Study reveals effect of krill availability on humpback whale pregnancy – ScienceDaily


New collaborative research led by scientists at the University of California, Santa Cruz, shows that reduced krill supplies lead to fewer pregnancies in humpback whales — a finding that could have major implications for industrial krill fishing.

The study, published January 15 in the The biology of global changeis based on eight years of data on humpback whale pregnancies (2013 to 2020) in waters along the West Antarctic Peninsula, where krill fishing is concentrated.

The availability of krill in the year prior to a humpback pregnancy is critical because females need to increase their energy stores to support the next pregnancy. In 2017, after a year in which krill was plentiful, 86% of the female humpbacks sampled were pregnant. But in 2020, after a year in which krill were less abundant, only 29% of female humpbacks were pregnant.

The study demonstrates for the first time the relationship between population growth and krill availability in Antarctic whales, said lead author Logan Palin, a postdoctoral researcher in the Department of Oceanography at UC Santa Cruz.

“This is important because until now, krill was thought to be an unlimited food source for Antarctic whales,” said Palin, who received his Ph.D. in ecology and evolutionary biology at UCLA while working on this study. “Continued warming and increased fishing along the Western Antarctic Peninsula, which continues to reduce krill stocks, is likely to affect numbers of humpback whales and other predators in the area.”

“This information is critical as we can now be proactive in managing how, when and how much krill is taken from the Antarctic Peninsula,” he added. “In years of bad krill recruitment, we shouldn’t be compounding that by removing krill from critical foraging areas for baleen whales.”

Co-author Ari Friedlander, a professor of oceanography at the University of California, Santa Cruz, said the West Antarctic Peninsula is experiencing some of the fastest climate warming of any region on the planet. Winter air temperatures have risen dramatically since the 1950s, and the annual extent of sea ice is, on average, 80 days shorter than it was four decades ago.

“Krill supplies vary depending on the amount of sea ice because young krill feed on the algae that grows on the sea ice and also depend on the ice for shelter,” Friedlander said. “In years when there is less sea ice in the winter, fewer young krill survive into the following year. The effects of climate change and likely krill fisheries are contributing to lower reproductive rates for humpback whales in years when there is less krill available to whales.” .”

“This research shows that very precautionary management measures are necessary to protect all marine life in Antarctica that depends on krill for survival, including bluefin, humpback whales, minke, and southern right whales, as well as other krill predators such as penguins, seabirds, seals, and fish.

“Krill is not an inexhaustible resource, and there is increasing overlap between industrial krill hunting and feeding whales at the same time,” Johnson said. “Humpback whales feed in the Antarctic for a few months a year to feed their annual active migration needs that stretch thousands of kilometres. We need to tread carefully and protect this unique part of the world, which will benefit whales across their entire range.”

Pallin and Friedlaender collaborated on this research with co-authors from several national and international universities, NGOs, non-profit organizations, and government agencies. This work was supported in part by the National Science Foundation, the National Geographic Society, and the Marine Mammal Commission.



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