The North Atlantic right whale is endangered because of a combination of human-caused threats, primarily vessel strikes and entanglement in fishing gear, compounded by climate-driven shifts in food supply that are pushing whales into unprotected waters. As of late 2024, only an estimated 372 individuals remain, with roughly 70 reproductively active females. That number is far too small for a species that reproduces slowly and faces lethal hazards on nearly every migration.
Ship Strikes: A Leading Killer
Collisions with vessels are one of the two primary causes of right whale deaths. Between 2016 and 2020, an average of at least 2.4 right whales per year were killed or seriously injured by ship strikes. That figure is almost certainly an undercount: researchers estimate that only about 36 percent of all right whale deaths are ever observed. Many carcasses sink or drift into the open ocean and are never recovered.
The risk is not limited to massive cargo ships. Modeling of real-world vessel traffic along the U.S. East Coast found that large ocean-going vessels over 350 feet long posed the greatest total risk, but boats as small as 26 feet also contributed to mortality. A strike from the largest ships is almost always fatal regardless of speed, because their deep draft and propeller suction make them nearly impossible for a whale to avoid. Slowing all vessels to roughly 10 knots reduced modeled mortality by about 22 percent for the biggest ships and 31 to 38 percent for smaller ones. Speed restrictions help, but they do not eliminate the problem.
Entanglement in Fishing Gear
Rope lines connecting lobster and crab traps on the seafloor to buoys on the surface create a web of hazards along the whale’s coastal habitat. Right whales swim through these vertical lines and become wrapped in heavy rope that can cut into their skin, restrict movement, and slowly starve or drown them. Between 1980 and 2009, at least 62 individually identified right whales were involved in 66 reported entanglement events. Like ship strikes, the true number is higher than what researchers observe.
Even whales that survive entanglement often carry lasting damage. Dragging heavy gear for weeks or months burns enormous calories, causes chronic infections, and can impair a whale’s ability to feed or reproduce. Entanglement and vessel strikes together have been significant enough to trigger an official “unusual mortality event” declaration, a federal designation that signals deaths are occurring at a rate far above what is normal for the species.
Warming Waters and Vanishing Food
Right whales are filter feeders that depend on dense patches of tiny, fat-rich copepods called Calanus finmarchicus. These creatures thrive in cold, nutrient-rich waters. Starting around 2010, deep water temperatures in the Gulf of Maine and on the Scotian Shelf began rising significantly, and the abundance of these copepods dropped.
The consequences rippled through the whale’s entire life cycle. As their traditional feeding grounds in the Bay of Fundy and along the Western Scotian Shelf became less productive, whales shifted northward into the southern Gulf of St. Lawrence. Sightings there became noticeably more frequent after 2015. The problem is that this new habitat had few protections in place. There were no established speed restrictions for ships, limited monitoring for whale presence, and active fishing operations using vertical trap lines. Whales that followed their food into new territory encountered threats they had not historically faced in that area.
The mechanism behind the food shift is complex but well documented. Ocean currents that once reliably delivered copepods into whale feeding zones changed course. In warmer years, reduced river runoff caused the Gaspé Current to separate from the coastline, carrying copepod populations eastward along the deep Laurentian Channel rather than into the western Gulf of St. Lawrence where whales were foraging. In cooler years, stronger runoff kept the current tight against the coast, funneling prey into the right places. As warm years have become more common, the reliable delivery of food has become less predictable.
Slow Reproduction Makes Recovery Fragile
Even without human threats, right whales would be slow to bounce back from low numbers. Females don’t begin reproducing until around age nine. Historically, a healthy female would give birth every three to four years. That interval has now stretched to seven to ten years on average. With only about 70 reproductively active females in the population, this means fewer than a dozen calves may be born in a given year.
Several factors appear to be driving the reproductive slowdown. Chronic stress from entanglement injuries and poor nutrition reduces a female’s body condition, delaying the point at which she can successfully carry a pregnancy. There is also evidence that low genetic diversity in such a small population may be depressing reproductive success over the long term, though this alone doesn’t explain the sharpest drops in calving rates. In some years, such as 1998 to 2000, calving fell to extremely low levels in ways that genetic factors alone cannot account for, pointing to environmental and human-caused stressors working in combination.
Ocean Noise Adds Chronic Stress
Right whales communicate using low-frequency calls to maintain contact with each other, coordinate feeding, and locate potential mates. Shipping traffic, seismic exploration by oil and gas companies, and recreational boating all produce noise in the same frequency range. Near busy ports and shipping lanes, this background noise can mask whale calls, effectively making it harder for whales to find each other across distances that once posed no communication barrier.
A striking natural experiment illustrated the scale of the problem. After the September 11, 2001 attacks, shipping traffic in the Bay of Fundy dropped sharply for several days. Researchers studying right whales in the area found that stress hormone levels in the whales decreased during this quiet period. It was the first direct evidence linking reduced ship noise to lower physiological stress in the species. In habitats with heavy traffic, whales have been observed shifting their calls to higher frequencies, a behavioral adaptation that suggests they are struggling to be heard over the din.
For a population this small, any interference with mating or nursing behavior matters. If females and calves cannot stay in acoustic contact, or if courtship groups are disrupted by noise-related stress, the already-stretched calving interval may lengthen further.
Protections Have Helped but Not Enough
The North Atlantic right whale has been federally protected since the early 1970s, and seasonal speed restrictions requiring vessels to slow to 10 knots in certain areas along the East Coast have been in place for years. These rules have prevented some deaths, but the population has continued to decline. Part of the problem is enforcement. Compliance with voluntary slow zones has been inconsistent, and mandatory zones only cover limited areas during specific months.
The shift into the Gulf of St. Lawrence exposed a fundamental limitation of place-based protections: when whales move, the rules don’t automatically follow. Canada responded by implementing temporary fishing closures and speed restrictions in the Gulf after a cluster of deaths in 2017, but the broader challenge of protecting a mobile species in a changing ocean remains unresolved.
In the United States, NOAA Fisheries proposed expanding speed restrictions to cover more vessel sizes and broader areas, but that proposal was withdrawn in early 2025. The agency has since announced it is exploring alternative approaches, including technology-based strike avoidance systems and redesigned management zones, while weighing the economic impact on coastal industries. The species remains in a precarious position where the pace of regulatory change has not kept up with the pace of population decline.