In recent centuries, there has been a drastic drop in the number of cetaceans due to human activities. It is estimated that over 90 % of the population of large whales has disappeared. As for small cetaceans, their numbers are often not well known since they are difficult to study. At present, one species has already disappeared: the China dolphin (Lipotes vexillifer), also known as Baiji was declared extinct in 2006.

Thanks to protective measures, the population of some species seems to be stabilising or even increasing slightly. However, most species are critically endangered and some are in critical condition (for example, the blue whale ).

This situation is explained by:
- the low reproductive rate of cetaceans
- their migratory behaviour
- the large number of threats to these animals
- the inefficiency or lack of protective measures.

In order to protect cetaceans, it is therefore essential to act at both at the level of national jurisdictions and at the level of the high seas.