Fish populations continue to tank in the
Sacramento-San Joaquin Delta, according to figures released last
week by the California Department of Fish and Game.
After
tossing the trawl nets and tallying the numbers, the agency found a
record low population of longfin smelt in the Pacific Coast’s
largest estuary. Populations of Sacramento splittail, American
shad, striped bass and the threatened Delta smelt also neared their
lowest since the annual fall survey began in 1967.
“These data are just one more clear indication that the
overall ecosystem of the Delta is in dire straits,” says
Christina Swanson, senior scientist at The Bay Institute, a
nonprofit that protects the San Francisco Bay. “Longfin and
Delta smelt are teetering on the brink of extinction. They could be
gone next year.”
The state’s Department of
Fish and Game agrees that the fish are in serious trouble.
“We’re very concerned about the trend that these data
indicate,” says Marty Gingras, supervising biologist. The
department says it cannot determine exactly how close to extinction
the five species are, because the survey compares current fish
populations to past abundance rather than providing a precise tally
of the number of fish. Nonetheless, says Gingras, “there is
merit in listing longfin smelt under the California Endangered
Species Act, and uplisting the Delta smelt from threatened to
endangered.”
A major factor harming the
Delta’s fish is the overdraft of water from Delta watersheds.
State and federal records indicate that water project diversions,
which supply 24 million Californians and a $31 billion dollar
agricultural industry, gulp an average of nearly 2 trillion gallons
of Delta water per year. That’s more than half of the water
that trickles into the Delta in a dry year, and 20 to 30 percent of
total flows in a wet year.
“Clearly these data are
confirming that we regularly take too much water out of the Delta
and rivers,” says Swanson. The Bay Institute recommends that
the state consider higher water efficiency, better management of
groundwater, and water recycling to ease Delta demand.
Other problems threaten the Delta’s fish as well. Non-native
species, such as the overbite clam, tend to out-compete natives and
create less suitable habitat for them. Additionally, the water
contains unhealthy levels of herbicides and pesticides from
upstream agriculture and ammonia from sewage.
Habitat
loss is another important factor in the Delta. Over the past 150
years, most of its marshes and waters have been leveed, drained and
rerouted for agricultural and urban development.
A recent
court ruling may provide some relief for the Delta’s fish.
Last August, U.S. District Court Judge Oliver Wanger of
California’s Eastern District imposed restrictions on export
pumping from the Delta after ruling in favor of environmental
groups. The groups had sued the U.S. Fish and Wildlife Service for
failing to protect the federally listed smelt. Until the agency
completes a new biological opinion on Delta management, the smelt
and their ecosystem remain under interim
protections.
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