Arne Bjørge

Institute of Marine Research in Norway | IMR · Research Group of Marine Mammals

Sperm whales (Physeter macrocephalus) are widely distributed in the Norwegian Sea and feeding aggregations occur. One of these aggregations is in the Bleik Canyon, close to shore in Norway, where the present study was performed. The study used a whale safari company as a platform from which to conduct a photo-identification study of male sperm whal...

The kelps Laminaria digitata and Saccharina latissima are typically sub-littoral species. It is therefore surprising to find large intertidal kelp beds dominated by these two species in the inner Porsangerfjord, North Norway. The areas of the nine intertidal kelp beds ranged from 0.01 to 3 km2 and covered a total area of 8.3 km2. Both species had a...

Harbour porpoises inhabit coastal waters, in habitats that are characterized by high diversity and complexity in terms of their bathymetry, substrate, fish communities and point sources of contaminants. The complexity in these habitats influences both the habitat use and feeding ecology of porpoises. Congregations of porpoises feeding primarily on...

The species is widespread and abundant (with current population estimates around 300,000) and there have been no reported population declines or major threats identified. http://www.iucnredlist.org/details/full/11140/0

The species is widespread and abundant (with current population estimates exceeding 100,000) and there have been no reported population declines or major threats identified. http://www.iucnredlist.org/details/full/11142/0

Lissodelphis borealis is widespread and abundant, with population estimates in the high tens to low hundreds of thousands throughout their North Pacific range. High levels of bycatch during the 1970s and 1980s are estimated to have reduced their population size within the last three generations by an unknown amount, but the most realistic scenarios...

The species is widespread, but abundance has not been estimated for the mid- and east Atlantic (and where abundance estimates do exist for other regions, these are low) and there are bycatches and directed takes in West Africa of unknown, but likely escalating, scale. http://www.iucnredlist.org/details/full/20730/0

The eastern Spinner Dolphin population has ceased to decline but shows no clears signs of recovery. While there are few estimates of abundance and takes available in regions other than the eastern tropical Pacific, they are taken throughout their range by a diverse number of direct and indirect fisheries; some of these indirect takes may evolve int...

All bottlenose dolphins around the world were previously recognized as T. truncatus, but recently the genus has been split into two species: T. truncatus and T. aduncus (the smaller Indo-Pacific Bottlenose Dolphin – Wang et al. 1999, 2000a,b). However, the taxonomy of bottlenose dolphins is confused, due to geographical variation, and it is very po...

The species is widespread and abundant (with current population estimates around 150,000) and there have been no reported population declines or major threats identified. http://www.iucnredlist.org/details/full/20738/0

The species is widespread and abundant, with current range-wide population estimates in the hundreds of thousands. Although bycatch in high-seas drift gillnet fisheries during the 1970s and 1980s may have caused population declines, these fisheries have been banned since 1993. Current takes and threats are small relative to reported global populati...

There is a lack of adequate information to make an assessment of extinction risk for this species (including the lack of a population estimate, and lack of an assessment of the impact of by-catch in Chile). http://www.iucnredlist.org/details/full/12126/0

The abundance estimates available total more than 2.5 million, and additional likely large populations in the Atlantic, Indian and Pacific Oceans have not been assessed. The northeastern population in the ETP declined 76% within the last three generations (69 years), but that decline has ceased and was not large enough to constitute a global declin...

Although the species is widespread, abundance has not been estimated for the mid- and eastern Atlantic. Bycatches in West Africa are of unknown scale and potentially large. http://www.iucnredlist.org/details/full/20732/0

Until recently, the genus Tursiops was monospecific, but a second species - the Indo-Pacific Bottlenose Dolphin - is now also recognized (Rice 1998). It is known to be taxonomically distinct based on concordance in genetics, osteology, and external morphology (Wang et al. 1999, 2000a,b). The taxonomic status of several subpopulations of Tursiops (f...

Retningslinjer for miljøundersøkelser i marint miljø etter akutt oljeforurensning

We investigated the spatial associations between minke Balaenoptera acutorostrata, fin B. physalus and humpback Megaptera novaeangliae whales and their prey in the Barents Sea in late summer of 2003 to 2007. During these years the abundance of their assumed primary prey, capelin Mallotus villotus, was low due to a stock collapse. The whales were th...

In this paper we use mitochondrial and microsatellite DNA variation to investigate the mechanisms that underlie the evolution of population structure in a highly mobile marine mammal, the white-beaked dolphin. We found moderate genetic diversity (h) at mtDNA, but low nucleotide diversity (π) (0.7320 ± 0.0031 and 0.0056 ± 0.0004, respectively), cons...

Introduction to Volume 8: Harbour seals in the North Atlantic and the Baltic

This chapter discusses the characteristics, taxonomy, distribution, abundance, and ecology of the harbor porpoise or Phocoena phocoena. The harbor porpoise is a small odontocete inhabiting coastal temperate and boreal waters of the Northern Hemisphere. Harbor porpoises have a short, stocky body resulting in a rotund shape, an adaptation that helps...

The northern Benguela ecosystem adjoining Namibia has undergone considerable changes in recent decades, with reductions and northwards shifts of key prey species that have had severe implications for marine top predator populations. We investigated how such environmental variability may impact foraging behaviour of the Cape fur seal Arctocephalus p...

The weight gain in lactating harbour seal pups and sex-specific growth curves are described. The relationship between body length, body weight and age were derived by regression analysis based on length and age data from 365 seals, and weight values from 136 seals. The asymptotic values of the curves describing body length were 148.0 cm and 147.2 c...

A bstract Between 1975 and 1998, 3,571 gray and 630 harbor seal pups were tagged along the Norwegian coast, and 259 (7%) gray and 80 (13%) harbor seal tags were returned. Incidental mortality, mainly in bottom‐set nets, accounted for the majority of deaths (79% in gray and 48% in harbor seals, respectively). Seals were most vulnerable to incidental...

The male harbor seal (Phoca vitulina) produces broadband nonharmonic vocalizations underwater during the breeding season. In total, 120 vocalizations from six colonies were analyzed to provide a description of the acoustic structure and for the presence of geographic variation. The complex harbor seal vocalizations may be described by how the frequ...

An increasing number of studies indicate that marine mammals and some seabirds are exposed to organotins. However, results from northern and Arctic areas are few. Here results from analysis of tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT) and monophenyltin (MPhT) in harbour porpoise (Phocoena phoco...

We studied the behaviour of harbour seal (Phoca vitulina) female-pup pairs during joint diving sessions in the lactation period. During this period, females and pups most often started diving simultaneously. However, at night the pups most often started the diving events. The pair rarely resurfaced simultaneously, and there was no pattern in who re...

Managing complex environments requires suitable tools to integrate data from a variety of sources and efficiently analyse and present them within a geographical context. Recently there has been a growing interest in the integration of geographical, environmental and behavioural data for use in coastal zone management and planning. Our study shows h...

A bstract We studied the summer home range and habitat selection of harbor seal pups tracked using VHF radio telemetry along the coast of central Norway in 1997 and 1998. Median fixed kernel home range of six pups tracked in 1998 was 10.4 km ² and the median core area was 1.2 km ² . One particular deep basin (>100 m deep) was highly selected, and e...

A 1680 km² coastal archipelago area in Norway around Sandøy (62°N 6°E), with a resident population of approximately 750 harbour seals was modelled in a geographic information system (GIS). The proportions of different habitat types available to harbour seals for foraging were estimated. Empirical data on levels of activity and foraging of VHF radio...

E. 2002. Interactions between harbour seals, Phoca vitulina, and fisheries in complex coastal waters explored by combined Geographic Information System (GIS) and energetics modelling. – ICES Journal of Marine Science, 59: 29–42. A 1680 km 2 coastal archipelago area in Norway around Sandøy (62N 6E), with a resident population of approximately 750 ha...

Marine mammals are highly mobile and capable of travelling long distances. Some species do undergo long seasonal migrations, mainly north-south movements between breeding and foraging grounds. Other species may follow their prey species in an offshore-onshore seasonal migration pattern. Some species, despite their capacity for migration, are reside...

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 genetically...

To study the diving activity of harbour seal (Phoca vitulina) from nursing to independent feeding, we VHF radio tagged and tracked seven pups. The pups gradually developed the diving skills necessary to obtain enough food after weaning and to avoid natural and man-made dangers. The maximum dive duration remained unchanged with pup age, indicating t...

The harbour porpoise (Plwcoena phocoena) is subject to a high rate of incidental mortality in fisheries worldwide and, in some areas, these rates are sufficiently high to warrant concern over population sustainability. Thus, the definition of sub-populations is paramount to the conservation of this species. To investigate the population structure i...

Report of the Workshop on Chemical Pollution and Cetaceans

View this paper at: http://onlinelibrary.wiley.com/doi/10.1111/j.1748-7692.1998.tb00750.x/abstract

Background: the harbour seal is coastal non-migratory and suitable for behavioural studies using short-range telemetry and tracking. Methods: a combination of VHF radio telemetry and underwater ultrasonic telemetry was used to obain behavioural and physiological data from 13 harbour seals tagged at an archipelago in Norway. VHF signals were used to...

Background: in order to describe the fish prey in the diet of the harbour seal Phoca vitulina, field studies were carried out in the Hvaler area in outer Oslofjord in 1990 and 1991, and in Froan in mid-Norway in 1991. Method: the studies were based on analysis of harbour seal faeces with identification of fish prey otoliths. The studies also includ...

Background: the haul-out behaviour of the Norwegian harbour, seals had previously not been studied throughly. Methods: the intent was to examine the haul-out behaviour in relation to three factors: (1) the diel light cycle, (2) the tidal cycle and (3) the interaction between these two cycles. Observations were therefore made on days with low tide a...

During Norwegian and Danish harbour porpoise projects 1987-1991, subcutaneous blubber samples of 34 male harbour porpoises (Phocoena phocoena) were collected. Animals from three geographical locations, ranging from 56 degrees N, 12 degrees E to 71 degrees N, 26 degrees E, were chosen in order to study the organochlorine (OC) contamination in this s...

Habitat use and diving behaviour of harbour seals in a coastal archipelago in Norway International Symposium on the Biology of Marine Mammals in the North-East Atlantic NOV 29-DEC 01, 1994 TROMSO, NORWAY

A workshop on age determination in harbour porpoises (Phocoena phocoena) was held in Oslo, Norway, 21-23 May 1990. During the workshop. the principles of formation of dental layers were reviewed, as were the growth layer patterns in odontocete teeth and evidence for interpreting the layering patterns as annual. Specific information on how to estima...

The study is based on stomach contents from 247 porpoises bycaught or stranded between 1985 and 1990. A minimum of 30 species of fish were identified, representing 16 families. Off northern Norway, capelin (Mallotus villosus) was an important species. In Scandinavian waters as a whole, herring (Clupea harengus) was the single most important species...

The information available indicates a divided offshore distribution during summer for harbour porpoises in Norwegian waters, with a southern component in the North Sea area and a northern component from Lofoten and into the Barents Sea. The abundance estimates were about 82 600 porpoises (CV 0.24) for the southern component and about 11 000 porpois...

Small groups of harbour seals are scattered along the entire Norwegian coastline and in some fjords. Some of these groups are separated by long distances from larger populations, and these groups may run a risk of extinction due to demographic and environmental stochasticity. Here we studied the viability of small groups of harbour seals assuming n...

Biomass distribution and energetics of trophic levels in the pelagic ecosystem of the Barents Sea are presented as averages over several years for the whole Barents Sea using data from the research programme Pro Mare in 1984–1989 and mathematical ecosystem models. Average biomasses range from more than 3 tonnes carbon km–2 (zooplankton) to 0.1 kg C...

We studied the component community of lung-worms of the harbour porpoise, attempting to establish the relative importance of ecological and evolutionary factors on its development. The lungs of 64 porpoises by-caught in Norwegian waters were examined for helminths. Three pseudaliid species were detected. The porpoises appear to be readily colonized...

Concentrations of mercury and selenium have been determined in liver and kidney of 92 harbor porpoises (Phocoena phocoena) caught along the Norwegian coast. The hepatic and renal mercury concentrations ranged from 0.26 to 9.9 and 0.15 to 3.5 μg g−1, respectively, whereas the corresponding selenium concentrations ranged from 0.74 to 14.2 and 0.60 to...

We describe scaling of morphological variables that influence total insulation in eight species of marine mammals ranging in average size from 35 to 30000 kg. We also calculate total heat loss and the partitioning of heat loss through the body surface and appendages. For the eight species investigated, heat loss in 0°C water is appreciably higher t...

This study is aimed at establishing the mean age at attainment of sexual maturity and birth rates of harbour seals at the Norwegian coast, using information from 172 female and 184 male harbour seals sampled between 62 and 66° N during the period 1977-1982. Based on the occurrence of first time ovulation, the mean age at attainment of female sexual...

The current estimate of the number of harbour seal Phoca vitulina in Norwegian waters, including Svalbard, is 4129, based on actual counts of seals at the haul-out sites during the period 1977–1988. Comparison with an estimate obtained during the early 1960s indicates that there has been little change in the overall number of harbour seals in Norwa...