Brown trout eradication program progress report

In the Gran Paradiso National Park, the Ghiglieri fish hatchery has begun raising marble trout. The hatchery belongs to the category of “Valley floor fish hatchery,” a definition which links the fish rearing activities carried out at the facility to the valley and the river basin of which the structure is part. The Ghiglieri hatchery is comprised of two sections: an inner part dedicated to eggs hatching and fish growth, and an outer part where marble trout individuals intended for breeding are hosted and raised. 

The hatchery also meets didactic purposes, addressing conservation issues and defining measures for the improvement of aquatic habitats in general. The hatchery receives water directly from the water supply system overflow outlets, a solution that ensures virtually pure water and provides for a sustainable use of water resources. The water leaving the facility is discharged into the Piantonetto Torrent after feeding a small pond used for teaching purposes and designed to encourage the presence of amphibians.

The artificial breeding of a fish species of conservation concern often works as an effective protection measure, since the number of individuals that can be raised is appreciable; for the marble trout, production is said to range from 1,500 to 2,500 eggs per kg of weight.

The extremely small marble trout larvae, about 1.5 cm long at this point, are fed with Artemia salina, an aquatic crustacean whose size is compatible with the mouth of the juvenile trout. These zooplankton organisms will also be bred at the Ghiglieri hatchery in ad hoc hatching structures: Artemia salina is a species originating from salt water bodies, and its tiny eggs require continuous hydration and the proper temperature to hatch. Once separated from the shells, the crustaceans are fed to the growing trout.

During the 2015 summer season, within the framework of the initiatives in favour of the marble trout, a total of 1291 brown trouts were removed, and namely:

- from the Piantonetto torrent: 870 trouts in the course of 3 removal sessions

- from the Valsoera torrent: 421 trouts in the course of 3 removal sessions 

Samples were taken from some of them for the analysis of oxidative stress, an issue which is being investigated within the framework of a doctorate program.