective, pheomelanin has been linked to cellular damage and high cancer risk. Despite this negative effect, pheomelanin is present in many, but not all, species, suggesting that it could confer an evolu-reddishtionary advantage. To date, it is unknown whether the cetacean epidermis contains both melanin variants. Herein, we implemented a simple technique, previously developed for bird feathers, to quantify eumelanin and pheomelanin in blue whale (Balaenoptera musculus) skin, and we explored the potential biological role of pheomelanin based on histological analysis and gene expression quantitation. Both melanin variants were observed in the epidermis, with eumelanin being 42% more abundant than pheomelanin. Blue whale skin pigmentation or mottling type was predicted by the ratio of eumelanin to pheomelanin (EPR), with darker whales showing a higher EPR. Tyrosinase transcription levels influenced the EPR, with higher transcription being associated with higher EPR. Neither transcription of tumor suppressor gene p53 nor occurrence of epidermal photo-damage epiderwere related to the concentration of melanin varipheants, although there appeared to be a trend in which whales with blisters and microvesicles tended to have a lower EPR. Our study expands current understanding of epidermal pigmentation and photoprotection of large cetaceans. [ABSTRACT FROM AUTHOR]

Group behavior and interactions of endangered blue whales (Balaenoptera musculus) have not been systematically studied. Such behavioral data are often overlooked when assessing anthropogenic effects. Yet behavioral data are necessary to compare “normal” behaviors with behavior affected by anthropogenic factors of concern relative to effective management and recovery of blue whales. For a baseline study, we hypothesized that the response variables sighting rate, group size, calf presence and group cohesion (i.e., spacing between individuals within a group) differed according to the spatio-temporal explanatory variables behavioral state, time of day, season, water depth and distance from shore. To address our hypotheses, we flew systematic line transect surveys in southern California and collected focal group data. Two sets of data were separately analyzed using different sampling approaches: (1) point sample data associated with the first sighting of a blue whale(s), and (2) extended all-occurrence focal group behavioral sampling data (i.e., focal follows) collected on a subsample of all sightings while the aircraft circled at a radial distance of approximately 0.5-1 km and an altitude of 1,500 m for extended periods of 5 – 60 minutes. Chi-square contingency table and G² analyses were used to assess statistical relationships between response and explanatory variables. We conducted 18 one-week-long aerial surveys spanning October 2008 through May 2013 (at least once during every month except December), totaling 87,555 km of observation effort. Seventy blue whale sightings (117 individuals) were seen, ranging in size from 1 – 6 whales, and focal follow was performed on over half (55%) of these sightings. Results supported our hypotheses that blue whale group characteristics were related to behavioral state and spatio-temporal variables. Sighting rates were significantly highest during summer followed by spring, fall, and winter. Group type differed significantly by season: groups (at least three individuals) were seen only during summer but singles and pairs were seen from spring through fall. Noncalf groups and mother/calf pairs engaged predominantly in mill and slow travel/rest, while singles and pairs were only observed in medium/fast travel. Behavioral state differed significantly by time of day, group type, water depth and distance from shore. On average mother/calf pairs (n = 3) and singles (n = 43) were found in deeper offshore waters than groups (n = 8) and pairs (n = 16). Group cohesion and group size were negatively correlated: as group size increased whales became less cohesive and more spread out. Our study suggests that group characteristics and behavior are sensitive to spatio-temporal factors. These data are important in providing the first systematic quantitative study of blue whale behavior, providing a baseline against which to assess potential impacts of increasing anthropogenic marine activities in the study area and elsewhere. Results further indicate that social, behavioral and spatio-temporal factors influencing blue whales must be considered when attempting to differentiate potential impacts of anthropogenic activities. We thus suggest that our study parameters be applied as behavioral indices of anthropogenic disturbance to blue whales. To identify effective management and conservation actions to assist in recovery of the blue whale population, it is imperative to describe and quantify natural behavior and habitatuse patterns.

Background The most traditional scheme for migration among baleen whales comprises yearly migrations between productive waters at high latitude summer feeding grounds and warmer waters at lower latitudes where whales calve and mate, but rarely feed. Evidence indicates, however, that large departures from this scheme exist among populations and individuals. Furthermore, for some populations there is virtually no information on migratory pathways and destinations. Such is the case of Chilean blue whales throughout the Eastern South Pacific; hence, the goal of this study was to assess its migratory behavior. Methods Dedicated marine surveys and satellite tagging efforts were undertaken during the austral summer and early autumn on blue whale feeding grounds off Chilean Northern Patagonia (CNP) during 2013, 2015 and 2016. Positional data derived from satellite tags regarding movement patterns and behavior were analyzed using Bayesian switching first-difference correlated random walk models. Results We instrumented 10 CNP blue whales with satellite transmitters and documented individual variation in departure time, northbound migratory routes and potential wintering grounds. The onset of migration occurred from mid/late austral autumn to well into the austral winter. Blue whales moved in various directions, but ultimately converged toward a general NW movement direction along a wide corridor exceeding 2,000 km. Area-Restricted Search behavior was exhibited within fjords and channels of CNP and also South of Galapagos Archipelago (GA) and northern Peru, but never during migration. Interestingly, dive profiles for one whale that reached GA showed a sharp and consistent increase in depth north of 5°S and extreme deep dives of up to 330 m. Discussion Information derived from satellite tagged blue whales in this study is the first of its kind off the Eastern Southern Pacific. Our results provide valuable information on their migratory timing, routes and behavior on their northbound migration, particularly regarding the varied migratory plasticity for this particular population. Our results also highlight the first record of two complete migratory paths between CNP and GA and strengthen the hypothesis that GA waters correspond to a potential wintering destination for CNP blue whales. We further hypothesize that this area might be selected because of its biological productivity, which could provide feeding opportunities during the breeding season. Our results suggest that special efforts should be put forward to identify blue whale critical areas and understand key behavioral aspects in order to provide the basis for their conservation on a regional context (i.e., reducing potential ship strike and promote Marine Protected Area (MPA) implementation in Chile, Ecuador and Peru). Indeed, we suggest joint blue whale conservation efforts at the regional level in order to identify and determine potential threats and impacts and, most importantly, implement prospective management actions.

Acoustic communication is an important aspect of reproductive, foraging and social behaviours for many marine species. Northeast Pacific blue whales (Balaenoptera musculus) produce three different call types—A, B and D calls. All may be produced as singular calls, but A and B calls also occur in phrases to form songs. To evaluate the behavioural context of singular call and phrase production in blue whales, the acoustic and dive profile data from tags deployed on individuals off southern California were assessed using generalized estimating equations. Only 22% of all deployments contained sounds attributed to the tagged animal. A larger proportion of tagged animals were female (47%) than male (13%), with 40% of unknown sex. Fifty per cent of tags deployed on males contained sounds attributed to the tagged whale, while only a few (5%) deployed on females did. Most calls were produced at shallow depths (less than 30 m). Repetitive phrasing (singing) and production of singular calls were most common during shallow, non-lunging dives, with the latter also common during surface behaviour. Higher sound production rates occurred during autumn than summer and they varied with time-of-day: singular call rates were higher at dawn and dusk, while phrase production rates were highest at dusk and night.

Steroid hormone assessment using non-invasive sample collection techniques can reveal the reproductive status of aquatic mammals and the physiological mechanisms by which they respond to changes in their environment. A portion of the eastern North Pacific blue whale ( Balaenoptera musculus ) population that seasonally visits the Gulf of California, Mexico has been monitored using photo-identified individuals for over 30 years. The whales use the area in winter-early spring for nursing their calves and feeding and it therefore is well suited for fecal sample collection. Using radioimmunoassays in 25 fecal samples collected between 2009 and 2012 to determine reproductive state and stress, we validated three steroid hormones (progesterone, corticosterone and cortisol) in adult female blue whales. Females that were categorized as pregnant had higher mean fecal progesterone metabolite concentrations (1292.6  ±  415.6 ng · g - 1 ) than resting and lactating females (14.0  ±  3.7 ng · g - 1 ; 23.0  ±  5.4 ng · g - 1 , respectively). Females classified as pregnant also had higher concentrations of corticosterone metabolites (37.5  ±  9.9 ng · g - 1 ) than resting and lactating females (17.4  ±  2.0 ng · g - 1 ; 16.8  ±  2.8 ng · g - 1 , respectively). In contrast, cortisol metabolite concentrations showed high variability between groups and no significant relationship to reproductive state. We successfully determined preliminary baseline parameters of key steroid hormones by reproductive state in adult female blue whales. The presence of pregnant or with luteal activity and known lactating females confirms that the Gulf of California is an important winter-spring area for the reproductive phase of these blue whales. The baseline corticosterone levels we are developing will be useful for assessing the impact of the increasing coastal development and whale-watching activities on the whales in the Gulf of California. [ABSTRACT FROM AUTHOR]

Background: The most traditional scheme for migration among baleen whales comprises yearly migrations between productive waters at high latitude summer feeding grounds and warmer waters at lower latitudes where whales calve and mate, but rarely feed. Evidence indicates, however, that large departures from this scheme exist among populations and individuals. Furthermore, for some populations there is virtually no information on migratory pathways and destinations. Such is the case of Chilean blue whales throughout the Eastern South Pacific; hence, the goal of this study was to assess its migratory behavior. Methods: Dedicated marine surveys and satellite tagging efforts were undertaken during the austral summer and early autumn on blue whale feeding grounds off Chilean Northern Patagonia (CNP) during 2013, 2015 and 2016. Positional data derived from satellite tags regarding movement patterns and behavior were analyzed using Bayesian switching first-difference correlated random walk models. Results: We instrumented 10 CNP blue whales with satellite transmitters and documented individual variation in departure time, northbound migratory routes and potential wintering grounds. The onset of migration occurred from mid/late austral autumn to well into the austral winter. Blue whales moved in various directions, but ultimately converged toward a general NW movement direction along a wide corridor exceeding 2,000 km. Area-Restricted Search behavior was exhibited within fjords and channels of CNP and also South of Galapagos Archipelago (GA) and northern Peru, but never during migration. Interestingly, dive profiles for one whale that reached GA showed a sharp and consistent increase in depth north of 5° S and extreme deep dives of up to 330 m. Discussion: Information derived fromsatellite tagged blue whales in this study is the first of its kind off the Eastern Southern Pacific. Our results provide valuable information on their migratory timing, routes and behavior on their northbound migration, particularly regarding the varied migratory plasticity for this particular population. Our results also highlight the first record of two complete migratory paths between CNP and GA and strengthen the hypothesis that GA waters correspond to a potential wintering destination for CNP blue whales. We further hypothesize that this area might be selected because of its biological productivity, which could provide feeding opportunities during the breeding season. Our results suggest that special efforts should be put forward to identify blue whale critical areas and understand key behavioral aspects in order to provide the basis for their conservation on a regional context (i.e., reducing potential ship strike and promote Marine Protected Area (MPA) implementation in Chile, Ecuador and Peru). Indeed, we suggest joint blue whale conservation efforts at the regional level in order to identify and determine potential threats and impacts and, most importantly, implement prospective management actions. [ABSTRACT FROM AUTHOR]

Tags have been used to examine migration routes and habitat use of large whales for >40 yr, however, evaluation of tag wound healing has largely been short-term, anecdotal or generalized. This study developed methods for systematic photographic assessment of long-term external consequences of tag placement, to determine potential differences in wound healing between species and tag types and thus advise future tagging efforts to possibly minimize undesirable side effects. Tag site appearance and healing characteristics were evaluated by two reviewers and a time series evaluated by five veterinarians from photographs during 995 postdeployment encounters with 34 gray and 63 blue whales tagged in the North Pacific. Blue whale resightings were less frequent, but spanned a longer time period due to earlier tag deployments than the more frequent gray whale follow-up observations. Swelling occurred in 74% of reencountered gray whales, with the highest frequency 6 mo postdeployment. Swellings were common in blue whales with early tag designs but rare with current models. Depressions occurred in 82% of gray and 71% of blue whales. This study demonstrates the value of follow-up studies of tagged animals and systematic scoring of photographs to quantitatively compare tag response. [ABSTRACT FROM AUTHOR]

Blue whale (Balaenoptera musculus) movements are often driven by the availability of their prey in space and time. While globally blue whale populations undertake long-range migrations between feeding and breeding grounds, those in the northern Indian Ocean remain in low latitude waters throughout the year with the implication that the productivity of these waters is sufficient to support their energy needs. A part of this population remains around Sri Lanka where they are usually recorded close to the southern coast during the Northeast Monsoon. To investigate inter-annual variability in sighting locations, we conducted systematic Conductivity-Temperature-Depth (CTD) and visual surveys between January–March 2011 and January–March 2012. In 2011, there was a notable decrease in inshore sightings compared to 2009 and 2012 (p < 0.001). CTD data revealed that in 2011 there was increased freshwater in the upper water column accompanied by deeper upwelling than in 2012. We hypothesise that anomalous rainfall, along with higher turbidity resulting from river discharge, affected the productivity of the inshore waters and caused a shift in blue whale prey and, consequently, the distribution of the whales themselves. An understanding of how predators and their prey respond to environmental variability is important for predicting how these species will respond to long-term changes. This is especially important given the rapid temperature increases predicted for the semi-enclosed northern Indian Ocean.

Vocal behavior of blue whales (Balaenoptera musculus) in the Gulf of Corcovado, Chile, was analysed using both audio and accelerometer data from digital acoustic recording tags (DTAGs). Over the course of three austral summers (2014, 2015 and 2016), seventeen tags were deployed, yielding 124 h of data. We report the occurrence of Southeast Pacific type 2 (SEP2) calls, which exhibit peak frequencies, durations and timing consistent with previous recordings made using towed and moored hydrophones. We also describe tonal downswept (D) calls, which have not been previously described for this population. As being able to accurately assign vocalizations to individual whales is fundamental for studying communication and for estimating population densities from call rates, we further examine the feasibility of using high-resolution DTAG accelerometers to identify low-frequency calls produced by tagged blue whales. We crosscorrelated acoustic signals with simultaneous tri-axial accelerometer readings in order to analyse the phase match as well as the amplitude of accelerometer signals associated with low-frequency calls, which provides a quantitativemethod of determining if a call is associatedwith a detectable acceleration signal. Our results suggest that vocalizations from nearby individuals are also capable of registering accelerometer signals in the tagged whale's DTAG record. We cross-correlate acceleration vectors between calls to explore the possibility of using signature acceleration patterns associated with sounds produced within the tagged whale as a new method of identifying which accelerometer-detectable calls originate from the tagged animal. [ABSTRACT FROM AUTHOR]

Management of highly migratory species is reliant on spatially and temporally explicit information on their distribution and abundance. Satellite telemetry provides time-series data on individual movements. However, these data are underutilized in management applications in part because they provide presence-only information rather than abundance information such as density., Eastern North Pacific blue whales are listed as threatened, and ship strikes have been suggested as a key factor limiting their recovery. Here, we developed a satellite-telemetry-based habitat model in a case-control design for Eastern North Pacific blue whales Balaenoptera musculus that was combined with previously published abundance estimates to predict habitat preference and densities. Further, we operationalize an automated, near-real-time whale density prediction tool based on up-to-date environmental data for use by managers and other stakeholders., A switching state-space movement model was applied to 104 blue whale satellite tracks from 1994 to 2008 to account for errors in the location estimates and provide daily positions (case points). We simulated positions using a correlated random walk model (control points) and sampled the environment at each case and control point. Generalized additive mixed models and boosted regression trees were applied to determine the probability of occurrence based on environmental covariates. Models were used to predict 8-day and monthly resolution, year-round density estimates scaled by population abundance estimates that provide a critical tool for understanding seasonal and interannual changes in habitat use., The telemetry-based habitat model predicted known blue whale hot spots and had seasonal agreement with sightings data, highlighting the skill of the model for predicting blue whale habitat preference and density. We identified high interannual variability in occurrence emphasizing the benefit of dynamic models compared to multiyear averages., Synthesis and applications. This near-real-time tool allows a more accurate examination of the year-round spatio-temporal overlap of blue whales with potentially harmful human activities, such as shipping. This approach should also be applicable to other species for which sufficient telemetry data are available. The dynamic predictive product developed here is an important tool that allows managers to consider finer-scale management areas that are more economically feasible and socially acceptable. [ABSTRACT FROM AUTHOR]

Many aspects of blue whale biology are poorly understood. Some of the gaps in our knowledge, such as those regarding their basic taxonomy and seasonal movements, directly affect our ability to monitor and manage blue whale populations. As a step towards filling in some of these gaps, microsatellite and mtDNA sequence analyses were conducted on blue whale samples from the Southern Hemisphere, the eastern tropical Pacific (ETP) and the northeast Pacific. The results indicate that the ETP is differentially used by blue whales from the northern and southern eastern Pacific, with the former showing stronger affinity to the region off Central America known as the Costa Rican Dome, and the latter favouring the waters of Peru and Ecuador. Although the pattern of genetic variation throughout the Southern Hemisphere is compatible with the recently proposed subspecies status of Chilean blue whales, some discrepancies remain between catch lengths and lengths from aerial photography, and not all blue whales in Chilean waters can be assumed to be of this type. Also, the range of the proposed Chilean subspecies, which extends to the Galapagos region of the ETP, at least seasonally, perhaps should include the Costa Rican Dome and the eastern North Pacific as well. [ABSTRACT FROM AUTHOR]

Six years of passive acoustic monitoring data from the Gulf of California reveal seasonality and movements for the northeastern Pacific blue whales. Three sites were studied, one from the southern (Punta Pescadero) and two from the northern (Isla Tiburon and Canal de Ballenas) regions. A total of 4,953 h were analyzed, and 15,539 blue whale calls were detected, of which 2,723 (18%) were A calls, 11,249 were B calls (72%), and 1,567 were D calls (10%). A and B calls were produced both as song units (2,524) or AB singular calls (2,026). The high rate of songs and their seasonality suggest that the GC is a winter-breeding ground. A shift from AB call predominance in winter, to D calls in spring and early summer, especially at the entrance of the GC, suggests the importance of this area for reproduction and foraging. Analysis of calling frequency suggests a clear movement of blue whales from the southern region (Punta Pescadero) to the northern regions (Canal de Ballenas and Isla Tiburon), with subsequent southern movement in March. The seasonality and mobility of blue whales in the Gulf of California, inferred from their calling, contributes to the ecological understanding of this population. [ABSTRACT FROM AUTHOR]

The distribution and abundance of blue whales (Balaenoptera musculus) was assessed from ship surveys conducted in the Central and Northeast Atlantic in 1987, 1989, 1995 and 2001. Blue whales were most commonly sighted off western Iceland, and to a lesser extent northeast of Iceland. They were very rare or absent in the Northeast Atlantic. Sightings were combined over all surveys to estimate the detection function using standard line transect methodology, with the addition of a covariate to account for differences between surveys. Total abundance was highest in 1995 (979, 95% CI 137-2,542) and lowest in 1987 (222, 95% CI 115-440). Uncertainty in species identity had little effect on estimates of abundance. There was a significant positive trend in abundance northeast of Iceland and in the total survey area.

Using bacterial and fungal tag-encoded FLX-Titanium amplicon pyrosequencing, the microbiota of the faecal material of two blue whales living in the wild off the coast of California was investigated. In both samples the most predominant bacterial phylum was the Firmicutes with Clostridium spp. being the most dominant bacteria. The most predominant fungi were members of the phylum Ascomycota with Metschnikowia spp. being the most dominant. In this study, we also preliminarily characterised the culturable anaerobic bacteria from the faecal material, using traditional culture and 16S rRNA gene sequencing approaches. In total, three bacterial species belonging to the phylum Firmicutes were identified. [ABSTRACT FROM AUTHOR]

Spectrogram correlation has been used successfully for automatic detection of baleen whale calls. However, applying this method consistently to long time series can be challenging. To illustrate the potential challenges of the automatic detection process, recordings collected in the Southern California Bight between 2007 and 2012 were used for detection of North-east Pacific blue whale (Balaenoptera musculus) B calls.The effects of the following factors were investigated: blue whale B call frequency shift and appropriate kernel modification, seasonal variability in call abundance, analyst variability and noise. Due to intra- and inter-annual changes in the call frequency of blue whale B calls, seasonal and annual adjustments to the call detection kernel were needed. To account for seasonal variability in call production, evaluation of the detector against ground truth data was performed at multiple times during the year. Analyst variability did not affect overall long-term trends in detection, but it had an impact on the total number of detections, as well as call rate estimation. Noise, particularly from shipping, was negatively correlated with detections at hourly time scales. A detailed analysis of variability in the performance of spectrogram correlation detectors should be performed when applying this method to long-term acoustic data-sets. [ABSTRACT FROM AUTHOR]

A number of parasitic diseases have gained importance as neozoan opportunistic infections in the marine environment. Here, we report on the gastrointestinal endoparasite fauna of three baleen whale species and one toothed whale: blue ( Balaenoptera musculus), fin ( Balaenoptera physalus), and sei whales ( Balaenoptera borealis) and sperm whales ( Physeter macrocephalus) from the Azores Islands, Portugal. In total, 17 individual whale fecal samples [ n = 10 ( B. physalus); n = 4 ( P. macrocephalus); n = 2 ( B. musculus); n = 1 ( B. borealis)] were collected from free-swimming animals as part of ongoing studies on behavioral ecology. Furthermore, skin biopsies were collected from sperm whales ( n = 5) using minimally invasive biopsy darting and tested for the presence of Toxoplasma gondii, Neospora caninum, and Besnoitia besnoiti DNA via PCR. Overall, more than ten taxa were detected in whale fecal samples. Within protozoan parasites, Entamoeba spp. occurred most frequently (64.7 %), followed by Giardia spp. (17.6 %) and Balantidium spp. (5.9 %). The most prevalent metazoan parasites were Ascaridida indet. spp. (41.2 %), followed by trematodes (17.7 %), acanthocephalan spp., strongyles (11.8 %), Diphyllobotrium spp. (5.9 %), and spirurids (5.9 %). Helminths were mainly found in sperm whales, while enteric protozoan parasites were exclusively detected in baleen whales, which might be related to dietary differences. No T. gondii, N. caninum, or B. besnoiti DNA was detected in any skin sample. This is the first record on Giardia and Balantidium infections in large baleen whales. [ABSTRACT FROM AUTHOR]