[env-trinity] THE DELTA
rickpruitt at earthlink.net
Sun Oct 30 02:11:00 PST 2005
$2 million project to analyze the diminution of delta smelt
The sharp drop-off indicates a decline in estuary's health.
Researchers discovered the decline in January. Although they cannot
say exactly how many smelt are in the delta,
they know that the number of the 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 slender fish that typically grow 2 inches
to 3 inches long. They have a blue sheen and appear
to be translucent.
The declining numbers are seen among other once-common 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."
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.
One suspected factor 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. Changes in when and how
much water is drawn have had a profound impact on delta wildlife,
Biologists are also concerned about the growth in once-clear
delta sloughs and channels of nonnative species, including Egeria,
a fast-growing weed. The weed grows quickly, creating a perfect habitat
for largemouth bass and other nonnative predators of delta smelt
and other fish.
Rising numbers of striped bass and the Asian clam, which compete
with the smelt and other small fish for food, also have hurt, she said.
Scientists also believe that increasing herbicide and pesticide runoff
from upstream farms 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."
Declining count of delta smelt
State authorities are alarmed by a dramatic drop in the
number of delta smelt last year. The Smelt
Abundance Index the number of fish pulled from the
water during research ventures each year has dropped below
the previous lows seen in the 1980s. Because of its sensitivity
to a number of factors including changes in water flow and
toxic chemicals, it is considered an indicator of the health of
theSacramento-San Joaquin River Delta..
Breeding season: From late winter to early summer.
Fast growing, with majority of growth within the
first 7 to 9 months of life.
Food: Small organisims called zooplankton
Life span: 1-2 years
Size: 2-3 inches, but can reach 5 inches
Habitat: Brackish waters in the Sacramento-San Joaquin River Delta
Odor: Smelt smell like cucumbers.
Source: California Department of Fish and Game
E-mail Chuck Squatriglia at csquatriglia at sfchronicle.com.
rickpruitt at earthlink.net
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