English summary

Tagged animals
In the period from 14 April 1997 to 6 October 2002 52 harbour porpoises was tagged with satellite transmitters in Denmark. Twentyone of these porpoises was tagged at Skagen (the northern point of Denmark), while the remaining 31 were tagged in the Kattegat and the Danish straits (Inner Danish Waters).

Movements and habitat use
The porpoises visited areas from the Shetland Islands (UK) in the west to Øland (Sweden) in the east. The most important habitats in the Inner Danish Waters in the summer (April-September) was: northern entrance of the Sound, Flensborg Fjord and the waters around the southern part of Als, Northern part of the Great Belt, northern coast of Fyn to the entrance of the Little Belt, and the area south of Djursland. In the winter (October-March) the porpoises generally utilised the same areas as in the summer, however, the porpoises tend to move further south and abandoned the northern entrance of the Sound in the winter. One porpoise swam to the North Sea where it overwintered along the westcoast of northern Jutland.

For the porpoises tagged near Skagen the most important summer habitats was: northern Kattegat, Skagerrak except for the deep trench along the coast of Norway, as well as a few areas in the central North Sea. In the winter a significantly larger area was used extending from northern Kattegat through Skagerrak and into a large part of the eastern part of the central North Sea. Furthermore, two porpoises moved to the northern North Sea and into the Atlantic on both sides of the Shetland Islands. One animal stayed the entire winter in a limited area northwest of the Shetland Islands.

The homerange areas was larger for the porpoises tagged in Skagen compared porpoises from the Inner Danish Waters. Females generally had a larger homerange than males.

Population structure
There was only a limited overlap in the homerange between the porpoises tagged near Skagen and in the Inner Danish Waters. This division was persistent throughout the year and suggests a population boundary across the sea of Kattegat between the islands of Læsø and Anholt.

Diving behaviour
The tagged porpoises dove during all hours but with higher diving activity during the day than at night. On average the porpoises from the Inner Danish Waters dove 56 % of the time during summer and 75 % of the time during winter. Generally the porpoises from Skagen had a higher diving activity with 72 % of their time spend submerged in summer and 82 % during winter.

Reaction to tagging
The reaction to the tagging procedure was limited. The breathing and heart rate of the animals was stabilised during the tagging by regular water application and in critical cases by lifting the animal in a stretcher into the water for a few minutes. The fact that some animals were followed for almost a year indicates that the tag has only a limited effect on their life. A captive porpoise was tagged for a month and behavioural changes were only observed during the first day after tagging.

Genetic analysis
The results of genetic analysis of the porpoises caught in the same pound net, revealed that 3 pairs were mother and calf, while 3 other pairs were found to be half siblings or cousins.

Freeze branding
Based on a tagged porpoises that was bycaugth in a bottom set gillnet after three months, the freeze branding is judged to work well. The number was white and clearly visible on the background of the black skin. No sign of infection or deeper tissue damage was found.

Health condition
Generally, the porpoise caught in pound nets were in good nutritional condition. Based on blood samples and blowhole samples, a large part of the animals (44 %), had signs of mild infection, while seven animals (14 %) had signs of more severe infection or anaemia. However, compared to porpoises investigated in other studies the porpoises caught in pound nets seem to be representative for the porpoise population of the respective areas with respect to health condition.

	Full report (pp. 1-25) in pdf format (1810 KB)
	Full report (pp. 26-92) in pdf format (3260 KB)