Shipping noise signatures.

Throughout 2010, underwater recordings have been made of each ship passing two separate Haro Strait nodes of the OrcaSound.net hydrophone network. About 20 ships pass each day. Each ship has been identified in real time [automatic identification system (AIS)]. Measurements of received underwater noise levels and AIS variables are recorded as each ship passes the listening stations. Individual ships are observed multiple times moving in either northerly or southerly directions at times separated by a day or two and also by intervals of months. A database has been developed that contains the spectrum level of each ship (bandwidth 96 kHz at one location and 22 kHz at the other) and the source level both in terms of intensity and angular distribution. Ship signatures in terms of frequency quantiles and angular distributions of emissions are quite reproducible. This database can be used to predict limitations on echolocating and vocalizing marine mammals’ active space due to specific ship noise emissions. In particular, predictions of marine mammal noise exposures in specific frequency bands can be made prior to specific vessels’ entry into an area opening the possibility of planning field observations to investigate correlations between behaviors and specific predicted noise exposures.