Whaling:

Whaling is the hunting of whales mainly for meat and oil.

Industrial Whaling emerged with organized fleets in the 17th century. Soon catches far exceeded the sustainable limit of the whale stocks. In 1986 the International Whaling Commition (IWC) banned commercial Whaling. Japan, Norway and some other nations still hunt whales. Japan and Norway annually catch around 730 and 590 whales respectively.

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Migration of whales:

Many whale species migrate each year from the warm tropical waters to the cold waters of either south or north polar regions. Mothers give birth to their young in the warm shallow waters of the tropics. But for her, there is nothing to eat there. While the calf still drinks its mother's milk, they start heading for the cold nutrient rich waters of the polar regions so that the mother can feed. Nutrients are washed off the continents with the rivers and are eaten by microornaisms near the coasts. When these organisms die, they sink to the bottom of the ocean where the nutrients are released. There are only a few ways the nutrients can come up to the surface again. One of them is the mixing of the water colomn in the cold period. In the tropics it doesn't get cold so the nutrients are trapped on the bottom of the ocean.

In the polar regions however, there is upwelling and in spring with a lot of light the phytoplanktons and hence the zooplanktons bloom, so the whales have enough to eat (an adult whale can eat up to 3.5 metric tons of krill per pay).