The primary reason was loss of habitat: drainage of wetlands and siltation resulted in higher concentrations of pollutants, causing (eutrophication) across Lake Tota.
The average water temperature of 13°C allowed for the introduction of rainbow trout (Onchorynchus mykiss) which created a valuable wild fishery (a mounted specimen in Restaurante Lucho, Aquitania, reportedly early in the 90's, weighed 7 kg) and cage culture aquaculture, but predation on native fish species as led to the now accepted extinction of the pez graso or grease fish (Rhizosomichthys totae) believed native to only this lake.
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