Hunting is usually the first thing that comes to peoples’ minds when considering threats to marine mammals.  Most people know that for centuries, marine mammals were harvested for food, fur, and various other commercial goods.

Whaling began over 3,500 years ago, and it progressed with technology to eventually become a worldwide occupation before being greatly reduced by an international ban in 1982.  Almost all species of whale had been hunted at some point in their history, leading to serious population depletions for many species.  

Although whales were hunted for their meat, the most important item attained from the hunt was oil.  Baleen whale oil was used in margarine and other food products.  Sperm whale oil was used in special lubricants.   In the 20^th century, whaling also became an important source of livestock food and chemical products.

In 1946, the International Whaling Commission (IWC) was set up to manage the hunting of whales in the face of decreasing populations.  This organization was originally created to manage whales so they would always be available for hunting.  However, as it evolved this organization came experienced internal conflict when the concerns of its scientific community were pitted against commercial needs.  In 1982, a ban on all commercial whaling was passed by the IWC, with exceptions made only for native cultures such as the Inuit of Northern Canada.  This made whaling for most nations a thing of the past.  (Although today some countries such as Norway and Japan continue to insist on the resumption of commercial whaling.)

Since the discontinuation of hunting, most whale species have been making a comeback.  However, given the very long life spans of these animals and their exceedingly slow reproduction rates, most populations have yet to fully recover.

Seals have also been hunted by man since they were first discovered.  They were large enough to provide an abundance of food, small enough so no great risk was involved, and largely available due to their population size and existence near shore.

Seals supplied many products for human use.  Their meat provided food, their skin protection from the elements, and their blubber light and warmth by burning in lamps.  Many cultures, such as the Arctic Inuit and Canoe Indians of South America, developed cultures that depended upon these creatures for survival.

Seal hunting changed from a native practice to a commercial occupation in the early 18^th century.  Harp seals were the first to be taken in vast herds.  Eared seals, such as the Northern Fur Seal, then also suffered a drastic decrease in numbers due to this practice.  The Antarctic Fur seal was almost driven to extinction by commercial hunting.  Walruses also suffered due to hunting for their tusks, oils, and skins.  As with whales, since the discontinuation of most hunting, many populations (like that of the Antarctic Fur Seal) have made excellent recoveries.  However, some population have yet to fully rebound to their previous levels. 

Although there are now laws in specific nations (such as the US Marine Mammal Act) that protect seals, there are no treaties protecting them worldwide and they continue to be hunted for food and fur in some places.

Sea Otters were also extensively hunted in the past for their specialized coats.  In fact, they were so popular that their populations also almost went extinct in the early 20^th century.  Fortunately, however, in 1911 an international agreement was created that protected the sea otter from further commercial hunting.  Today this animal survives and there are efforts underway by humans to reestablish the sea otter into its entire former range.