“It was a horrible sight,” says local resident Marian Joore about the fishing drama that took place last week in the locks at the Korte Ringweg in Zaandam. Hundreds of carp lay dead or moribund in the water in the water next to the riding school. More than a thousand carp have died. Its cause is still unclear.

    According to local residents, who walk their dogs every day in the polder area, the carp died from lack of oxygen. “The water did not flow through close to the riding school. It was completely closed there,” says Johan.

    “Only when fresh water flowed into the ditch again did you see fish grabbing en masse. And then you soon saw no more dead fish.” Johan’s story is endorsed by many other residents.

    Text continues below the report.

    Marian initially also thought that lack of oxygen was fatal for the carp. “We took the survivors to the ditch on the other side of the road.” But she was told by the municipality that a virus is probably the cause. Spokesperson Marko Cortel of the Hoogheemraadschap Hollands Noorderkwartier (HHNK) also says in a response that it was not due to a lack of oxygen.

    Oxygen is OK

    “The oxygen has been measured and is fine,” says Cortel. Immediately after the report, the water board opened a weir. “Then you try to admit fresh water and extra oxygen,” explains Cortel. “We always do.” According to him, the residents may have noticed this.

    “But even today, dead carp have been found again. There is something among the carp.” It is only this species of fish that dies. Cortel: “All other fish species are swimming around.” The water board therefore suspects that it is a virus only among carp, such as the herpes virus. This virus is highly contagious and deadly to carp.

    Highly contagious

    The fact that so many fish have died at the Korte Ringweg may be due to overpopulation. “There are too many close together,” says Cortel. “There has to be one that is infected and all fish then become infected. You cannot vaccinate the animals. Such a virus just has to rage out.”

    Healthy carp were sent to the lab for testing to confirm that it was really the herpes virus. Cortel expects the results to be in next week. Until then, the water board can do nothing.