Stone loach

Identification

The stone loach is a small, elongated bottom-dwelling fish of 8 to 15 cm (maximum 21 cm). The body is round in cross-section (not flattened like a goby) with a broad, flat head and six short barbels around the mouth — three pairs of sensory organs used to locate food on the bottom. The color is yellow-brown to grey-brown with irregular dark spots and marbling. The belly is lighter. The stone loach resembles the spined loach but lacks the characteristic spine below the eye and has fewer barbels.

Behavior & ecology

The stone loach is a nocturnal bottom fish that spends daylight hours hiding under stones, among gravel, or in bank vegetation. It feeds on small invertebrates: midge larvae, mayflies, caddisflies, and worms. The species has a strong preference for flowing, clear water with a gravel bottom — typical stream habitat. The stone loach requires well-oxygenated water and quickly disappears from polluted or stagnant conditions. Spawning occurs in spring, with eggs deposited on stones and gravel.

In the Netherlands

The stone loach is an indicator for healthy stream ecosystems. In the Netherlands, it occurs primarily in the streams of the eastern and southern provinces: the Veluwe, Achterhoek, Twente, Noord-Brabant, and Limburg. Stream restoration projects have improved its distribution over recent decades. The species is protected under Dutch nature conservation law and has no significance for sport fishing. The presence of stone loach is a positive signal for ecological stream quality — where stone loach live, the water is clean and the substrate natural.