Life on the earth began in the ocean. However, much of the oceans remains to be fully explored and new species continue to be identified. Some species which were thought to be extinct for years have been rediscovered. The coelacanth was thought to have become extinct 30 million years ago. In the 1930s, an odd looking fish was caught by fishermen off the eastern coast of Africa. Research revealed that this was the coelacanth, showing how much the ocean can encompass and hide from us.

Freshwater

Pakistan has 198 freshwater fish (Pakistan Museum of Natural History PMNH data) including species introduced for sports fishing. The fish fauna is dominated by South Asian species although there are some West Asian elements also present. There are 29 endemic species (Biodiversity Action Plan, 1998). Nine species of snow trout or mountain barbels occur in the rivers of the northern mountains and are of ecological importance as they represent a group that is endemic to snow-fed rivers and lakes of the high Asian sub-region.

The diversity of fish is highest in the Indus River plains, Kirthar range and the Himalayan foothills while it is lowest in the montane zone and the arid parts of northwest Balochistan. The river systems of northeast Balochistan have the highest levels of endemism. A variety of non-indigenous fish have also been introduced in hill streams for the purpose of sport fishing.

Marine

More than a 1000 species reportedly inhabit Pakistan's coastal waters. However, there is no analysis of their population and distribution range. The fish fauna can be divided into two groups, the cartilaginous and bony fishes. Cartilaginous fish include sharks, skates and rays and their skeleton is made of cartilage. Bony fish have hard bony skeletons.