By the Cembra Valley the Avisio is one of the less anthropic basins - or even the only one - in the valley bottoms at lower altitudes in Trentino.
The river environment is characterized by a high nature quality thanks to its relative stability and the poor human presence. It is a shelter area of extraordinary value thanks to the many invertebrate species and an ideal place due to the presence of an animal population we can define as naturally structured.
Among the amphibians there are the mountain frog, the common water frog, the agile frog, the European tree frog, the yellow-bellied toad, the common toad, the fire salamander, the alpine newt, which in the Avisio valley bottom can find very significant areas for their reproduction. Among the reptilians (as far as the fauna living in water environments is concerned) there is an even presence in the valley bottom of both the dice snake and the grass snake.
Among birds it is worth mentioning the white-throated dipper, the mallard, the grey heron, the common sandpiper and the common kingfisher. Some of these species are endangered in Europe, therefore we can understand the value these local populations have from a natural point of view.
Among the mammals the Eurasian water shrew certainly is the most widespread.
The marble trout deserves a special mention: its importance derives from strictly natural scientific and ecological reasons, as well as from the implications connected with the amateur fishing.
It belongs to the Salmonidae family endemic to a geographically limited region, therefore it has a high natural value. It is a seriously threatened species, therefore it is very important to preserve the remaining populations such as those living in the Avisio area: in other parts of northern Italy many local governments have decided to set huge financial and human resources aside for the recovery and the restoration of the remaining populations.