MORBILLIVIRUS INFECTION IN BOTTLENOSE DOLPHINS: EVIDENCE FOR RECURRENT EPIZOOTICS IN THE WESTERN ATLANTIC AND GULF OF MEXICO

Morbillivirus infection is widespread among odontocetes of the western Atlantic and Gulf of Mexico. Serologic evidence of infection in bottlenose dolphins, Tursiops truncatus , was first detected during an epizootic along the mid-Atlantic coast in 1987. Here, we report recurrent epizootics in the coastal dolphin population since at least the early 1980s based on serological surveys and regional stranding frequencies. The first observed epizootic of this series occurred in the Indian and Banana Rivers in 1982 and was followed by others on the mid-Atlantic coast in 1987–1988 and in the Gulf of Mexico between 1992 and 1994. This temporal pattern of infection is likely facilitated by the population size and its fragmentation into relatively discrete coastal communities. Introduction of morbillivirus into a community with a sufficient number of naive hosts may precipitate an epizootic, depending on the potential for transmission within the group. Propagation of an epizootic along the coast is probably determined by frequency of contact between adjacent communities and seasonal migrations.
Morbillivirus antibodies were also detected in serum from offshore bottlenose dolphins. The sero-prevalence in the latter may be higher than in coastal dolphins because of their close association with enzootically infected pilot whales ( Globicephala spp.). Occasional contact between offshore and coastal dolphins may provide an epizootiologic link between pilot whales and coastal dolphin communities.     

Comparison between the complete mtDNA sequences of the blue and the fin whale,two species that can hybridize in nature

The sequence of the mitochondrial DNA (mtDNA) molecule of the blue whale (Balaenoptera musculus) was determined. The molecule is 16,402 by long and its organization conforms with that of other eutherian mammals. The molecule was compared with the mtDNA of the congeneric fin whale (B. physalus). It was recently documented that the two species can hybridize and that male offspring are infertile whereas female offspring may be fertile. The present comparison made it possible to determine the degree of mtDNA difference that occurs between two species that are not completely separated by hybridization incompatibility. The difference between the complete mtDNA sequences was 7.4%. Lengths of peptide coding genes were the same in both species. Except for a small portion of the control region, disruption in alignment was usually limited to insertion/deletion of a single nucleotide. Nucleotide differences between peptide coding genes ranged from 7.1 to 10.5%, and difference at the inferred amino acid level was 0.0–7.9%. In the rRNA genes the mean transition difference was 3.8%. This figure is similar in degree to the difference (3.4%) between the 12S rRNA gene of humans and the chimpanzee. The mtDNA differences between the two whale species, involving both peptide coding and rRNA genes, suggest an evolutionary separation of 5 million years. Although hybridization between more distantly related mammalian species may not be excluded, it is probable that the blue and fin whales are nearly as different in their mtDNA sequences as hybridizing mammal species may be. Correspondence to: Ú. Árnason     

Past and present distributions of southern right whales(Eubalaena australis)

Abstract

During the 19th century, sail whalers hunted right whales throughout the southern oceans north of 50 degrees. This review seeks to document the recovery of southern right whales by comparing the northernmost recent sightings with older sightings that survive “fossilised” in historical records of the sail whaling era. Despite a steady expansion northwards in recent years, the present distribution of right whales is still far short of that recorded by sail whalers over a century ago.     

Exploring movement patterns and changing distributions of baleen whales in the western North Atlantic using a decade of passive acoustic data

Six baleen whale species are found in the temperate western North Atlantic Ocean, with limited information existing on the distribution and movement patterns for most. There is mounting evidence of distributional shifts in many species, including marine mammals, likely because of climate‐driven changes in ocean temperature and circulation. Previous acoustic studies examined the occurrence of minke (Balaenoptera acutorostrata) and North Atlantic right whales (NARW; Eubalaena glacialis). This study assesses the acoustic presence of humpback (Megaptera novaeangliae), sei (B. borealis), fin (B. physalus), and blue whales (B. musculus) over a decade, based on daily detections of their vocalizations. Data collected from 2004 to 2014 on 281 bottom‐mounted recorders, totaling 35,033 days, were processed using automated detection software and screened for each species' presence. A published study on NARW acoustics revealed significant changes in occurrence patterns between the periods of 2004–2010 and 2011–2014; therefore, these same time periods were examined here. All four species were present from the Southeast United States to Greenland; humpback whales were also present in the Caribbean. All species occurred throughout all regions in the winter, suggesting that baleen whales are widely distributed during these months. Each of the species showed significant changes in acoustic occurrence after 2010. Similar to NARWs, sei whales had higher acoustic occurrence in mid‐Atlantic regions after 2010. Fin, blue, and sei whales were more frequently detected in the northern latitudes of the study area after 2010. Despite this general northward shift, all four species were detected less on the Scotian Shelf area after 2010, matching documented shifts in prey availability in this region. A decade of acoustic observations have shown important distributional changes over the range of baleen whales, mirroring known climatic shifts and identifying new habitats that will require further protection from anthropogenic threats like fixed fishing gear, shipping, and noise pollution.     

Killer Whale (Orcinus orca) Deaths in Prince William Sound,Alaska, 1985–1990

During 1985–1990, two groups of killer whales in Prince William Sound, Alaska, experienced unusually high rates of mortality, while seven others did not. Those affected were AB pod, part of the southern Alaska population of resident (fish-eating) killer whales, and the AT1 transient (marine mammal–eating) group, a very small, reproductively isolated population that last reproduced in 1984. In 1985–1986, several AB pod members were shot by fishermen defending their catch from depredation, which explains some of the deaths. Understanding the other deaths is complicated by the Exxon Valdez oil spill (March 1989) and uncertainties about the causes and times of the deaths. For AB pod, possible factors involved in the post-spill mortalities are delayed effects of bullet wounds, continued shooting, oil exposure, and consequences of being orphaned. For the AT1 group, possible factors are oil exposure, small population size, old age, and high-contaminant burdens. An analysis of possible effects of inhalation of volatile organic compounds, contact with the oil slick, and ingestion of oil with water or prey did not reveal route(s) of exposure that could explain the mortalities. The cause(s) of the killer whale deaths recorded following the oil spill remain uncertain.     

Some problems concerning the delimitation of the maritime boundary between the republic of china (Taiwan) and the Philippines

Abstract

This paper analyzes the issue of how the relevant provisions of the 1982 United Nations Convention on the Law of the Sea can be applied to the delimitation of the maritime boundary in the Bashi Channel between Taiwan and the Philippine island of Luzon and in the South China Sea area. It concludes that the Philippines’ extensive territorial sea claim based on the 1898 U.S.‐Spanish Peace Treaty can hardly find any basis in customary rules of international law and the U.N. Convention and, therefore, should be disregarded in such delimitation. On the other hand, the archipelagic principle provided in the Convention can be applied here. With respect to rules of delimitation, it suggests that the equitable principle of the delimitation of the continental shelf, enunciated in the Anglo‐French Continental Shelf Arbitration (1977) and the Tunisian‐Libyan Continental Shelf Case (1982), can mutatis mutandis be applied to the delimitation of the maritime boundary. As an interim solution, the maritime boundary of certain disputed islands in the South China Sea should be declared neutral zones open to nationals of both countries.     

Humpback whale singing activity off the Goan coast in the Eastern Arabian Sea

For over two decades, passive acoustic monitoring (PAM) methods have been successfully employed around the world for studying aquatic megafauna. PAM-driven studies in Indian waters have so far been relatively very scarce. Furthermore, cetacean populations inhabiting the north western Indian Ocean are far less studied than those in many other regions around the world. This work likely constitutes the first systematic study of the vocal repertoire of humpback whales (Megaptera novaeangliae) at a near-shore site along the western coast of India. Analysis of the observed vocalizations provides an insight into the behaviour of the species. This is significant as it assists in developing a better understanding of the habitat use of the non-migratory Arabian Sea humpback whale population. In contrast, other breeding populations such as those around the North Atlantic, South Pacific and Australia have been relatively well studied. Underwater passive acoustic data were collected during March 2017 using an autonomous logger at a shallow-water site off the eastern edge of Grande Island off the coast of Goa. Humpback whale vocalizations were found to occur over multiple days in the recordings. Time–frequency contours of individual units of vocalization were extracted with the aid of an automatic detection technique and the characteristics of the units were measured. Further, successive units were analysed for formation of phrases and themes. Reconstruction of putative songs from the identified units and themes was not possible due to the limitations imposed by the nature of data collection. Detailed analyses of units, phrases and themes are presented.     

Population genetic structure of Bryde’s whales (<Emphasis Type="Italic">Balaenoptera brydei</Emphasis>) at the inter-oceanic and trans-equatorial levels

Bryde’s whales (Balaenoptera brydei) differ from other typical baleen whale species because they are restricted to tropical and warm temperate waters in major oceans, and frequent trans-equatorial movement has been suggested for the species. We tested this hypothesis by analyzing genetic variation at 17 microsatellite loci (N = 508) and 299 bp of mitochondrial DNA (mtDNA) control region sequences (N = 472) in individuals obtained from the western North Pacific, South Pacific, and eastern Indian Ocean. Combined use of microsatellite and mtDNA markers allowed us to distinguish between contemporary gene flow and ancestral polymorphism and to describe sex-specific philopatry. A high level of genetic diversity was found within the samples. Both nuclear and mtDNA markers displayed similar population structure, indicating a lack of sex-specific philopatry. Spatial structuring was detected using both frequency-based population parameters and individual-based Bayesian approaches. Whales in the samples from different oceanic regions came from genetically distinct populations with evidence of limited gene flow. We observed low mtDNA sequence divergence among populations and a lack of concordance between geographic and phylogenetic position of mtDNA haplotypes, suggesting recent separation of populations rather than frequent trans-equatorial and inter-oceanic movement. We conclude that current gene flow between Bryde’s whale populations is low and that effective management actions should treat them as separate entities to ensure continued existence of the species.     

Mechanical understanding of hunting waves generated by killer whales

The wave wash hunting employed by Orcinus orca, also known as killer whales, is unique in that the prey is hunted outside of the water by generating waves. To quantitatively analyze the specific mechanism of the wave wash, data were obtained using computational fluid dynamics (CFD), and wave theory was introduced as the theoretical background to clarify the mechanism. The relationships between the swimming characteristics and wave parameters are defined in this paper. The results obtained by numerical investigation revealed that the wavelength increased with the swimming speed. Additionally, the wave height increased as the swimming speed increased and the swimming depth became shallower, and subsequently converged to a maximum of 2.42 m. The success of hunting is determined by two wave parameters, which indicate the intensity of the wave wash: the wave height and force exerted on the prey. The metabolic rate and the drag force are considered to evaluate the efficiency of the locomotion, which varied according to the swimming speed (V) and swimming depth (d) of the whales. To generate hunting waves efficiently, the optimal ranges of V and d were estimated to be 3 ~ 5 m/s and 0.5 m ~ 1.1 m respectively.