Bat rays die after getting into Bay Area salt ponds

Fifteen dead bat rays washed ashore over the weekend at a South Bay wildlife refuge in what officials called an isolated incident.

The influx of the dead bat-like sea creatures, first reported by NBC Bay Area, was spotted at the Don Edwards San Francisco National Wildlife Refuge in the San Jose neighborhood of Alviso.

Biologists with the U.S. Fish and Wildlife Service said Wednesday the deaths may have been caused by a process environmentalists are using to restore marsh land in the area and that there was no cause for alarm.

Water from the bay is allowed to flow into the saline pockets to bring back the marsh, but federal wildlife officials are keeping some as salty “managed ponds” because they don’t want to kick out all the stilt and avocet birds, as well as brine shrimp, that thrive in the environment.