Grass Carp

Identification

The grass carp is a large, elongated cyprinid with a broad, slightly flattened head. The body is olive-green to yellow-brown on the back, with silvery flanks and a white belly. Characteristic are the large, dark-edged scales with a notably regular pattern. The mouth is terminal and relatively small for such a large fish — adapted to grazing on aquatic plants. Grass carp average 80 cm in length, but specimens over a meter are not unusual. It is one of the largest freshwater fish in the Netherlands.

Behavior & ecology

The grass carp is the only true herbivore among large cyprinids. Adults eat up to a quarter of their body weight in aquatic plants daily (juveniles up to 100%) — reeds, pondweed, waterweed and duckweed are favorites. This voracious appetite makes the grass carp both popular and controversial: water managers use them to keep overgrown waters clear, but too many grass carp can destroy all aquatic vegetation. The species is warmth-loving and becomes most active above 15°C. Spawning is virtually impossible in the Netherlands as the species requires flowing, warm water — all Dutch populations are stocked.

Fishing techniques

The grass carp is a challenging target that requires specific techniques. The herbivorous diet demands adapted bait. Boilies (especially fruity and sweet flavors) on a hair rig are standard. Corn, bread and tiger nuts are also effective.

• Bait: boilies (fruit flavors), corn, bread, tiger nuts, grass(!)
• Method: carp rod with hair rig, method feeder, float with bread crust
• Special: a blade of grass or piece of reed on the hook is a classic grass carp trick

Grass carp are extremely wary and light-sensitive. Fish in overcast conditions (median cloud cover 75%), early morning or late evening. Look for waters where you can see grass carp grazing at the surface.

In the Netherlands

The grass carp is a non-native species, originally from East Asia. In the Netherlands, the species has been stocked since the 1960s for biological control of aquatic plants. As natural reproduction does not occur in the Netherlands, all populations depend on stocking. The species is found scattered in ponds, lakes and polder waters throughout the country. Grass carp can live very long (30+ years) and continue growing, which is why they reach enormous sizes in some waters.