by It sounds like an episode of a crime show at sea: In late January 2024, federal regulators learned that a female North Atlantic right whale had been spotted near Martha’s Vineyard, Massachusetts. The whale was pulled to shore, where more than 20 US and Canadian scientists gathered to perform a necropsy, or animal autopsy.
On February 14, the US National Oceanic and Atmospheric Administration announced that whale #5120 was in a catalog that tracks individual right whales. In addition, the agency said, rope embedded deep in the whale’s tail likely came from lobster fishing gear in Maine.
Entanglement in fishing gear is a deadly threat to these critically endangered animals. Scientists estimate that there may have been as many as 10,000 right whales in the North Atlantic before the rise of commercial whaling in the 18th and 19th centuries. Today, fewer than 360 people remain. Almost 90% of them have been arrested at least once.
When whales get entangled in fishing gear, they use extra energy pulling them while swimming. If the rope is caught around their mouth, it could struggle for life and slowly starve. Ropes wrapped around the whales’ bodies, fins or tails can cut into the animals’ skin and become embedded deep in their flesh, as happened with whale #5120. This can cause infections, chronic inflammation and damage to the whales’ color, muscles, bone and baleen – the bristly structures in their mouths that they use to filter prey from the water.
North Atlantic right whales enjoy legal protection, both internationally and in US waters, including policies that seek to reduce deaths or serious injuries resulting from capture. However, even when recruitment does not kill a whale, it can affect the ability of individuals to reproduce, which is critical for a species with such low numbers.
In a newly published study, we show that even exposures that scientists classify as minor have devastating effects on female right whales and that expectant mothers who experience “minor” exposure are least likely to begin breeding. As researchers with expertise in marine biology, ecology and statistics, we believe our findings highlight the urgent need for ropeless fishing gear that can reduce threats to the survival of this species.
Smaller females have fewer young
Understanding reproductive patterns is essential to support critically endangered species. Historically North Atlantic right whales began breeding at about 9 years of age and one calf was born every three to four years thereafter for many years.
Today, however, many females have yet to reproduce at all. Furthermore, those that have successfully produced calves now do not produce offspring for an average of more than seven years.
As we showed in a 2022 study, after an encouraging recovery of the North Atlantic right whale population from the 1970s to the early 2000s, the number of reproductively mature female right whales declined from 2014 onwards. By 2018 there were only about 73 breeding females left, which is about half of all females and a sixth of the entire species.
Other research shows that poor health and physical condition are making it harder for the females to even start breeding. Since the early 1980s, right whales in the North Atlantic have literally gone extinct: Adults have shorter bodies than a few years ago. This trend has to do with catching in fishing gear. As is true for all mammals, a reduction in female body size reduces the likelihood of reproduction. Smaller whales have fewer calves.
Low calving rates are a significant factor in the decline of whales in the North Atlantic, so it is important to understand what causes them. Many organizations are involved in tracking North Atlantic right whales, including government agencies, aquariums and conservation groups. Aerial photographs enable researchers to identify individuals and thus monitor whale population trends, births and deaths, patterns of ocean habitat use, health and rates of scarring from encounters and collisions with ships.
Our new study found that female right whales that experienced breeches may not even start breeding before they reach sexual maturity. Even females that have reproduced before are less likely to breed again after becoming stranded.
We determined this by using a mathematical model to incorporate information on the identity of individual whales, derived from photographs of natural markings called callosities on the whales’ heads. By repeatedly identifying and photographing whales over time, scientists can assess different stages of their lives, such as when females give birth.
Weakness of current regulations
Researchers categorize the severity of injuries resulting from entrapment as minor, moderate or severe. The scientists who manage the right whale catalog classify scars or injuries on the skin as minor if they are less than 0.8 inches (2 centimeters) without penetrating the blubber. If they are larger and go into the blubber, they are classified as moderate. Injuries that extend deep into the muscle or bone are categorized as serious injuries.
Our research makes it clear that such value-laden terms can be misleading as even small nets of reproductive whales can be at risk.
Multiple laws appear to protect the rights of North Atlantic right whales, including the US Endangered Species Act and the Marine Mammal Protection Act, and Canada’s Endangered Species Act. In our view, these measures do not carry enough weight to prevent all forms of arrest, regardless of severity.
Under the Marine Mammal Protection Act, NOAA develops and implements conservation plans and so-called Take Reduction Plans, designed to minimize wildlife deaths and serious injury as a result of commercial fishing gear.
The Atlantic Whale Reduction Plan, developed in 1997, requires fishermen to use weak ties, with a maximum breaking strength of 1,700 pounds (771 kilograms), to connect lobster and crab pots to surface buoys. These links are intended to be broken when whales swim into them, so that the whales do not become entangled and burdened with ropes and traps.
The plan also requires fishermen to use heavy ground lines to connect multiple traps or pots. These lines are designed to sink to the bottom rather than float in the water column. And the plan closes trap fishing areas seasonally when whales are known to be present in those areas.
Coming back from shore
Current population estimates suggest that the number of right whales in the North Atlantic may be stabilizing, meaning that the number of deaths is roughly equal to the number of births. Although these estimates seem promising, females must start and continue producing calves to increase the number of whales.
From our work, it is very clear that the lethal and sub-lethal effects of sublethal impacts are of great concern to these whales. As we see it, ending capture, not mitigating it, is the only way to avoid the extinction of this species. Every catch, no matter the severity, is bad news for the whales.
This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. It was written by: Joshua Reed, Macquarie University; New Leslie, Ursinus College; Peter of Cork, Griffith Universityand Rob Harcourt, Macquarie University
Read more:
Leslie New receives funding from the US Office of Naval Research and the National Science Foundation. She is also a member of the Scientific Committee of the International Whaling Commission.
Peter Corkeron consults with Public Employees for Environmental Responsibility on whale conservation issues. He led the National Oceanic and Atmospheric Administration’s large whale research program for the northeastern US from 2011 to 2019, and then led the New England Aquarium’s right whale research program until 2022.
Rob Harcourt receives funding from the Australian Federal Government’s Department of Climate Change, Environment, Energy and Water for right whale research. He was a member of the National Marine Mammal Scientific Committee
Joshua Reed does not work for, consult with, own shares in or receive funding from any company or organization that would benefit from this article this, and has not disclosed any relevant connections beyond their academic appointment.
