*3.2. Biertan River*

Based on the field inventory, on the Biertan River, only three refuges were identified with a depth of 100–120 cm (i.e., Figure 5); the other non-refuge sectors (i.e., Figure 6) had different depths between 5 and 100 cm.

**Figure 5.** Biertan River refuge habitat.

**Figure 6.** Biertan River non-refuge sector.

In the Biertan River, 11 fish species have permanent populations: *Squalius cephalus* (Linnaeus 1758) (total caught individuals 21), *Alburnus alburnus* (Linnaeus 1758) (7), *Alburnoides bipunctatus* (Bloch 1782) (20), *Chondrostoma nasus* (Linnaeus 1758) (8), *Gobio gobio* (Linnaeus 1758) (19), *Barbus barbus* (Linnaeus 1758) (9), *Barbus meridionalis* Risso 1827 (23), *Carassius gibelio* (Bloch 1782) (5), *Barbatula barbatula* (Linnaeus 1758) (11), *Sabanejewia romanica* (Băcescu 1943) (31), and *Sabanejewia aurata* (De Filippi 1863) (14).

The ratio between the number of fish between the refuge habitats of maximum 10 m in length and the adjacent/downstream non-refuge sectors of 500 m length was six to one.

The identified refuge habitats are present only in the lower one-fifth sector of the river (Scheme 2), revealing the drought-related risks for the biodiversity in four-fifths of the river sectors.

Given the shallow depth of the Biertan River and the vulnerabilities that occur for fish during periods of drought, it is proposed to build artificial refuges for fish from about 500 to 500 m. In total, it would be necessary to build a number of 34 such refuges with a depth of at least one meter (Scheme 2).

#### *3.3. Valchid River*

Based on the field inventory, on the Valchid River, 27 refuge habitats were identified with a depth of 100–160 cm (i.e., Figure 7); the other non-refuge sectors (i.e., Figure 8) had different depths between 5 and 100 cm.

In the Valchid River, 10 fish species have permanent populations: *Squalius cephalus* (Linnaeus 1758) (total caught individuals 28), *Alburnus alburnus* (Linnaeus 1758) (6), *Alburnoides bipunctatus* (Bloch 1782) (22), *Chondrostoma nasus* (Linnaeus 1758) (3), *Gobio gobio* (Linnaeus 1758) (26), *Barbus barbus* (Linnaeus 1758) (3), *Barbus meridionalis* Risso 1827 (30), *Barbatula barbatula* (Linnaeus 1758) (19), *Sabanejewia romanica* (Băcescu 1943) (20), and *Sabanejewia aurata* (De Filippi 1863) (19).

The ratio between the number of fish and the refuge habitats of maximum 10 m in length and the adjacent/downstream non-refuge sectors of 500 m length was seven to one.

Refuge habitats are present in four-fifths of the lower and middle parts of the river, and should be extended to the upper part and multiplied so that at every 500 m there is at least one.

Given the general depth of the Valchid River and the vulnerabilities that occur for fish during periods of drought, the building of artificial refuges for fish from about 500 to 500 m is proposed. In total, it would be necessary to build a number of 17 such refuges with a depth of at least one meter (Scheme 3).

**Figure 7.** Valchid River refuge habitat.

**Figure 8.** Valchid River non-refuge sector.
