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Seal Populations (seal + population)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

On the Structure of the Adrenal Gland of the Common Seal (Phoca vitulina vitulina)

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2004
H. Bragulla
Summary The adrenal gland is a vitally important endocrine gland that occupies a central role in the regulatory mechanisms of the body metabolism. Environmental stress factors lead to permanent strain and overload of the body resulting in structural alterations of the adrenals that in turn are followed by hormonal imbalances. This leads to an increased susceptibility to bacterial and viral diseases. The recurrence of numerous fatalities in the different seal populations of the North Sea (during the years 1988, 1989 and 2002), of the Baikal Lake and Caspian Sea (during the years 2000 and 2001) were the motive for a morphological investigation of the species-specific structure of the adrenal gland of the common seal in order to differentiate environmental stress-induced pathological alterations from the physiological structure of this organ. The study was based on adrenals of 112 common seals (Phoca vitulina vitulina) using light microscopic and transmission and scanning electron microscopic methods. The phocine adrenal gland displays several structural characteristics. Originating from the connective tissue organ capsule, narrow and broad septa intersperse the adrenal cortex. These septa contain blastemata as a reserve for the regeneration of hormone-producing cortical cells. Such blastemata are also occurring in the form of an intermediate zone in between the zona glomerulosa and zona fasciculata in the phocine adrenal cortex. Another species-specific characteristic is an inverse part of the adrenal cortex encircling the central vein of the organ. These structural features have to be considered in assessment and definition of pathological alterations of the adrenals as observed in the form of exhausted blastema cell pools in the adrenocortex of seals perished in the mentioned phocine mass mortalities. [source]

Assessing the potential impact of salmon fisheries management on the conservation status of harbour seals (Phoca vitulina) in north-east Scotland

ANIMAL CONSERVATION, Issue 1 2007
P. M. Thompson
Abstract Conservation efforts are often constrained by uncertainty over the factors driving declines in marine mammal populations. In Scotland, there is concern over the potential impact of unrecorded shooting of seals, particularly where this occurs near Special Areas of Conservation. Here, we show that the abundance of harbour seals Phoca vitulina in the Moray Firth, north-east Scotland, declined by 2,5% per annum between 1993 and 2004. Records from local salmon fisheries and aquaculture sites indicated that 66,327 harbour seals were shot each year between 1994 and 2002. Matrix models and estimates of potential biological removal indicate that this level of shooting is sufficient to explain observed declines. Nevertheless, uncertainty over the number and identity of seals shot means that other factors such as changes in food availability may be contributing. Recent conservation measures markedly reduced the recorded levels of shooting in 2003 and 2004. In 2005, a coordinated management plan was developed to protect salmon fisheries interests while minimizing impacts on local seal populations. Comprehensive monitoring of future population trends and improved regulation of culls are now required to provide more robust assessments of the impact of human persecution on harbour seal populations in the Moray Firth and in other parts of the UK. [source]

Occurrence of killer whales in Scottish inshore waters: temporal and spatial patterns relative to the distribution of declining harbour seal populations

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009
Harriet E. Bolt
Abstract 1.Sightings of killer whales around Shetland were recorded between 1991 and 2006 and for the whole of Scotland for 2007. The data were used to investigate temporal patterns in killer whale occurrence around Shetland and spatial patterns in occurrence around Scotland. 2.There was a strong seasonal peak in sightings around Shetland during June,July, coinciding with the harbour seal pupping season. 3.There was no clear trend in annual sightings around Shetland between 1991 and 2006. 4.Killer whales were sighted most frequently around Shetland and the Pentland Firth as well as around Mull and the Treshnish Isles. 5.These findings are discussed in terms of potential impacts upon local declining harbour seal populations and future research requirements. Copyright © 2009 John Wiley & Sons, Ltd. [source]