The following report is now available, summarizing our 33rd consecutive year of humpback whale population monitoring in Glacier Bay and Icy Strait in southeastern Alaska: Neilson, J. L., C. M. Gabriele, and L. F. Taylor-Thomas. 2018. Humpback whale monitoring in Glacier Bay and adjacent waters 2017: Annual progress report. Natural Resource Report NPS/GLBA/NRR—2018/1660. National Park Service, Fort Collins, Colorado. https://irma.nps.gov/DataStore/DownloadFile/602012 [2.8 MB] *ABSTRACT* Migratory humpback whales (*Megaptera novaeangliae*) use southeastern Alaska as summer feeding habitat, including the waters in and around Glacier Bay National Park and Preserve (GBNPP). This report summarizes GBNPP’s humpback whale monitoring program in Glacier Bay and Icy Strait (GB-IS) in 2017, our 33rd consecutive year of consistent data collection in June-August. We documented 128 unique whales, our lowest count since 2003, and effort-corrected counts also revealed steep decreases. By all measures, humpback whale abundance has declined >40% since peaking in 2013. We documented decreases in within-year and between-year site fidelity, with 44% (29 of 66) of whales exhibiting long-term (2004-2013) fidelity to GB-IS interrupting their regular annual return in 2014-2017. This was the fourth consecutive year of calving anomalies, with only two mother/calf pairs in GB-IS (one lost her calf by mid-July), resulting in the second lowest crude birth rate (1.6%) since 1985. We documented no known juveniles (ages 1-4), indicating a possible decline in recruitment, as well as many abnormally thin whales (24%). This was the first year that a reduced vessel speed limit (13 kts) was not warranted in lower GB. The Point Adolphus ‘core group’ was not sighted and the fate of many group members is unknown. Within Alaska, the long-term, consistent monitoring of humpback whales is limited to GB-IS, making it difficult to determine over what geographic scale these declines in abundance, site fidelity, calving, recruitment, and physical condition are occurring, however there is evidence that declines may be occurring throughout the central North Pacific. For reports from past years, go to https://www.nps.gov/glba/learn/nature/whale_acoustic_reports.htm -- Janet Neilson Humpback Whale Monitoring Program Glacier Bay National Park & Preserve PO Box 140 Gustavus, Alaska 99826 907-697-2658