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HABITAT OPEN WATER 3 INDEX 2 1 Poor Anglers in Delta open waters. Photo: Bird’s Eye View seasonally with freshwater inflows from the Estuary’s tributary rivers and streams. 0 Open water salinities can range from near freshwater conditions in Suisun Bay to as salty as the nearby Pacific Ocean in the South Bay. In this Estuary, low salinity, open water habitat in Suisun Bay produced by high freshwater inflows during the late winter and spring is a particularly important habitat feature, driving productivity and increasing the abundance of many native fish and invertebrate species. Open water habitat in the Delta, the Estuary’s most upstream reach, occurs in narrower channels and has even lower salinities, indeed it is almost always fresh. UPPER ESTUARY Fair B A Y 4 2010s 2000s 1990s 1980s 1970s 1960s 1950s 1940s On the surface, the open blue- green waters of the Estuary help define the region’s beauty. Under the surface, In the Estuary’s they provide the least shallow bays — Su- accessible of the isun Bay, San Pablo Estuary’s habitats to Bay and South 4000 Bay — open humans but one that sustains many fish, water habitat Open waters near the Rio Vista Bridge on the Sac- invertebrates and other ramento River, 100 kilometers from the Golden Gate 3000 conditions wildlife. All of the Estu- where low salinity habitat is not as beneficial to the are largely ecosystem as it would be if pushed further down- ary’s Endangered Species defined stream by higher flows. Photo: Bird’s Eye View. Act-listed fish species — 2000 by salinity, Delta smelt, longfin smelt, which Chinook salmon, steelhead and sturgeon — live varies longitudinally along the Estuary’s in or pass through this open water habitat during axis from upstream to 1000 downstream and OPEN WATER HABITAT Good CONTEXT their life cycles. Harbor seals, bat rays, and marine species like sole, herring and sardines also use the Bay’s open waters. The condition of the Es- tuary’s open water habitat is directly linked to the health of aquatic wildlife and their ecosystem. 27 OPEN WATER Delta hydrodynamics Suisun low salinity conditions UPPER ESTUARY . . S TAT U S . . Poor . . . .T R E N D . . . . Deteriorating .....BENCHMARK..... Habitat conditions that protect species survival With large inputs of freshwater from Sacramento-San Joaquin watershed rivers and proximity to massive water diversion facilities, Delta open water habitat conditions are more affected by water movement patterns within channels than downstream bays. Low freshwater inflows and high water diversion rates can reverse flows in Delta channels and draw fish and other small organisms upstream to the Delta water pumps, where they can be killed at the pumps or eat- en by non-native, predatory fish common in this area.