The North Atlantic right whale population is in poor condition

April 27, 2020

New research by an international team of scientists reveals that endangered North Atlantic right whales are in much poorer body condition than their counterparts in the southern hemisphere. The alarming results from this research, led by Dr Fredrik Christiansen from Aarhus University in Denmark, were published last week in the journal Marine Ecology Progress Series.

Since large-scale commercial whaling stopped in the last century, most populations of southern right whales have recovered well, and now there are about 10,000 - 15,000 right whales in the southern hemisphere. Unfortunately, the same cannot be said for the North Atlantic right whales, found today off the east coast of North America. There are only around 410 individuals left, and the species is heading to extinction.

A number of known challenges cause the dissimilar and unfortunate development of the two different whale populations: Lethal vessel strikes and entanglement in fishing gear continue to kill and harm the North Atlantic right whales. Individual North Atlantic right whales also have to deal with frequent entanglements in fishing gear, in particular lobster and crab pots, which drains their energy. These burdens, along with a change in the abundance and distribution of their main source of food, copepods and krill, have left the whales thin and unhealthy, which makes them less likely to have a calf.

All this contributes to the current overall decline of the species. But so far, it has not been fully understood, how the body condition of the whales was affected by the different conditions in the north Atlantic.

Cross-continental study of whales' body condition

To quantify the 'thin and unhealthy' state of the North Atlantic right whales, Dr Christiansen and an international team of scientists have investigated the body condition of individual North Atlantic right whales, and compared their condition with individuals from three increasing populations of Southern right whales: off Argentina, Australia and New Zealand.

"Good body condition and abundant fat reserves are crucial for the reproduction of large whales, including right whales, as the animals rely on these energy stores during the breeding season when they are mostly fasting," said Dr Fredrik Christiansen from Aarhus Institute of Advanced Studies and Department of Biology, Aarhus University, Denmark, and lead author of the study. "Stored fat reserves are particularly important for mothers, who need the extra energy to support the growth of their newborn calf while they are nursing."

How fat are right whales?

The study is the largest assessment of the body condition of baleen whales in the world, and involved researchers from 12 institutes in five countries. The international research team used drones and a method called 'aerial photogrammetry' to measure the body length and width of individual right whales in these four regions around the world. From aerial photographs, the researchers were able to estimate the body volume of individual whales, which they then used to derive an index of body condition or relative fatness.

The analyses revealed that individual North Atlantic right whales, juveniles, adults and mothers, were all in poorer body condition than individual whales from the three other populations of Southern right whales. This difference is alarming, since poor body condition for North Atlantic right whales explains why too many of them are dying, and why they are not giving birth to enough calves to boost the population's recovery. It may also be affecting their growth, and delaying juveniles in reaching sexual maturity. The combined impacts on individuals help explain why the species is in decline.

"For North Atlantic right whales as individuals, and as a species, things are going terribly wrong. This comparison with their southern hemisphere relatives shows that most individual North Atlantic right whales are in much worse condition than they should be," said Dr Michael Moore from the Woods Hole Oceanographic Institution. "Sub-lethal entanglement trauma, along with changing food supplies is making them too skinny to reproduce well, and lethal entanglement and vessel trauma are killing them. To reverse these changes, we must: redirect vessels way from, and reduce their speed in, right whale habitat; retrieve crab and lobster traps without rope in the water column using available technologies; and minimize ocean noise from its many sources."

"Right whales are a sentinel species of ocean health. They are warning us, and their message is strong - the seas that used to be a safe haven for whales are now a threat. We must act now to protect their home, everybody´s home," said Dr Mariano Sironi from Instituto de Conservación de Ballenas and right whale researcher in Argentina.

Aarhus University

Related Whales Articles from Brightsurf:

Blue whales change their tune before migrating
While parsing through years of recorded blue whale songs looking for seasonal patterns, researchers were surprised to observe that during feeding season in the summer, whales sing mainly at night, but as they prepare to migrate to their breeding grounds for the winter, this pattern reverses and the whales sing during the day.

Shhhh, the whales are resting
A Danish-Australian team of researchers recommend new guidelines for noise levels from whale-watching boats after having carried out experiments with humpback whales.

Fishing less could be a win for both lobstermen and endangered whales
A new study by researchers at Woods Hole Oceanographic Institution (WHOI) found that New England's historic lobster fishery may turn a higher profit by operating with less gear in the water and a shorter season.

North Atlantic right whales are in much poorer condition than Southern right whales
New research by an international team of scientists reveals that endangered North Atlantic right whales are in much poorer body condition than their counterparts in the southern hemisphere.

Solar storms could scramble whales' navigational sense
When our sun belches out a hot stream of charged particles in Earth's general direction, it doesn't just mess up communications satellites.

A better pregnancy test for whales
To determine whale pregnancy, researchers have relied on visual cues or hormone tests of blubber collected via darts, but the results were often inconclusive.

Why whales are so big, but not bigger
Whales' large bodies help them consume their prey at high efficiencies, a more than decade-long study of around 300 tagged whales now shows, but their gigantism is limited by prey availability and foraging efficiency.

Whales stop being socialites when boats are about
The noise and presence of boats can harm humpback whales' ability to communicate and socialise, in some cases reducing their communication range by a factor of four.

Endangered whales react to environmental changes
Some 'canaries' are 50 feet long, weigh 70 tons, and are nowhere near a coal mine.

Stranded whales detected from space
A new technique for analysing satellite images may help scientists detect and count stranded whales from space.

Read More: Whales News and Whales Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to