Background
The apron (Zingel asper) is a small, nocturnal bottom-dwelling fish listed in Annex II of the Habitats Directive. It only occurs in the Rhône river basin. It is about 15 to 20 cm in size and thrives in clear, oxygen-rich waters with clean gravel bottoms. The apron's behaviour is sedentary and territorial. At daytime, it remains hidden among r ...