Seal Species Research Articles

Real‐time PCR assays for the identification of harbor and gray seal species and sex: A molecular tool for ecology and management

IVETA MATEJUSOVA1 and FIONA BLAND, Marine Scotland Science, Marine Laboratory, Victoria Road, PO Box 101, Aberdeen AB11 9DB, United Kingdom; AILSA J. HALL and ROBERT N. HARRIS, Sea Mammal Research Unit, University of St. Andrews, St Andrews, Fife KY16 8LB, United Kingdom; MICHAEL SNOW, Biodiversity and Biosecurity Branch, Western Australia Fisheries and Marine Research Laboratories, 6920 Perth, Australia; ALEX DOUGLAS, Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, United Kingdom; STUART J. MIDDLEMAS, Marine Scotland Science, Freshwater Laboratory, Faskally, Pitlochry PH16 5LB, United Kingdom.

A review of spatial and temporal variation in grey and common seal diet in the United Kingdom and Ireland

Knowledge about the diet of fish-eating predators is critical when evaluating conflicts with the fishing industry. Numerous primary studies have examined the diet of grey seals Halichoerus grypus and common seals Phoca vitulina in a bid to understand the ecology of these predators. However, studies of large-scale spatial and temporal variation in seal diet are limited. Therefore this review combines the results of seal diet studies published between 1980 and 2000 to examine how seal diet varies at a range of spatial and temporal scales. Our results revealed extensive spatial variation in gadiform, perciform and flatfish consumption, likely reflecting variation in prey availability. Flatfish and gadiform consumption varied between years, reflecting changes in fish assemblages as a consequence of factors such as varying fishing pressures, climate change and natural fluctuations in populations. Perciform and gadiform consumption varied seasonally: in addition there was a significant interaction between season and seal species, indicating that grey and common seals exhibited different patterns of seasonal variation in their consumption of Perciformes and Gadiformes. Multivariate analysis of grey seal diet revealed spatial variation at a much smaller scale, with different species dominating the diet in different areas. The existence of spatial and temporal variation in seal diet emphasizes that future assessments of the impact of seal populations should not be based on past or localized estimates of diet and highlights the need for up-to-date, site specific estimates of diet composition in the context of understanding and resolving seal/fisheries conflict.

Records of vagrant phocid seals (family Phocidae) in South Australia

Five species of phocid seal of the Southern Ocean and Antarctica come ashore occasionally on the southern Australian coast but do not breed there. We document records (specimens and sightings) of visits to South Australia (SA) by southern phocids from 1883 until August 2011. We used records from the SA Museum, reports from coastal officers of SA Department of Environment and Natural Resources (DENR), the DENR fauna database, information from the public, the literature and newspapers. Thirty-six southern elephant seal records included two births, in November 1932 and October 1986. The latter pup suckled for 20 days and then stayed ashore for eight weeks; both are similar to average durations at Macquarie Island. Of 33 dated records, 31 were between August and April, when elephant seals at Macquarie Island (the closest breeding site) are ashore to breed or moult. A recognisable male on Kangaroo Island has been sighted often over 10 years to 2010. Of the ice-breeding species, there were 54 leopard seal records. All of 40 dated records were between June and December, with the maximum (12) in August, similar to the seasonal distribution in Tasmania. There were five records of crabeater seals, one of a Ross seal, and one of a Weddell seal.

Mycoplasmas in Australian fur seals (Arctocephalus pusillus doriferus): identification and association with abortion

Bacteria from the genus Mycoplasma are common inhabitants of the respiratory, gastrointestinal, and genital tracts of mammals. The understanding of the pathological significance of mycoplasmas in seals is poor, as few studies have utilized the specific culture techniques required to isolate these bacteria. The current study surveyed for the Mycoplasma species present in Australian fur seals (Arctocephalus pusillus doriferus) and investigated the association between infection and pathology. Mycoplasmas were found in the nasal cavities of 55/80 (69%) of apparently healthy individuals. Isolates from 18 individuals were investigated through 16S ribosomal RNA sequencing, and 3 species were identified: M. zalophi, M. phocae, and Mycoplasma sp. (GenBank no. EU714238.1), all of which had previously been isolated from Northern Hemisphere pinnipeds. In addition, mycoplasmas were isolated from the lungs of 4 out of 16 juveniles and 1 out of 5 adults sampled at necropsy. Isolates obtained were M. zalophi, Mycoplasma sp. EU714238.1, and M. phocicerebrale, but infection was not associated with lung pathology in these age classes. Inflammatory disease processes of the heart and/or lungs were present in 12 out of 32 (38%) aborted fetuses on microscopic examination. Predominant findings were interstitial pneumonia, pericarditis, and myocarditis. Mycoplasma phocicerebrale was isolated from the thymus of an aborted fetus, and 3 out of 11 (27%) fetuses with inflammatory heart or lung lesions were PCR-positive for Mycoplasma. In conclusion, several species of Mycoplasma are part of the normal flora of the nasal cavity of Australian fur seals, and some mycoplasmas may be associated with abortion in this species of seal.

Detection of Cryptosporidium sp. in Two New Seal Species, Phoca vitulina and Cystophora cristata, and a Novel Cryptosporidium Genotype in a Third Seal Species, Pagophilus groenlandicus, from the Gulf of Maine

Data on the geographic distribution and host specificity of Cryptosporidium spp. are critical for developing an understanding of likely transmission patterns in nature. During a molecular-based survey of fecal samples from 293 terrestrial and aquatic animals in Maine, USA, we detected Cryptosporidium sp. in 11 harbor seals (Phoca vitulina), 1 hooded seal (Cystophora cristata), and 1 harp seal (Pagophilus groenlandicus). None of the terrestrial or freshwater mammal fecal samples or bird samples tested positive for Cryptosporidium sp. However, the sequencing results of the small subunit (ssu) rRNA gene indicate that the seals were infected with an undescribed species of Cryptosporidium , previously isolated only from ringed seals (Phoca hispida) in northern Quebec, Canada. In addition, the Cryptosporidium sp. detected in the harp seal is significantly different from the previously observed Cryptosporidium sp. in other seals. We confirmed the genetic distinctiveness of this Cryptosporidium genotype and the identity of the other Cryptosporidium sp. seal ssu rRNA sequences by using data from the 70-kDa heat shock protein gene. Based on phylogenetic reconstructions of both genes, it seems that either Cryptosporidium canis or C. felis are sister species to the seal associated Cryptosporidium spp. Our findings extend the range of " Cryptosporidium sp. seal" well south of the 55th parallel, add other species to the list of seals affected by Cryptosporidium sp., and highlight the presence of unrecognized population and potentially species level variation in Cryptosporidium.

FATAL MASS INGESTION OF GASTRIC FOREIGN BODIES IN JUVENILE HOODED SEALS (CYSTOPHORA CRISTATA) STRANDED IN NORTH-WESTERN IBERIAN PENINSULA

The hooded seal (Cystophora cristata) is a subarctic and arctic pinniped species with its limit of distribution in southern Europe established west of the British Isles. Nevertheless, since 1970, strandings of juvenile individuals have been reported much further south than this limit. The special clinical and management considerations to take into account with these arctic seals have become a new challenge to veterinary clinicians of southern North-Atlantic stranding networks. We present here three clinical cases involving mass ingestion of foreign bodies, which seems to be a generalized finding in this species. Although the presence of gastroliths are considered to be normal in pinnipeds, the fast and ultimately lethal cases presented here highlights how an excessive presence of gastric foreign bodies could result in a gastrointestinal stasis syndrome, which has to be quickly resolved, medically or surgically. Portable ultrasound and X-ray equipments have demonstrated their value as gastric foreign bodies diagnostic procedures with nervous wildlife patients, such as the juvenile hooded seals. Finally, we conclude that it is extremely important to avoid the use of loose stones or sand over resting areas and to take extreme precautions with small items near the rehabilitation pools when dealing with this seal species.

Environmental Change and Potential Impacts: Applied Research Priorities for Alaska's North Slope

roughly the size of Minnesota, most of which is wetland habitat underlain by permafrost and part of which contains the largest operating oil fields in the United States. The nearshore and offshore waters of the Chukchi and Beaufort seas add another 295 000 km 2 (114 000 mi 2 ) and hold what may be the largest undeveloped oil reserves remaining in the United States. The region is home to an abundant and diverse array of fish, wildlife, and plants, resources that sup port the vibrant subsistence culture of about 6000 Inupiat Eskimos. The caribou herds that summer on the North Slope are an important food resource for Inupiat communities, as are some native plants, bowhead whales, beluga whales, four species of ice seals, and walruses living in the Beaufort and Chukchi seas. Further, Alaska’s North Slope is at the forefront of global climate change, with an increase in mean annual temperature of about 1˚C per decade in Barrow, Alaska (ACRC, 2008). Federal, state, and local agencies manage the biotic and abiotic resources of the North Slope to maintain fish and wildlife populations and their habitats while also allowing energy development. The laws and regulations applied by government agencies managing the North Slope are rigorous, complex, and often controversial. Appropriate management requires information that can be gained only through applied research. We provide a brief history of applied research on the North Slope, introduce the North Slope Science Initiative (NSSI) as an organization tasked with improving the coordination of science across the region, and posit applied science priorities that are essential for successful and informed management.

Prey Size Reconstruction Based on Myctophid Otoliths in Scats of Northern Fur Seals (Callorhinus ursinus)

Diet studies of eared seals (Otariidae) are very important, because they are high-level consumers in marine ecosystems (Bowen 1997). Recently, non-lethal methods such as scat analysis have been applied to diet studies of eared seals (e.g., Zeppelin and Ream 2006; Sigler et al. 2009). In this analysis, diet compositions are estimated from the undigested hard part remains of prey items (fish otoliths, squid beaks, crustacean exoskeletons, etc.; Pierce and Boyle 1991). Fish species are identified based on the morphology of otoliths. Size and weight of fish consumed can also be estimated from the lengths of otoliths in scats (Sinclair et al. 1994). Although scat analysis is a useful method that provides dietary information without animal capture, the resultant information could include biases caused by digestion (Jobling and Breiby 1986; Yonezaki et al. 2003; Gudmundson et al. 2006). Fish otoliths are partially, or even completely, digested during passage through the alimentary system. Feeding experiments of various eared seals have been conducted to investigate the potential biasing effects of digestion on otoliths (e.g., Staniland 2002; Tollit et al. 2003). Numerical loss and length reduction rates of fish otoliths in scat samples were assessed from captive experiments, and correction factors calculated to enable the reconstruction of the original number and body lengths of fishes that were consumed. These correction factors are known to vary with prey species, eared seal species and experimental conditions (e.g., Bowen 2000; Orr and Harvey 2001; Staniland 2002). However, few studies have applied the correction factors to wild samples and tested the validity of the diet reconstruction. The purpose of this study was to use experimentally designed meals and captive northern fur seals (Callorhinus ursinus) to calculate correction factors (CFs) for reconstruction of the myctophid fish size to compensate for the effects of digestion. Moreover, we apply the CFs to otoliths recovered from the large intestine contents of wild fur seal specimens, and estimated the size of the myctophid fish eaten. Myctophid fish used in the experiment are dominant components of micronekton communities in oceanic ecosystems and are important prey items of northern fur seals in the western North Pacific Ocean (Yonezaki et al. 2003; Yonezaki et al. 2008). Therefore, the calculation of CFs of myctophid fish otoliths enables data for use in the reconstruction of the diet of northern fur seals based on scats.

At-sea behavior of South American fur seals: Influence of coastal hydrographic conditions and physiological implication

At-sea behavior and effects of hydrographic conditions on the pelagic habitat use of South American fur seals ( Arctocephalus australis) seasonally inhabiting the surrounding waters of shallow rocky reefs off Punta Mogotes (Mar del Plata, Argentina) were analyzed integrating geographic locations of fur seal groups (FSGs) with coastal hydrographic conditions and behavioral data in a Geographic Information System. Punta Mogotes rocky reefs represent a potentially high quality patch foraging area, crucial to a central place foraging species during their pelagic dispersion at sea. Fur seal behavior at-sea was strongly influenced by hydrographic conditions such us bathymetry, Beafourt sea state and sea surface current direction. Fur seals General Use Area (GUA) was associated with the 10 m isobaths, whereas Critical Use Area (CUA) was almost completely enclosed within the 5 m isobaths. A concentration-dispersion dynamic trend according to sea state was evident (GUA Beafourt ≤3 = 3.3 km 2 vs. GUA Beafourt >3 = 1.7 km 2), with a “use area displacement” according to sea surface current direction. A general prevalence of long, at-sea resting periods ( passive floating was the most frequently performed behavior, and usually for long periods) and a differential occurrence of each behavior associated with Beafourt sea states were detected. During calm seas (Beafourt ≤3), fur seals exhibit passive floating, occupying extended areas, and drifting according to sea surface current direction. With increasing sea states (Beafourt sea state >3), fur seals tended to perform shallow prolonged immersion and directional movements, and concentrated in restricted areas weakly affected by currents. The importance of floating periods at-sea, probably associated with resting and digestion, was interpreted as an energy conserving strategy that would allow an increase overall foraging efficiency. Results suggested that the ability of fur seals to perform certain behaviors that will allow completing physiological process and ultimately determine reproduction and survival success, would be conditioned by the hydrographic regime at foraging areas. This last could be extrapolated to other fur seal species spending long times at-sea, both as part of migration movements or during typical long foraging round trips.

Spatio-temporal variations and age effect on Toxoplasma gondii seroprevalence in seals from the Canadian Arctic

Toxoplasmosis is a significant public health threat for Inuit in the Canadian Arctic. This study aimed to investigate arctic seals as a possible food-borne source of infection. Blood samples collected from 828 seals in 7 Canadian Arctic communities from 1999 to 2006 were tested for Toxoplasma gondii antibodies using a direct agglutination test. Polymerase chain reaction (PCR) was used to detect T. gondii DNA in tissues of a subsample of seals. Associations between seal age, sex, species, diet, community and year of capture, and serological test results were investigated by logistic regression. Overall seroprevalence was 10·4% (86/828). All tissues tested were negative by PCR. In ringed seals, seroprevalence was significantly higher in juveniles than in adults (odds ratio=2·44). Overall, seroprevalence varied amongst communities (P=0·0119) and by capture year (P=0·0001). Our study supports the hypothesis that consumption of raw seal meat is a significant source of infection for Inuit. This work raises many questions about the mechanism of transfer of this terrestrial parasite to the marine environment, the preponderance of infection in younger animals and the natural course of infection in seals. Further studies to address these questions are essential to fully understand the health risks for Inuit communities.

From awe to satisfaction: immediate affective responses to the Antarctic tourism experience

ABSTRACTAntarctica is a rugged, austere, and yet stunningly beautiful continent with charismatic fauna including several species of penguins, whales, and seals. Mass media, writings from the early explorers, and modern film all describe firsthand experiences as delightful, beautiful, challenging, humbling, and even awe-inspiring. This dramatic allure of Antarctica now fuels one of the fastest growing tourism markets in the world with over 30,000 visitors annually traveling to the continent. Despite the fact that Antarctic tourism has occurred for over 30 years, little research has investigated the psychological and affective influence of these immersive tourism experiences in the Antarctic environment. This study explored visitors' affective judgments regarding their Antarctic tourism experience. An onsite post experience survey was administered to Antarctic tourists to investigate their satisfaction with a range of tour attributes. In addition, the researchers used the open-ended question, “How did this Antarctic experience affect you?” to explore tourists’ affective response to their interaction with the Antarctic tourism environment. These open ended responses were coded usinga priorithemes generated from Kellert's environmental values typology. Additionally, each response was analysed for the presence of an awe experience. Further analysis revealed that tourists described five sub-dimensions of an ‘awe’ experience (nature-human relationship, spiritual connection, transformative experience, goal clarification, and sense of feeling humbled), with many individuals experiencing multiple dimensions of awe. Consequently, this analysis reveals that the impact of an Antarctic tour experience is powerful, rich, and extremely complex.

Genetically effective population sizes of Antarctic seals estimated from nuclear genes

We analyzed eight nuclear microsatellite loci in three species of Antarctic seals; Weddell seal (Leptonychotes weddellii; mean N = 163), crabeater seal (Lobodon carcinophaga; 138) and Ross seal (Ommatophoca rossii; 35). We estimated genetic diversity (Θ) and effective population size (N E) for each species. Autosomal microsatellite based N E estimates were 151,200 for Weddell seals, 880,200 for crabeater seals, and 254,500 for Ross seals. We screened one X-linked microsatellite (Lw18), which yielded similar N E estimates to the autosomal loci for all species except the Ross seals, where it was considerably larger (~103 times). Microsatellite N E estimates were comparable with previously published N E estimates from mitochondrial DNA, but both are substantially lower than direct estimates of population size in all species except the Ross seals. The ratio of maternally versus biparentally derived estimates of N E for Ross seals was not consistent with the hypothesis that they are a polygynous species. We found no sign of a recent, sustained genetic bottleneck in any of the species.

Changes in Seal Habitat Use of Nearshore Waters around Newfoundland and Southern Labrador: Implications for Potential Predation on Salmon

The reasons for the decline in some Atlantic salmon (Salmo salar) stocks in Newfoundland and southern Labrador are not fully understood, but many resource users consider predation by seals in rivers and nearshore waters to be a contributing factor. To address these concerns, local ecological knowledge (LEK) interviews with resource users (n = 57) were conducted at 29 rivers throughout the Province to evaluate the potential for seal predation over a 25-year period when major changes were occurring in the structure of the Northwest Atlantic ecosystem. Based on LEK, eight rivers frequented by harp seals (Pagophilus groenlandicus), nine by harbor seals (Phoca vitulina) and three by gray seals (Halichoerus grypus) were evaluated as having a high potential for predation. According to respondents, the relative abundance of seals at these rivers started increasing in the mid 1990s or 2000, depending on the seal species involved. Variation in potential predation from river to river was attributed to a number of factors including the distribution of forage fish, variability in local ice conditions, the geography of the river and ecology of seal species frequenting the area. Resource users provided a useful and, in many cases, new perspective on the spatial and temporal overlap of seals, particularly harp seals, capelin (Mallotus villosus) and salmon in some areas. However, quantitative seal diet information and knowledge of seal-salmon relative abundances are required to assess the biological significance of these results from a salmon conservation perspective.

Acoustic work with Ron Schusterman and Dave Kastak.

This paper describes auditory-related work done with Ron Schusterman from 1964 through 2002, and with Dave Kastak from 1999 to 2007. Some of Schusterman’s early experiments failed to demonstrate echolocation in pinnipeds, resulting in a conflict with Poulter in 1965 that Ron did not resolve until 2000. He conducted several experiments to investigate what functions other than echolocation sea lion click vocalizations might serve. In 1965 he advised on measuring underwater auditory localization in sea lions, and between 1970 and 1976 he and his colleagues produced aerial and underwater audiograms for two seal species. His many other projects on hearing and vocalization, conducted with his colleagues, may be reviewed by other speakers in this symposium. Schusterman joined the NOAA panel writing noise exposure criteria for marine mammals from 1998 to 2002. In 2002 he asked Dave Kastak to replace him. Kastak then made significant contributions to the criteria from 2002 until his untimely death in 2007, just before the criteria were published. Auditory research lost two giants with their passing.

Feeding habits of three seal species at the Danco Coast, Antarctica: a re-assessment

The analysis of prey overlap among Weddell, Antarctic fur and leopard seals was conducted using fecal samples collected at the Danco Coast, Antarctic Peninsula, in 1998 and 2000. The re-occurrence of prey species was moderate in samples collected in 1998, and low in 2000, and reflects resource partitioning among seal species. Prey species that mostly co-occurred in seals’ diet were the Antarctic krill Euphausia superba, bivalves, and the myctophids Gymnoscopelus nicholsi and Electrona antarctica. A dietary similarity index of prey overlap has been calculated and demonstrates evident fluctuations in pairwise comparisons between the seal species. The highest and lowest values of prey overlap were observed between Antarctic fur seals and leopard seals, and between Weddell seals and leopard seals, respectively. Prey overlap between Antarctic fur seals and Weddell seals was moderate in both seasons.

Development of a predicted physical map of microsatellite locus positions for pinnipeds, with wider applicability to the Carnivora

Understanding genetic variation responsible for phenotypic differences in natural populations is significantly hampered by a lack of genomic data for many species. Levels of variation can, however, be estimated using microsatellite markers, which may be useful for relating individual fitness to genetic diversity. Prior studies have demonstrated correlations between heterozygosity and individual fitness in some species. These correlations are sometimes driven by a subset of markers, and it is unclear whether this is because those markers best reflect genome-wide heterozygosity, or whether they are linked to fitness-related genes. Differentiating between these scenarios is hindered when the genomic location of markers is unknown. Here, we develop a predicted genomic map of pinniped microsatellite loci based on conservation of primary sequence and genomic location between dog, cat and giant panda. We mapped 210 of 260 (81%) microsatellites from pinnipeds to locations in dog, cat and giant panda genomes. Based on the demonstrable synteny between the genomes of closely related taxa within the Carnivora, we use these data to identify those microsatellites with the greatest chance of cross-species amplification success and demonstrate successful amplification of 21 of 26 loci for cat, dog and two seal species. We also demonstrate the potential to identify candidate genes that may underpin the functional relationship with individual fitness. Overall, we show that this approach provides a rapid and robust method to elucidate genome organisation for nonmodel organisms and have established a resource that facilitates further genetic research on pinnipeds that also has wider applicability to other carnivores.

First Confirmed Record of Grey Seals in Greenland

The presence of grey seals has never before been confirmed in Greenland, but on 30 August 2009 a grey seal was photographed near shore in Southeast Greenland (59˚53′ N, 43˚28′ W). The seal was observed within a small group of islands that hosts a harbour seal colony. The following day, a seal that might be a young grey seal was photographed at the same location. Information from Inuit hunters suggests that grey seals periodically visit Greenland, but the pictures taken in summer 2009 are the first solid proof of this seal species in Greenland.

PBDEs in serum and blubber of harbor, grey and harp seal pups from Eastern Canada

Serum and blubber of pup harbor ( Phoca vitulina), grey ( Halichoerus grypus) and harp ( Phoca groenlandica) seals from the Estuary and the Gulf of St. Lawrence were analyzed for polybrominated diphenyl ethers (PBDEs). Concentrations of ∑PBDEs (on lipid weight basis) in tissues of harbor seal pups inhabiting the St. Lawrence Estuary were about five times higher than in those from a colony located in the northern Gulf. Harp seal pups have the lowest levels of ∑PBDEs among the seal species born in the Gulf of St. Lawrence. Lipid normalized concentrations of ∑PBDEs in serum and blubber were strongly correlated, suggesting that the blood collection as a less invasive method could be used to monitor ∑PBDEs in pups. This study shows that fluvial inputs of PBDEs are important to the St. Lawrence marine ecosystem and that inhabiting harbor seal pups have a substantial exposure to PBDEs at a critical developmental stage. In addition, the observed difference in PBDE levels between harp and grey or harbor seal pups from the Gulf of St. Lawrence is explained by the difference in diets of their mothers which is linked with their residency time in the Gulf and their seasonal migration pattern.

A review of the status of harbour seals (<i>Phoca vitulina</i>) in the Northeast United States of America

We conducted a review of the literature and unpublished databases to describe the distribution, abundance, ecology and status of harbour seals (Phoca vitulina concolor) in U.S. Atlantic waters. The harbour seal is the most abundant and widespread seal species in this area. Since passage of the U.S. Marine Mammal Protection Act of 1972, the number of harbour seals observed during the pupping season in this region has increased from about 10,500 animals in 1981 to 38,000 animals in 2001 (uncorrected counts), an average annual rate of 6.6%. This increase has beenrelatively consistent over the 20 years, and there is no indication that the population size has stabilized. Correspondingly, the seasonal distribution has expanded and interactions between seals and anthropogenic activities have increased.

Predicting recurrent PDV epizootics in European harbour seals (Phoca vitulina)

Phocine Distemper Virus (PDV) caused mass mortality in European harbour seals (Phoca vitulina) in 1988 and in 2002. Both epizootics likely originated from refugia in Arctic seals, where data indicate PDV hops among populations and species. The metapopulation structure of host populations is suggested to be the reason why PDV is preserved among Arctic seals, since the high rate of spread of PDV would require much larger panmictic populations to maintain an infection. The pattern of sudden outbreaks of PDVis also seen in grey seals (Halichoerus grypus), the only to date identified species that could act as a vector between Arctic and North Sea seal populations. Harbour seal populations along mainland Europe were below critical herd immunity levels by 3-5 years after the events, and thus vulnerable for new outbreaks, but historical data and the 14 years between the 2 epizootics suggest that harbour seals in the North Sea area are only rarely exposed to the infective agent. The risk for new outbreaks of the seal plague in North Sea harbour seals is likely linked to the dynamics of the disease in Arctic seal species as well asvector species.