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False killer whales swimming in the ocean
(Image courtesy: Trent O. Ellis/Cascadia Research)

To help in the future monitoring efforts of an endangered population of resident false killer whales in Hawaiian waters, where only 167 individuals are estimated to remain, researchers at the University of Hawaiʻi at Mānoa Health and Stranding Lab examined blubber samples of a false killer whale that died as bycatch in a fishery interaction, and published the findings in Frontiers.

Blubber is a multifunctional and complex tissue essential to the survival of dolphins and whales, and an indicator of individual condition. Blubber samples of this whale are now informing the health of the living population.

“Preservation of our oceans and especially the marine mammals who inhabit it is of critical importance to the people of Hawaiʻi,” said Jana Phipps, a PhD student in nutrition in the College of Tropical Agriculture and Human Resources who works at the UH Health and Stranding Lab. “By expanding knowledge of how to best assess the impacts of potential threats to endangered false killer whales, we can better manage local populations.”

Marine mammals are culturally significant to the people of Hawaiʻi and are recognized sentinels of ocean health.

An understanding of how to best assess threats such as declining prey resources faced by endangered false killer whales are critical for effective conservation and management.

Blubber to assess overall body condition

Whales and dolphins have a thick layer of blubber under the skin, and changes in this layer are an indicator of the overall body condition and health of the animal. Blubber consists of fat cells and connective tissue and the size of the fat cells and relative amount of connective tissue varies depending on the amount of fat stored in the body.

The endangered population of false killer whales may be faced with declining prey resources, and this research provides valuable baseline data on blubber properties according to blubber depth and body location. This is important for assessing the nutritional status of free-swimming live false killer whales.

“A greater understanding of how blubber cell size and connective tissue ratio vary in false killer whales is needed,” said Kristi West, director of the UH Health and Stranding lab. “This research will strengthen the interpretation of blubber biopsy data from live whales in order to better assess individual and population health.”

Measurements included the thickness of the blubber layer across body girths and planes and the accompanying size of fat cells and relative amount of connective tissue at each sampling location. Researchers used statistical analysis to describe differences in the blubber across the body and according to blubber layer depth. They compared these findings to blubber properties in the body region where small blubber biopsies are routinely collected by researchers from free-swimming whales.

Funding for this research was from NOAA Section 6 Endangered Species Recovery Grants, the NOAA John H. Prescott Marine Mammal Assistance Grant Program and Office of Naval Research Defense University Research Instrumentation Program.

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