Visual and acoustic surveys have shown that endangered North Atlantic right whales overwinter in the waters of the Northeast US. Detailed knowledge of this population’s distribution is critical to reducing anthropogenic mortality events. Passive acoustic studies have confirmed that Stellwagen Bank National Marine Sanctuary (SBNMS) and Jeffreys Ledge are areas of high baleen whale acoustic activity during the winter. Right whales produce three main types of calls, the up-call, gun-shot and tonal calls. However, no thorough assessment has yet been made of whether this call type is the most appropriate one to use. SBNMS has been part of an ongoing passive acoustic study since 2006 and provides an opportunity for understanding the relationship between up-calls and gun-shots for this region. From December 18th 2007 to May 28th 2008 an array of 10 marine acoustic recording units was deployed in SBNMS. An automated detector was used to determine seasonal occurrence of calls. Gun-shots and upcalls occurred throughout the winter period, with gun-shots peaking in January, and up-calls peaking in December. Comparative analyses of up-calls and gun-shots show that they occur simultaneously around 17:00. Gun-shots primarily tended to occur between 16:00 and 4:00, while up-calls primarily occurred between 11:00 and 18:00. Average gun-shot activity was 2.15 calls/min, while average up-call activity was 3.45 calls/min. Future research should be directed towards assessing occurrence of different call types between seasons, and in the south-east US breeding grounds and northern foraging areas.
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