Migratory movements of fin whales from the Gulf of St. Lawrence challenge our understanding of the Northwest Atlantic stock structure.

Fin whales, Balenoptera physalus, are capital breeders, having the potential to separate breeding and feeding both spatially and temporally. Fin whales occur throughout the Northwest Atlantic, but stock structure and seasonal movements remain unclear. By deploying satellite transmitters on 28 individuals, we examine movement patterns within and beyond the Gulf of St. Lawrence (GSL), Canada, and challenge the current understanding of stock structure. Eight individuals left the GSL in autumn, with five tags persisting into January. Migration patterns of these whales showed considerable variation in timing and trajectory, with movements extending south to 24°N, and thus beyond the assumed distribution limit of the species in the Northwest Atlantic. A rapid return to the Scotian Shelf or Gulf of Maine was observed from several whales after incursions in southern waters, suggesting that fin whales in the Northwest Atlantic may not have a common winter destination that fits the definition of a breeding ground. Area-restricted search (ARS) behavior dominated fin whale activities during summer (92%) and fall (72%), with persistence into the winter (56%); ARS occurred at multiple locations in the GSL, Scotian Shelf and Shelf edge, and near seamounts of the North Atlantic, having characteristics consistent with foraging areas.

Hydroacoustic study of fin whales around the Southern Wake Island: Type, vocal behavior, and temporal evolution from 2010 to 2022.

The progress of fin whale study is hindered by the debate about whether the two typical type-A and type-B calls (characterized by central source frequencies of 17-20 Hz and 20-30 Hz, respectively) originate from a single fin whale or two individual fin whales. Here, hydroacoustic data is employed to study the type, vocal behavior, and temporal evolution of fin whale calls around the Southern Wake Island from 2010 to 2022. It is identified that (1) type-A and type-B calls come from two individuals based on the large source separation of the two calls through high-precision determination of source location; (2) type-A fin whales exhibit vocal influence on type-B fin whales, where type-B fin whales become paired with type-A calls and vocalize regularly when type-A fin whales appear, and type-A fin whales always lead the call sequences; and (3) some type-A fin whales stop calling when another type-A fin whale approaches at a distance of about 1.6 km. During 2010-2022, type-A calls occur every year, whereas type-B calls are prevalent only after November 2018. A culture transmission is proposed from type-A fin whales to type-B fin whales and/or a population increase of type-B fin whales in the region after November 2018.

Return of large fin whale feeding aggregations to historical whaling grounds in the Southern Ocean.

Fin whales (Balaenoptera physalus quoyi) of the Southern Hemisphere were brought to near extinction by twentieth century industrial whaling. For decades, they had all but disappeared from previously highly frequented feeding grounds in Antarctic waters. Our dedicated surveys now confirm their return to ancestral feeding grounds, gathering at the Antarctic Peninsula in large aggregations to feed. We report on the results of an abundance survey and present the first scientific documentation of large fin whale feeding aggregations at Elephant Island, Antarctica, including the first ever video documentation. We interpret high densities, re-establishment of historical behaviours and the return to ancestral feeding grounds as signs for a recovering population. Recovery of a large whale population has the potential to augment primary productivity at their feeding grounds through the effects of nutrient recycling, known as 'the whale pump'. The recovery of fin whales in that area could thus restore ecosystem functions crucial for atmospheric carbon regulation in the world's most important ocean region for the uptake of anthropogenic CO2.

Decadal-scale phenology and seasonal climate drivers of migratory baleen whales in a rapidly warming marine ecosystem.

Species' response to rapid climate change can be measured through shifts in timing of recurring biological events, known as phenology. The Gulf of Maine is one of the most rapidly warming regions of the ocean, and thus an ideal system to study phenological and biological responses to climate change. A better understanding of climate-induced changes in phenology is needed to effectively and adaptively manage human-wildlife conflicts. Using data from a 20+ year marine mammal observation program, we tested the hypothesis that the phenology of large whale habitat use in Cape Cod Bay has changed and is related to regional-scale shifts in the thermal onset of spring. We used a multi-season occupancy model to measure phenological shifts and evaluate trends in the date of peak habitat use for North Atlantic right (Eubalaena glacialis), humpback (Megaptera novaeangliae), and fin (Balaenoptera physalus) whales. The date of peak habitat use shifted by +18.1 days (0.90 days/year) for right whales and +19.1 days (0.96 days/year) for humpback whales. We then evaluated interannual variability in peak habitat use relative to thermal spring transition dates (STD), and hypothesized that right whales, as planktivorous specialist feeders, would exhibit a stronger response to thermal phenology than fin and humpback whales, which are more generalist piscivorous feeders. There was a significant negative effect of western region STD on right whale habitat use, and a significant positive effect of eastern region STD on fin whale habitat use indicating differential responses to spatial seasonal conditions. Protections for threatened and endangered whales have been designed to align with expected phenology of habitat use. Our results show that whales are becoming mismatched with static seasonal management measures through shifts in their timing of habitat use, and they suggest that effective management strategies may need to alter protections as species adapt to climate change.

Individual and population dietary specialization decline in fin whales during a period of ecosystem shift.

This study sought to estimate the effect of an anthropogenic and climate-driven change in prey availability on the degree of individual and population specialization of a large marine predator, the fin whale (Balaenoptera physalus). We examined skin biopsies from 99 fin whales sampled in the St. Lawrence Estuary (Canada) over a nine year period (1998-2006) during which environmental change was documented. We analyzed stable isotope ratios in skin and fatty acid signatures in blubber samples of whales, as well as in seven potential prey species, and diet was quantitatively assessed using Bayesian isotopic models. An abrupt change in fin whale dietary niche coincided with a decrease in biomass of their predominant prey, Arctic krill (Thysanoessa spp.). This dietary niche widening toward generalist diets occurred in nearly 60% of sampled individuals. The fin whale population, typically composed of specialists of either krill or lipid-rich pelagic fishes, shifted toward one composed either of krill specialists or true generalists feeding on various zooplankton and fish prey. This change likely reduced intraspecific competition. In the context of the current "Atlantification" of northern water masses, our findings emphasize the importance of considering individual-specific foraging tactics and not only population or group average responses when assessing population resilience or when implementing conservation measures.

Fin whale acoustic populations present in New Zealand waters: Description of song types, occurrence and seasonality using passive acoustic monitoring.

Southern fin whales (Balaenoptera physalus) are known to migrate from the Antarctic to mid-latitudes during winter for breeding, but the occurrence and distribution of this species is not well known in the waters around New Zealand. The 'doublet' calls are one of the main calls emitted specifically by fin whales and repeated in a regular pattern, which make the acoustic detection of these calls relevant to detect the presence of fin whales. Using a signal processing algorithm to detect 'doublet' calls emitted by fin whales, we studied the occurrence, characteristics and seasonality of these 'doublet' calls in two regions around New Zealand; Cook Strait in 2016/2017 and offshore Gisborne in 2014/2015. The call detection procedure consisted of binarization of the spectrogram and a cross-correlation between the binarized spectrogram and a template of binarized 'doublet' calls spectrogram. A binarization threshold for the data spectrograms and a cross correlation threshold were then determined through multiple trials on a training dataset and a Receiver Operating Characteristics (ROC) curve. Fin whale 'doublet' calls occurred on the east side of New Zealand's Cook Strait during austral winter, specifically in June 2017 and offshore Gisborne in June-August 2014. No 'doublet' calls were detected on the west side of Cook Strait. The 'doublet' calls' Inter-Note Interval (INI) was similar in both datasets. However, there was a difference in alternation of the mean frequency for both HF components of 'doublet' calls in Cook Strait and Gisborne. As the song types were compared with those previously described in the literature, our findings suggest that some fin whales wintering in New Zealand waters may be part of a broader 'acoustic population' whose range extends west to southern Australia and south to Antarctica.

Seismic crustal imaging using fin whale songs.

Fin whale calls are among the strongest animal vocalizations that are detectable over great distances in the oceans. We analyze fin whale songs recorded at ocean-bottom seismometers in the northeast Pacific Ocean and show that in addition to the waterborne signal, the song recordings also contain signals reflected and refracted from crustal interfaces beneath the stations. With these data, we constrain the thickness and seismic velocity of the oceanic sediment and basaltic basement and the P-wave velocity of the gabbroic lower crust beneath and around the ocean bottom seismic stations. The abundant and globally available fin whale calls may be used to complement seismic studies in situations where conventional air-gun surveys are not available.

Autumn movements of fin whales (Balaenoptera physalus) from Svalbard, Norway, revealed by satellite tracking.

Insight into animal movements is essential for understanding habitat use by individuals as well as population processes and species life-history strategies. In this study, we instrumented 25 fin whales with ARGOS satellite-transmitters in Svalbard, Norway, to study their movement patterns and behaviour (Area Restricted Search (ARS), transiting or unknown) during boreal autumn/early winter. Ten of the whales stayed in the tagging area (most northerly location: 81.68°N) for their entire tracking periods (max 45 days). The other 15 whales moved in a south-westerly direction; the longest track ended off the coast of northern Africa (> 5000 km from the tagging location) after 96 days. The whales engaged in ARS behaviour intermittently throughout their southward migrations. During transit phases the whales moved quickly; one individual maintained an average horizontal speed of 9.3 km/h (travelling 223 km per day) for a period of a week. This study documents that: (1) some fin whales might remain at high latitudes during winter; (2) the whales that do migrate probably feed along the way; (3) they can maintain high transiting speed for long periods and; (4) one breeding area for this species is likely located in deep, warm water some 100 km west of Morocco.

Baleen whale acoustic presence and behaviour at a Mid-Atlantic migratory habitat, the Azores Archipelago.

The identification of important areas during the annual life cycle of migratory animals, such as baleen whales, is vital for their conservation. In boreal springtime, fin and blue whales feed in the Azores on their way to northern latitudes while sei whales migrate through the archipelago with only occasional feeding. Little is known about their autumn or winter presence or their acoustic behaviour in temperate migratory habitats. This study used a 5-year acoustic data set collected by autonomous recorders in the Azores that were processed and analysed using an automated call detection and classification system. Fin and blue whales were acoustically present in the archipelago from autumn to spring with marked seasonal differences in the use of different call types. Diel patterns of calling activity were only found for fin whales with more calls during the day than night. Sei whales showed a bimodal distribution of acoustic presence in spring and autumn, corresponding to their expected migration patterns. Diel differences in sei whale calling varied with season and location. This work highlights the importance of the Azores as a migratory and wintering habitat for three species of baleen whales and provides novel information on their acoustic behaviour in a mid-Atlantic region.

Helminth Load in Feces of Free-Ranging Blue and Fin Whales from the Gulf of California.

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.

Fin whale movements in the Gulf of California, Mexico, from satellite telemetry.

Fin whales (Balaenoptera physalus) have a global distribution, but the population inhabiting the Gulf of California (GoC) is thought to be geographically and genetically isolated. However, their distribution and movements are poorly known. The goal of this study was to describe fin whale movements for the first time from 11 Argos satellite tags deployed in the southwest GoC in March 2001. A Bayesian Switching State-Space Model was applied to obtain improved locations and to characterize movement behavior as either "area-restricted searching" (indicative of patch residence, ARS) or "transiting" (indicative of moving between patches). Model performance was assessed with convergence diagnostics and by examining the distribution of the deviance and the behavioral parameters from Markov Chain Monte Carlo models. ARS was the predominant mode behavior 83% of the time during both the cool (December-May) and warm seasons (June-November), with slower travel speeds (mean = 0.84 km/h) than during transiting mode (mean = 3.38 km/h). We suggest ARS mode indicates either foraging activities (year around) or reproductive activities during the winter (cool season). We tagged during the cool season, when the whales were located in the Loreto-La Paz Corridor in the southwestern GoC, close to the shoreline. As the season progressed, individuals moved northward to the Midriff Islands and the upper gulf for the warm season, much farther from shore. One tag lasted long enough to document a whale's return to Loreto the following cool season. One whale that was originally of undetermined sex, was tagged in the Bay of La Paz and was photographed 10 years later with a calf in the nearby San Jose Channel, suggesting seasonal site fidelity. The tagged whales moved along the western GoC to the upper gulf seasonally and did not transit to the eastern GoC south of the Midriff Islands. No tagged whales left the GoC, providing supporting evidence that these fin whales are a resident population.

Automated localization of whales in coastal fjords.

Localization and tracking of vocalizing marine mammals are powerful tools for understanding and mitigating the impacts of anthropogenic stressors such as vessel noise on habitat use of cetaceans. A large-aperture hydrophone network has been installed in the Kitimat Fjord System, an ecologically, culturally, and economically valued marine environment in northern British Columbia, Canada. This network consists of four synchronized bottom-mounted hydrophones that permanently record and radio-transmit data to a land-based laboratory. An automated system has been developed which includes routines to localize transient bio-acoustic signals from three or more streaming hydrophones in near real-time. These routines comprise the correlation of hydrophone signals, the construction of a time lag model, and signal localization and error estimation from a spatial likelihood surface. The localization method was tested experimentally and subsequently applied to vocalizations from humpback whales, fin whales, and killer whales. Refractive and reflective sound propagation effects in the confined fjords are assessed using ray tracing propagation models. Automated localization results are compared to ground-truth data and shown to provide good accuracy.

Fin whale density and distribution estimation using acoustic bearings derived from sparse arrays.

Passive acoustic monitoring of marine mammals is common, and it is now possible to estimate absolute animal density from acoustic recordings. The most appropriate density estimation method depends on how much detail about animals' locations can be derived from the recordings. Here, a method for estimating cetacean density using acoustic data is presented, where only horizontal bearings to calling animals are estimable. This method also requires knowledge of call signal-to-noise ratios, as well as auxiliary information about call source levels, sound propagation, and call production rates. Results are presented from simulations, and from a pilot study using recordings of fin whale (Balaenoptera physalus) calls from Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) hydrophones at Wake Island in the Pacific Ocean. Simulations replicating different animal distributions showed median biases in estimated call density of less than 2%. The estimated average call density during the pilot study period (December 2007-February 2008) was 0.02 calls hr-1 km2 (coefficient of variation, CV: 15%). Using a tentative call production rate, estimated average animal density was 0.54 animals/1000 km2 (CV: 52%). Calling animals showed a varied spatial distribution around the northern hydrophone array, with most detections occurring at bearings between 90 and 180 degrees.

Are stable isotope ratios and oscillations consistent in all baleen plates along the filtering apparatus? Validation of an increasingly used methodology.

RATIONALE: Baleen plates are anatomical structures composed of inert tissue that hang from the upper jaw in mysticetes. Baleen plates may differ in size and in coloration between different segments of the filtering row or between sides of the mouth. Concern has been raised that variation in baleen plate characteristics may reflect dissimilar structural composition and growth rates liable to affect stable isotope ratios and their oscillation patterns. METHODS: We measured stable carbon (δ13 C values) and nitrogen (δ15 N values) isotope ratios at intervals of 1 cm along the longitudinal axis of six baleen plates collected from different positions along the mouth of a fin whale. All samples were analysed using a continuous flow isotope ratio mass spectrometer. Generalized additive models were fitted to the data from each baleen plate and the results of the models were compared visually. RESULTS: A total of 206 samples were analysed. Visually, all baleen plates presented nearly identical oscillations, independent of the position or the coloration of the baleen plate. However, the variation in δ13 C and δ15 N values occurring between the different baleen plates was higher in the segments of oscillations exhibiting steeper slopes. CONCLUSIONS: Differences in size between plates in an individual are due to differential erosion rates according to their position in the mouth. Therefore, the position of sampling along the baleen plate row should not be a reason for concern when conducting stable isotope studies.

Fin whales as bioindicators of multi-decadal change in carbon and oxygen stable isotope shifts in the North Atlantic.

Global changes, and particularly the massive release of CO2 to the atmosphere and subsequent global warming, have altered the baselines of carbon and oxygen stable isotopic ratios. Temporal shifts in these baselines can be advantageously monitored through cetacean skin samples because these animals are highly mobile and therefore integrate in their tissues the heterogeneity of local environmental signals. In this study, we examine variation of δ13C and δ18O values in the skin of fin whales sampled over three decades in two different North Atlantic feeding grounds: west Iceland and northwest Spain. These locations are situated about 2700 km apart and thus represent a wide latitudinal range within the North Atlantic Ocean. The δ13C decrease in both areas is attributed to the burning of fossil fuels and increased deforestation worldwide, the so-called Suess effect. The dissimilarity in the magnitude of the shift between the two areas is coincidental with previous information on local shifts and lies within the ranges of variation observed. δ18O values experienced a minimal, yet significant change in fin whales from W Iceland (a decline of -0.44‰ between 1986 and 2013) but not in those from NW Spain. This is in concordance with a higher rise in temperatures in the former area than in the latter. The study validates the use of cetacean skin to monitor temporal and geographical shifts in stable isotopic values and alerts that, when applying this tool to ecological research, comparisons between sample sets should take into account temporal and latitudinal scales.

Locomotor muscle fibre heterogeneity and metabolism in the fastest large-bodied rorqual: the fin whale (Balaenoptera physalus).

From a terrestrial ancestry, the fin whale (Balaenoptera physalus) is one of the largest animals on Earth with a sprinter anti-predator strategy, and a characteristic feeding mode, lunge feeding, which involves bouts of high-intensity muscle activity demanding high metabolic output. We investigated the locomotor muscle morphology and metabolism of this cetacean to determine whether its muscle profile (1) explains this unique swimming performance and feeding behaviour, (2) is or is not homogeneous within the muscle, and (3) predicts allometric variations inherent to an extreme body size. A predominantly fast-glycolytic phenotype characterized the fin whale locomotor muscle, composed of abundant fast-twitch (type IIA) fibres with high glycolytic potential, low oxidative capacity, relatively small size, and reduced number of capillaries. Compared with superficial areas, deep regions of this muscle exhibited a slower and more oxidative profile, suggesting a division of labour between muscle strata. As expected, the fin whale locomotor muscle only expressed the two slowest myosin heavy chain isoforms (I and IIA). However, it displayed anaerobic (glycolytic) and aerobic (lipid-based metabolism) capabilities higher than would be predicted from the allometric perspective of its extreme body size. Relationships between muscle metabolism and body mass were fibre-type specific. The 'sprinter' profile of the fin whale swimming muscle, particularly of its superficial compartment, supports physiological demands during both high-speed swimming and the lunge, when energy expenditure reaches maximal or supramaximal levels. Comparatively, the slower and more oxidative profile of the deep compartment of this muscle seems to be well designed for sustained, low-intensity muscle activity during routine swimming.

Estimating range to a vocalizing fin whale using the timing and amplitude of multipath arrivals.

A semi-automated method is described to range to vocalizing fin whales using the timing and amplitude of multipath arrivals measured on seafloor receivers. Calls are detected and multipath arrivals identified with a matched filter. Multipath times and relative amplitudes are predicted as a function of range by ray tracing. Because the direct and first water-column multiple arrivals are not always observed, different hypotheses for the observed arrival paths must be considered. For two arrivals, an amplitude threshold is used to determine if the first arrival is the direct path and if not, the call is disregarded as distant. When three or more arrivals are detected, three hypotheses for the paths of arrivals are considered; the solution is the hypothesis and range that minimizes the timing and optionally, amplitude ratio or absolute amplitude residual. The method is tested with data from two ocean bottom seismometers, one on the Juan de Fuca Ridge and the other in the Cascadia Basin. Solutions obtained by minimizing a combined residual from timing and an empirical absolute amplitude model extracted from the data yield reliable ranges up to 5 km at both sites, and are sufficient to estimate call density using point transect distance sampling.

The Functional Anatomy of Nerves Innervating the Ventral Grooved Blubber of Fin Whales (Balaenoptera Physalus).

Nerves that supply the floor of the oral cavity in rorqual whales are extensible to accommodate the dramatic changes in tissue dimensions that occur during "lunge feeding" in this group. We report here that the large nerves innervating the muscle component of the ventral grooved blubber (VGB) in fin whales are branches of cranial nerve VII (facial nerve). Therefore, the muscles of the VGB are homologous to second branchial arch derived muscles, which in humans include the muscles of "facial expression." We speculate, based on the presence of numerous foramina on the dorsolateral surface of the mandibular bones, that general sensation from the VGB likely is carried by branches of the mandibular division (V3) of cranial nerve V (trigeminal nerve), and that these small branches travel in the lipid-rich layer directly underlying the skin. We show that intercostal and phrenic nerves, which are not extensible, have a different wall and nerve core morphology than the large VGB nerves that are branches of VII. Although these VGB nerves are known to have two levels of waviness, the intercostal and phrenic nerves have only one in which the nerve fascicles in the nerve core are moderately wavy. In addition, the VGB nerves have inner and outer parts to their walls with numerous large elastin fibers in the outer part, whereas intercostal and phrenic nerves have single walls formed predominantly of collagen. Our results illustrate that overall nerve morphology depends greatly on location and the forces to which the structures are exposed. Anat Rec, 300:1963-1972, 2017. © 2017 Wiley Periodicals, Inc.

Spatial and temporal trends in fin whale vocalizations recorded in the NE Pacific Ocean between 2003-2013.

In order to study the long-term stability of fin whale (Balaenoptera physalus) singing behavior, the frequency and inter-pulse interval of fin whale 20 Hz vocalizations were observed over 10 years from 2003-2013 from bottom mounted hydrophones and seismometers in the northeast Pacific Ocean. The instrument locations extended from 40°N to 48°N and 130°W to 125°W with water depths ranging from 1500-4000 m. The inter-pulse interval (IPI) of fin whale song sequences was observed to increase at a rate of 0.54 seconds/year over the decade of observation. During the same time period, peak frequency decreased at a rate of 0.17 Hz/year. Two primary call patterns were observed. During the earlier years, the more commonly observed pattern had a single frequency and single IPI. In later years, a doublet pattern emerged, with two dominant frequencies and IPIs. Many call sequences in the intervening years appeared to represent a transitional state between the two patterns. The overall trend was consistent across the entire geographical span, although some regional differences exist. Understanding changes in acoustic behavior over long time periods is needed to help establish whether acoustic characteristics can be used to help determine population identity in a widely distributed, difficult to study species such as the fin whale.

Fin whale song variability in southern California and the Gulf of California.

Songs are distinct, patterned sounds produced by a variety of animals including baleen whales. Fin whale songs, which consist of short pulses repeated at regular interpulse intervals (IPIs), have been suggested as a tool to distinguish populations. Fin whale songs were analyzed from data collected from 2000-2012 in Southern California and from 2004-2010 in the Gulf of California using autonomous acoustic recorders. IPIs were measured for each identifiable song sequence during two random days of each month with recordings. Four distinct song types were identified: long doublet, short doublet, long triplet, and short triplet. Long and short doublets were the dominant songs in Southern California, while long and short triplets were dominant in the Gulf of California. An abrupt change in song type occurred in both areas during the monitoring period. We argue that each song type is unique to a population and these changes represent a shift in the primary population in the monitoring area. Occasional temporal and spatial song overlap indicated some exchange or visitation among populations. Fin whales appear to synchronize and gradually modify song rhythm over long time scales. A better understanding of the evolutionary and ecological importance of songs to fin whale populations is needed.