Title: Baleen whale acoustic ecology with focus on minke whales (Balaenopteraacutorostrata) and reference to anthropogenic noise
Abstract: Passive acoustic approaches for studying marine mammals have developed
substantially over the past decade. Advances in technology now allow data
collection in remote areas and over extended timescales. The first two
chapters of this thesis focused on the application of passive acoustics for
monitoring migratory baleen whales in the Northwest Atlantic Ocean. The
development and application of new localization algorithms showed how
small-scale arrays can be used to obtain baseline data about the acoustic
behavior of individuals, which will help to improve interpretation of longterm
acoustic data sets. Acoustic monitoring in the Stellwagen Bank National
Marine Sanctuary (SBNMS) revealed seasonal peaks of acoustic abundance
for right (Eubalaena glacialis) and sei whales (Balaenoptera borealis) in
spring and fall, respectively. Both species are primarily present during these
two seasons and to a lesser extent in winter and summer, indicating the
importance of this area as part of their migration route. Fin whales
(Balaenoptera physalus) were acoustically present year-round, although
song production was reduced during summer. While recorded on only a few
days of the entire period, blue whale (Balaenoptera musculus) song was
detected near SBNMS in three separate years.
There is considerable uncertainty concerning migration routes, winter
calving habitats and thus population structure of North Atlantic minke
whales (Balaenoptera acutorostrata). Given that this species is still being
hunted across its summer range, this uncertainty has important
conservation and management implications. In chapters III-V I used 3.5
years of acoustic array data from the Gulf of Maine to describe the species'
vocal repertoire, examine individual calling behavior and provide first source level estimates. Based on these data, an automatic detector was developed
and applied to year-round data from several sites along the US East coast
and beyond to track minke whale migration. Minke whales produced three
call categories at a mean source level of 165 ± 4 dB rms re 1 μPa. Individual
whales combined calls in non-random order, leading to two distinct calling
patterns. Unlike other baleen whales, animals sharing the same acoustic
space used different patterns simultaneously, without switching. Analysis of
seasonal occurrence patterns revealed peak acoustic presence in higher
latitudes during summer and fall and in lower latitudes during winter.
Migration appears to follow the general direction and location of the Gulf
stream in the spring and occurs in more open waters in the fall. A higher
abundance of calls at offshore recording sites, suggests that there is a
winter habitat located in deeper waters off the Southeastern US.
Antarctic minke whales (Balaenoptera bonaerensis) have long been
suggested as the likely source for the mysterious 'bioduck' signal, which is
the predominant underwater sound in the Souther Ocean during austral
winter. I analyzed data from the first two multi-sensor acoustic tags
attached to Antarctic minke whales and was able to confirm the production
of the bioduck by this species. This finding will allow the interpretation of a
wealth of existing recordings, and thereby substantially improve our
understanding of the distribution, abundance, and behavior of Antarctic
minke whales. This is critical information for a species that lives in a rapidly
changing polar environment and is subject of ongoing lethal sampling
efforts.
The effects of widespread anthropogenic noise in the marine
environment is of increasing concern. Most discussions have centered on
highly visible and regulated activities, such as seismic airguns and naval
sonar. In this last chapter we showed, that humpback whale (Megaptera novaeangliae) song was reduced, concurrent with transmissions of an Ocean
Acoustic Waveguide Remote Sensing (OAWRS) experiment approximately
200 km distant. This is the first time that active sonar used in fisheries
science has been shown to have this effect, highlighting the importance to
study and regulate the impact of all anthropogenic noise sources, including
research applications.
In conclusion, this thesis highlighted the suitability of passive
acoustic monitoring for an increased understanding of the spatio-temporal
distribution patterns and behavior of highly mobile and little studied baleen
whales. In particular, it considerably improved current knowledge about the
acoustic ecology and spatio-temporal distribution of minke whales.
Publication Year: 2014
Publication Date: 2014-11-21
Language: en
Type: dissertation
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