What are the dangers to cetaceans?

One of the greatest dangers to cetaceans is something referred to as “by-catch,” which is when cetaceans are caught in nets during fishing operations.  Each year, thousands of small cetaceans are caught in fishing nets around the world and many species are endangered due to this.  The harbor porpoise is particularly affected.  Many cetaceans are also killed in collisions with ships.  Another major threat to cetaceans is commercial whaling operations.  Whaling has been practiced for more than 3000 years and although whaling in prehistoric times and pre-modern times did not have a significant impact on whale populations, modern day resources has severely depleted whale populations all over the world.  Whales are generally killed for their meat and oil.