THE NARWHAL, MONODON MONOCEROS, IN THE NORWEGIAN HIGH ARCTIC

Narwhals ( Monodon monoceros ) are known to frequent the waters of the Norwegian arctic archipelago of Svalbard. An attempt is made to summarize narwhal observations from the Svalbard area, and from this to deduce their distribution. Observations have been gathered from the literature, sealing vessel log books and official statistics. Interviews have also been conducted with residents of Svalbard. I con&de that narwhals are most frequently observed in the area off the north-west corner of Spitsbergen.     

RATE OF INCREASE, 1978–1988, OF BOWHEAD WHALES, BALAENA MYSTICETUS, ESTIMATED FROM ICE-BASED CENSUS DATA

The number of bowhead whales, Balaena mysticetus , passing within viewing range of the ice-based census at Point Barrow, Alaska, during spring migrations from 1978 to 1988 is estimated from the visual census data. The trend in the annual numbers yields an estimated rate of increase of 3.1% per year with a 95% confidence interval ranging from 0.1% to 6.2% for the Bering-Chukchi-Beaufort Seas bowhead stock during this period. Alternative treatments of the data suggest less precise or somewhat lower estimates, but all results indicate that the stock was increasing.     

Population structure of nuclear and mitochondrial DNA variation among South American Burmeister’s porpoises (<Emphasis Type="Italic">Phocoena spinipinnis</Emphasis>)

Little is known about the biology of Burmeister’s porpoises (Phocoena spinipinnis), a small cetacean species endemic to South American waters. Information on stock structure, however, is urgently needed, as the species suffers from considerable mortality due to local fishery activities throughout its distribution range. Using mitochondrial control region sequences and 11 species-specific microsatellite loci, we assessed the genetic differentiation among 118 stranded, incidentally or directly-caught Burmeister’s porpoises from different localities in Peruvian, Chilean, and Argentine waters. F-statistics and Bayesian clustering analyses indicate a major population differentiation along the South American Pacific coast, separating Peruvian from both Chilean and Argentine individuals. Interestingly, this population boundary is consistent with the population structure found in another sympatrically-occurring cetacean species: the dusky dolphin (Lagenorhynchus obscurus). Given that vulnerability to local depletion for South American coastal porpoises and dolphins is probably highest in the Peruvian population (due to high exploitation levels and recurrent El Niño events), the genetic data reported here considerably strengthen the need for conservation efforts focused on regulation of catches in local waters. Moreover, we discuss possible genetic differentiation among Burmeister’s porpoises (i) from the Atlantic and Pacific Ocean and (ii) from different Peruvian harbors. Finally, cross-species amplifications suggest that our newly-developed microsatellite markers will be useful in population genetic studies in the five other extant porpoise species.     

Occurrence of the parasitic sea lamprey<Emphasis Type="Italic">Petromyzon marinus</Emphasis> on western North Atlantic right whales <Emphasis Type="Italic">Eubalaena glacialis</Emphasis>

Few data exist on the marine distribution and host organisms of the parasitic sea lamprey, Petromyzon marinus. Some observers have speculated that cetaceans serve as hosts for these fish based on scars, but few lamprey – cetacean interactions have been described in detail in the literature. Here we discuss 35 previously unreported records of sea lampreys that were observed while attached to western North Atlantic right whales, Eubalaena glacialis, during the period 1984 – 2002. Of these observations, 11 were photographically documented with images of sufficient quality to identify the lamprey as P. marinus based on morphological characteristics. The majority of the attachments were recorded in the Bay of Fundy during the summer months when P. marinus are preparing to spawn. It is unknown how lampreys might benefit from this association or what cost may be incurred by their right whale hosts. Feeding and transport are two possible reasons for the attachments.     

Demography or selection on linked cultural traits or genes? Investigating the driver of low mtDNA diversity in the sperm whale using complementary mitochondrial and nuclear genome analyses

Mitochondrial DNA has been heavily utilized in phylogeography studies for several decades. However, underlying patterns of demography and phylogeography may be misrepresented due to coalescence stochasticity, selection, variation in mutation rates and cultural hitchhiking (linkage of genetic variation to culturally‐transmitted traits affecting fitness). Cultural hitchhiking has been suggested as an explanation for low genetic diversity in species with strong social structures, counteracting even high mobility, abundance and limited barriers to dispersal. One such species is the sperm whale, which shows very limited phylogeographic structure and low mtDNA diversity despite a worldwide distribution and large population. Here, we use analyses of 175 globally distributed mitogenomes and three nuclear genomes to evaluate hypotheses of a population bottleneck/expansion vs. a selective sweep due to cultural hitchhiking or selection on mtDNA as the mechanism contributing to low worldwide mitochondrial diversity in sperm whales. In contrast to mtDNA control region (CR) data, mitogenome haplotypes are largely ocean‐specific, with only one of 80 shared between the Atlantic and Pacific. Demographic analyses of nuclear genomes suggest low mtDNA diversity is consistent with a global reduction in population size that ended approximately 125,000 years ago, correlated with the Eemian interglacial. Phylogeographic analysis suggests that extant sperm whales descend from maternal lineages endemic to the Pacific during the period of reduced abundance and have subsequently colonized the Atlantic several times. Results highlight the apparent impact of past climate change, and suggest selection and hitchhiking are not the sole processes responsible for low mtDNA diversity in this highly social species.