Ecology and conservation of bottlenose dolphins (Tursiops truncatus) in the north-eastern Adriatic Sea
Abstract
Bottlenose dolphins of the Kvarnerić (NE Adriatic Sea) live in an area of increasing
human impact, through tourism and small-scale fisheries. This thesis aimed to assess the
status of the local population and to inform managers on factors affecting their
distribution and abundance, using data from 1995-2003. Habitat modelling indicated a
significant negative impact of proximity to the main ‘marine highway’ and to marine
petrol stations. Evidence was found that dolphins may recently have reached a tolerance
limit to the number of boats using the area and that they remember crowded areas from
one year to the next. Dolphin presence was positively related to particular depths and
trawling areas. Apparent adult survival rate was estimated to be significantly lower than
for any other bottlenose dolphin population and first year calf survival was also low. A
decreasing trend in fecundity rate was found. The population showed a considerable rate
of non-random temporary emigration from the study area. The estimated size of the
population was small and similar to two other European bottlenose dolphin populations
(Moray Firth in Scotland and Shannon Estuary in Ireland). A significant decrease in
abundance of about 39% from 1995 was estimated. PVA confirmed the importance of
female adult survival to population viability and indicated that the current rate of
human-induced mortality is unsustainable. Local extinction risk within three
generations was estimated to be high (35%). Applying the IUCN Red List Criteria, the
Kvarnerić population should be listed as Endangered under Criterion C and E. This
study gives an important insight into the ecology of Adriatic bottlenose dolphins and
indicates the need for a regionally and locally synergistic approach to conserve this
population.
Type
Thesis, PhD Doctor of Philosophy
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