Biology Reference
In-Depth Information
landscape-scale habitat corridor that is a mosaic of riverine habitat, tidal
sloughs, sinewy channels, shallows, and floodplains—the kind of habitat
mix most needed by salmon and splittail. According to a recent sampling,
more prespawning adult Delta Smelt lingered in Cache Slough than any-
where else in the delta in 2007.
Unfortunately, some of the shallows already restored in the delta have
ended up harboring more non-native bass—predators that eat young
salmon and smelt—and the Brazilian aquatic weed
Egeria,
than native
species. More successful, perhaps, were efforts to remake a few of the del-
ta's levees into mini-habitats—widening them and setting them back from
the river so they could nurture narrow bands of riparian and wetland veg-
etation.
Other restoration targets for the future are those areas with the fewest
private landowners and expensive standing infrastructure. These areas in-
clude the Mokelumne and Consumnes river corridors, the McCormick-
Williamson Tract, and Suisun Marsh, where the delta merges into the
greater San Francisco Bay.
Extensive as the physical habitat improvements have been, they have not
provided what native fish populations may need most: more water. Native
fishes rely on ample flows of fresh water in certain seasons and places in
the watershed to rear, migrate, and spawn. “In all our delta conservation
plans and visions, we've placed heavy emphasis on habitat and some em-
phasis on stressors. But there's been a big battle over the need for water. If
you don't do all three things, no one thing alone is going to work,” accord-
ing to Stuart Siegel.
The battle over water has resulted in a few concessions for beleaguered
fish. Restoration advocates have managed to negotiate releases from up-
stream dams to re-create some elements of the natural annual flow pat-
tern. Yet these flows have been so small that some refer to them merely as
“life support.” But eventually, stakeholders and government managers
agreed to three landmark allocations of water for the benefit of fish, wild-
life, and the estuarine ecosystem.
The first allocation came about in 1994, when California created a
unique water quality standard designed for fish. The standard required
that a special zone of low-salinity habitat be maintained in the region of
Suisun Bay. The zone moves up and downstream with tides, freshwater
withdrawals, and seasonal shifts. When the zone occurs around Suisun
Bay, however, aquatic organisms—and the fish that eat them—are particu-
