In thIs fIrst Installment of the “If fIsh
dElTa
Could talk” segment In Westerbass.Com, CalIfornIa natIve and retIred department
of fIsh and game fIshery bIologIst dennIs
p. lee dIsCusses some of the sCIenCe and management behInd nonnatIve delta preda-
FISHERIES
Fishery Scientist
By Dennis P. Lee,
p pre R y E re d la a tio T n O sh R ips–
tors lIke strIped and largemouth bass, and theIr relatIonshIp to natIve speCIes.
who eats whom?
P
rior to the late
19th century, the
Sacramento-San
Joaquin Delta was comprised of a maze of
interconnected waterways,
sloughs, and islands
formed by the meeting of
the Sacramento and San
Joaquin rivers. Historically
water flowed in and out of
the Delta in relation to river inflow and tidal influences.
However, early agriculture led to levee construction
and eventually, the Delta was transformed into an
engineered water movement system where the
flow is altered by levee construction, water control
structures, and diversions. Instead of natural tidal
marshes, wetlands, and abundant stands of mixed
vegetation, the waterways and sloughs are now lined
with riprap rock, overhanging black berry bushes,
narrow stands of native California Tule, and shallow
waterweed beds comprised of introduced aquatic
species such as Brazilian pondweed Egeria densa.
The US Geological Survey reports that about
83% of the water exported from the Delta is used
for agricultural and the remaining goes to urban
and domestic supplies. How much water is actually
exported from the Delta is often debated. Jerry Meral,
Deputy Secretary of the California Natural Resources
Agency in charge of the Bay Delta Conservation
Planning Program, indicated that about 5 million
acre feet of water is exported annually. Total water
production from the Sacramento and San Joaquin
rivers combined can range
from 7 to as much as 42 million
acre feet annually depending
on the type of water year. In
addition, the amount of water
that eventually reaches the
Delta has increased as greater
demands are placed on existing
supplies.
Not only has the character
andhabitatsoftheDeltachanged butsohasthefishfauna. Historically,theSacramento and San Joaquin rivers, and California waters in general, didnotsupportthevarietyoffishspeciescomparedto geologicallyolderEastCoastandSoutheasternrivers. In thelate1800’s,theintroductionoffishfromtheotherparts ofthecountrywasconsideredgoodmanagement. Early anglersandfishculturistsencouragedthenotionofmoving and introducing fish into new waters, generally to develop commercialandsportfisheries. ManyoftheearlyCalifornia fishintroductionsdidnotsurvivetoproduceself-sustaining populations,whileothershavebecomeestablished throughoutstatewaters. Inthecaseofmanyspecies,some peoplearestillsurprisedwhentheyaretoldthataparticular fishisnotnativetoCalifornia.
The first introduction of a nonnative fish to California was the goldfish, Carassius auratus. The species was noted in the East Coast in the 1600’s, coming from Japan via Europe. The first California specimens were noted in 1862 and most likely originated from pet releases. The common carp Cyprinus carpio was not introduced to California until 1879 as a replacement for the “worthless and
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