I don't know anything about the area, but after doing a short search I found out that...

EBPRD=East Bay Regional Parks District

I read where in the past while doing habitat preservations, the parks department and fish and game tagged certain fish before relocating them. They referred to times when fish had strayed into areas that were not fit for longevity. So, they tagged the fish in that area and put them somewhere else. They mainly referred to Coho and Chinook, but I guess it's possible they could have tagged bass as well.