Winter is definitely not the favourite time for fishermen on the Mura River. Similar to hibernation in terrestrial animals, the fish stop feeding and they seek shelter in deep, slow flowing pools to conserve energy, so the fishermen’s catch is insignificant. However, following decades of overfishing, the Danube salmon (Hucho hucho) population in the Mura River is recovering due to extensive conservation restocking efforts in Austria. The last couple of years, the Mura River has thus seen more and more fishermen out and about during winter. Danube salmon is a trophy species, which spawns in March and April and their conservation period in Slovenia lasts from September until February.

The target species in the MEASURES project - sterlet (Acipenser ruthenus), nase (Chondrostoma nasus), barbel (Barbus barbus), cactus roach (Rutilus virgo) and vimba bream (Vimba vimba) are no exception, so a sampling campaign was launched to confirm their presence at previously identified potential wintering habitats. A number of 25 m long and 1,5 m high fixed trammel nets were set at selected locations in the afternoon and raised the next morning. The catch expectedly varied and besides fish, it often included large amounts of leaves and stones.

The nets were set at 14 different locations, the presence of fish was confirmed for 8 of them and the MEASURES target species were confirmed only at 2 locations. In total, 40 fish of different species were caught, such as european chub (Squalius cephalus), nase, cactus roach, vimba bream, northern pike (Esox lucius), common zingel (Zingel zingel), freshwater bream (Abramis brama), common carp (Cyprinus carpio) and white bream (Blicca bjoerkna).

This was the first of the tested methods with which the presence of the target migratory fish species at wintering habitats was confirmed in Slovenia. Compared to the results of the previous surveys, this was the most successful fish sampling method, with the highest number and diversity of the caught fish/species.

Measured and weighted cactus roach from the Mura River (Cokan, 2020)                       Weighting of predatory fish northern pike (Cokan, 2020)

When the water temperature in March and April rise to 10 °C, we plan to use the same approach to sample fish on their migration to spawning and feeding habitats in the Mura and Sava Rivers. So, keep an eye out for our next field brief in the Interreg News in which we will update you on the success of our migration sampling and the species caught. 

Members of Institute REVIVO and VUKA team pulling up the fish net in the Mura river (Cokan, 2020)