Saltwater Fish in Freshwater Lakes
Natural Disasters Blocked Fish from Ocean Waters
Fish formerly found in saltwater were forced to adapt to their new habitat.
Earthquakes, floods and volcanoes changed the drainage pattern of former saltwater lakes and rivers so they evolved into freshwater. Many saltwater fish did not survive the change but some did adapt and continue to thrive along with their saltwater counterparts.
African Cichlids in the African Great Lakes
Although African Cichlids will live in most any kind of water, they do much better in salted water with a high PH and mineral content. African Cichlids are considered freshwater fish but they do best in semi-salted water, but not in oceans.
Lake Malawi, Lake Tanganyika, Lake Victoria and Lake Edwards were all inland seas about ten million years ago. These seas became landlocked due to the shifting in the earth’s crust which cut them off from the ocean. Ten million years is a short time by evolution standards but African Cichlids have already adapted to living with less salt in their water.
In another 10 million years, these lakes most likely will lose all traces of salt water and high PH and mineral content. As a result, most signs of African Cichlids living in salted water will disappear. These fish are adapting to the gradual reduction of salt in the Great Lakes of Africa.
Stingrays in the Amazon River
The source of the Amazon River is located in the Andes Mountains on the west side of South America. Although the Amazon drains into the Atlantic Ocean, it is very close to the Pacific Ocean. Around 10 to 20 million years ago, a major event caused the waters of the Pacific Ocean to rise and flow into the Amazon and its tributaries. During this event, Stingrays from the Pacific entered the Amazon. These species survived and adapted to freshwater.
Today, the freshwater Stingray is only found in the Amazon and its tributaries. Some of these grow to very large sizes. There is something interesting about the freshwater Stingray. When these fish breed, they go to the mouth of the Amazon to where the water is more salty.
Sardines and Sharks in LakeTaal
At one time, Taal Lake was an arm of Balayan Bay in the Philippines. In the late 1600s, Taal Volcano erupted and narrowed down the channel that connected Taal Lake to the ocean. The channel was renamed Pansipit River. Over time, the lake changed to freshwater.
Lake Taal is known for its venomous Black and White Sea Snake. This lake is the place where the world’s only freshwater sardine is found. Bull Sharks were also found in Lake Taal but were made extinct due to over-fishing.
Seals in Lake Baikal
Lake Baikal is located in a rift zone in Southern Siberia where the crust of the earth is pulling apart. It is the deepest lake in the world. Although there is no proof that Lake Baikal was closely connected to the ocean, it is the only place where a unique freshwater species of seal called the Nerpa is found. There are two other freshwater seals in the world but they are subspecies of the Ringed Seal.
Lake Baikal also has its unique species of freshwater salmonoid called the Omul and the Baikal Grayling. A species of sturgeon called the Baikal Sturgeon is only found in this lake.
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