Abstract: Over a decade after the Cook Inlet beluga (Delphinapterus leucas) was listed as endangered in 2008, the population has shown no sign of recovery. Lack of ecological knowledge limits the understanding of, and ability to manage, potential threats impeding recovery of this declining population. National Oceanic and Atmospheric Administration Fisheries, in partnership with the Alaska Department of Fish and Game, initiated a passive acoustics monitoring program in 2017 to investigate beluga seasonal occurrence by deploying a series of passive acoustic moorings. Data have been processed with semi-automated tonal detectors followed by time intensive manual validation. To reduce this labor intensive and time-consuming process, in addition to increasing the accuracy of classification results, the authors constructed an ensembled deep learning convolutional neural network model to classify beluga detections as true or false. Using a 0.5 threshold, the final model achieves 96.57% precision and 92.26% recall on testing dataset. This methodology proves to be successful at classifying beluga signals, and the framework can be easily generalized to other acoustic classification problems.

Abstract: Host-specific microbiomes play an important role in individual health and ecology; in marine mammals, epidermal microbiomes may be a protective barrier between the host and its aqueous environment. Understanding these epidermal-associated microbial communities, and their ecological- or health-driven variability, is the first step toward developing health indices for rapid assessment of individual or population health. In Cook Inlet, Alaska, an endangered population of beluga whales (Delphinapterus leucas) numbers fewer than 300 animals and continues to decline, despite more than a decade of conservation effort. Characterizing the epidermal microbiome of this species could provide insight into the ecology and health of this endangered population and allow the development of minimally invasive health indicators based on tissue samples. We sequenced the hypervariable IV region of bacterial and archaeal SSU rRNA genes from epidermal tissue samples collected from endangered Cook Inlet beluga whales (n = 33) and the nearest neighboring population in Bristol Bay (n = 39) between 2012 and 2018. We examined the sequences using amplicon sequence variant (ASV)-based analyses, and no ASVs were associated with all individuals, indicating a greater degree of epidermal microbiome variability among beluga whales than in previously studied cetacean species and suggesting the absence of a species-specific core microbiome. Epidermal microbiome composition differed significantly between populations and across sampling years. Comparing the microbiomes of Bristol Bay individuals of known health status revealed 11 ASVs associated with potential pathogens that differed in abundance between healthy individuals and those with skin lesions or dermatitis. Molting and non-molting individuals also differed significantly in microbial diversity and the abundance of potential pathogen-associated ASVs, indicating the importance of molting in maintaining skin health. We provide novel insights into the dynamics of Alaskan beluga whale epidermal microbial communities. A core epidermal microbiome was not identified across all animals. We characterize microbial dynamics related to population, sampling year and health state including level of skin molting. The results of this study provide a basis for future work to understand the role of the skin microbiome in beluga whale health and to develop health indices for management of the endangered Cook Inlet beluga whales, and cetaceans more broadly.

Abstract: In the current study we used transthoracic echocardiography to measure stroke volume (SV), heart rate (fH), and cardiac output (CO) in adult bottlenose dolphins (Tursiops truncatus), a male beluga calf (Delphinapterus leucas, body mass [Mb] range: 151-175 kg), and an adult female false killer whale (Pseudorca crassidens, estimated Mb: 500-550 kg) housed in managed care. We also recorded continuous electrocardiogram (ECG) in the beluga, bottlenose dolphin, false killer whale, killer whale (Orcinus orca), and pilot whale (Globicephala macrorhynchus) to evaluate cardiorespiratory coupling while breathing spontaneously under voluntary control. The results show that cetaceans have a strong Respiratory Sinus Arrythmia (RSA), during which both fH and SV vary within the interbreath interval, making average values dependent on the breathing frequency (fR). The RSA-corrected fH was lower for all cetaceans compared to similarly sized terrestrial mammals breathing continuously. As compared with terrestrial mammals, the RSA-corrected SV and CO were either lower or the same for the dolphin and false killer whale, while both were elevated in the beluga. When plotting fR against fH for an inactive mammal, cetaceans had a greater cardiac response to changes in fR as compared with terrestrial mammals. We propose that these data indicate an important coupling between respiration and cardiac function that enhances gas exchange, and that this RSA is important to maximize gas exchange during surface intervals, similar to that reported in the elephant seal.

Abstract: Ecosystems and community structure fluctuate over time as a result of natural and anthropogenic factors that may affect prey availability and population dynamics. Most of what we know about St. Lawrence Estuary (SLE) Beluga (Delphinapterus leucas) diet comes from stomach contents collected 80 years ago mainly from a hunting site that Beluga no longer use. How reflective these data are of Beluga diet at other sites and at the current time is unknown. In the context of the recent population decline, general information of prey species alone may help identify useful conservation actions for potentially important prey or habitats. Here, we examined the diet of SLE Beluga using digestive tracts collected from carcasses recovered over the past 30 years, in the context of historical diet data and recent changes in the St. Lawrence ecosystem. We showed they have a varied diet composed of fish and invertebrates generally <30 cm in length, and that adult males and females differ in their summer diet in a way that is consistent with the sex segregation observed in this population. Our results also indicate that polychaete worms, squid, and cod are still among the most prevalent prey, and that species such as redfish (Sebastes spp.) might be important prey items. This study shows that Beluga diet has changed since the 1930s, and that prey from digestive tracts identified to species are valuable for making comparisons to the past, and for improving applications of molecular analyses, such as stable isotopes and fatty acids.

Abstract: Monitoring marine mammal populations and their habitats is crucial for assessing population status and defining realistic management and conservation goals. Environmental and anthropogenic changes in the Arctic have prompted the pursuit for improved understanding of female beluga whale (Delphinapterus leucas) spatial and temporal reproductive patterns. There are relatively few estimates for female reproductive parameters of beluga whale populations across the Arctic, and those few that are available are outdated. Here we summarize female reproductive data from samples collected through Inuit subsistence hunts of three eastern Canadian Arctic beluga populations: High Arctic/Baffin Bay (HA), Western Hudson Bay (HB), and Cumberland Sound (CS) from 1989 to 2014. We grouped the CS and HA populations into a Baffin Bay region (BB) population based on similar body growth patterns and genetic similarity. Asymptotic body length of BB beluga whales (370.9 cm) was greater than HB whales (354.4 cm) as established from Gompertz growth curves fitted for whales ranging in age from 1 – 89 y. We did not detect a significant difference in average number of pseudocervices (8.6) between regions. Differences in average age of sexual maturity (ASM) and length at sexual maturity (LSM) were identified, with evidence of BB females maturing earlier than females from HB (probability method BB = 9.9 y versus HB = 11.0 and logistic method ASM50% HB = 9.99 and BB unresolved). BB females were also longer than HB females at maturing age (logistic LSM50%: BB = 314.5 cm vs HB = 290.3). Total corpora counts were strongly correlated with age, although the number of corpora (≥ 10 mm) suggests reproductive senescence between 40 and 50 y. Improved understanding of female reproductive patterns and knowledge of changes in the spatial and temporal timing of reproductive processes are fundamental for effective conservation and sustainable management of beluga whale populations.

Abstract: Passive acoustics is used to monitor the threatened St. Lawrence estuary beluga between 2007 and 2017 from a site downstream of the beluga summer habitat. Acoustic metrics of presence and occurrence based on beluga acoustic band activity (BABA) are extracted by a dedicated algorithm adapted for the shipping noise from the St. Lawrence Seaway. A formal optimization process is used to set the algorithm parameters. Results evidence a year-round occurrence of belugas in the region, seasonal and diel patterns, and significant inter-annual variations. This study shows how passive acoustics methodology can be applied to monitor a loquacious species over multi-year periods in a shipping-noise-dominated environment, in order to understand its use of the habitat over the continuum of ecologically significant time scales.

Abstract: We report on the first beluga whale (Delphinapterus leucas), an adult female, from the Eastern Chukchi Sea (ECS) stock to be tagged with a Satellite Relay Data Logger (SRDL) that included a miniaturized Conductivity, Depth, and Temperature (CTD) sensor capable of collecting temperature (T) and salinity (S) profiles as the beluga dove. Prior work speculated that ECS belugas may target fronts and stratified regimes between water masses, because these boundaries may aggregate zooplankton, which in turn may attract fish that belugas prey upon. However, the SRDLs used in those studies were not capable of collecting CTD data necessary to identify water masses. The CTD-SRDL transmitted for 71 days, 8 July–17 September 2019, providing 492 time-depth profiles, indicating the shape and duration of beluga dives, and 255 CTD profiles, providing information on the location of water masses and ocean stratification used by the animal. We found that this beluga typically targeted fronts and stratified layers between water masses or colder water masses of Pacific origin. Of particular significance, we found that within the main summering area in Barrow Canyon, dives were co-located with the frontal zone between relatively warm and fresh Alaskan Coastal Water (derived from river discharge), and colder, saltier water of Pacific origin.

Abstract: The influence of boat tourism on the beluga whale Delphinapterus leucas in the White Sea, Russia, was studied based on regular observations of belugas near the Solovetskiy Islands from 1995 to 2015. Changes in beluga behaviour, which were affected both by the distance between the boats and the whales and the character of boat activity (e.g. anchoring, drifting, or moving with the engine running) were observed. Boats following the belugas caused the greatest impact on the whales. This negative reaction was observed throughout all periods of observations. The results indicate the need to evaluate the potential long‐term, cumulative anthropogenic impact on beluga behaviour and the development of appropriate mitigation measures.

Abstract: The Tarium Niryutait Marine Protected Area within the Mackenzie Estuary provides a critical summer habitat for the Eastern Beaufort Sea (EBS) beluga whales (Delphinapterus leucas). Given the lack of seabed characterization in the Mackenzie Estuary, there is a need to characterize key features and governing processes that may influence or drive beluga habitat use. Thus, we sample and describe the Mackenzie Estuary seabed and examine the influence of ice conditions, fluvial processes and wave interactions to define seabed processes and spatially defined habitats. Lastly, we examine how beluga selects specific seabed characteristics or habitat types. Seabed mapping, sediment sampling and delineation of seafloor features are used to define the seabed habitat. The majority of the seabed consists of medium to coarse-grained silt and is void of any bathymetric variations and disturbances. Five seabed habitat zones were defined: (1) featureless and flat, (2) scours and disturbed, (3) sandy shoal, (4) deep channel and (5) longshore bars. Beluga observations analysed retrospectively from 1972 to 1992 were associated with the featureless and flat seabed habitat 72% of the time. However, a preference for the sandy shoal habitat provides some indication there are substrates in the estuary which are suitable for whales to rub against (to scrape off moulting skin), supporting the hypothesis there are certain habitats that may attract belugas during the annual moult.

Abstract: There is a significant lack of data for the biological parameters of beluga or great sturgeon, the largest fish in the Caspian Sea. The age, growth and fisheries indices for the stock status of beluga was investigated in the south Caspian Basin of Iran between 1990 and 2011. Fork lengths ranged between 113-420 cm and weights from 8.0 to 725.0 kg. The growth parameters were L∞ = 440 cm, K = 0.027 year−1, t = − 5.8 years. The age at first capture0(tc) was 13.1 years. The long-term age composition data showed age up to 63 years, and the ages 12-19 years comprised 76.7% of the total catch. The generation length was 33 years. The values of “KF” were close to 1 or >1, indicating that beluga sturgeon is in a favorable condition in the southern Caspian Sea. The length distribution showed that 24.2% of the catch is comprised of juveniles. Based on the age structure and age at first maturity, recruitment and growth overfishing occurred in beluga stocks. Therefore, increased length or age at first capture in future fishery policies should be implemented. The mega-spawners represented 4.4% of the fish captured and revealed an unhealthy population structure.

Abstract: This study was carried out on the effect of cyclopoid copepod Acanthocyclops trajani on beluga Larvae (Huso huso) first feeding in March 2018. The applied diets contained: the composition of Artemia naupli and Daphnia magna (A diet) and the composition of Artemia naupli, Daphnia magna and A. trajani (B diet). Different methods were used to prepare live feeds and the analysis of the fatty acids of live feeds and beluga larval tissues was performed according to the instruction. The results of this study indicated that the lenghth, body weight and specific growth rate average in larvae of A and B diets were not significantly different. In spite of the fact that A. trajani was significantly different in amount of n-3 fatty acids in comparison to Artemia naupli and D. magna but indicated more effectivity in survival rates (80%) of beluga larvae with these latter live feeds compound, as a supplement. Furthermore, the B diet was significantly different in essential fatty acid DHA, in comparison to A diet, So, with due attention to important effects of this fatty acid on stress resistance of larvae, the better results with the view to survival rate in this treat will be explainable.This study indicated that freshwater copepod was potential supplemental live food, specifically to increase nutritional value and survival rate of valuable fish larvae as beluga.

Abstract: Beluga sturgeon (Huso huso), the largest freshwater fish, has attracted the attention of sturgeon culturists worldwide. The profitability of aquaculture beluga production mainly depends on physiologically suitable formulated diets. The objective of this research is to determine the optimal level of dietary selenium (Se) for beluga using the following parameters: growth performance traits (WG, SGR, PER, and FER), body proximate composition, and serum biochemical and immunological indices (glucose, total protein, Ig M, lysozyme, ALT and AST). To this aim beluga (n=315; with initial weight of 15.66±0.77 g) were fed with diets supplimented with sodium selenite (0.18, 5.43, 12.6, 24.3, 37.2, 71.4, and 144 mg kg-1) for 10 weeks. Unexpectedly, all of the parameters exhibited considerable responses to the applied levels of Se. Growth performance indices displayed the highest values for the animals treated with diets containing 12.6 and 24.3 mg kg-1 Se, yet the lowest ones with 71.4 and 144 mg kg-1 (i.e., U-form response). Similar response was seen for crude lipid and protein content as well as for the activity of ALT and AST, whereas IgM and lysozyme did an anticline manner (i.e., the highest values in the midle Se levels). Moisture and ash contents and also serum total protein exhibited a Se-dose dependent increase. Based on the broken line regression model, optimal dietary Se requirement for juvenile beluga is about 18.2 mg kg-1. Taken together this study extends our knowledge on one of the most essential trace elements and its optimal level for incorporating into beluga diet. It could also be a basic one in the sturgeon aquaculture industery.

Abstract: Fish roe is an extremely rare cause of anaphylaxis and although its consumption has increased in recent years. We described the case of a 59-year-old man, who experienced an anaphylactic reaction after consuming caviar. Skin prick-test were performed with Beluga caviar, salmon caviar, cod, salmon, hen egg yolk and egg white, ovalbumin, ovomucoid, shrimp and mold. Only SPT to Beluga caviar was positive. The absence of sensitization to fish and hen egg was confirmed by undetectable specific IgEs to cod, parvalbumin (Gad c 1 and Cyp c 1), egg yolk and egg white, ovalbumin and ovomucoid. An immunoblot was also performed and showed an IgE-reactive band indicated that the patient was sensitized to a 26 kDa protein in Beluga caviar. In the present case, immunoblotting of the patient's serum revealed a single IgE-reactive band at 26 kDa band, which does not appear to correspond to the previous cases.

Abstract: Aerial line transect surveys were conducted during 19 July – 20 August in each of the years 2012 – 17, with onshore – offshore transects covering a study area of approximately 110 000 km2, from 140˚ W to 157˚ W longitude and from shore to 72˚ N latitude. These data were used to estimate abundance of the eastern Chukchi Sea (ECS) stock of beluga whales. The data were stratified based on bathymetry to reflect strong large-scale gradients in beluga density. A half-normal key function was used to model detection from a dataset of 999 sightings of 2465 belugas. The detection function was found to depend significantly on sky condition and ice coverage. For the years 2012 through 2017, respectively, the estimated numbers of ECS belugas in the study area during the study period were 7355 (CV = 0.17), 6813 (CV = 0.18), 16 598 (CV = 0.21), 6456 (CV = 0.21), 6965 (CV = 0.23) and 13 305 (CV = 0.27). There is no statistically significant trend. These estimates do not correct for belugas outside the study region. Indeed, diverse data indicate that belugas venture far outside the study region and their distribution varies interannually due to prey availability and other factors. Recently reviewed tagging data suggest that correcting for whales outside the study area would approximately double our abundance estimates. These results provide no indication that the stock has substantially declined during these six years due to the impact of subsistence hunting, industrial activity or climate change, although interannual variation and estimated CVs are both large, thereby potentially masking small-scale impacts.

Abstract: The objects of research are Beluga (Huso huso, Linnaeus), sturgeon spike (Acipenser nudiventris, Lovetsky) and their interspecific hybrids of artificial generation grown on the Research and Experimental Base BIOS (the Astrakhan region) by using the basin method. To assess the physiological status of fish, a set of morphophysiological indicators (absolute and relative weight of gills, heart, liver, and gonads) were used. The dynamics of the indices of the corresponding viscera of Beluga and sturgeon spike and their interspecific hybrids in the second year of cultivation was studied. The necessity for the research is explained by the fact that most work performed was carried out on land vertebrates and on fish of natural generation. There have been presented the average values of morphophysiological indices for each of the four groups of unmixed sturgeon species and their hybrids. The obtained values of the studied parameters of sturgeon species can be used for further monitoring of the fish growing conditions using the basin method.

Abstract: Echolocation signals of wild beluga whales (Delphinapterus leucas) were recorded in 2013 using a vertical, linear 16-hydrophone array at two locations in the pack ice of Baffin Bay, West Greenland. Individual whales were localized for 12 min of 1:04 h of recordings where on-axis clicks were isolated to calculate sonar parameters. We report the first sonar beam estimate of in situ recordings of belugas with an average 3-dB asymmetrical vertical beam width of 5.7 deg, showing a wider ventral axis. This is narrower than the commonly used estimates in the literature obtained from captive whales, suggesting beluga sonar beam width may be different in captive and wild contexts and is not necessarily symmetrical. Apparent source levels ranged from 210 to 220 dB pp re 1 μPa and whales were shown to vertically scan the array from 120 m distance. Our findings support the hypothesis that highly directional sonar beams and high source levels are an evolutionary adaptation for Arctic odontocetes to reduce noise and surface echoes from ice. These results provide the first baseline beluga sonar metrics from free-ranging animals using a hydrophone array and are important for acoustic programs throughout the Arctic, particularly for acoustic classification between belugas and narwhals (Monodon monoceros).

Abstract: This collection documents the date, group ID, group size, group composition, and location for each group of beluga whale encountered during surveys conducted in Upper Cook Inlet Alaska during ice-free months. It also documents individuals identified in photographs taken during these surveys. Data were collected in field notes, vessel GPS track lines (where appropriate) and GIS software and is available in spreadsheet format.

Abstract: Three-year-olds (15 individuals) and eight-year-olds (15 individuals) of the sterlet × beluga hybrid (Asipenser ruthenus × Huso huso), grown in mesh cages in the Volga delta, were studied in the third decade of September 2019 in order to establish the functional state of the organism by blood parameters reflecting the state erythron and metabolism. The results of the performed study found that the erythron system differs in a smaller number of blood erythrocytes in eight-year-olds (0,76 ± 0,04 × 1012l –1) compared with three-year-olds (0,98 ± 0,04 × 1012l –1), in the absence of differences in blood hemoglobin and serum iron. Analysis of the state of protein metabolism showed that the content of total protein and the activity of ASAT in serum were the same in the groups. The serum albumin content in eight-yearolds was 17,87 ± 0,92 g/l, which was significantly less than in three-year-olds (24,15 ± 1,78) (p < 0,05). The relative content of serum albumin (as a percentage of total protein) in eightyear-olds was 51,04 ± 3,12%, which is less than in three-year-olds (72,51 ± 6,04%) (p < 0.01). The serum ALAT activity in eight-year-olds was lower than in three-year-olds (2,33 ± 0,16 and 2,93 ± 0,17 μkat/l, respectively) (p < 0,05). The results of the study of lipid metabolism revealed that serum cholesterol in eight-year-olds (2,62 ± 0,11 mmol/l) is less than in three-year-olds (1,39 ± 0,05) (p < 0,05). However, the serum triglyceride content did not differ between threeyear-olds and eight-year-olds, being 3,50 ± 0,07 and 3,26 ± 0,13 mmol/l, respectively. The glycemic values in three-year-olds and eight-year-olds are significantly different and amount to 1,80 ± 0,08 and 1,42 ± 0,11 mmol/l, respectively (p < 0.05). The results of the study can be used to assess the state of physiological adaptation of the hybrid and to determine the reference values of the parameters of the erythron system and metabolic homeostasis.

Abstract: Additional file 1: Supplemental Figure S1.. PCoA based on Bray-Curtis dissimilarity comparison of the epidermal microbiota of duplicate samples included in this study.

Abstract: The paper focuses on fish consumption and long-distance fish trade in the medieval monastery Studenica in Serbia, from the perspective of archaeozoology and historical evidence. Medieval written sources on the subject suggest that fish was available primarily to particular social classes – the royalty, nobles and monasteries. Preserved muniments indicate that during the 13th-15th centuries the majority of distinguished monasteries had their own fishing ponds, fishing grounds and their own fishermen. Fish
consumption occupied an important role in monastic contexts, both in Christian religious practices (e.g. Lent) and in celebrations commemorating the Virgin Mary and the monastery founder, during which high-quality fish was obtained from greater distances. The ichthyoarchaeological remains discussed in this paper originate from waste deposition areas within and outside of the ramparts of
the Studenica Monastery, accumulated during the 14th and the first half of the 15th century. Apart from the remains of the species available more or less locally (Wels catfish [Silurus glanis Linnaeus, 1758], carp [Cyprinus carpio Linnaeus, 1758], pike [Esox lucius Linnaeus, 1758]), the faunal assemblage contained the remains of migratory sturgeons (beluga [Huso huso Linnaeus, 1758], Russian sturgeon [Acipenser gueldenstaedtii Brandt & Ratzeburg, 1833], stellate sturgeon [Acipenser stellatus Pallas, 1771]) most likely transported from the Danube area, about 200 km away as the crow flies. Skeletal element distribution, butchering traces and size estimations (of beluga in particular) indicate that large specimens (c. 2-3.6 m in total length) were brought whole to the monastery, possibly dried or salted. Their occurrence is an additional indicator of long-distance fish trade recorded in muniments,
and it offers new insights into economic, social and religious practices in medieval Eastern Orthodox monasteries.

Abstract: To determine the effect of coriander on beluga, Huso huso, a total of 150 fish (250 ± 2 g) were fed a diet containing 0, 5, 10, 15, or 20 g kg−1 of coriander for 60 days (Phase 1) The fish were th

Abstract: Additional file 2: Supplemental Table S1.. Sample metadata for all samples included in this study (i.e. all samples that passed quality control analyses), including sampling location and population, year, and NCBI Genbank Accession number, among other data.

Abstract: Funding information Canada Foundation for Innovation, Grant/ Award Number: JELF 36506; Canada Research Chairs, Grant/Award Number: 950-231012; Natural Sciences and Engineering Research Council of Canada; Social Sciences and Humanities Research Council of Canada Abstract Marine mammals often exhibit significant sexual segregation in their diet and habitat use but these differences have not been studied systematically in historic or ancient populations due to the difficulties associated with determining the sex of skeletal elements based on gross morphology. Using a combined ancient DNA and stable isotope approach, we document a sexual difference in the foraging ecology of late 19th century beluga whales (Delphinapterus leucas) from the Canadian High Arctic. Using two PCR assays that coamplify fragments of the Y-linked SRY and X-linked ZFX genes, we assigned reproducible sex identities to 35 beluga specimens. This provided a basis for investigating sex-specific differences in foraging ecology using stable carbon and nitrogen isotope analyses of bone collagen. These isotopic data demonstrate that although both males and females primarily consumed Arctic cod, males utilized a wider range of prey than females, feeding on high trophic level benthic prey (sculpins) to a greater extent. Because bone collagen integrates prey isotopic compositions over the course of several years these sex-based differences in beluga bone collagen isotopic compositions reflect long-term and sustained sexual differences in foraging.