In many cases, the presence of non-native fish in high-altitude alpine lakes represents an ecological exclusion factor for many native taxa and also affects the energy and material flow from water to land. Thanks to the Salvelinus fontinalis eradication process, a quick recovery of the natural functioning of treated ecosystems is expected, which includes the restoration of the natural wildlife, ecosystem structure and energy flow between coastal and aquatic environments.

The effectiveness of the eradication will be regularly monitored from the beginning of the project on all lakes subjected to Conservation Actions 1 and 2 (Djouan, Nero, Dres and Laynir lakes). The objective is to describe the recovery of the aquatic ecosystem during and at the end of the eradication process, i.e. from 2013 to 2015. Each of the operations listed below will be repeated twice a year in the early and mid-summer seasons to monitor both the initial and advanced development of the native communities. Biological and chemical samples will be collected during the summer months, to be analysed in winter. Monitoring actions include:

1. Monitoring the density of the fish population

2. Monitoring via bioindicators: monitoring data will be compared to those collected between 2006 and 2011 making it possible to assess the resilience of treated ecosystems.

3. The effect of fish eradication on the chemico-physical characteristics and trophism of lakes will be assessed collecting water samples integrated on the water column in the deepest point of each lake. The limnological characterisation of lakes will also be integrated with temperature and dissolved oxygen profiles using an immersion multi-parameter probe.

Interventions to safeguard marble trout will be monitored through the marking/re-catching of the trout released in the three water courses being repopulated.

Marking of the 5,000 troutlet will be carried out on those that were bred until summer and are at least 6 cm long. Plantings will be made with a density of 1 fish every 10m2 (low-water area). The objective of marking/re-catching activities is to assess the colonisation and survival percentage of marble trout planted.

The assessment will be carried out during the electrofishing days which are part of the safeguarding activities that include the catching and transfer of alien species. In addition, all fish will be observed and the marked ones will be caught, measured and released again. In addition to measuring the survival between 0+ and 1+, after the first monitoring, subsequent monitorings will also enable the assessment of the population of marble trout, by defining the quantity of trout transferred with respect to those naturally present. Besides, as the population is structured into different age classes, it will also be possible to assess it according to the different classes. As for the monitoring of the hybrids, which will occur on a phenotypic basis, results are expected to occur from the third year after the planting, as we expect that the repeated removal of alien trout and planting of marble trout will have affected the presence of the various alien/hybrid/marble types. Currently there is no quantitative data available concerning the composition of the fish population, but only semi-quantitative. A percentage ratio of 90/5/5 respectively of alien/hybrid/marble trout has been hypothesised. After the first three years of planting/removal activities, we expect a ratio of 20/40/40, which will progressively reach a 10/30/60 ratio at the end of the project and a 10/20/70 ratio 6 years after the first planting.

Starting from year four (fish 3+), acclimatised marble trout will have reached sexual maturity, so it will also be possible to assess natural reproduction by counting low-water redds in sample areas. Monitoring will continue for 5 years after the end of the project.

Phytopurification interventions to improve the quality of the water in lake Nivolet Superiore and Telessio will be examined through campaigns to measure the main chemico-physical and bacteriological parameters to assess the purification efficiency of the system downstream from the Pontese Refuge.

In particular, during year three and four, fortnightly monitoring campaigns are hypothesised for the three maximum-load summer months in two sampling points – at the entrance and at the exit of the purification system. 24 checks are planned in total.

The parameters to measure are: BOD5, COD, Nitrates, Nitrites, Ammonia, total Phosphorous, Orthophosphate Phosphorous, pH, Specific electrical conductivity and Temperature. In addition, to assess the variation in the state of the lake, monthly campaigns using a multiparameter probe will be carried out during the months when the lake is accessible. The Dissolved oxygen, Temperature, Specific electrical conductivity and pH parameters will be measured every metre on the water column.

During the first monitoring campaign after thawing and at the end of the summer season, water samples will also be taken at the surface and near the deepest area so that Total Phosphorous, Orthophosphate Phosphorous, Nitrates, Nitrites, Ammonia and Chlorophyll-a concentrations can be measured. 4 campaigns over 2 years are hypothesised, which will continue in the 5 years after the project has ended.