Whale watching ranks as one of the hottest topics in the diving world, and the humpback whale holds a special place in the hearts of many ocean enthusiasts as the ultimate dream encounter. A new study, however, reveals that between 2012 and 2021, the North Pacific humpback whale population declined by 20% — approximately 7,000 individuals — with scientists pointing to heatwaves and elevated ocean temperatures as likely primary causes.
This article offers a brief introduction to the humpback whale, breaks down the findings of this latest study, and explores the role that citizen marine scientists played in the research. It also draws on past humpback whale sightings in waters around Taiwan to share some tips for whale watching.
Humpback Whale: A Brief Introduction
The humpback whale, Megaptera novaeangliae, also known as the humpback whale, belongs to the family Balaenopteridae.
- Physical characteristics: Adults measure approximately 14–17 metres in length; adult females are 1–1.5 metres longer than adult males.
- Behaviour and lifestyle:
- Feeds on krill, various small fish, and cephalopods; natural predators include orcas and large sharks.
- Creates bubble nets underwater to encircle and lure prey, then lunges forward with mouth wide open to engulf large groups of food.
- Frequently displays breaching, pectoral fin slapping, and tail-lob behaviours.
- Male whales sing during breeding season, likely to attract mates.
- Sexual maturity is reached at 5–10 years; females have a reproductive interval of two years and a lifespan of up to 50–77 years.
Declining Humpback Whale Numbers: What Scientists Say
Humpback whales are facing an existential crisis. Photo credit: Zola Studio
The latest study, published in Royal Society Open Science, saw researchers comb through data from citizen marine science databases to track changes in humpback whale populations over nearly 20 years, estimating North Pacific humpback whale numbers across different time periods.
Humpback Whale Population Trends
- 2002 to 2012: Population grew from 16,875 to 33,488 — nearly doubling.
- 2012 to 2021: Population declined from 33,488 to 26,662 — a reduction of nearly 7,000 individuals.
Looking further back, humpback whales remained targets of large-scale commercial whaling in the North Pacific right up to the end of the 20th century. Human hunting drove the species to the brink; data cited in the study estimates that by 1976 only a little over a thousand individuals remained. It wasn't until the International Whaling Commission (IWC) banned commercial whaling in 1982 that the humpback whale's extinction crisis began to reverse.
The end of hunting clearly enabled a significant recovery, but because earlier population figures cannot be calculated precisely, it remains difficult to define how many whales would constitute a full "recovery." The research team had originally expected that, under the whaling ban, humpback whale numbers would continue to climb before levelling off — yet the data show a recent decline instead.
The Underlying Causes of Humpback Whale Decline
Beyond the known threats of vessel strikes and entanglement in fishing gear, the study highlights the unprecedented marine heatwaves of 2013 to 2016 as a major threat. Rising ocean temperatures altered the composition and abundance of plankton communities, reducing overall ocean productivity and lowering both the reproductive rate and survival rate of fish.
Humpback whales feed on small fish and crustaceans such as krill and herring; a shrinking food supply has placed their survival under mounting pressure. Researchers found a sharp decline in calf numbers, an increasing prevalence of emaciated whales, and a rise in strandings.
Scientists are sounding the alarm: because human-caused global warming is intensifying, marine heatwaves are no longer isolated events. As they become more frequent, they could cause ever-greater harm to marine life and ecosystems.
Why We Need to Protect Humpback Whales
Humpback whales play a vital ecological role. Photo credit: Zola Studio
Protecting humpback whales ultimately means protecting the ocean food chain — and with it, the entire marine ecosystem. What other critical roles do humpback whales and whales in general play in ocean ecology? Let's take a look!
- Ocean pump: As whales move vertically through the water column — surfacing to breathe and releasing waste — they act like pumps, transporting nutrients from the ocean floor up to surface layers and stimulating plankton growth.
- Carbon sequestration: Scientists have found that whales capture carbon from the atmosphere and store it in their bodies. When a whale dies and sinks to the seafloor, that carbon is kept out of the atmosphere. A 2019 report by the International Monetary Fund (IMF) noted that each large whale sequesters an average of 33 tonnes of CO₂ — the equivalent of 1,513 times the annual absorption of a single tree.
- Ecological indicator: The numbers and health of humpback whales and other cetaceans serve as a key indicator of ocean ecosystem health — as the latest study powerfully illustrates, the alarm bells for our marine ecosystems are already ringing.
Humpback Whale Research: The Unsung Heroes of Citizen Marine Science
This study brought together contributions from diverse organisations and scientists to produce its landmark findings — and behind it all was the indispensable work of countless citizen marine scientists.
A large portion of the research drew on data from the citizen marine science platform Happywhale — a database built from photos uploaded by more than 4,000 citizen marine scientists, combined with AI technology. As of the end of April 2024, it had accumulated over 820,000 photos and identified more than 112,000 individual whales.
Happywhale
Citizen marine scientists' photo contributions serve as a vital reference for researchers — and this is precisely the direction BlueTrend continues to cultivate. Since 2021, our team has been building a "Marine Citizen Biological Database," which has to date engaged more than 8,000 citizen marine scientists and amassed over 12,000 marine life photos. In 2023, we began gradually integrating AI identification, with the goal of expanding the reach and impact of citizen marine science through "AI Ocean."
Humpback Whales Can Also Be Spotted in Waters Around Taiwan
You, too, have a chance of spotting a humpback whale in Taiwan. Photo credit: Zola Studio
Of the more than 80 species of cetaceans found worldwide, nearly 30 have been recorded in waters around Taiwan — most of them small species. The probability of encountering a large whale is relatively low, at less than 10%. Fortunately, in recent years humpback whales have been sighted by members of the public at Orchid Island, Green Island, and other locations, drawing many divers to nearby waters hoping to catch a glimpse of these magnificent animals. However, when multiple vessels crowd around a whale, or when divers attempt to approach humpback whales underwater, it can cause the animals significant stress and distress. Unfamiliarity with humpback whale behaviour also makes it difficult to anticipate risks, raising the likelihood of injury to both humans and whales.
Although Taiwan does not yet have comprehensive whale-watching regulations — with only the Taiwan Marine Whale-Watching Guidelines serving as the primary reference — harassing cetaceans can still be prosecuted under the Wildlife Conservation Act, with penalties including imprisonment of up to one year, detention, or a fine of between NT$60,000 and NT$300,000.
Should you be fortunate enough to come face to face with a humpback whale, keep a few basic principles in mind: do not feed or touch the animals; respect their natural behaviours; do not throw any man-made objects into the sea; and do not deliberately chase or encircle cetaceans. And of course, don't forget to upload any precious photos to the Marine Citizen Biological Database — every contribution helps power AI Ocean.
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Further Reading
