Spatial patterns of humpback whale (Megaptera novaeangliae) sightings and survey effort: Insight into North Atlantic population structure

Understanding the population structure of a species is critical to its effective management and conservation. The humpback whale ( Megaptera novaeangliae ) has been the target of numerous research projects in several ocean basins, but no clear picture of its population structure has emerged. In the North Atlantic Ocean, genetic analyses and photo-identification movements have shown significant heterogeneity among the summer feeding grounds. Building on this knowledge, we test the hypothesis that the feeding grounds represent distinct populations by analyzing the spatial pattern of summer humpback whale sightings and survey effort. Controlling for the spatial pattern of effort, sightings are clustered, with peaks at radial distances of 300 km, 600 km, and 1,500 km. These results provide insight into the spatial extent of the summer population structure of humpback whales in the North Atlantic Ocean. Fine-scale clustering at distances of 300 km and 600 km is compatible with multiple populations consisting of the Gulf of Maine, eastern Canada, western Greenland, and Iceland. Broad-scale clustering at distances of 1,500 km may represent divisions between the western and eastern North Atlantic populations. These results provide spatial bounds to the feeding grounds of humpback whales and emphasize their distinct nature as management units.     

Distribution and movements of fin whales in the North Pacific Ocean

• 1 We summarize fin whale Balaenoptera physalus catch statistics, sighting data, mark recoveries and acoustics data. The annual cycle of most populations of fin whales had been thought to entail regular migrations between high‐latitude summer feeding grounds and lower‐latitude winter grounds. Here we present evidence of more complex and varied movement patterns.
• 2 During summer, fin whales range from the Chukchi Sea south to 35 °N on the Sanriku coast of Honshu, to the Subarctic Boundary (ca. 42 °N) in the western and central Pacific, and to 32 °N off the coast of California. Catches show concentrations in seven areas which we refer to as ‘grounds’, representing productive feeding areas.
• 3 During winter months, whales have been documented over a wide area from 60 °N south to 23 °N. Coastal whalers took them regularly in all winter months around Korea and Japan and they have been seen regularly in winter off southern California and northern Baja California. There are also numerous fin whale sightings and acoustic detections north of 40 °N during winter months. Calves are born during the winter, but there is little evidence for distinct calving areas.
• 4 Whales implanted with Discovery‐type marks were killed in whaling operations, and location data from 198 marked whales demonstrate local site fidelity, consistent movements within and between the main summer grounds and long migrations from low‐latitude winter grounds to high‐latitude summer grounds.
• 5 The distributional data agree with immunogenetic and marking findings which suggest that the migratory population segregates into at least two demes with separate winter mating grounds: a western ground off the coast of Asia and an eastern one off the American coast. Members of the two demes probably mingle in the Bering Sea/Aleutian Islands area.
• 6 Prior research had suggested that there were at least two non‐migratory stocks of fin whale: one in the East China Sea and another in the Gulf of California. There is equivocal evidence for the existence of additional non‐migratory groups in the Sanriku‐Hokkaido area off Japan and possibly the northern Sea of Japan, but this is based on small sample sizes.

     

Future recovery of baleen whales is imperiled by climate change

Historical harvesting pushed many whale species to the brink of extinction. Although most Southern Hemisphere populations are slowly recovering, the influence of future climate change on their recovery remains unknown. We investigate the impacts of two anthropogenic pressures—historical commercial whaling and future climate change—on populations of baleen whales (blue, fin, humpback, Antarctic minke, southern right) and their prey (krill and copepods) in the Southern Ocean. We use a climate–biological coupled “Model of Intermediate Complexity for Ecosystem Assessments” (MICE) that links krill and whale population dynamics with climate change drivers, including changes in ocean temperature, primary productivity and sea ice. Models predict negative future impacts of climate change on krill and all whale species, although the magnitude of impacts on whales differs among populations. Despite initial recovery from historical whaling, models predict concerning declines under climate change, even local extinctions by 2100, for Pacific populations of blue, fin and southern right whales, and Atlantic/Indian fin and humpback whales. Predicted declines were a consequence of reduced prey (copepods/krill) from warming and increasing interspecific competition between whale species. We model whale population recovery under an alternative scenario whereby whales adapt their migratory patterns to accommodate changing sea ice in the Antarctic and a shifting prey base. Plasticity in range size and migration was predicted to improve recovery for ice‐associated blue and minke whales. Our study highlights the need for ongoing protection to help depleted whale populations recover, as well as local management to ensure the krill prey base remains viable, but this may have limited success without immediate action to reduce emissions.     

CATCHES OF HUMPBACK AND OTHER WHALES FROM SHORE STATIONS AT MOSS LANDING AND TRINIDAD, CALIFORNIA, 1919–1926

Logbook data from California shore whaling stations at Moss Landing (1919–1922 and 1924) and Trinidad (1920 and 1922–1926) are analyzed. The logs for the two stations record the taking of 2,111 whales, including 1,871 humpbacks, 177 fin whales, 26 sei whales, 3 blue whales, 12 sperm whales, 7 gray whales, 1 right whale, 1 Baird's beaked whale, and 13 whales of unspecified type (probably humpbacks). Most whales were taken from spring to autumn, but catches were made in all months of some years. The sex ratios of humpback, fin, and sei whales (the three species with sufficient sample sizes to test) did not differ from parity. Primary prey, determined from stomach contents, included sardines and euphausiids for both humpback and fin whales, and 'plankton' (probably euphausiids) for sei whales. The prevalence of pregnancy was 0.46 among mature female humpbacks and 0.43 among mature female fin whales, although these values are reported with caution. Information on length distribution for all species is summarized. Analysis of the catch data for this and other areas supports the current view that humpback whales along the west coast of the continental United States comprise a single feeding stock and also suggests that the present population is well below pre-exploitation levels.     

Distribution and abundance of fin whales (Balaenoptera physalus) in the western Mediterranean sea during the summer

A sightings survey was conducted in the summer of 1991 in the western Mediterranean to describe the distribution of fin whales and to estimate their absolute abundance during the summer feeding season. Fin whales were only found in the Liguro-Provençal basin, in deep waters (mean depth 2,360, S.E.: 46.8 m), beyond the continental shelf. The highest densities of fin whales were found in relatively cool waters (mean = 23.9°C), and water in areas in which fin whales were found was significantly cooler than that in areas without fin whales. Patterns of distribution of whales, with remarkably high densities in the feeding grounds, and composition of schools, which were found to be smaller than in other regions, suggest that food resources for the species in the north-western Mediterranean feeding grounds occur at higher densities but are more patchily distributed than in other fin whale feeding grounds so far studied. Abundance was estimated as 3,583 individuals (S.E.: 967; 95% CI: 2,130-6,027).     

Quantifying spatial and temporal variation of North Pacific fin whale (Balaenoptera physalus) acoustic behavior

In order to help develop hypotheses of connectivity among North Pacific fin whales, we examine recordings from 10 regions collected in the spring and fall. We develop a Random Forest model to classify fin whale note types that avoids manual note classification errors. We also present a method that objectively quantifies the note and pattern composition of recordings. We find that fin whale recordings near Hawaii have distinctive patterns, similar to those found in other regions in the central North Pacific, suggesting potential migration pathways. Our results are consistent with previous studies that suggest there may be two different populations utilizing the Chukchi Sea and central Aleutians in the fall and mix to some degree in the southern Bering Sea. Conversely, we found little difference between spring and fall recordings in the eastern Gulf of Alaska, suggesting some residency of whales in this region. This is likely due to fine scale similarities of calls among the inshore regions of British Columbia, while offshore areas are being utilized by whales traveling from various distant areas. This study shows how our novel approach to characterize recordings is an objective and informative way to standardize spatial and temporal comparisons of fin whale recordings.     

Tracing the spatio-temporal dynamics of endangered fin whales (<Emphasis Type="Italic">Balaenoptera physalus</Emphasis>) within baleen whale (Mysticeti) lineages: a mitogenomic perspective

To explore the spatio-temporal dynamics of endangered fin whales (Balaenoptera physalus) within the baleen whale (Mysticeti) lineages, we analyzed 148 published mitochondrial genome sequences of baleen whales. We used a Bayesian coalescent approach as well as Bayesian inferences and maximum likelihood methods. The results showed that the fin whales had a single maternal origin, and that there is a significant correlation between geographic location and evolution of global fin whales. The most recent common female ancestor of this species lived approximately 9.88 million years ago (Mya). Here, North Pacific fin whales first appeared about 7.48 Mya, followed by a subsequent divergence in Southern Hemisphere approximately 6.63 Mya and North Atlantic about 4.42 Mya. Relatively recently, approximately 1.76 and 1.42 Mya, there were two additional occurrences of North Pacific populations; one originated from the Southern Hemisphere and the other from an uncertain location. The evolutionary rate of this species was 1.002?×?10^?3 substitutions/site/My. Our Bayesian skyline plot illustrates that the fin whale population has the rapid expansion event since ~?2.5 Mya, during the Quaternary glaciation stage. Additionally, this study indicates that the fin whale has a sister group relationship with humpback whale (Meganoptera novaeangliae) within the baleen whale lineages. Of the 16 genomic regions, NADH5 showed the most powerful signal for baleen whale phylogenetics. Interestingly, fin whales have 16 species-specific amino acid residues in eight mitochondrial genes: NADH2, COX2, COX3, ATPase6, ATPase8, NADH4, NADH5, and Cytb.     

Stable isotope analysis and fin whale subpopulation structure in the eastern North Atlantic

The North Atlantic fin whale was subject to heavy exploitation in the past and, despite partial recovery, it is still considered endangered. Recent research has questioned its currently accepted subpopulation structure and migratory movements, challenging management and conservation efforts. Here we contribute to this discussion by presenting results of stable isotope analysis of fin whale bones and krill samples collected from fin whale stomachs from two exploited areas, west Iceland and northwest Spain, and comparing these results with North Atlantic isoscapes. In krill, δ¹⁵N values were highly variable and no significant differences in δ¹⁵N and δ¹³C between areas emerged. δ¹⁵N and δ¹³C values in bone were higher than in krill, due to trophic enrichment, and were not significantly different between areas. Both krill and bone results were slightly inconsistent with the local isoscapes, maybe due to seasonal variations in local productivity and in krill diet and, in the case of bone, to its capability to integrate long‐term isotopic values, derived from food consumed in distant areas. Conversely, δ¹⁸O values, which reflect the basal signal of sea water, were consistent with isoscapes and significantly higher in whales from northwestern Spain, possibly indicating migration to breeding grounds located at lower latitudes.     

A comparison of Northeast Atlantic killer whale (Orcinus orca) stereotyped call repertoires

Killer whale call repertoires can provide information on social connections among groups and populations. Killer whales in Iceland and Norway exhibit similar ecology and behavior, are genetically related, and are presumed to have been in contact before the collapse of the Atlanto-Scandian herring stock in the 1960s. However, photo-identification suggests no recent movements between Iceland and Norway but regular movement between Iceland and Shetland. Acoustic recordings collected between 2005 and 2016 in Iceland, Norway, and Shetland were used to undertake a comprehensive comparison of call repertoires of Northeast Atlantic killer whales. Measurements of time and frequency parameters of calls from Iceland (n = 4,037) and Norway (n = 1,715) largely overlapped in distribution, and a discriminant function analysis had low correct classification rate. No call type matches were confirmed between Iceland and Norway or Shetland and Norway. Three call types matched between Iceland and Shetland. Therefore, this study suggests overall similarities in time and frequency parameters but some divergence in call type repertoires. This argues against presumed past contact between Icelandic and Norwegian killer whales and suggests that they may not have been one completely mixed population.     

Movement,site fidelity and connectivity in a top marine predator,the killer whale

Movement, site fidelity and connectivity have important consequences for the evolution of population structure and therefore the conservation and management of a species. In this study photographs of naturally marked killer whales collected from sites across the Northeast Atlantic are used to estimate fidelity to sampling locations and movement between locations, expressed as transition probabilities, pt, using maximum likelihood methods. High transition probabilities suggest there is high inter-annual site fidelity to all locations, and large-scale movement between the spawning and wintering grounds of both Norwegian and Iceland stocks of Atlantic herring. There was no evidence of movement between the Norwegian herring grounds and Icelandic herring grounds, or between the mackerel fishing grounds and the herring fishing grounds. Thus the movement of predictable and abundant prey resources can lead to intrinsic isolation in this species We also find movement between the Northern Isles, Scotland and East Iceland. An association network indicates that killer whales predating seals around the Northern Isles, Scotland are linked to the community of killer whales that follow the Icelandic summer-spawning herring. This adds support to existing evidence of a broad niche width in some populations.     

OPEN-BOAT WHALING ON THE STRAITS OF GIBRALTAR GROUND AND ADJACENT WATERS

Logbooks ( n = 317) from whaling expeditions made in the North Atlantic during the 19th century were examined to investigate activity in the Gibraltar Straits grounds. At least forty expeditions of whaling vessels from European and American ports visited the area. In all cases the main target was the sperm whale, but pilot whales, dolphins, sea turtles, and even a blue whale were also taken. Whaling effort concentrated on the Atlantic side of the Straits; only two expeditions ventured into the Mediterranean Sea, obtaining negligible catches. The whaling season extended during spring and summer and peaked in June–July. This seasonality appeared not to be governed by changes in whale density but by the trade winds necessary to sail southward or westward to cross the Atlantic. Searching effort continued while trying out, but the rate of sighting cetaceans was about half that of searching periods. However, the rate of sighting or capturing a sperm whale remained unchanged during processing, probably because the gregarious habits of the species produced clumping of catches. For every whale secured, 1.31 whales were struck. After correcting for struck but lost whales and for "gammed" vessels, the minimum number of removals of sperm whales during 1862–1889 is estimated at 237.     

BEHAVIORAL RESPONSE OF FOUR SPECIES OF BALAENOPTERID WHALES TO BIOPSY SAMPLING

Behavioral responses to biopsy sampling of four species of northwestern Atlantic balaenopterid whales summering in the estuary and Gulf of St. Lawrence, Quebec, from 1990 to 1995 were studied to determine if this technique was an important disturbance to the whales. A total of 447 biopsy samples were taken using a small punch-type biopsy tip fired from a crossbow. Biopsies were successfully taken from 91.2% of the whales approached. Whales displayed no reaction to 45.2% of the successful biopsy attempts. Whales that responded to biopsy sampling typically resumed their normal behavior immediately or within a few minutes. Most humpback whales displayed a hard tail flick, and the majority of fin and blue whales submerged following biopsy sampling. Significantly different frequencies and intensities of responses were found between whale species. Minke and humpback whales were found to be more sensitive to biopsy sampling than fin and blue whales. Response frequencies were similar between females and males for all species, with the exception of fin whales where females had a higher response frequency than males. Biopsy sample length, i. e., penetration depth, did not explain variations in response intensity but may influence response frequency to biopsy sampling. Group size, geographical region, and number of biopsies taken per whale were not factors that explained variation in behavioral responses. The biopsy technique was found to be an efficient method for obtaining high-quality whale skin and blubber samples with limited behavioral disturbance to balaenopterid whales.     

From the southern right whale hunting decline to the humpback whaling expansion: a review of whale catch records in the tropical western South Atlantic Ocean

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The oldest marine vertebrate fossil from the volcanic island of Iceland: a partial right whale skull from the high latitude Pliocene Tjörnes Formation

Extant baleen whales (Cetacea, Mysticeti) are a disparate and species‐rich group, but little is known about their fossil record in the northernmost Atlantic Ocean, a region that supports considerable extant cetacean diversity. Iceland's geographical setting, dividing North Atlantic and Arctic waters, renders it ideally situated to shed light on cetacean evolution in this region. However, as a volcanic island, Iceland exhibits very little marine sedimentary exposure, and fossil whales from Iceland older than the late Pleistocene are virtually unknown. Here, we present the first fossil whale found in situ from the Pliocene Tjörnes Formation (c. 4.5 Ma), Iceland's only substantial marine sedimentary outcrop. The specimen is diagnosed as a partial skull from a large right whale (Mysticeti, Balaenidae). This discovery highlights the Tjörnes Formation as a potentially productive fossil vertebrate locality. Additionally, this find indicates that right whales (Eubalaena) and bowhead whales (Balaena) were sympatric, with broadly overlapping latitudinal ranges in the Pliocene, in contrast to the modern latitudinal separation of their living counterparts.     

Mysticete migration revisited: are Mediterranean fin whales an anomaly?

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WEIGHTS AND ANATOMICAL MEASUREMENTS OF NORTHEASTERN ATLANTIC FIN (BALAENOPTERA PHYSALUS, LINNAEUS) AND SEI (B. BOREALIS, LESSON) WHALES

Piecemeal body weights of eleven fin and four sei whales and intact weights of three foetuses, obtained from Iceland, are compared with published weight data. The Icelandic fin are similar to other northern hemisphere animals but are significantly leaner than their Antarctic counterparts. The Icelandic sei appear heavier than the North Pacific sei whales. Their weights cannot be predicted from a North Pacific sei whale weight/length formula. Length, girth and blubber thickness measurements indicate changes in relative body dimensions in the early fin whale foetus compared with juveniles and adults; however, the midterm sei whale foetus is similar to the adult and juvenile sei whales. The blubber appears to form a major component even in the foetal body. The integration of a standard series of lengths, girths and blubber thicknesses in juveniles and adults can provide an estimate of the blubber component. Both girth and length are significant parameters in estimating body weight, a simple weight/length formula being found to be inadequate to allow for variability in body fatness. Evaluation of such a multiple parameter formula for calculating weight appears satisfactory for both fin and sei whales. Apparent weight/length differences between species and stocks may thus be partly due to variations in body fatness.     

A NEW HYBRID BETWEEN A BLUE WHALE, BALAENOPTERA MUSCULUS, AND A FIN WHALE, B. PHYSALUS: FREQUENCY AND IMPLICATIONS OF HYBRIDIZATION

A female hybrid between a fin ( Balaenoptera physalus ) and a blue whale ( B. mnusculus ) was caught in whaling operations in 1984 off northwestern Spain. Its coloration and body proportions were intermediate between those of a fin and a blue whale, although it was anomalously large (19.4 m) when compared to fin whales of similar age (4 yr). It was sexually immature, concomitant with its age but not its length if it were a fin whale. Molecular analyses revealed that the mother of the hybrid was a blue whale and the father a fin whale. Examination of data for the five fin-blue whale hybrids in the literature, plus other anecdotal reports, indicates that hybridization between these two species occurs in various geographic regions and is relatively frequent, notably in light of the absence of reported hybrids between other mysticetes. Either species may act as father or mother, and there does not appear to be a selection for a given sex among the hybrids. The reproductive capacity of these hybrids remains unknown, although incidence of reproductive impairment appears to be higher in hybrid males than in hybrid females.     

Observations of cetaceans in the south-east Atlantic sector of the Southern Ocean,during summer 2008

Knowledge of cetacean species composition and their distribution in the south-east Atlantic sector of the Southern Ocean is scarce. During a survey in February–March 2008, systematic whale sightings were carried out along transect lines following the 5° and 15° E meridians between 35° and 67° S. In total, 67 toothed whales and 126 baleen whales were observed. Both fin whales (four animals) and Antarctic minke whales Balaenoptera bonaerenses (three animals) in addition to 16 individuals of unidentified species were among the observed baleen whales. The dominating baleen whale species in our study was humpback whales Megaptera novaeangliae with 108 individuals observed. They occurred single or in groups up to seven individuals (N _mean = 2.5 ind) and eight of the counts were of calves. The relationship between humpback whale occurrence and environmental variables including Antarctic krill (Euphausia superba) abundance from acoustic recordings, hydrography, bathymetry and production was tested using general additive models. Only temperature increased the predictive power of the model with whale occurrence increasing with the decreasing temperature in more southern areas.