Freshwater sharks in the Ukurikitucara lake
Danilo Anton

In the coastal and volcanic regions of America the lake landscapes abounded in the past. There were lakes in the Purépecha country of Michoacan, in the central region of Mexico where Otomi and Nahuas lived and there were lakes on the plateaus and volcanic valleys of the Maya country. There were also many lakes  in the lands of the Lencas and Guatusos of Central America, and even further south, in the coasts, mountains and plateaus of the South American continent.
These lakes were privileged places for human occupation. In addition to supplying fresh water to towns and cities, they contained very rich ecosystems with fish, birds, invertebrates and aquatic plants that could provide food for many people.
On the shores of the lakes, fishing villages were established which, in addition to fishing, took advantage of other resources of the lagoon environment, such as crustaceans, molluscs, batrachians, algae or plant fibers.

In Mesoamerica, more progress was made in the use of lacunar waters and productive agriculture was developed through floating orchards, which mexicans nahuatl called chinampas.
In the larger bodies of water, such as the lakes of the Anahuac valley on the Mexican plateau, Lake Titicaca on the Peruvian-Bolivian plateau, and Lake Cocibolca in Nicaragua the wide lake surfaces provided an adequate environment for navigation and trade between the coastal regions. In many ways these lakes represented prosperity and abundance and allowed the development of complex societies with dense population concentrations and high productivity.
European colonization produced profound changes in the relation of populations to the interior waters of the continent. After five centuries of foreign occupation of the lacunar coasts, the landscape is no longer the same.

Many lakes in America have suffered from human predation. Some have disappeared. Others have been reduced to a minimum expression. There are lakes that are contaminated and do not harbor animal life in their waters. And finally there are those that have been degraded, who have lost diversity, with species extinct or in the process of extinction.
The Great Lake of Nicaragua, called Cocibolca by the nahuas and Ukurikitucara by the guatusos and matagalpas was long home of sharks. It was a unique species of freshwater sharks. The scientists called him Carcharhinus nicaraguensis.
It is a species that is closely related to Torus Shark that abounds in tropical seas.
The studies made it possible to verify that the lake shark migrated along the San Juan River to the Caribbean, in the style of salmon, and then returned. This was ratified by means of some tagged specimens.
In ancient times the species was very abundant. While there were stories about their aggressiveness, attacks on people, the danger they could pose, in fact it was a fairly harmless fish.
In 2004 it was reported that in the waters of the San Juan River a massacre of the species was occurring as a consequence of the very high price that was paid for the fin of the animal in Japan and other countries of the East. The figure was $ 256 per pound (more than $ 500 a kilogram). Indiscriminate fishing is still going on and it is thought that the lake shark is about to die out.
Or maybe it's gone.
From: "Chronicles of Human Peripecie", D.Anton, Piriguazu Ediciones.