Research Document 2018/032

Patterns of Fin whale (Balaenoptera physalus) Seasonality and Relative Distribution in Canadian Pacific Waters Inferred from Passive Acoustic Monitoring

By James F. Pilkington, Eva H. Stredulinsky, Robin M. Abernethy, and John K.B. Ford

Abstract

We used acoustic data from eight different locations distributed throughout British Columbia marine waters to examine geographic and seasonal trends in Fin whale calling. Data were analysed using an acoustic power method resulting in a call index related to the intensity of calling activity in frequency bands relevant to Fin whale song. Detection results were corrected for site-specific differences in propagation and ambient noise in order to compare call indices between locations and seasons. We also investigated diel-calling trends to infer habitat use patterns across sites. Of the sites analysed, song was present throughout all fall and winter months; notably, sites in the Hecate Strait region had the highest and most sustained activity. Peak periods of song in Hecate Strait were offset seasonally from peak periods at all other sites analysed, indicating the possibility of a seasonal movement into the Hecate Strait region during the highpoint of the breeding season. Peaks in singing aligned with estimated breeding and calving periods for Fin whales in the North Pacific and British Columbia, supporting previous acoustic studies indicating that breeding activity likely occurs in these waters. Diel patterns in calling were found in one offshore site as well as a site on the west coast of Vancouver Island, but no diel patterns were found in Hecate Strait. Our results will be useful in efforts to identify habitats of importance to Fin whales in British Columbia, but also highlight the need for further studies to fill geographic data gaps as well as seasonal gaps in wintertime ship-based effort.

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