Round goby

Identification

The round goby is a stocky, bottom-dwelling fish with a large, broad head and thick lips. The body is brown-grey to olive-brown with dark marble-like blotches. The most striking feature: a distinct black spot on the first dorsal fin, absent in any other goby species in Dutch waters. Males turn almost entirely black during spawning season. Like all gobies, the pelvic fins are fused into a suction disc that allows them to cling to hard substrates. Most specimens are 8-12 cm, but the round goby can reach up to 25 cm.

Behavior & ecology

The round goby originates from the Ponto-Caspian region (Black Sea, Caspian Sea) and was first recorded in the Netherlands around 2004. The species has since spread explosively through the major rivers and is now one of the most common fish in the Waal, Meuse, Rhine and IJssel. They are aggressive nest guarders and territorial bottom fish that displace native species through competition for food and shelter. Round gobies feed on mussels (especially dreissenid mussels), amphipods, insect larvae and eggs of other fish species. At the same time, they have become an important new food source for pikeperch, perch and cormorants.

Fishing techniques

The round goby is usually caught by accident, but can be targeted:

• Dropshotting — small shad or worm on a dropshot rig just above the bottom; effective along rocky banks
• Light float fishing — piece of worm or maggot right on the bottom; in harbors and along stone quays they bite almost instantly

Round gobies bite aggressively and eagerly — they take virtually anything offered on the bottom. They may be taken without limit; many anglers discourage catch-and-release due to their invasive nature.

In the Netherlands

The round goby is the most successful fish invader in recent Dutch history. Via ballast water from ships from the Black Sea region, the species reached the major rivers and has since spread to canals, harbors and even streams. The ecological impact is considerable: the species competes with native bottom fish like stone loach and gudgeon, and actively eats eggs and fry of other fish species. There is no protected status, no closed season and no minimum size. Many anglers consider the round goby a pest, but the fish has enriched the diet of pikeperch and perch.