Christina Lockyer

PCBs, cause of death and body condition in harbour porpoises (Phocoena phocoena) from British waters

Abstract Polychlorinated biphenyls (PCBs) suppress immunity, and may have exacerbated the effects of recent morbillivirus epizootics in harbour seals ( Phoca vitulina ) and striped dolphins ( Stenella coeruleoalba ). To test the hypothesis that PCBs cause immunosuppression in harbour porpoises ( Phocoena phocoena ) and increase their risk of dying from an infectious or parasitic disease, we compared the levels of PCBs in the blubber between animals that died from these causes and those that died from physical trauma. We established the cause of death and measured the blubber levels of HCB, α-HCH, γ-HCH, p , p ′-DDE, p , p ′-DDT, p , p ′-TDE, dieldrin, and 25 individual chlorobiphenyls in 94 harbour porpoise carcases, found in Great Britain between 1989 and 1992. After correcting for the effect of region, there were no significant differences between disease groups in the levels of any of these contaminants. Thus, our results provide no support for the hypothesis. However, there were significant differences in body condition between animals that died from an infectious or parasitic disease, physical trauma, or starvation. Therefore, we suggest that a quantitative measure of body condition, such as relative body girth, could be used as a diagnostic aid in the pathological examination of harbour porpoises.

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 (FST) andgenetic distance measures (DLR andDC) 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.

Mitochondrial Control Region and microsatellite analyses on harbour porpoise (Phocoena phocoena) unravel population differentiation in the Baltic Sea and adjacent waters

The population status of the harbour porpoise (Phocoena phocoena) in the Baltic area has been a continuous matter of debate. Here we present the by far most comprehensive genetic population structure assessment to date for this region, both with regard to geographic coverage and sample size: 497 porpoise samples from North Sea, Skagerrak, Kattegat, Belt Sea, and Inner Baltic Sea were sequenced at the mitochondrial Control Region and 305 of these specimens were typed at 15 polymorphic microsatellite loci. Samples were stratified according to sample type (stranding vs. by-caught), sex, and season (breeding vs. non-breeding season). Our data provide ample evidence for a population split between the Skagerrak and the Belt Sea, with a transition zone in the Kattegat area. Among other measures, this was particularly visible in significant frequency shifts of the most abundant mitochondrial haplotypes. A particular haplotype almost absent in the North Sea was the most abundant in Belt Sea and Inner Baltic Sea. Microsatellites yielded a similar pattern (i.e., turnover in occurrence of clusters identified by STRUCTURE). Moreover, a highly significant association between microsatellite assignment and unlinked mitochondrial haplotypes further indicates a split between North Sea and Baltic porpoises. For the Inner Baltic Sea, we consistently recovered a small, but significant separation from the Belt Sea population. Despite recent arguments that separation should exceed a predefined threshold before populations shall be managed separately, we argue in favour of precautionary acknowledging the Inner Baltic porpoises as a separate management unit, which should receive particular attention, as it is threatened by various factors, in particular local fishery measures.

Organochlorine residues in harbour porpoise and bottlenose dolphins stranded on the coast of Scotland, 1988-1991.

The organochlorine (OC) residues, chlorobiphenyls (CBs), DDT and its metabolites, dieldrin, hexachlorobenzene and technical chlordane mixtures have been determined in the blubber of harbour porpoise and bottlenose dolphins from around the north and east coasts of Scotland as a result of strandings and bycatches between 1988 and 1991. The concentrations of OCs range from some of the lowest values reported at 280 micrograms kg-1 for t-CBs, 145 micrograms kg-1 for t-DDT and 71 micrograms kg-1 for dieldrin to some of the highest values, 23,000 micrograms kg-1 for t-CBs, and 10,200 micrograms kg-1 for t-DDT. OC levels were correlated with the age and sex of the sample of harbour porpoise and bottlenose dolphins from the Moray Firth area. The study confirms that the concentration of these compounds is highly dependent on co-factors of age and sex, and that data from single or small numbers of animals may be of limited value in comparing information on organochlorine residues in mammals within or between regions.

Adrenocortical hyperplasia, disease and chlorinated hydrocarbons in the harbour porpoise (Phocoena phocoena)

We tested the hypothesis that the adrenal cortex in the harbour porpoise (Phocoena phocoena) is enlarged due to chronic exposure to chlorinated hydrocarbons. Postmortem examinations were performed on 28 harbour porpoise carcases found in Great Britain in 1990 and 1991. The levels of HCB, α-HCH, γ-HCH, p,p′-DDE, p,p′-DDT, p,p′-TDE, dieldrin and 25 individual chlorobiphenyls in the blubber, and the volumes of the right adrenal cortex, medulla and stroma were measured. Although adrenocortical hyperplasia was found, it was not associated with increased levels of chlorinated hydrocarbons. Instead, harbour porpoises that died from a chronic cause of death (N = 14) had a significantly higher adrenocortical volume (F1,23 = 13.15, P<0.01), due to hyperplasia, than harbour porpoises that died from an acute cause of death (N = 11). Therefore, adrenocortical hyperplasia probably resulted from chronic stressors associated with their cause of death, rather than exposure to chlorinated hydrocarbons.

Aspects of the biology of the harbour porpoise, Phocoena phocoena, from British waters

Background: Specimens of harbour porpoises, Phocoena phocoena, from both strandings and by-catch around the British Isles between 1985 and September 1994 have been collected, although it has not been possible to distinguish reliably between by-catch and natural strandings. Methods: more than 300 individuals have been examined. Full autopsies were undertaken on most carcasses, and the following data and samples collected: sex, data of finding, location, total body length, girth, body and organ weights, blubber thickness and blubber tissue for lipid content analysis, reproductive organs, and teeth. Decalcified thin stained sections of teeth were used for determining age. Results and conclusions: the age range of the sample included animals from neonates to age 24 years. The largest individual age group comprised yearlings and neonates, and survival appeared to be low in the first year of life. Birth size was in the range 60–75 cm length and 3–9 kg weight. The maximum length recorded for individuals in the sample was 163 cm in males and 189 cm in females indicating that females grow larger than males. Maximum weights of 54 kg and 81 kg were recorded for males and females, respectively. There is a close correlation between body weight and both length and girth, although mid-girth is a better predictor of body weight than length, and small juvenile animals are both relatively and actually fatter than adults. The latter point may reflect the greater surface/volume ratios of young and their need for insulation and thermoregulation. Length, cm (L) and mid-girth, cm (G) together provide the means of most accurate estimation of body weight, kg (W): W=0.000081L1.2401G1.5524. Limited female data indicate that pregnant females were heaviest and fattest, and that lactating females were lighter and leaner than anoestrous females. Blubber lipid content averaged 83–87% wet weight tissue for all classes of animals except neonates which appeared in the samples mainly during June, and had a lower mean of <70% wet weight tissue. The inferred peak calving period is June, with high numbers of neonates and calves found stranded in June to September. Data on testes weight suggest that the likely age at sexual maturation in males may be about 3 years onwards. Peak testes weight was observed in June–August and peak births in June. This suggests a gestation of 1 year or less in porpoise.

Stable Isotopes Provide Insight into Population Structure and Segregation in Eastern North Atlantic Sperm Whales

In pelagic species inhabiting large oceans, genetic differentiation tends to be mild and populations devoid of structure. However, large cetaceans have provided many examples of structuring. Here we investigate whether the sperm whale, a pelagic species with large population sizes and reputedly highly mobile, shows indication of structuring in the eastern North Atlantic, an ocean basin in which a single population is believed to occur. To do so, we examined stable isotope values in sequential growth layer groups of teeth from individuals sampled in Denmark and NW Spain. In each layer we measured oxygen- isotope ratios (δ18O) in the inorganic component (hydroxyapatite), and nitrogen and carbon isotope ratios (δ15N: δ13C) in the organic component (primarily collagenous). We found significant differences between Denmark and NW Spain in δ15N and δ18O values in the layer deposited at age 3, considered to be the one best representing the baseline of the breeding ground, in δ15N, δ13C and δ18O values in the period up to age 20, and in the ontogenetic variation of δ15N and δ18O values. These differences evidence that diet composition, use of habitat and/or migratory destinations are dissimilar between whales from the two regions and suggest that the North Atlantic population of sperm whales is more structured than traditionally accepted.

The history and behaviour of a solitary wild, but sociable, bottlenose dolphin (Tursiops truncatus) on the west coast of England and Wales

Summary The description of the appearance, behaviour and movements of a wild bottlenose dolphin are given. The dolphin, which was a male, was measured as approximately 360 cm in length during May 1976. The dolphin was estimated to be a mature adult. Certain distinguishing permanent body scars on the head and dorsal fin areas, and a damaged tooth, were a convenient means of identification of the dolphin. The movements of the dolphin were traced to April 1972. Between then and March 1975 it was resident in the coastal areas around the Isle of Man. Between April 1975 and January 1976 the dolphin had moved to and remained resident in the region around Milford Haven in Pembrokeshire. From January 1976 until December 1976, the dolphin moved south again, and patrolled an area stretching from St. Ives on the north coast of Cornwall to Falmouth on the south coast of Cornwall, although during most of this time favoured localities were St. Ives and Mousehole, where it remained for long periods. All areas which were ...

Life history and ecology of harbour porpoises ( Phocoena phocoena ) from West Greenland

During 1988, 1989 and 1995, 187 harbour porpoises ( Phocoena phocoena ) were sampled from the catches off West Greenland. The samples were taken in 3 areas between 62° N and 70° N: northerly (n=134, Maniitsoq and locations Kangaamiut, Qeqertarsuaq and Qasigiannguit further north), southerly (n=30, Nuuk) and southernmost (n=23, Paamiut). A suite of biological measurements and data were collected from these samples. Comparison of age and length distributions between years and areas indicated that while there were no statistical differences between the Maniitsoq and northerly samples in different years, the southerly Nuuk and Paamiut samples were biased to younger age classes. Application of the Gompertz growth model to length and weight at age data indicated an asymptotic length of 154 cm in females and 143 cm in males with weights of 64 kg and 52 kg respectively. A number of correlations were observed between length, midgirth (G3), body and blubber weights and blubber thickness. Indicators of body condition showed that overall pregnant females were fattest but that blubber thickness was greatest in juveniles. The blubber lipid content was generally 92-95% wet weight of tissue. Stomach content analysis for 92 animals indicated regional differences, although capelin ( Mallotus villosus ) was predominant in all samples. The presence of fish, squid and crustaceans indicated opportunistic feeding. Females ovulated from age 3-4 years at a length of about 140 cm; combined testis weights >200 g indicated maturation in males from age 2 years upwards at a length >125 cm. Several small embryos were found, consistent with a mating season in late summer. Testis hypertrophy in August also supported a late summer breeding. Analysis of ovarian corpora indicated annual ovulation. Certain biological parameters, including body condition indicators, indicate differences between West Greenland and eastern North Atlantic populations that agree with published genetic findings.

Dentinal anomalies in teeth of harbour porpoises (Phocoena phocoena) from Scottish waters: are they linked to sexual maturation and environmental events?

We examined the tooth ultra-structure of harbour porpoises ( Phocoena phocoena ) from Scottish waters to determine whether the incidence of mineralization anomalies could be related to certain life history events (e.g. the achievement of sexual maturation) as well as other factors that affect the general health of the individual (e.g. persistent organic pollutant (POP) concentrations in blubber). Five distinct types of mineralization anomalies were recorded: accessory lines, marker lines, dentinal resorption, cemental disturbance and pulp stones and the occurrence of these anomalies was scored by sex, age and maturity state. Overall, the incidence of mineralization anomalies was high and tended to increase with age. Marker lines and accessory lines were the most commonly recorded anomalies while pulp stones were least frequent. Duplicate teeth (i.e. from the same individual) always showed the same pattern of anomaly occurrence. Fitted binary generalized linear and additive models indicated that the presence of dentinal resorption, cemental disturbance and marker lines in harbour porpoise teeth increased with age, body length and maturity. Males displayed marker lines more frequently than females. Age was the best predictor of the incidence of dentinal resorption and cemental disturbance while age and sex were the best predictors of the incidence of marker lines. The time course of appearance of dentinal resorption and cemental disturbance suggests that their occurrence could be related to physiological stress linked to sexual maturation. Marker lines were found within growth layer groups which coincided with the beginning of weaning and sexual maturation, suggesting an association with these two major life history events. Accessory lines were found in most teeth and may be a normal characteristic of porpoise teeth or reflect regular events. Pulp stones appeared only in mature animals. We found no evidence that the presence of anomalies in teeth was significantly related to POP concentrations in the blubber.