Fish have been around on our planet around 600 million years ago and still continue to exist today. In the world, there are 2 types of fish that live in water. There is the saltwater fish and the freshwater fish. Each 2 species cannot live in each others water or else they would die. The equivalent of a saltwater fish moving into freshwater would be like if a human were in space without a suit. Only a very small amout of species of fish can live in both salt and fresh water like the Bull Shark as an example.

Here are some freshwater fish in the pictures below with their names respectively. The Goliath Tigerfish is very ferocious, meaning it will try to feed on anything in the water it lives in. There are many species of fish like the Bull shark that can live in freshwater. Many of these cases appear in Africa, Australia and Florida, in the United States. Salmon have seen cases of disapearing for a year and reappearing for others. Catfish have been known in certain places to grow on huge size like the Wels Catfish in Spain. The Wels Catfish were introduced into spain more than 30 years ago in the River Ebro, Spain.

Freshwater fish and mammals

 Here are some saltwater fish in the oceans today. You may think that since there are so many species of fish that they are not being over-fished but you maybe wrong with many species. Sharks are on the verge of disapearing because some movies show them as being evil creatures. Sharks are actually nice if you dont make any sudden movement or wear specific items that shine. Many other species are dying as well because of pollution or global warming and the heating of the oceans. There are many species of fish that people think are evil like the Manta ray but in fact the Manta is a gentle giant that is misrepresented almost just like the shark. The Coelacanth on the other hand is one of the rarest fish in the world. It was thought that the fish became extinct with the dinosaurs 65 million years ago and was rediscovered off the coast of Africa in 1938. Its body has nearly never changed form over the whole time it existed fasinating scientists.

 Saltwater fish and mammals

Many fish species every year are being lost to extinction because of our pollution of the seas, lakes, rivers, etc and sometimes we find new ones that have never been seen by mankind before in the world's water supply. The ocean's life has always been fragille meaning that it was always easy to kill them in the water since they live in it. If you add mercury (a horrible heavy metal) to water, it will poison the fish and whatever eats it. The metal will slowly kill you and the symptoms usually are paresthesia, itching, burning, pain, skin discoloration, swelling, shedding of skin. Kids will have red cheeks, nose and lips, loss of hair, teeth and nails, transient rashes, hypotonia and increased sensitivity to light, kidney dysfunction, neuropsychiatric symptoms.

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