The marble trout is a large-sized salmonid found both in alpine lakes and in subalpine lakes on valley floors and on the plains.
At European level, this species is diminishing, mostly because of the ongoing destruction and fragmentation of its habitats, and due to crossbreeding with another salmonid species, the brown trout (Salmo trutta fario). For these reasons, the marble trout has been included in the red list of threatened species compiled by the International Union for the Conservation of Nature (IUCN) and is mentioned in Annex II to the Habitats Directive.
Based on this status, conservation initiatives for this species have a high priority rating.
In the Gran Paradiso National Park, the marble trout has still been found in recent times in few watercourses, such as the Piantonetto, Campiglia and Forzo streams, which provide an ideal habitat for this species.
On the other hand, large brown trout populations constitute a threat to the survival of the marble trout, in that the two species may crossbreed and produce fertile offspring.
Over time, the hybridisation of a species leads to a progressive dilution of its genetic makeup, eventually culminating in the loss of its unique characteristics. This is why it is important to limit hybridisation between these two salmonids.
The LIFE+ BIOAQUAE project includes two initiatives in support of the marble trout:
- Construction of a fish incubator for breeding pure marble trouts to be introduced into the Piantonetto, Forzo and Campiglia streams, so as to improve the size of the populations in these watercourses. The incubator will be set up in the Park, in a pre-existing building in Vallone Piantonetto. Training on incubator management will be provided to volunteers and Park personnel so as to ensure that the project is carried on until sufficiently large populations are formed. The program will get underway in the fall of 2014;
- Capture and transfer of reproductive brown trout adults: during the pre-reproductive season, expert ichthyologists, together with the operators in training, will catch adult brown trout specimens in the Campiglia and Forzo streams. The specimens will be moved to suitable environments, where the marble trout is not already present. This initiative will make it possible to dilute the presence of the brown trout in favour of the marble trout. The method used to catch the fish – electrical stunning – is widely used and does not cause the death of the animals.