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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DNA profile of a sixteenth century western North Atlantic right whale (Eubalaena glacialis)

Low levels of genetic variability identified within the North Atlantic right whale (Eubalaena glacialis), when compared to the Southern right whale (E. australis) and other large whales, have been suggested to result from population reductions due to whaling. Previous genetic analysis of 218 whale bones from sixteenth century Basque whaling sites in the western North Atlantic revealed only a single right whale bone. We determined the genotypes of 27 microsatellite loci using DNA isolated from this bone. All alleles from the historic specimen occur in the extant western North Atlantic population and both the probability of identity of the specimen and the number of heterozygous loci are similar to that in the extant population. Assessments of how genetically different the historical population might have been suggest genetic characteristics have not changed substantially over four centuries of whaling.     

Species identification and likely catch time period of whale bones from South Georgia

Skeletal remains of baleen whales killed during the onset of 20th century commercial whaling lie scattered across the shores and abandoned whaling stations of the subantarctic island of South Georgia. Here we report on genetic species identification of whale bones collected from South Georgia using standard historical DNA protocols. We amplified and sequenced short fragments of the mitochondrial DNA (mtDNA) control region from 281 available bone samples. Of these, 231 provided mtDNA sequences of sufficient quality and length (174–194 bp) for species identification: 158 bones were identified as humpback whale (Megaptera novaeangliae), 51 bones were identified as fin whale (Balaenoptera physalus), 18 bones were identified as blue whale (B. musculus), two bones were identified as sei whale (B. borealis), one bone was identified as a southern right whale (Eubalaena australis), and one bone was identified as a southern elephant seal (Mirounga leonina). The prominence of humpback, fin, and blue whale bones in the sample collection corresponds to the catch record of the early years of whaling on the island of South Georgia (pre‐1915), prior to the depletion of these populations.     

World whale stocks

The history of whaling is very largely one of repeated over-exploitation of the various whale stocks which became available through discovery or technological advance. Modern whaling has similarly caused considerable reductions in the numbers of some species in the major whaling grounds. Stock assessment methods are based on catch and effort statistics, biological information including age and reproductive status, marking and sightings records. Catch effort data have to be used with caution, because of changes in species preference, shifts in the whaling grounds and national fleet variations. With allowance made for these factors, cumulative catches adjusted for recruitment can be used to estimate the initial stock number. Changes in stock density after known catches also lead to abundance estimates. Logarithmic regression of age composition data are used to find the total mortality rates. The natural mortality can be estimated from early season catches in a fishery or pre-fishery year classes caught more recently; fishing mortality is found by subtraction, which again leads to abundance estimates. Mathematical approaches incorporating recruitment estimates from actual age composition data and theoretical population models have been employed. Additional estimates come from mark release-recapture experiments and direct sightings counts from whaling vessels and research ships. The latter are the only means of estimating the protected species. The yields which the various stocks can sustain are calculated from direct observations and theoretical considerations of the changes in recruitment, largely due to increased pregnancy rates and the lower ages at sexual maturity which occur in exploited stocks. The results of all the available analyses have been compared and combined to produce the population estimates and yields tabulated. The object of whale management is to bring all stocks to the levels providing the maximum or optimum sustainable yields. These are defined in terms of numbers at the moment, but may be expressed as biomass in the future.     

The world's smallest whale population?

The North Pacific right whale (Eubalaena japonica) was heavily exploited by both nineteenth century whaling and recent (1960s) illegal Soviet catches. Today, the species remains extremely rare especially in the eastern North Pacific. Here, we use photographic and genotype data to calculate the first mark–recapture estimates of abundance for right whales in the Bering Sea and Aleutian Islands. The estimates were very similar: photographic = 31 (95% CL 23–54), genotyping = 28 (95% CL 24–42). We also estimated the population contains eight females (95% CL 7–18) and 20 males (95% CL 17–37). Although these estimates may relate to a Bering Sea subpopulation, other data suggest that the total eastern North Pacific population is unlikely to be much larger. Its precarious status today—the world''s smallest whale population for which an abundance estimate exists—is a direct consequence of uncontrolled and illegal whaling, and highlights the past failure of international management to prevent such abuses.     

The fin whale Balaenoptera physalus (L. 1758) in the Mediterranean Sea

1. The ecology and status of fin whales Balaenoptera physalus in the Mediterranean Sea is reviewed. The species’ presence, morphology, distribution, movements, population structure, ecology and behaviour in this semi‐enclosed marine region are summarized, and the review is complemented with original, previously unpublished data. 2. Although the total size of the fin whale population in the Mediterranean is unknown, an estimate for a portion of the western basin, where most of the whales are known to live, was approximately 3500 individuals. High whale densities, comparable to those found in rich oceanic habitats, were found in well‐defined areas of high productivity. Most whales concentrate in the Ligurian‐Corsican‐Provençal Basin, where their presence is particularly noticeable during summer; however, neither their movement patterns throughout the region nor their seasonal cycle are clear. 3. Based on genetic studies, fin whales from the Mediterranean Sea are distinct from North Atlantic conspecifics, and may constitute a resident population, separate from those of the North Atlantic, despite the species’ historical presence in the Strait of Gibraltar. Fin whales are known to calve in the Mediterranean, with births peaking in November but occurring at lower rates throughout the year. They feed primarily on krill Meganyctiphanes norvegica which they capture by diving to depths in excess of 470 m. It is suggested that the extensive vertical migratory behaviour of its main prey may have influenced the social ecology of this population. 4. Known causes of mortality and threats, including collisions with vessels, entanglement in fishing gear, deliberate killing, disturbance, pollution and disease, are listed and discussed in view of the implementation of appropriate conservation measures to ensure the species’ survival in the region.     

Gray whale Eschrichtius robustus population and stock identity

• 1 In response to conservation and management concerns about gray whale Eschrichtius robustus population and stock structure, we provide an overview of the life history and ecology of gray whales as a context for discussion of population and stock structure within the species. Historically eastern and western North Pacific gray whales were managed separately because: (i) their ranges do not overlap; (ii) genetic analyses indicate that the two populations are significantly different; and (iii) eastern gray whales have increased in abundance over the past century while western gray whales have not.
• 2 Here, we review gray whale migration timing and segregation, feeding and prey species, and reproduction and reproductive behaviour. For the eastern and western gray whale, we review their distribution, history of exploitation, abundance and current status, although most of what is known is founded on the better studied eastern gray whale and only implied for the lesser known western gray whale. Methods to investigate population and stock identity are reviewed including genetics, morphology, chemical signatures, carbon isotopes, parasites, photographic identification and trends in abundance.
• 3 While the evidence indicates that there is at least some degree of mixing within each of the gray whale populations, no stocks or sub‐stocks can be defined. Population structure is not evident in nuclear data, and because selection occurs primarily on the nuclear genome, it is unlikely that there is structuring within each population that could result in evolutionary differences. For western gray whales, there are insufficient data to assess the plausibility of stock structure within the population, owing to its extremely depleted state. Research on eastern gray whales has focused mostly on documenting changes in abundance, feeding biology and behaviour, and suggests separate breeding groups to be unlikely. Both males and females are promiscuous breeders lending little opportunity for the nuclear genome to be anything other than well mixed as is suggested by the high haplotypic diversity of the eastern population.
• 4 The available data strongly indicate that western gray whales represent a population geographically isolated from eastern gray whales and therefore that the western and eastern populations should be treated as separate management units.

     

Global distribution of fin whales Balaenoptera physalus in the post‐whaling era (1980–2012)

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North Atlantic killer whale Orcinus orca populations: a review of current knowledge and threats to conservation

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Simulation of the entanglement of a North Atlantic right whale (Eubalaena glacialis) with fixed fishing gear

Population estimates of the critically endangered North Atlantic right whale (Eubalaena glacialis) put the number of individuals at 458 with the actual number likely being lower due to a recent unusual mortality event. Entanglement with fixed fishing gear is the most significant cause of mortality of North Atlantic right whales. There remains little documentation of how North Atlantic right whales become enwrapped during an encounter with fixed fishing gear. In order to gain a better understanding of how entanglements might occur, an interactive simulator was developed that allows the user to swim a virtual whale model using a standard game controller through a gear field in an attempt to re‐create an entanglement. The morphologically accurate right whale model produces realistic swimming motions and is capable of pectoral fin motions in response to user input. Using the simulator, gear entanglements involving the pectoral flippers including ropes wrapping around the body and entanglements involving the tailstock were re‐created. Entanglements involving the pectoral flippers with body wraps were more easily generated than entanglements involving the tailstock only. The simulator should aid scientists, fisheries experts, fishing gear designers, and bycatch reduction scientists in understanding entanglement dynamics and testing potential new gear configurations.     

A review of cetacean occurrence in West African waters from the Gulf of Guinea to Angola

• 1 The cetacean fauna of the west coast of Africa is poorly described. Therefore, literature on the occurrence of cetacean species in the waters of 13 potential West African range states from the Gulf of Guinea to Angola was reviewed, including sighting, stranding, capture, bycatch and whaling records.
• 2 At least 28 species of cetacean were documented in the study region, comprising seven baleen whale species and 21 species of toothed whale (including at least 17 delphinid species).
• 3 Cetaceans could be broadly split into seven ecological categories, based on their distribution. A warm temperate/tropical deep‐water cetacean community dominated the study area. Cooler water from the Benguela Current influenced southern Angola (≤16°S latitude) and at least three cetacean species occurred predominantly in this region.
• 4 Only three or fewer species were confirmed in the waters of Togo, Nigeria, Cameroon and the Democratic Republic of Congo. Seventeen or more species were documented in Ghana, Gabon and Angola, where dedicated cetacean research projects have been initiated in recent years. Angola had the most diverse documented cetacean community: 28 confirmed species.
• 5 The humpback whale Megaptera novaeangliae was the most widely recorded species, and was documented in 11 (85%) countries. Sperm whales Physeter macrocephalus, Bryde's whales Balaenoptera cf. brydei, bottlenose dolphins Tursiops truncatus and Atlantic spotted dolphins Stenella frontalis were recorded in over half of the countries.

     

Uncertain recovery of the North Atlantic right whale in a changing ocean

Human activities have placed populations of many endangered species at risk and mitigation efforts typically focus on reducing anthropogenic sources of mortality. However, failing to recognize the additional role of environmental factors in regulating birth and mortality rates can lead to erroneous demographic analyses and conclusions. The North Atlantic right whale population is currently the focus of conservation efforts aimed at reducing mortality rates associated with ship strikes and entanglement in fishing gear. Consistent monitoring of the population since 1980 has revealed evidence that climate‐associated changes in prey availability have played an important role in the population's recovery. The considerable interdecadal differences observed in population growth coincide with remote Arctic and North Atlantic oceanographic processes that link to the Gulf of Maine ecosystem. Here, we build capture‐recapture models to quantify the role of prey availability on right whale demographic transitional probabilities and use a corresponding demographic model to project population growth rates into the next century. Contrary to previous predictions, the right whale population is projected to recover in the future as long as prey availability and mortality rates remain within the ranges observed during 1980–2012. However, recent events indicate a northward range shift in right whale prey, potentially resulting in decreased prey availability and/or an expansion of right whale habitat into unprotected waters. An annual increase in the number of whale deaths comparable to that observed during the summer 2017 mass mortality event may cause a decline to extinction even under conditions of normal prey availability. This study highlights the importance of understanding the oceanographic context for observed population changes when evaluating the efficacy of conservation management plans for endangered marine species.     

Fin whale (Balaenoptera physalus) population identity in the western Mediterranean Sea

Archival bottom‐mounted audio recorders were deployed in nine different areas of the western Mediterranean Sea, Strait of Gibraltar, and adjacent North Atlantic waters during 2006–2009 to study fin whale (Balaenoptera physalus) seasonal presence and population structure. Analysis of 29,822 recording hours revealed typical long, patterned sequences of 20 Hz notes (here called “song”), back‐beats, 135–140 Hz notes, and downsweeps. Acoustic parameters (internote interval, note duration, frequency range, center and peak frequencies) were statistically compared among songs and song notes recorded in all areas. Fin whale singers producing songs attributable to the northeastern North Atlantic subpopulation were detected crossing the Strait of Gibraltar and wintering in the southwestern Mediterranean Sea (Alboran basin), while songs attributed to the Mediterranean were detected in the northwest Mediterranean basin. These results suggest that the northeastern North Atlantic fin whale distribution extends into the southwest Mediterranean basin, and spatial and temporal overlap may exist between this subpopulation and the Mediterranean subpopulation. This new interpretation of the fin whale population structure in the western Mediterranean Sea has important ecological and conservation implications. The conventionally accepted distribution ranges of northeastern North Atlantic and Mediterranean fin whale subpopulations should be reconsidered in light of the results from this study.     

Overview of sperm whale Physeter macrocephalus mortality events in the Adriatic Sea, 1555–2009

• 1 In the Mediterranean Sea, the sperm whale Physeter macrocephalus is one of eight regular cetacean species. Poor knowledge of its ecology and status, together with suspected decline in numbers, make studies of historical and present occurrence especially relevant. Long‐term time series of stranding events are the most reliable data to provide a scientific framework for testing hypotheses that seek to explain the mechanisms responsible for cetacean strandings.
• 2 We present a comprehensive overview of cases of sperm whale mortality and human response to such events encompassing five centuries (1555–2009) within a portion of the Mediterranean Sea that offers a wealth of historical information – the Adriatic Sea.
• 3 A total of 36 mortality events were validated, involving 68 animals. Two findings of skeletal materials are also reported. The geographic distribution of strandings within the basin clearly was uneven: 44% of records (n = 16) were clustered along a 280km portion of the western Adriatic coast. A relatively high number of mortality events occurred along gently sloping sandy beaches away from suitable sperm whale habitat.
• 4 Until the first half of the 20th century, live‐stranded animals were routinely killed: all but one cases with known human response elicited killing attempts. Starting from the 1980s, killing was replaced by efforts to rescue the animals.
• 5 Mass strandings of sperm whales have occurred since historical times in the Adriatic Sea. Mortality events involving multiple individuals accounted for at least 17% of the total sample (6 of 36 mortality events). At least 29% of live strandings (6 of 21) involved more than one individual.
• 6 This study contributes a long‐term dataset based on careful validation of historical information, suitable for hypothesis testing aimed at investigating spatial and temporal correlates of sperm whale strandings – particularly live strandings – as a clue to their causes.

     

Molecular genetic identification of whale and dolphin products from commercial markets in Korea and Japan

We report the methods and results of molecular genetic identification of the species and, in some cases, geographical origins of whale and dolphin products purchased from retail markets and restaurants in Japan and South Korea. As reported previously (Baker & Palumbi 1994), we used the polymerase chain reaction (PCR) and a portable laboratory to amplify, purify and later sequence a portion of the mitochondrial DNA control region from 16 commercial products purchased in Japan. This ‘spot check’ revealed a surprising variety of species for sale, including minke, fin and humpback whales and one or two species of dolphins sold as ‘kujira’ or whale. In the Korean survey, DNA amplifications were conducted by two of us (C.S.B. and F.C.) working with independent equipment and reagents. The two sets of DNA amplifications were returned to our respective laboratories and sequenced independently for cross-validation. Among the total of 17 species-specific sequences we found a dolphin, a beaked whale, 13 Northern Hemisphere minke whales (representing at least seven distinct individuals) and two whales which are closely related to the recognized sei and Bryde's whales but could not be identified as either using available type sequences. We suggest that these two specimens represent a currently unrecognized species or subspecies of Bryde's whale, possibly the so-called ‘small-form’ reported from the tropical waters of the Indo-Pacific. We conclude that molecular systematic analyses of DNA sequences have tremendous utility for the identification of whale and dolphin products. However, there are certain constraints on the application of these techniques for monitoring whaling or trade in whale products. First, PCR and DNA sequencing can generate misleading artefacts. These can generally be recognized or eliminated through experimental controls. Second, phylogenetic reconstructions of DNA sequences can be misinterpreted if the database of type sequences is inadequate or the taxonomy of the group is incomplete. This constraint is, at present, a more serious obstacle to molecular monitoring of whaling. Our results highlight uncertainties about the taxonomic status of oceanic populations and morphological forms of two species (or species complexes) targeted by legal and illegal hunting, the minke and Bryde's whales. Despite these uncertainties, it is difficult to reconcile some of the species available in Japanese and Korean commercial markets with recent catch records made available to the International Whaling Commission. It is particularly disturbing that two specimens of an unrecognized species or subspecies of baleen whale were for sale in a restaurant in South Korea in October, 1994, 8 years after the acceptance of an international moratorium on commercial whaling.     

Evidence of two subaggregations of humpback whales on the Kodiak,Alaska, feeding ground revealed from stable isotope analysis

Knowledge of humpback whale (Megaptera novaeangliae) foraging on feeding grounds is becoming increasingly important as the growing North Pacific population recovers from commercial whaling and consumes more prey, including economically important fishes. We explored spatial and temporal (interannual, within‐season) variability in summer foraging by humpback whales along the eastern side of the Kodiak Archipelago as described by stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios of humpback whale skin (n = 118; 2004–2013). The trophic level (TL) of individual whales was calculated using basal food web δ¹⁵N values collected within the study area. We found evidence for the existence of two subaggregations of humpback whales (“North,” “South”) on the feeding ground that fed at different TLs throughout the study period. Linear mixed models suggest that within an average year, Kodiak humpback whales forage at a consistent TL during the feeding season. TL estimates support mixed consumption of fish and zooplankton species in the “North” (mean ± SE; 3.3 ± 0.1) and predominant foraging on zooplankton in the “South” (3.0 ± 0.1). This trend appears to reflect spatial differences in prey availability, and thus, our results suggest North Pacific humpback whales may segregate on feeding aggregations and target discrete prey species.     

Medieval and Early Modern Whaling in Portugal

ABSTRACT

Mainland Portugal is not renowned for having been a whaling nation of significance. However, preliminary studies have brought to light enough historical references to suggest that whaling occurred from at least the 13th century, and the present work identifies 38 historical sources documenting whale use or whaling on the Portuguese coast between 1201 and 1728. A peak of whale-related sources occurred during the 13th and 14th centuries, and almost all Portuguese accounts are contemporary to those found from the French and Spanish Basque countries, such that the beginning of the whaling activity seems to be coeval. No geographical cluster of whaling activities can be established—they seem to have been unevenly scattered along the entire coastline. Nor can a chronological north–south movement of coastal whaling activities be discerned. The geographical and chronological patterns give support to the assumption that whaling was not introduced to Portugal by the Basques, who are known to have spread westward from the French Labourd (11th century), via Golf of Biscay, to Asturias, and southward to Galicia (14th century). Rather, Portuguese whale use seems to have originated independently of Basque influence. Several of the sources specify “black whales” as the target species. This is consistent with modern knowledge about the distribution and migration patterns of North Atlantic right whales during Basque medieval and early modern whaling. The Portuguese sources are not clear as to numbers of whales taken, nor to the whaling technology used, but the activity was sufficiently well organized and developed to warrant the levying of tithes in the feudal system of 13th-century Portugal.     

Fine‐scale spatial differences in humpback whale diet composition near Kodiak,Alaska

On the North Pacific feeding grounds, humpback whales (Megaptera novaeangliae) are recovering from commercial whaling at a rapid rate (6.8%). The potential effect that this recovery will have on trophic dynamics involving these predators is currently unknown. To better elucidate complex trophic dynamics, variability in diet composition of apex predators on their respective feeding grounds needs to be understood. Thus, we explored the diet composition of two defined subaggregations of humpback whales of the Kodiak Archipelago population (“North,” “South”) using stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotope ratios of humpback whale skin and regional prey samples in Bayesian dietary mixing models. Humpback whales in the “North” region consumed proportionally more fish, dominated by capelin (Mallotus villosus), whereas, whales in the “South” region consumed predominantly krill. The difference in diet composition appears to reflect regional differences in prey availability. Thus, regional variability in diet composition by humpback whales may have disproportionate impacts on prey resources of sympatric predators depending on available prey biomass. As a result, we suggest fine‐scale studies of apex predator diets are needed to better model trophic dynamics with accuracy.     

A review of the human activities impacting cetaceans in the eastern tropical Atlantic

• 1. The eastern tropical Atlantic (ETA), extending from Mauritania south to Angola, is inhabited by at least 34 cetacean species. Knowledge of cetaceans and the human activities affecting them in the ETA is scant.
• 2. Available literature was reviewed over three eras of ETA cetacean research: the whaling era (1700s–1950s); the stranding and specimen era (1950s–70s); and the modern field research era (1980s–present). Eight human activities were documented to impact ETA cetacean species: directed takes (whaling and small cetaceans); by‐catch or entanglement in fishing gear; the ETA tuna purse seine fishery; overfishing; habitat loss and degradation; vessel strikes; marine ecotourism; and live captures for display. Climate change may represent a future threat.
• 3. Directed takes of small cetaceans were documented in 12 ETA countries, and incidental by‐catch (especially in gillnets) in at least nine countries. Additionally, unknown levels of cetacean mortality occur in ETA tuna purse seine fisheries. The use of cetaceans as ‘bushmeat’ was documented in 15 countries and involved at least 23 species. Little information could be found on cetacean mortality in Liberia, Benin, Cameroon, Equatorial Guinea, São Tomé and Príncipe or the Democratic Republic of the Congo.
• 4. Human activities were most frequently and widely reported to impact on common bottlenose dolphins Tursiops truncatus and Atlantic humpback dolphins Sousa teuszii, which are particularly vulnerable to anthropogenic interactions due to their nearshore occurrence.
• 5. The lack of information on the scale of impacts and on cetacean abundance and population structure in the ETA currently hinders assessments of the sustainability of mortality levels.