Incorporating information on bottlenose dolphin distribution into marine protected area design

Abstract

The steady growth of the whale-watching activities in the Azores and its concentration in a small area that partly overlaps the home range of a resident group of bottlenose dolphins (Tursiops truncatus) was one of the driving forces to proposing part of the range of this group as a Marine Protected Area (MPA). We used 6-years of data collected during boat surveys to investigate how dolphins used the candidate MPA (cMPA) and whether they showed any preference for the cMPA over adjacent areas. We also estimated the fraction of the resident individuals and group’s range included in the cMPA and examined whether there were any temporal changes in its use. Mean daily encounter rate of bottlenose dolphins was higher inside than outside the cMPA. Dolphin sightings inside the cMPA were nearly double than what was predicted by the survey effort. Dolphins used the cMPA with similar intensity throughout the years. Resident dolphins were frequently sighted in the cMPA. However, less than 20% of the known range (650 km2) and 41% (39 km2) of the core area of the group lay within the cMPA. The reliability in the use of the cMPA over a 6-year period suggests its importance for the dolphin population remained relatively stable but its surface area was clearly insufficient to satisfy the spatial requirements of the resident group. Based on these findings, we proposed to the Regional Government of the Azores to extend the boundaries of the cMPA. Accordingly, the modified protected area established in 2008 includes 100% of the core area of the resident group of bottlenose dolphins. This study provides an example of how information on cetacean habitat-use patterns may be used to design ecologically meaningful protected areas for this group.