Radiated noise from commercial ships in the Gulf of Maine: implications for whale/vessel collisions.

To understand mysticete acoustic-based detection of ships, radiated noise from high-speed craft, cruise ships, catamarans and fishing vessels was recorded June-September 2009. Calibrated acoustic data (<2500 Hz) from a vertical hydrophone array was combined with ship passage information. A cruise ship had the highest broadband source level, while a fishing vessel had the lowest. Ship noise radiated asymmetrically and varied with depth. Bow null-effect acoustic shadow zones were observed for all ship classes and were correlated with ship-length-to-draft-ratios. These shadow zones may reduce ship detection by near-surface mysticetes.

Rhythmic structure in humpback whale (Megaptera novaeangliae) songs: preliminary implications for song production and perception.

The hierarchical organization of the male humpback whale song has been well documented. However, it is unknown how singers keep these intricate songs intact over multiple repetitions or how they learn variations that occur sequentially during each mating season. Rather than focus on the sequence of sounds within a song, results presented here demonstrate that the individual sounds are organized into rhythmic groups that make the production and perception of the lengthy songs tractable by yielding a set of simple groups that, although arranged in rigid order, can be repeated multiple times to generate the entire song.

Geographic variation in Northwest Atlantic fin whale (Balaenoptera physalus) song: implications for stock structure assessment.

Passive acoustic data are increasingly being used as a tool for helping to define marine mammal populations and stocks. Fin whale (Balaenoptera physalus) songs present a unique opportunity to determine interstock differences. Their highly stereotyped interpulse interval has been shown to vary between geographic areas and to remain stable over time in some areas. In this study the structure of songs recorded at two geographically close feeding aggregations in the Gulf of St. Lawrence (GSL) and Gulf of Maine (GoM) was compared. Recordings were made from September 2005 through February 2006 in the GSL and intermittently between January 2006 and September 2007 at two locations in the GoM. 6257 pulse intervals corresponding to 19 GSL and 29 GoM songs were measured to characterize songs from both areas. Classification trees showed that GSL songs differ significantly from those in the GoM. The results are consistent with those derived from other stock structure assessment methodologies, such as chemical signature and photoidentification analysis, suggesting that fin whales in these areas may form separate management stocks. Song structure analysis could therefore provide a useful and cost-efficient tool for defining conservation units over temporal and geographical scales relevant to management objectives in fin whales.