June 15, 2016 — Australia has a plan to rid its waterways of a destructive fish species by making the fish their own worst enemies.
The targets are European carp, also known as koi: toothless, mud-sucking, bottom-dwelling fish that breed like crazy, destroy the habitat of other species and go unchecked by native predators. And the weapon is a dose of venereal disease.
The carp got loose accidentally in the 1960s, released from farm dams. Their habit of stirring up tons of silt as they foraged for food turned the once-clear Murray and Darling Rivers murky, cutting the sunlight for aquatic plants and preventing some native fish from spotting prey. These days the rivers seethe with the highly adaptable carp, which make up as much as 90 percent of the fish biomass in the river systems.
Now scientists are turning to a virus, Cyprinid Herpesvirus 3, that they hope will kill all the carp but spare other species. The government has allocated $11 million in grant money to test the idea.
European carp spread herpes when they mate, but not quite the way mammals do. The fish jostle and bump one another in a swirling tight-knit mass as the females lay eggs that are fertilized by males. The skin-grazing frenzy leaves carp susceptible to infection.