Bystřina, Nature reserve in Hranice, Czech Republic.

Bystřina is a nature reserve stretching over 4 km along the stream of the same name and the German border northeast of Hranice u Aše, covering 49 ha in the northernmost part of the Aš salient. It protects oligotrophic flowing water with a population of the freshwater pearl mussel (Margaritifera margaritifera). Since 1 July 2020 it has been replaced by the Bystřina – Lužní potok national nature monument.

Bystřina was declared a nature reserve in 1992, covering over 4 km along the stream of the same name and the German border northeast of Hranice u Aše. On 1 July 2020 the reserve was abolished and replaced by the Bystřina – Lužní potok national nature monument. Since 22 December 2004 the wider site has formed part of the Natura 2000 locality of the same name, 1129.6 ha in extent.

The reserve's name comes from the Bystřina stream, which forms the border with Germany along its more than 4 km length. The protected area lies in the Aš salient near the Bavarian-Czech-Saxon tripoint, where the Bystřina reserve and the Lužní potok national nature monument are linked within the Natura 2000 site.

The protected area lies in the northernmost tip of the Aš salient, in the cadastral territories of Hranice u Aše and Trojmezí, along the border with Germany. The stream forms the state border here, so marked trails stay on the Czech bank; the terrain is wet and uneven. A bypass of road II/217 Hranice – Ebmath runs near the easternmost tip.

The area holds one of the last populations of freshwater pearl mussels in Central Europe. This rare species needs clean, cold water and serves as a reliable indicator of ecosystem health.