Newsletter 17 of December 10, 2017

Stories of Sturgeons

In this newsletter, we wanted to tell you two "stories" about the Adriatic sturgeon that took place over the last few months in the Conflupo project area.

With the construction in the 1960s of a damn serving the Isola Serafini hydroelectric power plant, the River Po was interrupted at about 300 km from its delta, thus blocking the migration of those species that, like the sturgeons, swim upstream from the sea to spawn.

The web and the press have reported on Adriatic sturgeon specimens, also of considerable size, being fished in the stretch of the river downstream of the Isola Serafini dam.

However, we consider it important to point out the accidental capture, in September, of an adult specimen of Adriatic sturgeon (photographed below) near the entrance to the passageway for fish, downstream of the Isola Serafini dam.

 Storione cobice catturato accidentalmente in prossimità dell’area di imbocco del passaggio per pesci di Isola Serafini
Adriatic sturgeon caught accidentally near the entrance to the passageway for fish at Isola Serafini

The specimen was photographed and then released back into the river. Unfortunately, in this case it was not possible to verify whether the fish had a subcutaneous microchip, and therefore whether it was a wild sturgeon swimming upstream from the sea or a specimen released by one of the programs supporting this endangered species.

Although it has not yet been possible to document the passage of Adriatic sturgeon specimens in the facility since the fish ladder came into operation on the 17th of February, the fact of finding adult specimens upstream and downstream of the Isola Serafini dam in the vicinity of the entrance to the facilities bodes well; indeed, the sturgeons may take some time to learn of the presence of this new passageway and use it.

On the 23rd of November, during a monitoring expedition falling under the scope of the Conflupo project, partnered by the Parco Lombardo del Ticino natural park, the park rangers Davide Cameroni and Massimo Balocco managed to track down the remains of an adult specimen of Adriatic sturgeon of about 180 cm in a small oxbow lake off the Ticino River, near Motta Visconti.

Resti di Storione cobice rinvenuti nel Parco Lombardo del Ticino
Remains of a specimen of Adriatic sturgeon found in the Parco Lombardo del Ticino natural park

The specimen had reached an advanced state of decomposition, but the back area still retained a certain amount of muscles, where a microchip was detected by means of a special reader.

The code thus obtained was compared - by the Park's researchers Mauro Bardazzi and Andrea Casoni - with those in the Conflupo project's database, which collects data on the Adriatic sturgeon specimens released over the years under the various conservation projects involving this species.

 Codice identificativo del microchip sottocutaneo dello storione cobice rinvenuto nel Parco Lombardo del Ticino
ID of the subcutaneous microchip found on the Adriatic sturgeon tracked down in the Parco Lombardo del Ticino natural park

The ID detected by the reader relates to a specimen released as part of the Life Natura project “Conservation of Acipenser naccarii in the Ticino River and in the middle course of the River Po” carried out by the Parco Ticino and ended in 2007.

At the time of release from the Lanca Ayala mooring area on the 27th of April 2005, this female specimen measured 110 cm and weighed 8 kg. The fish had also been marked with an ultrasound transmitter that allowed the project operators to follow its movements for a while. In particular, this specimen had been continuously monitored since the day of its release until the 9th of August 2006, after which it had been lost track of.

Its finding has provided a considerable amount of important information.

First of all, it indicates that the breeding system used for sturgeons - breeding in semi-natural conditions in the renaturized basins of Cassolnovo with a gravel bed - allows the specimens to adapt to the natural conditions that they then encounter in the river once released.

Giovane di storione cobice selvatico ritrovato in Ticino

It is also likely that this specimen had reproduced in recent years, as it had definitely reached sexual maturity. In this regard, it is worth noting that in 2009, 2013, 2014 and 2015, it was possible to document the reproduction in nature of the land-locked population of Adriatic sturgeon present in the Ticino, in an area of the river located between Pavia and the municipality of Travaccò Siccomario, about 6 km from the confluence with the River Po.

Considering that more than 12 years have elapsed since the intraperitoneal implantation of the emitter, it is clear that the model chosen - with an operative duration of about 3 years - and the method of insertion were successful and did not affected the specimen's chances of survival.

These factors, therefore, would seem to confirm the validity for the breeding, releasing and monitoring programs devised to support the Adriatic sturgeon in nature, when adequately managed.

 

All texts and images may be used, citing the source, the author, the Life Project naturaLife11NAT/IT/188 “Restoring connectivity in the Po river basin, opening a migratory route for Acipenser naccarii* and 10 fish species in Annex II”, and the support of the European Union.

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