They don't give a shit about those fish. I think they want to keep the Sacremento San Joquin delta open to the ocean because that is their submarine rat line. Look at the tunnels under the old Hazel Altas silica mines under Mount Diablo next to the "Smelt" habitat. Those tunnels are huge.
https://hanfordsentinel.com/lifestyles/visit-the-hazel-atlas-mine/collection_e60245a3-156f-55a8-b383-f79e56c143b6.html#2