Dear MARMAM, My co-authors and I are happy to share our publication in the Journal of the Acoustical Society of America: Macklin, G. F., Moors-Murphy, H. B., & Leonard, M. L. (2024). Characteristics and spatiotemporal variation of sei whale (Balaenoptera borealis) downsweeps recorded in Atlantic Canada. The Journal of the Acoustical Society of America, 155(1), 145-155. A PDF copy can be made available upon request to macklingf@gmail.com The call characteristics and vocal behaviour of sei whales (Balaenoptera borealis) off eastern Canada, including potential spatiotemporal variation, is poorly understood. Such information can improve the performance of automated detector-classifiers, enhancing the accuracy and efficiency of identifying sei whales in large acoustic datasets. Ultimately, these data can be used to understand the occurrence, distribution, and population structure of sei whales in Atlantic Canada. We measured sei whale downsweep characteristics recorded from six locations off Nova Scotia (NS) and Newfoundland and Labrador (NFLD), Canada over a two-year period (2015–2017), and examined variation between call subtypes (singlets, doublets, triplets+), and seasons (Spring, Summer, Fall, Winter). We found that downsweeps had a mean duration of 1.58 s, sweeping from 75.66 to 34.22 Hz, with a peak frequency of 43.89 Hz and an intra-call interval of 2.22 s. Most call characteristics did not vary between location, subtype, or season; however, significantly longer downsweeps occurred off NS, within doublet calls, and in fall months. We also found that NFLD had a higher proportion of doublets (70%) than NS (52%). This variation may be evidence of acoustically diverging sei whale populations, as well as useful for improving detector-classifiers of sei whales in the region. Please do not hesitate to reach out if you have any questions, to macklingf@gmail.com Cheers, Gabrielle Macklin Aquatic Science Biologist/ Biologiste en sciences aquatiques Fisheries and Oceans/ Pêches et Océans Canada -- Gabrielle Macklin, M.Sc. Halifax, NS 1 204 232 0875 macklingf@gmail.com