A new scientific study by the University of Zurich in Switzerland shows that in the case of the sperm whale, they were around four metres shorter on average by the 1980s than they had been at the start of the century. It would suggest that the warning signs of what would happen to whales stocks were detectable up to 40 years before they collapsed.
A similar pattern has also been discovered in fish stocks that have been heavily depleted, indicating that recording the size of a species could be used as a method to monitor its population health and implement conservation efforts when warning signs appear.
Body size shifts and early warning signals precede the historic collapse of whale stocks
Christopher F. Clements, Julia L. Blanchard, Kirsty L. Nash, Mark A. Hindell, Arpat Ozgul
Nature Ecology & Evolution 1, Article number: 0188 (2017)