It appears that works on the light rail polluted a section of the river between Tel Aviv and Ramat Gan, and thousands of the endangered bleak have floated, dead, to the surface, where birds are eating their corpses; company responsible for construction has halted building and will investigate.
Itay Blumental & Erez Erlichman|Published: 16.07.16

Thousands of dead fish—bleak, specifically—floated to the surface of the Yarkon River Saturday morning on the Tel Aviv-Ramat Gan border. Their shared cause of death is believed to be serious pollution caused by construction of the Tel Aviv metropolitan area’s light rail, carried by the company NTA.

“I left home at six in the morning, and suddenly I saw thousands of dead fish in the river,” recounted Neti Levi, a resident of Ramat Gan. “There was a strong smell of dead fish for a few hours before; I think that it happened overnight between Friday and Saturday. I left the area after a quarter of an hour; I was nauseated form the smells.”

The river has gone through a prolonged process of rehabilitation in recent years. Along its length, pipes pump sewage in a controlled manner, but apparently during construction, something went wrong.

“Dead fish were strewn two to three kilometers along the river, and it was horrible. I say birds eating some of the fish, so it could be that the damage won’t be just to fish, but also to the birds,” Levi said.

The Yarkon bleak, a small freshwater fish, belongs to the carp family. In the 1950s, there was a decrease in the number of fish of this species, and it is now endangered. The fish usually swims near the bottom of the river, feeding on small invertebrates and algae. It lays its eggs on stones and flora in the river.

Contacted regarding the mass deaths, NTA replied, “A report was received in the afternoon on the deaths of fish in the Ayalon River near one of the worksites of Solel Boneh. NTA instructed the contractor to immediately take care of the hazard and to stop construction at the site until after a comprehensive investigation on the matter.”

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