$2 million set aside to address
delta fish decline
By Chuck
Squatriglia, Chronicle
Staff Writer
Monday, June 20, 2005
State and federal authorities, alarmed by a precipitous
decline in the number of delta smelt and other
species in the San Joaquin-Sacramento River Delta,
have set aside $2 million to figure out what's
wrong and what to do.
The dwindling number of delta smelt - which are
at their lowest level ever - is especially worrisome,
scientists said today, because the animal was
once among the most common fish in the delta and
are a bellwether of the estuary's health. Any
change in their numbers could indicate that something
is seriously amiss.
"One reason there is such a high level of concern is
because many biologists consider the delta smelt and their presence in the delta
to be a pretty good overall indicator of the biological health of the delta,"
said Tina Swanson, senior scientist with the Bay Institute in Novato. "They used
to be among the most abundant fish in the delta, and now they're
among the least abundant."
Researchers discovered the decline in January as they
analyzed new data on the animal's population. Although they cannot say with any
precision exactly how many delta smelt are in the delta, they do know that the
number of fish pulled from the water - called an abundance index - during
research ventures has reached an all-time low, Swanson
said.
"While
several of these declining species ... have shown evidence of long-term decline,
there appears to have been a precipitous step-change' to very low abundance
during 2002-2004," reads a scientific report on the
issue.
Delta smelt
are small, slender fish that typically grow to between 2 and 3 inches long. They
have a blue sheen and appear somewhat translucent.
The declining numbers
are seen among other once-common species of pelagic - or open water - fish,
including the longfin smelt and threadfin shad.
"(The shad) was the most
common fish you'd catch out there," Swanson said.
Their decline is "extremely
large, just a total crash. Even the bait fishermen
are saying 'Where are they?'."
Scientists believe there are several reasons for the
decline, and experts from more than half a dozen state
and federal agencies - including
the state and federal fish and game departments, the Environmental Protection
Agency and the federal Bureau of Reclamation - will
spend the next several months analyzing existing data
and gathering new information.
Topping
the list is the impact of drawing trillions of gallons
of water from the delta each year to supply Southern
California and the Central Valley, Swanson said. The
delta provides about one-third of the state's water
supply, and changes in when and how much water is drawn
from the estuary have had a profound impact on its
wildlife, she said.
Other concerns include non-native species,
including Egeria, a fast-growing weed that has grown
prevalent in the once-clear channels and sloughs of
the delta. The weed grows quickly, creating highly
vegetated areas. Those, in turn, create a perfect habitat
for largemouth bass and other non-native predators
that prey on delta smelt and other fish. Rising numbers
of striped bass - another predator - and the Asian clam - which compete
with the smelt and other small fish for food - also
have had an adverse impact she said.
Finally, scientists believe that increasing levels
of herbicide and pesticide runoff from farms upstream - coupled with herbicides
used to eradicate Egeria - have polluted the delta.
"This is a very
complex problem, and all of these causes are interrelated," Swanson said. "It
is not going to be easy to fix this, assuming we continue
relying upon the delta for our water supply as we do."
E-mail Chuck Squatriglia at
csquatriglia@sfchronicle.com
URL: http://sfgate.com/cgi-bin/article.cgi?file=/chronicle/archive/2005/06/20/MNsmelt20.DTL