The following report summarizing humpback whale monitoring results from Glacier Bay and Icy Strait, Alaska in 2018 is now available: Neilson, J.L., and C.M. Gabriele. 2019. Glacier Bay & Icy Strait Humpback Whale Population Monitoring: 2018 Update. National Park Service Resource Brief, Gustavus, Alaska. https://irma.nps.gov/DataStore/DownloadFile/620535 [692 K, 6 pages] *KEY FINDINGS:* - We documented 100 unique humpback whales, our lowest annual count since 2002. - Humpback whale abundance in Glacier Bay and Icy Strait has declined by

50% since peaking in 2013.

- This downtrend trend has been most dramatic in Glacier Bay, where we identified only 45 whales in 2018, a 72% decline compared to our record high count of 161 whales in 2013. - We documented only one mother/calf pair in 2018 but by mid-August the mother had lost her calf, marking total reproductive failure for the first time in this 34-year study. - An increasing number of whales that exhibited long-term site fidelity to GB-IS in 2004-2013 (n = 66) have not been documented since 2013. In 2018, over half (56%) of these well-known whales were missing. - For the third year in a row, we observed numerous abnormally thin whales, however it appears this was less common than in 2017. - Although our monitoring results clearly indicate dramatic population level changes over the past five years, we do not know if the declines in whale numbers represent a shift in distribution and/or increased mortality from 2014-2018. Efforts to locate the whales missing from Glacier Bay and Icy Strait in catalogs from other feeding areas (e.g., British Columbia and Prince William Sound) have so far yielded no matches. Through a new collaboration with Happywhale.com, we recently initiated expanding our search area to the broader North Pacific. - Within Alaska, the consistent, long-term, monitoring of humpback whales is limited to Glacier Bay and Icy Strait, although our findings are consistent with negative trends in abundance, reproduction, and body condition for humpbacks in other areas in the central North Pacific. - Growing evidence suggests that recent declines in humpback whales and other marine species may be related to the unprecedented marine heatwave that occurred in the North Pacific from 2014-2016. -- Janet Neilson Humpback Whale Monitoring Program Glacier Bay National Park & Preserve PO Box 140 Gustavus, Alaska 99826 907-697-2658