[env-trinity] THE DELTA

[Richard Pruitt]

THE DELTA 


$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, 
Swanson said. 

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." 



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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 

Status: Threatened 

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 

The Chronicle 

E-mail Chuck Squatriglia at csquatriglia at sfchronicle.com. 



Richard Pruitt
rickpruitt at earthlink.net
Why Wait? Move to EarthLink.
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