Stato di avanzamento a novembre 2015

Il periodo autunnale segna l’inizio delle attività riproduttive della Trota marmorata nei fiumi della

fascia pedemontana piemontese e la situazione idrologica (regime di magra) del Torrente Orco,

stabile da circa un mese all’inizio di Novembre, ha consentito l’organizzazione di due giornate (3-

6/11) esplorative alla ricerca di individui riproduttori da spremere in loco o da trasportare mediante

appositi contenitori ossigenati presso la vasca esterna adibita alla stabulazione dei riproduttori

dell’incubatoio di Ghiglieri, Locana (TO) al fine di consentire la maturazione delle gonadi e la

spremitura presso la struttura.

Precedentemente la vasca esterna in cemento è stata naturalizzata al fine di minimizzare

l’inevitabile stress al quale sono sottoposti i riproduttori (soprattutto se selvatici) quando vengono

traslocati in un altro ambiente.

Per questa ragione il pavimento della vasca è stato coperto con un consistente strato di ghiaia

proprio per evitare ai pesci temporaneamente stabulati abrasioni da contatto con il cemento della

vasca. Zone di rifugio sono state create mediante l’utilizzo di tubi di plexiglas e si è provveduto alla

copertura dell’intera vasca per evitare ai riproduttori l’esposizione diretta alla luce.

Il giorno 3 e 6 Novembre si sono quindi svolte le sessioni di pesca elettrica che hanno impegnato il

Personale di Sorveglianza del PNGP, la Città Metropolitana di Torino e l’Associazione Lenzatori di

Castellamonte (TO).

 

 

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.

Progress report of the conservation action for marble trout

 

Work in progress and work completed as at 15/03/2015

• Intervention design and population breeding, introduction and monitoring plans. A technical document was drawn up according to schedule, to serve as the reference action plan;

• Construction drawings for the incubator have been issued and the relative contract has been awarded. Work is underway and the structure will be ready by the end of March;

• Eradication of the brown trout. 8 days of intervention have been completed since autumn  2014, resulting in the removal of 645 specimens (460 in the Campiglia torrent and 91 in Piantonetto1). The fish captured were transferred downstream of (natural or artificial) barriers so as to prevent the subsequent re-colonisation of the areas where the marble trout will be introduced.

 

Progress status of high-altitude aquatic habitat quality improvement actions (Actions C.4 and C.5)

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