Possible Causes of a Harbour Porpoise Mass Stranding in Danish Waters in 2005

An unprecedented 85 harbour porpoises stranded freshly dead along approximately 100 km of Danish coastline from 7–15 April, 2005. This total is considerably above the mean weekly stranding rate for the whole of Denmark, both for any time of year, 1.23 animals/week (ranging from 0 to 20 during 2003–2008, excluding April 2005), and specifically in April, 0.65 animals/week (0 to 4, same period). Bycatch was established as the cause of death for most of the individuals through typical indications of fisheries interactions, including net markings in the skin and around the flippers, and loss of tail flukes. Local fishermen confirmed unusually large porpoise bycatch in nets set for lumpfish (Cyclopterus lumpus) and the strandings were attributed to an early lumpfish season. However, lumpfish catches for 2005 were not unusual in terms of season onset, peak or total catch, when compared to 2003–2008. Consequently, human activity was combined with environmental factors and the variation in Danish fisheries landings (determined through a principal component analysis) in a two-part statistical model to assess the correlation of these factors with both the presence of fresh strandings and the numbers of strandings on the Danish west coast. The final statistical model (which was forward selected using Akaike information criterion; AIC) indicated that naval presence is correlated with higher rates of porpoise strandings, particularly in combination with certain fisheries, although it is not correlated with the actual presence of strandings. Military vessels from various countries were confirmed in the area from the 7th April, en route to the largest naval exercise in Danish waters to date (Loyal Mariner 2005, 11–28 April). Although sonar usage cannot be confirmed, it is likely that ships were testing various equipment prior to the main exercise. Thus naval activity cannot be ruled out as a possible contributing factor.     

Bite Injuries of Grey Seals (Halichoerus grypus) on Harbour Porpoises (Phocoena phocoena)

Bite-like skin lesions on harbour porpoises (Phocoena phocoena) have been suspected to be caused by grey seals (Halichoerus grypus), and a few field observations have been reported. Bite-like skin lesions observed on stranded animals were characterized by two main components: large flaps of loose or missing skin and blubber with frayed edges and puncture lesions. Definitive demonstration of predation by a grey seal was not reported so far in those stranded animals. In this study, five stranded porpoises with bite-like skin lesions were swabbed for genetic investigations. In addition, the head of a recently dead grey seal was used to mimic bite-like skin injuries on a porpoise carcass. Subsequently, the artificial skin injuries were swabbed, along with the gum of the seal used for inflicting them (positive controls). Total DNA was extracted from the swabs and was used to retrieve a fragment of mitochondrial DNA by PCR. Primers were designed to amplify a specific stretch of mitochondrial DNA known to differ between grey seals and porpoises. The amplicon targeted was successfully amplified from the positive control and from two of the stranded porpoises, and grey seal-specific mitochondrial DNA was retrieved from all those samples. We conclude that (1) it is possible to detect grey seal DNA from dead porpoises even after several days in seawater and (2) bite-like skin lesions found on dead porpoises definitively result from grey seals attacks. The attacks are most likely linked with predation although, in a number of cases, scavenging and aggressive behaviour cannot be excluded.     

Population structure of Anisakis simplex (Nematoda) in harbor porpoises Phocoena phocoena off Denmark

The population structure and habitat selection of Anisakis simplex in 35 harbor porpoises off Denmark are described. The nematodes were collected from the stomach and duodenal ampulla and were categorized as third-stage larvae, fourth-stage larvae, subadults, and adults. The porpoises harbored 8,043 specimens of A. simplex. The proportion of adults and subadults increased with infrapopulation size. The number of development stages across infrapopulations covaried significantly (Kendall's test of concordance). Concordance was higher in hosts with the highest intensities than in those with low and medium intensities. All stages occurred mainly in the forestomach, but this trend was stronger for the adults. Adult and subadult sex ratios did not depart significantly from 1:1. Our data suggested that recruitment and duration of each stage were the main factors accounting for infrapopulation structure. The preference of A. simplex for the forestomach conformed with previous studies, but the narrower distribution of adults relative to other stages might indicate a strategy to enhance mating opportunities. Information on sex ratios of A. simplex is scarce and contradictory. We suggest that the discrepancies might partly reflect differences in categorization criteria and statistical methods.     

Reproduction in the common porpoise (Phocoena phocoena) of the North Atlantic

Examination of the reproductive organs from 137 Common porpoises ( Phocoena phocoena ) from the Gulf of St Lawrence, the Bay of Fundy and British waters has enabled observations to be made on reproductive events. Birth in Canadian waters occurs mainly in June and July: mating takes place from june to August . The evidence indicates that females do not become pregnant every year. Birth length is 80 to 90cm; juveniles attain a length of 100 to 110 cm after three to four months. Sexual maturity is reached at a length of about 133 cm in males and 145 cm in females, probably in their third or fourth year. The corpus luteum persists throughout gestation and retrogresses from their histological characteristics. One kind possesses much acellular material and is probably a corpus albicans gravitadionis; the other consists of a mass of obliterated vessels and is the remains either of a corpus luteum of an infertile ovulation or of a lutealized follicle. Evidence indicates that there is seasonal testicular activity, reaching a maximum during July and subsiding in late August.     

Seroprevalences Against Paracoccidioides cetii: A Causative Agent for Paracoccidiomycosis Ceti (PCM-C) and Coccidioides posadasii; for Coccidioidomycosis (CCM) in Dall's Porpoise (Phocoenoides dalli) and Harbor Porpoise (Phocoena phocoena) Stranded at Hokkaido,Japan

Mycopathologia - Paracoccidiodomycosis ceti (PCM-C) is a zoonotic mycosis characterized by chronic granulomatous cutaneous lesions in cetaceans. It is distributed worldwide and is caused by an...     

Harbour porpoisesPhocoena phocoena in the North Sea: Numerical responses to changes in environmental conditions

Changes during the last 40 years of abundance and occurrence of harbour porpoises in the North Sea are illustrated as consequences of changes in environmental factors. The major changes in environmental conditions which influenced the presence of harbour porpoises in the North Sea, in particular the southern North sea, are postulated to be changes in prey availability and changes in accidental catches. Limitations of prey made them move out of the coastal areas, but accidental catch has reduced their overall abundance. Prey availability was affected by limitation of herring and mackerel as the major food source, caused initially by overfishing, followed by a shift in spawning and feeding areas towards the North. Without ignoring the possible complementary impact of pollution and disturbance, it is believed that accidental catch is the only other major threat. The present size of the harbour porpoise population(s) in the northeast Atlantic, including the stock in the Danish inner waters, is estimated to average 160,000 (range 70,000–225,000) specimens. However, this should not divert the attention from the fact that bycatch and directed catch have significantly reduced the size of the North Sea harbour porpoise populations (including the Baltic), by at least between 53,000–89,000 animals, and more likely the higher end of the range. It is emphasized that management measures should be taken in order to reduce the bycatch of porpoises as was already agreed at the latest Ministerial North Sea Conference. The only short-term, pragmatic and efficient way to assess whether the population will benefit from increasing prey availability is to organise international sighting surveys. Then it may be possible to obtain a clear perception of whether the porpoise has only temporarily moved out of the southern North Sea or whether we are dealing with a decreased population, unable to recover because it can not sustain the existing accidental catches.     

Conservation genetics of harbour porpoises, Phocoena phocoena, in eastern and central North Atlantic

We examined polymorphism at 12 microsatelliteloci in 807 harbour porpoises , Phocoenaphocoena, collected from throughout thecentral and eastern North Atlantic to theBaltic Sea. Multilocus tests for allelefrequency differences, assignment tests,population structure estimates (F_ST) andgenetic distance measures (D_LR andD_C) all indicate six geneticallydifferentiated populations/sub-populationsafter pooling sub-samples within regions.Harbour porpoises from West Greenland, theNorwegian Westcoast, Ireland, the British NorthSea, the Danish North Sea and the inland watersof Denmark (IDW) are all geneticallydistinguishable from each other. A sample ofharbour porpoises collected off the Dutch coast(mainly during winter) was geneticallyheterogeneous and likely comprised a mixture ofindividuals of diverse origin. A mixed stockanalysis indicated that most of the individualsin this sample (77%) were likely migrantsfrom the British and Danish North Sea.     

Timing of epiphyseal development in the flipper skeleton of the harbour porpoise (Phocoena phocoena) as an indicator of paedomorphosis

Epiphyseal development was investigated on X‐rays of flippers from 158 harbour porpoises from Danish waters. Development followed a proximodistal pattern similar to what is known in other cetacean species. Ossification of epiphyses was rare in the phalanges of the first and fifth digits and in the more distal phalanges of the second, third and fourth digits. Along with the morphology of the first metacarpal and the more distal phalanges this suggested paedomorphosis relative to delphinids. Male and female porpoises showed similar progression of epiphyseal development until approximately the sixth year. From then on, female porpoises showed more progressed development than males. This suggests a higher level of paedomorphosis in the male porpoise. The mechanism behind phocoenid paedomorphosis seems to be progenesis, probably as an adaptation towards a high reproductive rate relative to the delphinids.     

First indication of gas embolism in a harbour porpoise (Phocoena phocoena) from German waters

In the last decade, a number of cetacean strandings have gas embolic pathology analogous to decompression sickness in man and experimental animals. Acute gas and fat embolic lesions have also been found in mass-stranded beaked whales causally linked to high-intensity anthropogenic mid-frequency sonar activities. Sporadic chronic gas embolic lesions have also been described. This communication describes a first case of numerous gas-filled fibrous cavities in the markedly enlarged liver of a dead adult male harbour porpoise stranded at the North Sea coast of Schleswig-Holstein, Germany. Additional pathological findings consisted of chronic parasitic granulomatous cholangiohepatitis, hepatic vein thrombosis, parasitic infestations of the bronchial tree and pulmonary blood vessels associated with bronchopneumonia and severe parasitic burden in both ear sinuses. The hepatic cavernous lesions are similar to those described in chronic gas bubble disease in other cetaceans, most likely resulting from decompression-related tissue supersaturation with nitrogen.     

Development and rudimentation of the peripheral olfactory system in the harbor porpoise Phocoena phocoena (Mammalia: Cetacea)

Serial sections of 13 embryos and fetuses of the harbor porpoise from 10 mm crown-rump length up to 167 mm total length were studied. Unlike the adult animals, ontogenetic stages of 18–27 mm crown-rump length still show a typical mammalian olfactory bulb. The olfactory bulb primordium is penetrated by olfactory nerve fibers, the latter passing through the cribriform plate. However, the olfactory bulb anlage is gradually reduced in later stages, its placodal component being largely uncoupled from the telencephalon. As a ganglionlike structure, the remains of the placodal component stay in contact with the nasal septum and mucosa via thin bundles of nerve fibers. The ganglion and plexus can be traced within the meninges until the adult stage of the porpoise. There is strong evidence that they represent the material of the terminalis system, which cannot be distinguished from the olfactory system in earlier stages. A vomeronasal organ could not be detected in the embryonal and fetal material investigated.     

Stratification and age-related differences in blubber fatty acids of the male harbour porpoise (Phocoena phocoena)

Fatty acid composition of blubber was determined at four body sites of 19 male harbour porpoises. A total of 65 fatty acids were quantified in each sample. The array of fatty acids contained in harbour porpoise blubber was similar to those found in other marine mammals. While chemical composition of total blubber was uniform over the body, with the exception of the caudal peduncle, vertical stratification was evident between the deep (inner) and superficial (outer) blubber layers. Fatty acids with chain lengths shorter than 18 carbons were present in significantly greater amounts in the outer blubber layer, while the longer-chain unsaturated fatty acids were more prevalent in the inner layer. This distribution suggests that the inner blubber layer is more active metabolically than the outer layer in terms of lipid deposition and mobilization. The degree of stratification between the two layers appears to increase with age, indicating a predictable turnover in the blubber layer of male porpoises. Harbour porpoise blubber contained high levels (2–27%) of isovaleric acid in the outer blubber layer, and these levels were positively correlated with age.Abbreviations Caud caudal dorsal body site - GC gas chromatograph - FA fatty acid(s) - IUPAC International Union of Pure and Applied Chemistry - PUFA polyunsaturated fatty acid(s) - II dor II dorsal body site - III dor III Dorsal body site - II Ven II ventral body site     

Body Acceleration as Indicator for Walking Economy in an Ageing Population

Background

In adults, walking economy declines with increasing age and negatively influences walking speed. This study aims at detecting determinants of walking economy from body acceleration during walking in an ageing population.

Methods

35 healthy elderly (18 males, age 51 to 83 y, BMI 25.5±2.4 kg/m2) walked on a treadmill. Energy expenditure was measured with indirect calorimetry while body acceleration was sampled at 60Hz with a tri-axial accelerometer (GT3X+, ActiGraph), positioned on the lower back. Walking economy was measured as lowest energy needed to displace one kilogram of body mass for one meter while walking (WCost_min, J/m/kg). Gait features were extracted from the acceleration signal and included in a model to predict WCost_min.

Results

On average WCost_min was 2.43±0.42 J/m/kg and correlated significantly with gait rate (r² = 0.21, p<0.01) and regularity along the frontal (anteroposterior) and lateral (mediolateral) axes (r² = 0.16, p<0.05 and r² = 0.12, p<0.05 respectively). Together, the three variables explained 46% of the inter-subject variance (p<0.001) with a standard error of estimate of 0.30 J/m/kg. WCost_min and regularity along the frontal and lateral axes were related to age (WCost_min: r² = 0.44, p<0.001; regularity: r² = 0.16, p<0.05 and r² = 0.12, p<0.05 respectively frontal and lateral).

Conclusions

The age associated decline in walking economy is induced by the adoption of an increased gait rate and by irregular body acceleration in the horizontal plane.     

A European Melting Pot of Harbour Porpoise in the French Atlantic Coasts Inferred from Mitochondrial and Nuclear Data

Field surveys have reported a global shift in harbour porpoise distribution in European waters during the last 15 years, including a return to the Atlantic coasts of France. In this study, we analyzed genetic polymorphisms at a fragment of the mitochondrial control region (mtDNA CR) and 7 nuclear microsatellite loci, for 52 animals stranded and by-caught between 2000 and 2010 along the Atlantic coasts of France. The analysis of nuclear and mitochondrial loci provided contrasting results. The mtDNA revealed two genetically distinct groups, one closely related to the Iberian and African harbour porpoises, and the second related to individuals from the more northern waters of Europe. In contrast, nuclear polymorphisms did not display such a distinction. Nuclear markers suggested that harbour porpoises behaved as a randomly mating population along the Atlantic coasts of France. The difference between the two kinds of markers can be explained by differences in their mode of inheritance, the mtDNA being maternally inherited in contrast to nuclear loci that are bi-parentally inherited. Our results provide evidence that a major proportion of the animals we sampled are admixed individuals from the two genetically distinct populations previously identified along the Iberian coasts and in the North East Atlantic. The French Atlantic coasts are clearly the place where these two previously separated populations of harbour porpoises are now admixing. The present shifts in distribution of harbour porpoises along this coast is likely caused by habitat changes that will need to be further studied.     

Evidence of exposure to Brucella sp. in harbor porpoises (Phocoena phocoena) from the Bay of Fundy, Canada

Novel strains of Brucella recently have been discovered in marine mammals. To investigate Brucella exposure and infection in a general population of cetaceans, blood and tissue samples were collected and analyzed from wild harbor porpoises (Phocoena phocoena) incidentally caught in fishing gear in the Bay of Fundy, Canada. Two of 170 (1.2%) animals had detectable antibodies against Brucella, but no organisms were isolated from genital swabs or tissues from 22 and 8 porpoises, respectively. Genetic analysis of inflamed testes from 20 animals yielded no amplification of Brucella DNA. This is the first evidence of exposure to Brucella in porpoises from the western North Atlantic, and the prevalence is much lower than documented for conspecifics from the eastern North Atlantic.