Monday, September 1, 2008
Jesper has set up meetings with a range of scientists who are researching in areas which may be useful in my work - specifically areas concerned with visualisation and sound. Today I met with Jakob Tougaard who is involved with acoustical surveys with hydrophones - above (similar to a microphone but with ceramic crystals which generate an electric signal when compressed) to gather data from marine creatures which emit bio-sonar. The ultrasound signals are recorded live from harbour porpoise and converted into audible 'clicks' by a data logger. Jakob explained how the animals use the noises for communication and orientation. As well as signal collection to analyse the animal's language (he found that the same signals are used by the small Hector's porpoise in NZ's banks peninsula) they also use the hydrophone to assess numbers of the porpoise in the Inner Danish Waters by towing a string of them behind a boat. Construction of giant windfarms at sea is effecting the movements of porpoise - they avoid construction areas and sometimes don't return to an area once construction is finished. Currently 15% of Denmark's energy comes from wind power and they are working towards 50% by 2030 - but this also has an environmental effect.
The tracking and assessment of the harbour animal's movement is used as leverage for the establishment of Marine Protected Areas - there are currently no areas areas which are protected from fisheries. This came as a shock to me since there are so many marine reserves already established in New Zealand. Jakob played me some of the recordings he has made - but he also discovered there is almost no variety in the signals the animals make - they are universally hard, fast and repetitive!
This is Jakob Tougaard giving me a hydro acoustic alarm (a pinger) which emits signals to keep porpoise away from fishing nets
the porpoise wave forms were very repetitive like this: