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Whale interactions with fishing gear pose a major anthropogenic threat, yet entanglements in South Atlantic trawl fisheries remain underreported, with no published records. This lack of data extends to reports of whales found stranded with amputated tails, despite documented cases of survival even without a fluke. This study presents a novel case: a video recorded in May 2020 captured a shrimp trawler in Santa Catarina, Brazil, entangled with a humpback whale (Megaptera novaeangliae). Vocalizing and bleeding, the whale had recently lost its fluke and remained caught in the vessel's gear. Following the video's public outcry, authorities identified and apprehended the responsible vessel, conducting a thorough investigation. Although initial sanctions were issued, and evidence confirmed illegal fishing practices and neglect towards the whale, subsequent legal proceedings deemed the act unintentional and acquitted the involved parties. This report seeks to not only document this unprecedented case but also to analyze why such infractions against cetacean often receive minimal legal consequences. Examining this case within the context of broader policy and enforcement frameworks, we discuss potential explanations for the perceived low legal severity of such incidents and argue for the need for enhanced legal accountability to effectively protect marine mammals in the South Atlantic. [Display omitted] • First recorded humpback whale entangled in the South Atlantic trawling gear, exposing gaps in environmental laws and legal cases. • The incident highlights fishings'' threats to whales, exacerbated by underreporting and weak legal action, despite being unintentional. • The analysis calls for stronger laws and penalties to better address environmental infractions, ensuring consistent legal enforcement. • Call for education and training for fishermen and fisheries managers to prevent entanglements and promote whale conservation. • The paper advocates urges collaboration between the fishing industry, regulatory bodies, and conservationist for solutions balancing conservation and with sustainable fishing. [ABSTRACT FROM AUTHOR]

Inspired by the tubercles on humpback whales, the 'tubercle-effect' first identified by (Fish and Battle, 1995; Fish and Lauder, 2006) had been studied extensively to understand their influence on overall efficiency for airfoils and wings. Pitching and/or heaving motion of foils produces net thrust inspired from fin-based locomotion of aquatic animals, and is often being proposed as a greener means of propulsion having reduced acoustic signature. With this aim in mind, the present work investigates the effect of using tubercles on pitching motion of foils. The hydrodynamic characteristics of finite aspect ratio pitching foils having leading-edge modifications in the form of two protuberances are investigated using experiments. The thrust and efficiency with and without protuberances are investigated for pure pitching motions at reduced frequencies (1.8 – 3.2) and pitching amplitudes (7.5°- 20°) for Reynolds number 2 × 10 4 . The experimental results are compared with inviscid linear theory calculations which over-predict the mean thrust, while the amplitude of the lift force and its variation with reduced frequency is similar. The performance improvements in terms of thrust and efficiency for the modified design are restricted to ≥15° pitching amplitudes at higher reduced frequencies. The wake vorticity patterns obtained using Computational Fluid Dynamics investigations show the influence of the leading-edge vortex, which gets modified when the protuberances are used. The transition from 2S wake to 2P wake with the increase in the amplitude of oscillation is captured. The reversal of von Kármán Vortex Street with the pitching frequency and thus the transition from drag to thrust generation is observed for both the baseline and modified foil designs. The results indicate that protuberances over the leading-edge of hydrofoils can influence the hydrodynamics during pitching motion and can be effectively employed for performance tailoring based on the geometry and motion characteristics. The simplified setup used here is also meant to serve as a basis towards future research including verification and validation work for numerical solvers. • The influence of leading-edge protuberances on a hydrofoil in pure pitching motion is studied. • Experimental and numerical studies are performed for the assessment of thrust, efficiency, and flow characteristics. • At the Reynolds number 20000, the modified design produces higher thrust and lift only at amplitudes greater than 15 deg. • The protuberances have a positive effect on thrust and efficiency at higher reduced frequencies. • The change in 2S to 2P wake patterns with the increase of the pitching amplitude is observed from CFD investigations. • For the modified hydrofoil, the leading-edge vortex pattern changes from the crest to the trough of the protuberances impacting the wake and propulsion performance at different Strouhal numbers. [ABSTRACT FROM AUTHOR]

Humpback whales (Megaptera novaeangliae) in Southeast Alaska have been studied for over 50 years, and are largely considered a recovery success since the cessation of commercial whaling. Reproductive physiology is an important factor to consider in studying population health and can provide important insights into the drivers contributing to population abundance fluctuations. Validated assays for progesterone and testosterone were used on blubber biopsies from humpback whales (N = 33 whales, 71 samples) near Juneau, Alaska, in 2020 and 2021. Long-term sighting histories were used to confirm detected pregnancies with calf sightings the following year. Blubber samples were divided into two seasonal bins (early and late summer). Pregnant females sampled in both early and late summer of both 2020 and 2021 showed elevated progesterone concentrations compared to other reproductive states (p

Human activities are increasingly impacting our oceans and the focus tends to be on their environmental impacts, rather than consequences for animal welfare. Global shipping density has quadrupled since 1992. Unsurprisingly, increased levels of vessel collisions with cetaceans have followed this global expansion of shipping. This paper is the first to attempt to consider the severity of ship-strike on individual whale welfare. The methodology of the ‘Welfare Assessment Tool for Wild Cetaceans’ (WATWC) was used, which is itself based upon the Five Domains model. Expert opinion was sought on six hypothetical but realistic case studies involving humpback whales (Megaptera novaeangliae) struck by ships. Twenty-nine experts in the cetacean and welfare sector took part. They were split into two groups; Group 1 first assessed a case we judged to be the least severe and Group 2 first assessed the most severe. Both groups then additionally assessed the same four further cases. This was to investigate whether the severity of the first case influenced judgements regarding subsequent cases (i.e. expert judgements were relative) or not (i.e. judgements were absolute). No significant difference between the two groups of assessors was found; therefore, the hypothesis of relative scoring was rejected. Experts judged whales may suffer some level (>1) of overall (Domain 5) harm for the rest of their lives following a ship-strike incident. Health, closely followed by Behaviour were found to be the welfare aspects most affected by ship-strikes. Overall, the WATWC shows a robust potential to aid decision-making on wild cetacean welfare.

The occurrence of humpback whales (Megaptera novaeangliae) across the 2600 km of Hawaiian archipelago, which include the remote atolls, banks, and seamounts of Papahānaumokuākea Marine National Monument (PMNM), remains poorly understood. Previous surveys for humpback whales beyond the main Hawaiian Islands have been scarce due to limited access and the challenging winter conditions typically found in PMNM when whales are present. To overcome these limitations, a combination of moored acoustic recorders and a Wave Glider autonomous surface vehicle were used to acoustically monitor eight locations and survey approximately 1500 km of the Hawaiian archipelago for the occurrence of humpback whale song during the 2019-2020 breeding season. Relative song prevalence was established using a machine learning tool and by quantifying the level of song chorusing. A generalized additive model framework was applied to understand the associations between habitat variables and humpback whale song occurrence, and sound propagation modeling was performed to examine whether acoustic propagation influenced observed patterns. Whale song was recorded at all monitored and surveyed locations across the archipelago, albeit in varying amounts. Among the locations monitored with moored recorders, the highest and most sustained seasonal chorusing levels were measured off Maui followed by French Frigate Shoals (Kānemilohai), Hawaii Island, Middle Bank, Oahu, Kauai, Gardner Pinnacles (Pūhāhonu) and Pearl and Hermes Reef (Holoikauaua), respectively. The Wave Glider mission to PMNM revealed that song prevalence was highest at Middle Bank and gradually decreased further to the northwest, reaching a minimum at Gardner Pinnacles (Pūhāhonu). However, song occurrence increased again at Raita Bank, remaining high between Raita Bank and the Northampton Seamounts. The results reveal that nearly the entire Hawaiian archipelago is exploited by humpback whales during the winter and early spring months. Moreover, song occurrence patterns suggest that there may be more structure in the distribution of whales in PMNM than previously known and raises questions about whether multiple subpopulations occur across the archipelago.

We constructed annual abundance of a migratory baleen whale at an oceanic stopover site to elucidate temporal changes in Bermuda, an area with increasing anthropogenic activity. The annual abundance of North Atlantic humpback whales visiting Bermuda between 2011 and 2020 was estimated using photo-identification capture-recapture data for 1,204 whales, collected between December 2009 and May 2020. Owing to a sparse data set, we combined a Cormack-Jolly-Seber (CJS) model, fit through maximum likelihood estimation, with a Horvitz-Thompson estimator to calculate abundance and used stratified bootstrap resampling to derive 95% confidence intervals (CI). We accounted for temporal heterogeneity in detection and sighting rates via a catch-effort model and, guided by goodness-of-fit testing, considered models that accounted for transience. A model incorporating modified sighting effort and time-varying transience was selected using (corrected) Akaike’s Information Criterion (AICc). The survival probability of non-transient animals was 0.97 (95% CI 0.91-0.98), which is comparable with other studies. The rate of transience increased gradually from 2011 to 2018, before a large drop in 2019. Abundance varied from 786 individuals (95% CI 593-964) in 2016 to 1,434 (95% CI 924-1,908) in 2020, with a non-significant linear increase across the period and interannual fluctuations. These abundance estimates confirm the importance of Bermuda for migrating North Atlantic humpback whales and should encourage a review of cetacean conservation measures in Bermudian waters, including area-based management tools. Moreover, in line with the time series presented here, regional abundance estimates should be updated across the North Atlantic to facilitate population monitoring over the entire migratory range.

Antarctic humpback whales are recovering from near extirpation from commercial whaling. To understand the dynamics of this recovery and establish a baseline to monitor impacts of a rapidly changing environment, we investigated sex ratios and pregnancy rates of females within the Western Antarctic Peninsula (WAP) feeding population. DNA profiling of 577 tissue samples (2010-2016) identified 239 males and 268 females. Blubber progesterone levels indicated 63.5% of the females biopsied were pregnant. This proportion varied significantly across years, from 36% in 2010 to 86% in 2014. A comparison of samples collected in summer versus fall showed significant increases in the proportion of females present (50% to 59%) and pregnant (59% to 72%), consistent with demographic variation in migratory timing. We also found evidence of annual reproduction among females; 54.5% of females accompanied by a calf were pregnant. These high pregnancy rates are consistent with a population recovering from past exploitation, but appear inconsistent with recent estimates of WAP humpback population growth. Thus, our results will help to better understand population growth potential and set a current baseline from which to determine the impact of climate change and variability on fecundity and reproductive rates.

The skin is the first line of defense between an animal and its environment, and disruptions in skin-associated microorganisms can be linked to an animals health and nutritional state. To better understand the skin microbiome of large whales, high-throughput sequencing of partial small subunit rRNA genes was used to study the skin-associated bacteria of 89 seemingly healthy humpback whales (Megaptera novaeangliae) sampled along the Western Antarctic Peninsula (WAP) during early (2010) and late (2013) austral summers. Six core groups of bacteria were present in 93% or more of all humpback skin samples. A shift was observed in the average relative abundances of these core bacteria over time, with the emergence of four additional core groups of bacteria that corresponded to a decrease in water temperature, possibly caused by season- or foraging-related changes in skin biochemistry that influenced microbial growth, or other temporal factors. The skin microbiome differed between whales sampled at several regional locations along the WAP, suggesting that environmental factors or population may also influence the whale skin microbiome. Overall, the skin microbiome of humpback whales appears to provide insight into animal- and environment-related factors and may serve as a useful indicator for animal health or ecosystem alterations.IMPORTANCE The microbiomes of wild animals are currently understudied but may provide information about animal health and/or animal-environment interactions. In the largest sampling of any marine mammal microbiome, this study demonstrates conservation in the skin microbiome of 89 seemingly healthy humpback whales sampled in the Western Antarctic Peninsula, with shifts in the bacterial community composition related to temporal and regional variability. This study is important because it suggests that the skin microbiome of humpback whales could provide insight into animal nutritional or seasonal/environment-related factors, which are becoming increasingly important to recognize due to unprecedented rates of climate change and anthropogenic impact on ocean ecosystems.

Many baleen whales undertake annual fasting and feeding cycles, resulting in substantial changes in their body condition, an important factor affecting fitness. As a measure of lipid-store body condition, tissue density of a few deep diving marine mammals has been estimated using a hydrodynamic glide model of drag and buoyancy forces. Here, we applied the method to shallow-diving humpback whales (Megaptera novaeangliae) in North Atlantic and Antarctic feeding aggregations. High-resolution 3-axis acceleration, depth and speed data were collected from 24 whales. Measured values of acceleration during 5 s glides were fitted to a hydrodynamic glide model to estimate unknown parameters (tissue density, drag term and diving gas volume) in a Bayesian framework. Estimated species-average tissue density (1031.6 ± 2.1 kg m-3, ±95% credible interval) indicates that humpback whale tissue is typically negatively buoyant although there was a large inter-individual variation ranging from 1025.2 to 1043.1 kg m-3. The precision of the individual estimates was substantially finer than the variation across different individual whales, demonstrating a progressive decrease in tissue density throughout the feeding season and comparably high lipid-store in pregnant females. The drag term (CDAm-1) was estimated to be relatively high, indicating a large effect of lift-related induced drag for humpback whales. Our results show that tissue density of shallow diving baleen whales can be estimated using the hydrodynamic gliding model, although cross-validation with other techniques is an essential next step. This method for estimating body condition is likely to be broadly applicable across a range of aquatic animals and environments.

Baleen whales have few identifiable external indicators of pregnancy state, making it challenging to study essential aspects of their biology and population dynamics. Pregnancy status in other marine mammals has been determined by measuring progesterone concentrations from a variety of sample matrices, but logistical constraints have limited such studies in free-swimming baleen whales. We use an extensive blubber sample archive and associated calving history data to retrospectively identify samples that correspond to pregnant females and develop a progesterone-based pregnancy test for humpback whales. The lowest pregnant blubber progesterone concentration was 54.97 ng g-1, and the mean for the known-pregnant group was 198.74 ± 180.65 ng g-1. Conversely, females known to be below the minimum age of sexual maturity (juvenile females) had an overall low mean progesterone concentration (0.59 ± 0.25 ng g-1), well below the known-pregnant range. Of the mature females that did not return with a calf (n = 11), three fell within the known-pregnant range (320.79 ± 209.34 ng g-1), while the levels for the remaining eight were two orders of magnitude below the lowest known-pregnant level (1.63 ± 1.15 ng g-1). The proportion of females that did not return with a calf but had values similar to known-pregnant females are consistent with rates of calf mortality, but other potential explanations were considered. Our findings support a validated blubber endocrine assignment of pregnancy corroborated with field life history information, a first for any baleen whale species. The progesterone values we measured were similar to those found in different pregnancy states of other cetaceans and support using blubber biopsy samples for assigning pregnancy in humpback whales. This method can be applied to existing archives or new samples to better study life history and population demography broadly across species and populations.

Researchers are often interested in the diets of species, although direct observations - such as this white shark (Carcharodon carcharias) feeding on a humpback whale (Megaptera novaeangliae) (image credit: Oliver Shipley) - are often not possible. Despite the importance of diet source on TDF values, most isotope studies did not account for it when selecting TDF values. However, stable isotope values of animal tissues are generally offset from diet, with this difference referred to as a trophic discrimination factor (TDF; 13C and 15N for carbon and nitrogen, respectively). [Extracted from the article]

A survey of the expedition on the R/V Akademik Mstislav Keldysh in the waters south of the southernmost tip of Argentina, in the Drake Passage, as well as in the vicinities of the Antarctic Peninsula, the Scotia Sea, and the northern part of the Weddell Sea, was undertaken during two trips: January 16–February 6 (hereafter, January) and February 8–March 3 (hereafter, February), 2020. We propose a new method for analyzing the results of ecological studies and, based on this method, present new information on the ecology and spatial distribution of marine mammals and seabirds of the Antarctic. A number of marine mammal and seabird species showed similar ecological fingerprints, indicating their similar spatial distributions and the same relations to the environmental conditions regardless of their systematic position. The fin whale, the humpback whale, the snow petrel, the Adélie penguin, the Antarctic petrel, and the southern fulmar showed similar specific patterns of ecological fingerprints in January, showing the association of these species to the sea areas with icebergs and/or cut ice. In February, the allocation of the whale species to icy areas weakened what was mirrored in their ecological fingerprints, while all the above-mentioned bird species still preserved this association. The ecological fingerprints clearly circumscribe the broadness of the abiotic ecological niche occupied by individual species or species clusters. Ecological fingerprints are capable of showing changes in species distribution areas in certain periods (the southern royal albatross), in the strategy of the area usage patterns (the Antarctic fur seal), as well as in other ecological features, including those not yet considered. [ABSTRACT FROM AUTHOR]

The economic relevance of Mysticetes has prompted marine ecologists and biologists to investigate this suborder of cetaceans. Mysticetes produce distinct vocal repertoires, which are recorded to analyse the behaviour of the species within its ecology. Passive acoustic monitoring (PAM) is a standard technique for tracking Mysticete movement and vocalisation. PAM collects enormous datasets over a long period, making it practically impossible to analyse with typical visual examination methods. Machine learning (ML) techniques such as hidden Markov models (HMMs) have made automatic recognition and analysis of extensive sound recordings possible. Nevertheless, the performance of ML tools is determined by the adopted feature extraction technique. Hence, this article introduces the method of principal component analysis (PCA) as a performance-efficient alternative feature extraction technique for detecting Mysticete vocalisations using HMM. Performance of the developed PCA-HMM detector is compared with state-of-the-art detectors using two different Mysticete vocalisations (Humpback whale songs and Bryde's whale short pulses). In both species, results show that the PCA-HMM detector has the best performance and is more suitable for use in real-time application since it exhibits less computational time complexity. [ABSTRACT FROM AUTHOR]

Predator diets are largely influenced by prey availability and abundance. Yet, in heterogenous marine environments, identifying the prey species consumed by diving mammals remains a fundamental challenge. For rorqual whales, the energetic constraints of prey engulfment require that the whales seek areas of high prey abundance and execute discrete lunge feeding events on patches of high‐density prey. Prey occurrences in feces should therefore provide meaningful insight into the dominant taxa in food patches selected by the animal. We investigated the prey consumed by humpback whales in three regions in southern British Columbia (BC), Canada, using opportunistic fecal sampling, microscopy, and DNA metabarcoding of 14 fecal samples. Fish including Pacific herring (Clupea pallasii), hake (Merluccius productus), and eulachon (Thaleichthys pacificus) were the most common fish species potentially targeted by humpback whales in two regions. The krill Euphausia pacifica was the most prevalent invertebrate DNA detected in all three regions, while sergestid and mysid shrimp may also be important. High DNA read abundances from walleye pollock (Gadus chalcogrammus) and sablefish (Anoplopoma fimbria) were also recovered in one sample each, suggesting that juveniles of these semi‐pelagic species may occasionally be targeted. In general, we observed heavily digested fecal material that drove substantial dissimilarities in taxonomic resolution between polymerase chain reaction‐based and morphological analyses of the feces. Pacific herring and walleye pollock were the only prey species confirmed by both methods. Our results highlight that molecular and visual analyses of fecal samples provide a complementary approach to diet analysis, with each method providing unique insight into prey diversity. [ABSTRACT FROM AUTHOR]

A numerical investigation is proposed to explore the flow past a novel wavy circular cylinder as a passive flow control, whose shape is determined by a sinusoidal function applied to its leading edge line, similar to studies with wavy leading-edge airfoils. The latter are motivated by the wavy-shaped tubercles found in the flippers of humpback whales, which are believed to improve their maneuverability. Our attempt is, therefore, to assess the effects of leading-edge waviness now on a simpler and canonical geometry: circular cylinders. The present work relies on iLES simulations conducted with Nektar++ at a Reynolds number of 3900. Besides the straight cylinder, two wavy geometries are assessed, which are determined by a single wavelength of 37.5% for two amplitudes, 3% and 11%, based on the mean diameter of the wavy cylinder. Our results showed that, contrary to what is usually the case with traditional wavy cylinders at similar Reynolds numbers, waviness caused a reduction in the near-wake recirculation length and an increase in the mean near-wake turbulent kinetic energy compared to the straight cylinder. This was followed by a reduction in base pressure (up to about 36%) leading to a rise in lift oscillations and also to a significant increase in the mean drag coefficient of up to about 28%. An attempt to detail the flow phenomena is provided, evidencing the emergence of counter-rotating pairs of streamwise vortices between peaks. It is argued that the differences observed in recirculation length, turbulent kinetic energy, and force coefficients start even prior to the formation of these coherent structures and end up with interactions with the near wake. [ABSTRACT FROM AUTHOR]

Cicadas usually sing and mate in the higher parts of trees. Studies addressing the effects of different acoustic signals on mate choice in Cicadidae are very limited. We investigated the effects of both acoustical features and morphological traits on mate choice in an East Asian cicada Platypleura kaempferi. Males produce high-rate calling songs that attract females, then produce low-rate courtship songs to secure mating when a female is attracted. Higher calling song rate (CR), shorter single-pulse duration, and shorter pulse period of the calling song, together with lower courtship song rate and longer echeme period of the courtship song, are the most desirable traits used by females to choose a mate. These traits indicate that the more a male can raise the rate of song production, the higher the probability he is sexually selected by the female. No correlation was found between morphological traits and mating success. After mating, a minority of males started emitting calling songs again, but the CR was significantly lower than before mating and none of them attracted a new mate later. This promotes females mating with unmated males. We hypothesize that P. kaempferi may have the best of both worlds due to the unique song modulation and the mechanism of female mate choice: males change energetically, costly acoustic signals to achieve mates, while females choose a mate based on males' acoustic properties. Our results contribute to better understanding the diversity of mating preference and enrich the mechanism of mate choice in acoustic insects. [ABSTRACT FROM AUTHOR]

Studies of the impacts of climate change on Arctic marine ecosystems have largely centered on endemic species and ecosystems, and the people who rely on them. Fewer studies have focused on the northward expansion of upper trophic level (UTL) subarctic species. We provide an overview of changes in the temporal and spatial distributions of subarctic fish, birds, and cetaceans, with a focus on the Pacific Arctic Region. Increasing water temperatures throughout the Arctic have increased “thermal habitat” for subarctic fish species, resulting in northward shifts of species including walleye pollock and pink salmon. Ecosystem changes are altering the community composition and species richness of seabirds in the Arctic, as water temperatures change the available prey field, which dictates the presence of planktivorous versus piscivorous seabird species. Finally, subarctic whales, among them killer and humpback whales, are arriving earlier, staying later, and moving consistently farther north, as evidenced by aerial survey and acoustic detections. Increasing ice-free habitat and changes in water mass distributions in the Arctic are altering the underlying prey structure, drawing UTL species northward by increasing their spatial and temporal habitat. A large-scale shuffling of subarctic and Arctic communities is reorganizing high-latitude marine ecosystems. [ABSTRACT FROM AUTHOR]

The applicability of leading-edge protuberances as a passive flow control approach inspired by humpback whale flippers has attracted significant research attention in aquatic and aeronautic systems because of their influence on critical hydrodynamic and aerodynamic aspects. An experimental investigation is conducted in a cavitation tunnel under various flow conditions to determine the effectiveness of leading-edge protuberances in controlling the detrimental effects of cavitation and suppressing flow-induced noise. The experiments are carried out on four National Advisory Committee for Aeronautics airfoil 0012 hydrofoils at 7° attack angles and free stream velocities up to 10 m/s. One of the four hydrofoils is considered the baseline, while the other models have wavy leading-edge modifications with different sinusoidal protuberances. These geometry modifications are defined by the amplitudes (A) (2% and 4% of the mean chord length) and wavelengths (λ) (12.5% and 25% of the mean chord length) of the sinusoidal protuberances. Investigations of flow over hydrofoils from top and side views at various Reynolds numbers exhibit that cavitation first appears in the modified hydrofoils' troughs and is restricted to just behind the protuberance troughs for the entire cavitating flow range. These results contrast the baseline geometry, where cavitation inception occurs at the flat leading edge, and the sheet cavity expands spanwise with extensive cloud shedding. Image processing under certain conditions reveals that the protuberances reduce cavitation by 25%–60%. The analysis of the sound pressure level demonstrates that the leading-edge protuberances effectively decrease flow-induced noise at higher flow velocities when cavitation is the dominant noise source. Finally, the direct comparison of cavitating flow characteristics, quantitative cavitation measurements, and noise production analysis between the baseline and modified hydrofoils, and their comparison among the modified geometries, provides a significant reference for future modeling of potential applications employing this passive flow control technique. [ABSTRACT FROM AUTHOR]

Observations of animals' vocal actions can provide important clues about how they communicate and about how they perceive and react to changing situations. Here, analyses of consecutive songs produced by singing humpback whales recorded off the coast of Hawaii revealed that singers constantly vary the acoustic qualities of their songs within prolonged song sessions. Unlike the progressive changes in song structure that singing humpback whales make across months and years, intra-individual acoustic variations within song sessions appear to be largely stochastic. Additionally, four sequentially produced song components (or "themes") were each found to vary in unique ways. The most extensively used theme was highly variable in overall duration within and across song sessions, but varied relatively little in frequency content. In contrast, the remaining themes varied greatly in frequency content, but showed less variation in duration. Analyses of variations in the amount of time singers spent producing the four themes suggest that the mechanisms that determine when singers transition between themes may be comparable to those that control when terrestrial animals move their eyes to fixate on different positions as they examine visual scenes. The dynamic changes that individual whales make to songs within song sessions are counterproductive if songs serve mainly to provide conspecifics with indications of a singer's fitness. Instead, within-session changes to the acoustic features of songs may serve to enhance a singer's capacity to echoically detect, localize, and track conspecifics from long distances. [ABSTRACT FROM AUTHOR]

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Context: Golfo Dulce is a wintering ground of the south-eastern Pacific population of humpback whales. Habitat use and spatial preferences of whales during their reproductive season must be addressed to effectively conserve this species. Aims: This study aims to determine spatial segregation depending on humpback whale group composition (groups that included mother–calf dyads versus adult-only groups). Methods: Spatial aggregation was assessed using sightings per unit of effort from June to October, 2010–2019. The group preferences were analysed as a function of water depth and distance from the coast, and habitat use was characterised using behavioural data. Key results: Our SPUE analysis showed important locations used by humpback whales. The mother–calf groups were present in waters <80 m deep, and their main behaviour was resting (nursing and social). Adult-only groups were in the deeper waters, and the main behaviours were social breaching and travelling. Spatial preferences and behaviour data allowed the identification of critical nursing areas near potential mating grounds. Conclusions and implications: Our study has highlighted the need for inshore habitat protection, and these habitat-use patterns should be considered when designing effective conservation and management strategies for marine spatial planning. Golfo Dulce is a wintering ground of the south-eastern Pacific population of humpback whales (Megaptera novaeangliae). The aim of this study was to determine spatial segregation and habitat use depending on humpback whale group composition (groups that included mother–calf dyads v. adult-only groups) from June to October, 2010–2019. Spatial partitioning of habitat among humpback whale groups depended on group composition and reproductive behaviours. These habitat-use patterns should be considered when designing effective conservation strategies for marine spatial planning. [ABSTRACT FROM AUTHOR]

Marine organisms inhabiting coastal waters are known to be driven by periodic cycles such as diel, tidal, and seasonal changes. Humpback whales (Megaptera novaeangliae) breed in shallow and warm coastal waters, with males singing complex songs during the breeding season. To investigate periodic variations in humpback whale singing activities, we conducted fixed passive acoustic monitoring in the Ogasawara (Bonin) Islands, Japan, from winter to spring during 2016–2018. The singing activity and individual number of singers were observed throughout the day and night using a very long baseline passive acoustic array. The occurrence of singers peaked before sunrise and in the evening and was reduced during the daytime. The frequency of song reception depended on the tidal phase. A generalised additive model demonstrated that the occurrence of singers increased during the flood tide and decreased during the ebb tide in the waters west of Chichijima Island. These results suggest that the singing behaviour of humpback whales in breeding areas is affected by the diel and tidal cycles. Male humpback whales may change their behaviour or singing location depending on the strength and direction of the tidal current, considering that the selection of a stable location is beneficial for singing whales. [ABSTRACT FROM AUTHOR]

Humpback whales in the western North Pacific are considered endangered due to their small population size and lack of information. Although previous studies have reported interchanges between regions within a population, the relationship between the geographic regions of a population in Japan is poorly understood. Using 3,532 fluke photo IDs of unique individuals obtained from four areas in Japan: Hokkaido, six IDs (2009–2019); Ogasawara, 1,477 IDs, from two organizations (1) Everlasting nature of Asia (1987–2020) and (2) Ogasawara Whale Watching Association, (1990–2020); Amami, 373 IDs (1992–1994, 2005–2016); Okinawa, 1,676 IDs (1990–2018), interchanges were analyzed. The ID matchings were conducted using an automated system with an 80.9% matching accuracy. Interchange and within-region return indices were also calculated. As a result, number of matches and interchange indices follow locations, Hokkaido-Okinawa (3, 0.31), Amami-Ogasawara (36, 0.06), Amami-Okinawa (222, 0.37), and Okinawa-Ogasawara (225, 0.08), respectively. Interchange indices among Japanese areas were much higher than the indices between Ogasawara/Okinawa and Hawaii (0.01) and Mexico (0.00) reported in previous studies, indicating that the Japanese regions are utilized by the same population. At the same time, the frequency of interchanges among the three breeding areas vary, and the high within-region return indices in respective breeding areas suggest the site fidelity of the whales in each area at some level. These results indicate the existence of several groups within the population which are possibly be divided into at least two groups based on geographical features: one tend to utilize Ogasawara and the Mariana Archipelago; the other utilize Amami, Okinawa, and the Philippines, migrating along the Ryukyu and Philippine Trench. The matching results also suggest that Hokkaido is possibly be utilized as a corridor between northern feeding areas and southern breeding areas at least by individuals migrating to Okinawa area. [ABSTRACT FROM AUTHOR]

Cetaceans spend most of their time below the surface of the sea, highlighting the importance of passive acoustic monitoring as a tool to facilitate understanding and mapping their year-round spatial and temporal distributions. To increase our limited knowledge of cetacean acoustic detection patterns for the east and west coasts of Gwaii Haanas, a remote protected area on Haida Gwaii, BC, Canada, acoustic datasets recorded off SG̱ang Gwaay (Sep 2009–May 2011), Gowgaia Slope (Jul 2017–Jul 2019), and Ramsay Island (Aug 2018–Aug 2019) were analyzed. Comparing overlapping periods of visual surveys and acoustic monitoring confirmed presence of 12 cetacean species/species groups within the study region. Seasonal patterns were identified for blue, fin, humpback, grey and sperm whale acoustic signals. Killer whale and delphinid acoustic signals occurred year-round on both coasts of Haida Gwaii and showed strong diel variation. Cuvier's, Baird's, beaked whale and porpoise clicks, were identified in high-frequency recordings on the west coast. Correlations between environmental factors, chlorophyll-a and sea surface temperature, and cetacean acoustic occurrence off Gwaii Haanas were also examined. This study is the first to acoustically monitor Gwaii Haanas waters for an extended continuous period and therefore serves as a baseline from which to monitor future changes. [ABSTRACT FROM AUTHOR]

The article reports that various species of cetaceans annually visit the Pacific coast of Colombia. Topics include considered while others are present throughout the year as humpback whales belongs to breeding stock G (BSG), recognized by the International Whaling Commission are commonly seen in the Gulf of Tribugá on an annual basis.

The article reports that ship traffic can negatively affect marine wildlife including cetaceans, especially in areas where these mammals carry out relevant ecological activities. Topics include examines ship strikes can be caused by several types of large vessels as well as by smaller recreational boats.

The article reports that drones, or Unmanned Autonomous Vehicles, have become a commonly used and powerful tool in capturing observations of wild marine mammals. Topics include examines the first drone-documented case of parallel lunge feeding by a mother–calf humpback whale pair in the Bay of Fundy within the Gulf of Maine.

The article reports that Humpback whales undergo long migrations between high latitudes where food sources are rich where calving and breeding occur in the winter. Topics include examines although monotypic, three separate populations are generally recognized such as North Pacific, North Atlantic and Southern Hemisphere.

The article reports that the Humpback whales are a cosmopolitan species that often visit inshore waters close to the coast, making it easier to see and study them. Topics include considered assessing whale behavior offers a better understanding of the importance of these species in marine ecosystems as well as give knowledge about their ecology and habitat use.

The article describe a different context for bubble use by humpback whales on the Hawaiian breeding grounds. Topics include examines in contrast to the bubbles produced by competing male humpbacks, individuals report an anecdotal observation of male production of bubbles directed at the female's genital-mammary region.

The article reports that an animal spends a proportion of the dive not moving, suspended in the water column while drifting up or downwards depending on its buoyancy. Topics include examines four bowhead whales in Disko Bay, West Greenland, were instrumented with AcousondeTM sound and movement tags in a tag-retention study carried out by the Greenland Institute of Natural Resources.

The article describes an interaction between two cetacean species such as the sperm whale and the short-finned pilot whale. Topics include examines the event occurred on June 6, 2021 during a research survey and considered the crew of Pelagic Life, AC and the Marine Mammal Laboratory at Universidad Veracruzana was surveying the Continental Slope off the Veracruz coast in the southwestern Gulf of Mexico when a mother–calf sperm whale pair was observed.

The article reports that North Atlantic minke whale is a common, but enigmatic, mysticete in New England waters. Topics include examines sightings are usually brief a glimpse of a dorsal fin and dark back before submergence and considered the Minke whales along the U.S. East Coast are considered part of the Canadian East Coast population, but key questions about stock structure and population trends remain uncertain.

The article reports that short-finned pilot whales inhabit tropical, subtropical and warm temperate waters of the world, generally offshore, where they feed mainly on squid. Topics include examines an observation of short-finned pilot whale aggressive behavior towards sperm whales during a cetacean survey in the southern Gulf of California.

The article focuses on the presence of humpback whales in the North Pacific between Hawaii and the western Pacific winter breeding assemblies. Topics include examines there have been few surveys and sightings in this vast area and considered a Japanese visual cetacean survey reported a single humpback whale on February 5, 1993.

The article focuses on Humpback whales like other rorquals, possess ventral pleats that allow them to engulf large volumes of water, dense with prey through an efficient lunging action. Topics include examines this feeding method is implemented by humpback whales in various ways by different populations that show behavioral plasticity between geographical locations.

The article reports that successful copulation is necessary for the continuation of many species, but the courtship behavior leads to a successful copulation that can vary greatly, even among cetaceans. Topics include examines the variation in pre-copulation behavior seems related to the mating system of a particular species.

The article reports that mating is critical to the propagation of cetaceans and while much of this system is biologically hardwired or uses innate behavioral systems there is evidence that learned behaviors contribute significantly to a species' success. Topics include examines the mechanisms by which cetaceans select their mates or develop the critical behaviors needed for mating success remain unknown.

The article reports that passive acoustic monitoring and multisensory tagging methods have increased the number of studies focused on the nocturnal behavior of whales. Topics include examines the humpback whales known as Megaptera novaeangliae migrate long distances between feeding and breeding grounds.

The article focuses on large whale stranding responses which present unique logistical challenges, particularly when the whale strands alive. Topics include examines several case reports exist that share successful approaches to the many phases of response and for live large whale strandings, response efforts need to consider animal welfare, human safety and the ability to collect, archive and share meaningful diagnostic information.

Purpose: With aims to increase the aerodynamic efficiency of aerodynamic surfaces, study on flow control over these surfaces has gained importance. With the addition of flow control devices such as synthetic jets and vortex generators, the flow characteristics can be modified over the surface and, at the same time, enhance the performance of the body. One such flow control device is the tubercle. Inspired by the humpback whale's flippers, these leading-edge serrations have improved the aerodynamic efficiency and the lift characteristics of airfoils and wings. This paper aims to discusses in detail the flow physics associated with tubercles and their effect on swept wings. Design/methodology/approach: This study involves a series of experimental and numerical analyses that have been performed on four different wing configurations, with four different sweep angles corresponding to 0°, 10°, 20° and 30° at a low Reynolds number corresponding to Rec=100,000. Findings: Results indicate that the effect of tubercles diminishes with an increase in wing sweep. A significant performance enhancement was observed in the stall and post-stall regions. The addition of tubercles led to a smooth post-stall lift characteristic compared to the sudden loss in the lift with regular wings. Among the four different wings under observation, it was found that tubercles were most effective on the 0° configuration (no sweep), showing a 10.8% increment in maximum lift and a 38.5% increase in the average lift generated in the post-stall region. Tubercles were least effective on 30° configuration. Furthermore, with an increase in wing sweep, co-rotating vortices were distinctly observed rather than counter-rotating vortices. Originality/value: While extensive numerical and experimental studies have been performed on straight wings with tubercles, studies on the tubercle effect on swept wings at low Reynolds number are minimal and mainly experimental in nature. This study uses numerical methods to explore the complex flow physics associated with tubercles and their implementation on swept wings. This study can be used as an introductory study to implement passive flow control devices in the low Reynolds number regime. [ABSTRACT FROM AUTHOR]

Studies of body condition are key to understanding the health, bioenergetics and ecological roles of marine mammals. Due to challenges in studying marine mammals at sea, body condition is often approximated using metrics representing the size of the dorsal surface visible from aerial imagery, but quantifying variability in body volume would enable a more holistic understanding of bioenergetics. Furthermore, the number and location of measurements needed to accurately quantify body condition has received little attention. Three‐dimensional (3D) models provide a promising tool for representing morphology and providing holistic estimates of marine mammal body condition when combined with field‐based morphometric measurements.We use humpback whales Megaptera novaeangliae to demonstrate the utility of 3D models for estimating body condition in marine mammals. We integrate morphometric measurements taken from unoccupied aerial vehicles (UAVs) with scalable 3D models to generate estimates of humpback whale body volume. We assess which and how many morphometric measurements are required to accurately estimate body volume and compare the error between volume estimates derived from 3D models and previously developed models representing volume as a series of ellipses. Using UAV measurements, we assess the contribution of each morphometric measurement to volumetric estimates, and quantify the error produced by all combinations and numbers of morphometric measurements (131,072 combinations).Error in volume estimates from 3D models generated with as few as five width measurements was <5% compared to the full models and was lower than the error produced when using five width measurements with the elliptical approach. We suggest that by conserving the external morphology of marine mammals, 3D models allow body volume and body condition to be estimated accurately with few measurements.We provide code and guidelines for creating 3D models using the open‐source software Blender and for assessing which measurements are needed to accurately capture the morphology of cetaceans. The 3D modelling approach we present will facilitate studies of intra‐ and interannual changes in body volume in marine mammals, which is vital to providing a more holistic understanding of bioenergetics and to assessing responses to environmental change and anthropogenic stressors. [ABSTRACT FROM AUTHOR]

Microparticles, such as microplastics and microfibers, are ubiquitous in marine food webs. Filter-feeding megafauna may be at extreme risk of exposure to microplastics, but neither the amount nor pathway of microplastic ingestion are well understood. Here, we combine depth-integrated microplastic data from the California Current Ecosystem with high-resolution foraging measurements from 191 tag deployments on blue, fin, and humpback whales to quantify plastic ingestion rates and routes of exposure. We find that baleen whales predominantly feed at depths of 50–250 m, coinciding with the highest measured microplastic concentrations in the pelagic ecosystem. Nearly all (99%) microplastic ingestion is predicted to occur via trophic transfer. We predict that fish-feeding whales are less exposed to microplastic ingestion than krill-feeding whales. Per day, a krill-obligate blue whale may ingest 10 million pieces of microplastic, while a fish-feeding humpback whale likely ingests 200,000 pieces of microplastic. For species struggling to recover from historical whaling alongside other anthropogenic pressures, our findings suggest that the cumulative impacts of multiple stressors require further attention. Combining microplastic data from the California Current Ecosystem with high-resolution foraging measurements from 191 tag deployments on blue, fin and humpback whales, this study quantifies plastic ingestion rates and routes of exposure risk in filter-feeding megafauna. [ABSTRACT FROM AUTHOR]

Short-range biomimetic covert communications have been developed using dolphin whistles for underwater acoustic covert communications. Due to a channel characteristics difference by range, the conventional short-range methods cannot be directly applied to long-range communications. To enable long-range biomimicking communication, overcoming the large multipath delay and a high degree of mimic (DoM) in the low-frequency band is required. This paper proposes a novel biomimetic communication method that preserves a low bit-error rate (BER) with a large DoM in the low-frequency band. For the transmission, the proposed method utilizes the time-dependent frequency change of the whistle, and its receiver obtains additional SNR gain from the multipath delay. Computer simulations and practical ocean experiments were executed to demonstrate that the BER performance of the proposed method is better than the conventional methods. For the DoM assessment, the novel machine learning-based method was utilized, and the result shows that the whistles generated by the proposed method were recognized as the actual whistle of the right humpback whale. [ABSTRACT FROM AUTHOR]