Dozens of marine species are currently endangered, ranging from the smallest porpoise to the largest animal on Earth. Some populations have declined by more than 90% in a single human lifetime, while others are slowly clawing their way back from the brink. The threats they face are varied, but a few common forces drive most of the damage: overfishing and bycatch, vessel strikes, pollution, habitat destruction, and increasingly, climate change.
Vaquita: The World’s Most Endangered Marine Mammal
The vaquita, a small porpoise found only in the upper Gulf of California, is the most critically endangered marine animal alive. Around 10 individuals are estimated to remain, down from roughly 600 in 1997. That collapse happened almost entirely because vaquitas drown in gillnets set for fish and shrimp. The decline accelerated dramatically after 2010, when illegal poaching of a large fish called totoaba surged. During that period, the population was dropping by more than 33% per year.
The vaquitas that have been examined are not starving. Necropsies of 60 animals that died in nets during the 1980s and 1990s found no signs of emaciation, and nine carcasses recovered between 2016 and 2018 had full stomachs and good body condition. Their habitat can still support them. The problem is purely entanglement in fishing gear.
Māui’s Dolphin
Found only off the west coast of New Zealand’s North Island, Māui’s dolphin is one of the rarest dolphins on Earth. About 54 individuals over the age of one year remain, with researchers 95% confident the true number falls between 48 and 64. Like the vaquita, Māui’s dolphins are primarily threatened by entanglement in fishing nets, along with disease and natural predation in a population too small to absorb losses easily.
North Atlantic Right Whale
North Atlantic right whales were hunted nearly to extinction centuries ago and have never fully recovered. Only about 70 reproductively active females remain, which makes every single death a serious blow to the species. Since 2017, NOAA has classified the situation as an “Unusual Mortality Event,” with at least 18 right whales confirmed dead or seriously injured from vessel strikes alone during that period. Entanglement in fishing rope is the other major killer. Recent modeling suggests mortality rates have improved somewhat compared to the steep decline through 2019, but the population remains in a precarious state.
Blue Whales
Blue whales, the largest animals ever to live, were devastated by commercial whaling in the early 1900s. Today’s global population is a small fraction of pre-whaling numbers, and the species remains listed as endangered. The encouraging news is that populations are increasing globally. NOAA’s recovery plan aims to eventually downlist blue whales from endangered to threatened, though reaching that milestone requires better data on population size, distribution, and whether current growth rates can hold. Blue whales are found in every ocean except the Arctic.
Sea Turtles
Six of the world’s seven sea turtle species are classified as vulnerable, endangered, or critically endangered. The hawksbill turtle is among the hardest hit. Long-term monitoring of a nesting population in northeast Queensland, Australia, documented a 57% decline in the number of nesting females and a 58% decline in egg clutches laid over a roughly 28-year study period from the early 1990s to 2018. Hawksbills face threats on multiple fronts: they’re killed for their ornamental shells, they lose nesting habitat to coastal development, and their coral reef feeding grounds are degrading.
Other endangered sea turtles include the Kemp’s ridley (the rarest sea turtle species), the green turtle, and the leatherback. All face overlapping threats from fishing bycatch, plastic ingestion, light pollution that disorients hatchlings, and rising sand temperatures that skew the sex ratio of eggs.
Whale Sharks
The whale shark, the world’s largest fish, is classified as endangered on the IUCN Red List. Its global population has declined by at least 60% over the last three generations, a timespan of about 120 years. The picture is worse in the Indo-Pacific, where the decline exceeds 65%, compared to a roughly 30% drop in the Atlantic. Whale sharks grow slowly, mature late, and reproduce infrequently, which means even modest increases in mortality can push populations into long-term decline. They’re killed in targeted fisheries in some regions and caught as bycatch in others, and vessel strikes are an emerging concern as shipping traffic increases in their habitat.
Corals
Corals are animals, and many species are in serious trouble. NOAA has listed 22 reef-building coral species under the Endangered Species Act. Five of those are Caribbean species, and 15 are found in the Indo-Pacific. Two Caribbean staghorn corals were already listed as threatened before the most recent round of protections added 20 more species. Ocean warming causes bleaching events that can kill entire reef systems, while ocean acidification weakens the calcium carbonate structures corals build. Pollution, sedimentation from coastal development, and disease compound the damage. Because coral reefs support roughly a quarter of all marine species, their decline cascades through entire ecosystems.
Southern Bluefin Tuna
Southern bluefin tuna were fished so heavily through the 20th century that their spawning population sits at roughly 23% of its original unfished level. International catch limits managed by the Commission for the Conservation of Southern Bluefin Tuna have helped stabilize the decline, but the species is still classified as endangered. These tuna are extraordinarily valuable in global sushi markets, which creates persistent pressure from both legal and illegal fishing.
What’s Driving These Declines
Historically, overfishing and bycatch have been the dominant drivers of marine species loss. Highly mobile species like whales, dolphins, sharks, and tuna have been hit hardest by direct exploitation. Less mobile species, including corals and shellfish, have suffered more from pollution, habitat destruction, and climate change.
That balance has shifted over the past three decades. Since the late 1990s, climate change and climate variability have become increasingly prominent in the scientific literature as causes of marine population declines. Rising ocean temperatures, acidification, deoxygenation, and shifting currents are reshaping marine habitats in ways that compound the older threats of overfishing and pollution. For many endangered marine species, survival now depends on addressing both the legacy of overexploitation and the accelerating impacts of a warming ocean.