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Conservation of Salmo marmoratus and Rutilus pigus.. (Salmo Ticino)
Conservation of Salmo marmoratus and Rutilus pigus in the River Ticino
(Salmo Ticino)
Date du début: 1 oct. 2001,
Date de fin: 30 sept. 2004
PROJET
TERMINÉ
Background
The stretch of the River Ticino which runs between Porto della Torre and the confluence with the River Po consists of four proposed Sites of Community Interest (pSCI) and contains two fish species of Community interest, the marble trout (Salmo marmoratus) and the Pigo roach (Rutilus pigus).
The Ticino is one of the rare cases where the two main fish families found in the river - Salmonidae and Ciprinidae - can be found together throughout the entire river. This is because it is a river of the high plains originating from a deep lake of glacial origin.
A recent survey on the environmental quality of the water, carried out precisely in the stretch concerned by this project, revealed the current state of decline in the numbers of both species. The presence of competitive, non-native fish and genetic pollution due to hybridisation with non-indigenous species, constitute the two major threats to the marble trout and the Pigo roach. Also, weirs have stemmed the continuous flow of the river and geographically isolated the fish, preventing their access to the spawning grounds and growth areas.
Objectives
This project aimed to protect the populations of Salmo marmoratus and Rutilus pigus in the River Ticino in Lombardia. The park management, which is the beneficiary of LIFE financing, planned to carry out various actions to achieve this aim:
1. Investigation on the biology of the Rutilus pigus with special emphasis on its reproductive ecology; characterization of the Ticino population by genetic analysis of DNA; observation of Salmo marmoratus and Rutilus pigus growth processes on specimens tagged before release into the river.
2. Limitation by electro fishing and underwater fishing of the non-native sheatfish (Silurus glanis), which, in addition to being a voracious predator, competes for food resources and shelter.
3. Creation of a fish farm to produce young of both target species to repopulate the river.
4. Acquisition of the fishing rights for the more important breeding areas in order to guarantee the correct management of the species
5. Planning of fish passes on two weirs, which represent a barrier for the movement of the fishes along the river.
Finally, the project foresaw monitoring of the effectiveness of the actions and awareness-raising activities and initiatives to present and publicise the results of the project to a wide audience.
Results
This project significantly increased knowledge and understanding of the target Salmo marmoratus and Rutilus pigus species. It enabled management plans to be drafted and concrete plans to be made for the construction of essential fish ladders.
The project partners conducted detailed genetic and morphological analysis of the target species on both live and dead specimens collected from fishermen or found in low waters. The analysis found that it was only possible to distinguish the marble trout (Salmo marmoratus) and brown trout (Salmo trutta fario) species from observable characteristics - phenotype.
Analysis of 25 specimens of roach, found that the local Pigo population was small and had low genetic variability, with the other species representing its main threat. Apart from predators at breeding sites, the other main threats are human. Existing restrictions allowing fishing of specimens over 18cm were found to be inadequate to protect breeding of the Pigo, since it only breeds once 5 years old and 43 cm in length. Fast variation in water levels from artificial management is another key threat, particularly since the sole breeding area is situated just downstream of the Porto della Torre dam .
A study on 1025 Silurus glanis was successfully completed, assessing their size, weight, stomach contents, age and gonadic development. It emerged that the fish are already 50 cm long when only two years old and that their diet is 51% fish. The project concluded that the non-native sheatfish population is increasing and constitutes a major threat to the target species.
Using these findings the project elaborated draft management strategies for the species in the Ticino river, suggesting appropriate modifications to fishing regulations. It also conducted a detailed feasibility study for the construction of two fish ladders to bypass barriers on the River Ticino. This led to detailed proposals for ladders taking advantage of water outflow from the technical installations to ensure a constant passageway and consecutive sinks to exceed a 6m drop.
The project successfully engaged the two private companies responsible for the barriers to be bypassed - the Porto della Torre and Panperduto weirs. After a first official public meeting supporting the projectâs plans, they met with the Lombardy Region and defined concrete steps for their implementation. This should lead to the successful re-establishment of the ecological continuity of the River Ticino with the Adriatic Sea.
The project realised a successful artificial reproduction programme for the species and restocked the natural populations with 20 300 trout and 3 million Rutilus pigus. It also captured 1 000 of the allochthonous fish predator Silurus glanis and bought the fishing rights of an important breeding area to prohibit fishing there.
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