Second alpine lake field season is over

30 September marked the end of the long field season for the brook trout (Salvelinus fontinalis) eradication program conducted within the framework of the BIOAQUAE project. Intensive fish capture operations, commenced in the summer of 2013, were resumed in early June 2014 after the winter break.

In the course of the second field season, GPNP researchers spent the entire summer in the Park, living in the local structures, and obtained some encouraging results. In particular, they believe the eradication process in the two smaller lakes included in the project (Lago Nero and LakeDjouan) was completed earlier than expected (Fig.1). Several thousand fish were captured in Lake Dres, but they mostly consisted of young specimens (only 10 of the fish captured in 2014 were longer than 15 cm), which, consistently with the indications provided in the research project, could not be captured during the first year of the program on account of their extremely small size (Fig.2). In the Leynir lake, the largest and deepest, capture rates dropped to extremely low levels, even though a few hundred fish, comprised of young and adult specimens, were captured during the 2014 field season (Fig 2).

Biodiversity recovery has been progressing at an unexpected pace. In particular, some groups of macro invertebrates (aquatic insects such as caddis flies) are thriving in the lakes treated.

On the whole, the results of the second field season have been satisfactory and give reason to hope for the future of brook trout eradication activities.

 

The brook trout eradication operations are nearing completion at Lago Nero and Lake Djouan. During the winter, 32 fish were captured in Lake Djouan and none in Lago Nero. During the summer season, no fish were captured in Lake Djouan and only 4 fish, ca 9 cm long, were captured in Lago Nero. On the X-axis: number of days elapsed since the start of the eradication operations; on the Y-axis; number of fish captured per session.

 

The number of fish captured at the Dres Lake continued to be high in 2014: 1600 in the winter (of which only 2 were potential reproducers) and about 3500 in the summer months (of which less than 10 were potential reproducers). At the Leynir Lake 300 fish were captured in the winter and ca 600 in the summer (with a few dozen potential reproducers). In both lakes capture rates have dropped appreciably. On the X-axis: number of days elapsed since the start of the eradication process; on the Y-axis; number of fish captured per session.

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