US EPA

3293631 

Journal Article 

Littoral fish assemblages of the alien-dominated sacramento - San Joaquin Delta, California, 1980-1983 and 2001-2003 

Brown, LR; Michniuk, D 

2007 

1 

Estuaries and Coasts
ISSN: 1559-2723
EISSN: 1559-2731 

SPRINGER 

NEW YORK 

30 

1 

186-200 

WOS:000245134200019 

We analyzed monthly boat electrofishing data to characterize
the littoral fish assemblages of five regions of the Sacramento-San Joaquin Delta (northern,
southern, eastern, western, and central), California, during two sampling periods, 1980-1983
(1980s) and 2001-2003 (2000s), to provide information pertinent to the restoration of fish
populations in this highly altered estuary. During the 1980s, almost 11,000 fish were captured,
including 13 native species and 24 alien species. During the 2000s, just over 39,000 fish were
captured, including 15 native species and 24 alien species. Catch per unit effort (CPUE) of total
fish, alien fish, and centrarchid fish were greater in the 2000s compared with the 1980s, largely
because of increased centrarchid fish CPUE. These differences in CPUE were associated with the
spread of submerged aquatic vegetation (SAV), particularly an alien aquatic macrophyte Egeria
densa. Native fish CPUE declined from the 1980s to the 2000s, but there was no single factor that
could explain the decline. Native fish were most abundant in the northern region during both
sampling periods. Nonmetric multidimensional scaling indicated similar patterns of fish
assemblage composition during the two sampling periods, with the northern and western regions
characterized by the presence of native species. The separation of the northern and western
regions from the other regions was most distinct in the 2000s. Our results suggest that native
fish restoration efforts will be most successful in the northern portion of the Delta. Management
decisions on the Delta should include consideration of possible effects on SAV in littoral
habitats and the associated fish Assemblages and ecological processes.