| dc.description.abstract | To be able to preserve areas in nature in a careful way a good understanding of the
biodiversity living there is needed. The harbour seals are a top predator that affect and is
affected by the whole food chain and plays a vital role in the ecosystem. Some seals migrate
long distances and some are relatively stationary, it is therefore very important that we can get
to know the population on an individual level. Earlier, the way to identify an individual has
been through physically tag them, this thesis explored both the possibility to use the natural
patterns in the fur to identify individual harbour seals by Photo-ID. The images were
processed using the software Wild-ID, the population sizes were estimated in two different
locations in Gullmarsfjorden, Sweden. The software worked well, 58 potentially unique
individuals were managed to be identified during the project, 22 of these with both their left
and right side of their face. The similarity scores the software gave the matched images were
to 99% scored beneath 0.3 (0 = no similarity, 1 = exact copies) which is a relatively low
score. Still, the software ranked about 75% of the matches as the best suggestion and 95% as
one of the top 10 suggestions. This shows that even though the scores were very low, the
software could still usually pick out the correct match. With the information gathered and
capture-recapture statistics, population sizes of two different locations in the fjord was
estimated, 26 (12 – 60) individuals on one site and to 73 (47 – 129) on the other. This is the
first time identification of harbour seal individuals in Sweden has been done with the help of
photo-ID and it’s a important step for better understand migration and spatial structures by the
harbour seal population. This information can lead to better management and conservation of
our marine ecosystems. | en_US |
