Are main fishing areas of the ocean in cold water or warmer water?

Question

Are there any reasons why?

Answer 1

In general the fish which are the most healthy for us to eat live and thrive in cold waters. They can do so naturally when given a chance.

However, there are also a lot of good fish to be had in warmer waters too, due to the greater rate of growth at these conditions. Fish-farming can be done in this case, so we can grow and enjoy fish grown in artifical condition such as in fish-ponds and in sea enclosures.

Answer 2

The most productive fishing areas are where there are upwellings of nutrient-rich water.

Answer 3

Cold water:

Cold water contains more dissolved oxygen, and hence supports a more abundant phytoplankton population, on which small marine organisms thrive, and so on up the food chain.

That is why whales are found in sub-polar waters; there is an abundant source of krill on which they feed.

Incidentally, this is why tropical waters tend to be clear - there are less microscpoic lifeforms in tropical waters.