An up to now unknown virus is blinding the Kinneret's remaining supply of Amnon (St. Peter's fish), scientists have determined. And the reason, they say, could be the overfishing of the Kinneret and the depletion of the lake's population of the popular fish.
Reports over the past year have documented many sightings by Kinneret fishermen of the mysterious disease, which actually causes fish to lose their eyes. The disease develops in three stages: First one eye of the fish shrivels and falls out, leaving an empty socket, and then the same happens to the second eye. Eventually, the fish turns black and dies of starvation.
Experts say that the phenomenon was first observed a decade ago, but it is now estimated that it appears in some 10% of Amnon coming from the Kinneret. Scientists in Israel and abroad have confirmed that an until-now unknown virus has been found in fish that have lost their eyes.
It should be noted that the fish is not dangerous for human consumption, because the virus can only survive in the cool waters of the Kinneret, and dies when exposed to the heat of the human body. Nevertheless, commercial fisherman who troll the Kinneret for Amnon fish destroy the eyeless ones they catch instead of delivering them to market, believing that customers will balk at buying a fish with such an obvious defect.
Recent reports said that the problem has spread beyond the Kinneret, and now affects Jordan River tilapia raised in ponds in the Hula Valley, as well as some carp and mullet.
Dr. Avi Eldar of the Israel Veterinary Service said that the phenomenon first came to his office's attention last year, and after months of intense work he and his staff were unable to determine the specific cause of the disease. He then sent samples of the fish to several colleagues abroad, but they, too, were unable to determine the cause.
The best they, and he, could come up with was that a mysterious virus in the fish was the cause, although the connection between the virus and the damage done to the fish was unclear. That the cause of the disease is a virus, as opposed to a parasite, comes as a relief to fish-lovers who keep kosher; a parasite commonly found in fish from the Kinneret might have prompted the Rabbinate to recommend against eating fresh fish from the lake altogether.
On the other hand, antibiotics do not work against viruses, said Dr. Eldar, so more research is needed on how to battle the disease.
One way to do that would be to determine what causes the virus to grow, and the Veterinary Service is working on that too, he said. One theory is that the overfishing of Amnon from the Kinneret somehow engenders the virus; Amnon have been shown to be essential to the lake's environmental balance, with the fish helping to cleanse the water of bacteria, algae, and other elements.