In the winter of 2001, four researchers and twelve intermediate and high school students took turns at a shore station more than 60 meters above Kawaihae Bay and counted 330 humpback whale pods in 54 timed scans. The Hawaiʻi Marine Mammal Consortium (HMMC) kept counting from the same station for the next two decades, and its record later showed whale numbers falling 60% between 2015 and 2016.
This page lists the studies we rely on when we write about Ocean Count results, with a plain summary of each: what was measured, where and when, the main finding, and, where it applies, how it compares with the Ocean Count. We link to each author’s or publisher’s own copy, or to an archived copy where the original is gone. The Ocean Count itself is run by NOAA’s Hawaiian Islands Humpback Whale National Marine Sanctuary; its official results are at oceancount.org/results, and this site is independent of the program.
Hawaiʻi Marine Mammal Consortium shore surveys off the Kohala Coast
HMMC is a nonprofit research group based in Kamuela on Hawaiʻi Island. Each winter from 2001 through at least 2023, mainly in February and early March, it counted humpback whales from one shore station above Kawaihae Bay, on the island’s northwest coast. The reports and the paper listed here all come from that station, which HMMC calls Old Ruins after the stone walls of a Hawaiian village on the nearby hillsides.
Kohala 2001 humpback whale report (HMMC, winter 2001)
The report’s full title is Summary of Winter 2001 Shore-based Monitoring of Humpback Whales, Megaptera novaeangliae, off the Kohala Coast, by Christine M. Gabriele, Susan H. Rickards, Adam S. Frankel and Jan Östman-Lind. It is HMMC’s final report to the Hawaiian Islands Humpback Whale National Marine Sanctuary, which paid for the equipment with a $4,800 grant. This is an HMMC report, separate from the Sanctuary Ocean Count and its results.
Between January 27 and March 17, 2001, the team watched from the station on 21 days, 47.2 hours of effort in all, and ran 54 fifteen-minute scans. They logged 330 pods, about 520 whales, or 9.6 whales per scan on average. A calf was present in 6.5% of pods, rising from 1.5% in January to 15.3% in March. Vessels averaged 5.1 per scan, and the most seen in one scan was 13, on February 18.
Twelve intermediate and high school students worked the scans through the Kula Naiʻa Foundation’s Ocean Explorers program, from schools including Waimea, Honokaʻa, Kohala, Kealakehe and Kanu o ka ʻĀina charter school. Project leaders worked as behavioral observer and theodolite operator (the theodolite is a surveying instrument that fixes each whale’s position by angle); students rotated through the computer and notetaking roles. Some took part during class time and others as an extracurricular activity.
The authors wrote that one year could not show a trend and that the value would come from repeating the scans at the same effort. HMMC repeated the scans every winter after that, and the later reports here come from those repeats. HMMC and the Ocean Count both count in fixed 15-minute periods, but HMMC scans from one site at four times of day, while the Ocean Count covers dozens of sites on one morning a month.
Gabriele, C. M., Rickards, S. H., Frankel, A. S., and Östman-Lind, J. Summary of Winter 2001 Shore-based Monitoring of Humpback Whales, Megaptera novaeangliae, off the Kohala Coast. Final report to the Hawaiian Islands Humpback Whale National Marine Sanctuary. Hawaiʻi Marine Mammal Consortium, Waikoloa, Hawaiʻi. Covers the winter 2001 season; the report carries no publication date.
The link goes to the Internet Archive’s capture of the hmmc.org file (PDF, 6 pages). HMMC’s current reports are on its research page.
Humpback whales in Kawaihae Bay, 1988–2003 (HMMC report to Hawaiʻi DLNR and the sanctuary)
This August 2003 report compares HMMC’s 2001–2003 scans with scans from a 1988 study at the same site (Helweg 1989). It was written for the State of Hawaiʻi Department of Land and Natural Resources (DLNR) and the sanctuary. Within 6.5 km of the station, the average count rose from 4.0 whales per scan in 1988 to 19.9 in 2003. Counting whales beyond 6.5 km too, the report’s comparison sample went from 9.0 whales per scan in 2001 (21 scans) to 14.5 in 2002 and 30.5 in 2003.
Vessel counts held steady at 5.0 to 6.3 per scan over 2001–2003, with the 10 am to 1 pm block usually having the most boats. The authors point to North Pacific population growth as the most likely reason for the rise in whales, and they list other explanations to consider, such as viewing conditions and whales moving between islands. Its acknowledgments thank students and teachers from West Hawaiʻi Explorations Academy, Kanu o ka ʻĀina charter school, and Kealakehe, Kohala and Honokaʻa high schools “for data collection help”.
Gabriele, C. M., Rickards, S. H., Yin, S. E., and Frankel, A. S. (2003). Trends in Relative Distribution, Abundance and Population Composition of Humpback Whales, Megaptera novaeangliae, in Kawaihae Bay, Hawaiʻi 1988–2003. Final report for the Department of Land and Natural Resources, State of Hawaiʻi, and the Hawaiian Islands Humpback Whale National Marine Sanctuary. Hawaiʻi Marine Mammal Consortium. PDF at hmmc.org.
Frankel et al., “Humpback whale abundance in Hawaiʻi” (Marine Mammal Science, 2022; online 2021)
This paper draws on 366 scans made at Old Ruins from 2001 to 2019. Whale numbers climbed through the 2000s, peaked in 2010 at an average of 34 whales per scan, swung up and down through 2015, then dropped 60% between 2015 and 2016. The 2016–2019 average was 13.1 whales per scan. The crude birth rate, calves as a share of all whales counted, averaged 6.5% in 2001–2015 and 2.1% in 2016–2019, and fell to 1.1% in 2016.
The authors tested North Pacific climate indices as stand-ins for the food supply on the whales’ summer feeding grounds. The model that best explained whale numbers used the Pacific Decadal Oscillation (PDO) from 1.5 years earlier: Kohala counts were higher after cool, productive summers up north. They found no effect of time of day on counts, and calf pods sat closer to shore than adult-only pods (1.1 km against 1.8 km).
The paper cites the sanctuary’s Ocean Count summary data, as “unpublished data”, in support of a rising whale population off several islands since 2000. The acknowledgments credit the sanctuary and DLNR for the funding that started the study.
Frankel, A. S., Gabriele, C. M., Yin, S., and Rickards, S. H. (2022). Humpback whale abundance in Hawaiʻi: Temporal trends and response to climatic drivers. Marine Mammal Science, 38(1), 118–138. First published online August 4, 2021. doi:10.1111/mms.12856. Author copy: PDF at hmmc.org.
HMMC newsletters: season totals since 2019
HMMC’s yearly newsletters report each season’s scan totals, which add seasons after the paper’s 2019 cutoff. The 2019 scans found 342 whales, including 10 calves. In 2020 it was 236 whales and 15 calves, in 2021 315 whales and 24 calves (7.6% calves), in 2022 242 whales and 11 calves, and in 2023 297 whales and 14 calves. These are season totals (20 scans in 2020 and 2022, 19 in 2023), so they are a different measure from the per-scan averages in the paper.
The 2021 newsletter puts the 2016–2019 calf share at 1.3% to 2.9%. The 2023 issue reports that an August 8, 2023 brush fire burned over the Old Ruins station.
Hawaiʻi Marine Mammal Consortium. Newsletters and year-end reports, 2019, 2020, 2021, 2022 and 2023 (PDFs at hmmc.org).
Studies of the 2015–2021 humpback decline
Two peer-reviewed papers measure the drop with methods other than shore scans: one from fluke photographs across the whole North Pacific, one from boat surveys off Maui. Our page on the whale decline puts their numbers side by side with the Kohala scans.
“Bellwethers of change” (Cheeseman et al., Royal Society Open Science, 2024)
This study matched fluke photographs of individual whales from 46 organizations and 4,292 community contributors, pooled through Happywhale.com, to estimate humpback numbers each year from 2002 to 2021. The North Pacific estimate grew from 16,875 in 2002 to a peak of 33,488 in 2012, then fell about 20%, to 26,662, by 2021.
The Hawaiʻi estimate peaked in 2013 at 18,728 and was 12,294 in 2021, a 34% decline that took the population back to 2006 levels. Whales wintering off mainland Mexico showed no decline over the same years. The authors link the drop to the northeast Pacific marine heatwave and a loss of prey. They list the Kohala shore scans among the records that show the same drop, and write that their results support the Frankel et al. conclusions.
Cheeseman, T., Barlow, J., Acebes, J. M., et al. (2024). Bellwethers of change: population modelling of North Pacific humpback whales from 2002 through 2021 reveals shift from recovery to climate response. Royal Society Open Science, 11(2), 231462. doi:10.1098/rsos.231462. Open access: PMC10898971. Data and code: github.com/tedcheese/RSOS-NPAC-abundance.
Cartwright et al., mother and calf encounter rates off Maui (2019)
Boat transects in Maui’s ʻAuʻau Channel, run from 2008 to 2018, found encounter rates peaking in 2013 and falling through 2018. Mother and calf encounter rates dropped 76.5% between 2013 and 2018. The authors tie the timing to three climate events: a shift in the Pacific Decadal Oscillation, the northeast Pacific marine heatwave and the 2016 El Niño. They also cite a personal communication from S. Yin of HMMC reporting a decline of about 75% in mother and calf sightings off Kohala over the previous five years.
Cartwright, R., Venema, A., Hernandez, V., Wyels, C., Cesere, J., and Cesere, D. (2019). Fluctuating reproductive rates in Hawaii’s humpback whales, Megaptera novaeangliae, reflect recent climate anomalies in the North Pacific. Royal Society Open Science, 6(3), 181463. doi:10.1098/rsos.181463. Open access: PMC6458358.
NOAA reports and the 2016 listing decision
These are federal documents: the meeting report where researchers pooled their evidence of the decline, the rule that removed Hawaiʻi’s humpbacks from the endangered list, and the monitoring report written afterward.
NOAA meeting report: humpback whale trends in Hawaiʻi and Alaska (November 2018)
In November 2018, the sanctuary and NOAA Fisheries brought whale researchers together in Honolulu to compare data on low sighting rates over the previous 4 to 5 years. The report summarizes boat transects, photo-identification, shore scans with theodolites and volunteer counts. Its conclusion was a drop in sightings of calves and other whales off Southeast Alaska, Prince William Sound, Hawaiʻi Island and Maui.
The sanctuary compared Ocean Count sightings off Kauaʻi for the three seasons before and after 2016 and found a 37.3% decrease. Pacific Whale Foundation’s Great Whale Count on Maui recorded 64.5% fewer whales and 37.4% fewer calves in 2018 than in 2015. The group ranked research priorities, with food supply and whale body condition among the top five.
NOAA (2019). Trends in Humpback Whale (Megaptera novaeangliae) Abundance, Distribution, and Health in Hawaiʻi and Alaska: Report from a meeting held on November 27–28, 2018. NOAA Office of National Marine Sanctuaries, Hawaiian Islands Humpback Whale National Marine Sanctuary, and NOAA Fisheries Pacific Islands Regional Office. Prepared by P. Wong, M. Lammers, E. Lyman and S. Pultz. PDF from the sanctuary.
The 2016 Endangered Species Act rule: Hawaiʻi humpbacks delisted
In September 2016, NOAA Fisheries split the world’s humpback whales into 14 distinct population segments (DPS). Four stayed endangered, one was listed as threatened, and nine, including the Hawaiʻi DPS, came off the list. The rule gives the Hawaiʻi DPS an abundance estimate of 11,398 whales and a growth trend of 5.5 to 6% a year. It took effect October 11, 2016.
All humpback whales remain protected under the Marine Mammal Protection Act, the rule states, and it points to the separate 100-yard approach limits in sanctuary waters and in state waters. The Frankel and Cheeseman papers both note that the delisting coincided with the decline.
National Marine Fisheries Service (2016). Endangered and Threatened Species; Identification of 14 Distinct Population Segments of the Humpback Whale (Megaptera novaeangliae) and Revision of Species-Wide Listing. Final rule. Federal Register 81: 62260–62320, September 8, 2016. Document 2016-21276. Federal Register; official PDF at govinfo.gov.
NOAA Fisheries interim post-delisting monitoring report (2022)
NOAA Fisheries must monitor delisted populations for at least five years. This 2022 report reviews the nine delisted humpback populations. For Hawaiʻi it summarizes the Kohala scan results and the 2018 meeting, and records that NOAA Fisheries discussed internally whether a “response trigger” for further action had been reached. Because sightings in Hawaiʻi had since increased, it judged the trends “not conclusive enough” to reach one, and says NOAA Fisheries, the sanctuary and research partners will keep monitoring the population closely.
Schakner, Z. A., Chan, A., Kurtz, A., Graham, K., Young, N., and Teerlink, S. (2022). Interim Report on Post-Delisting Monitoring of Nine Distinct Population Segments of Humpback Whales (Megaptera novaeangliae). NOAA Technical Memorandum NMFS-F/SPO-230. PDF from NOAA Fisheries.
NOAA sanctuary articles on the decline and the Ocean Count
Three articles from NOAA’s Office of National Marine Sanctuaries give the program’s own account. “Humpback whales navigating an ocean of change” (September 2018) reports that the Ocean Count showed fewer whales from 2016 on, and that HMMC’s Kohala season totals averaged 477 whales a year in 2010–2015 and 261 in 2016–2017. “30 Years and Counting” (January 2026) traces the count from about 150 volunteers on Oʻahu in February 1996 to more than 60 sites on four islands.
“Bellwethers of Change” (March 2026) covers the marine heatwave and the sanctuary’s monitoring methods. Its figures of about 33,000 whales in 2012 and 26,000 in 2021 are the Cheeseman study’s totals for the whole North Pacific. The same study’s Hawaiʻi estimates are 18,728 at the 2013 peak and 12,294 in 2021.
Weinberg, E. (2018). Humpback whales navigating an ocean of change. Among-Serrao, C., and Takata-Tonini, C. (2026). 30 Years and Counting: How Community Science Helps Track Humpback Whales Across Hawaiʻi. Takata-Tonini, C., and Plunkett, R. (2026). Bellwethers of Change. All published by NOAA Office of National Marine Sanctuaries.
Studies of volunteer whale counts
The only Ocean Count trend figure in the documents on this page is the Kauaʻi comparison in the 2018 NOAA meeting report. Pacific Whale Foundation’s Great Whale Count on Maui has a peer-reviewed trend analysis.
Tonachella et al., Great Whale Count trends on Maui (2012)
Pacific Whale Foundation’s Great Whale Count runs on the same Saturdays as the Ocean Count, from shore sites on Maui. This paper uses 15 years of those counts (1995–1996 and 1999–2011), over 11,000 sightings, and estimates growth of 5.16% a year (±2.76%), close to earlier estimates for Hawaiʻi. The abstract says the uncertainty in the trend depends strongly on sampling, especially differences between observers. The authors urge volunteer programs to plan for observer differences when they design their protocols and collect data.
Tonachella, N., Nastasi, A., Kaufman, G., Maldini, D., and Rankin, R. W. (2012). Predicting trends in humpback whale (Megaptera novaeangliae) abundance using citizen science. Pacific Conservation Biology, 18(4), 297–309. doi:10.1071/PC120297.
Citing the Ocean Count results in a school or research project
Cite the official results PDFs, which the sanctuary publishes after each count at oceancount.org/results, with the count date and the PDF’s title. The sanctuary’s own site keeps the 2016–2020 PDFs on its Ocean Count page. Each results sheet is titled “Sanctuary Ocean Count Preliminary Data” and covers one morning, so a report comparing years should say so. For questions about the data, the sanctuary lists its Ocean Count contact on that page.