MOYLE ET AL.: NONCOEVOLVED ASSEMBLAGE OF ESTUARINE FISHES 



mon in the marsh in February, March, and April 

 (times of high outflows) and were taken mainly in 

 seines. The tendency of the salmon to remain close 

 to the banks and vegetation and to get sucked into 



YELLOWFIN goby 



CARP 



STRIPED BASS 



diversions of marsh water consequently has led to 

 the screening of one major diversion in the marsh. 

 Squawfish were abundant in the Sacramento River 

 and juveniles are known to disperse widely during 

 high flows (Smith 1982). Mosquitofish and rainwater 

 killifish were present in ponds adjacent to the 

 sloughs, along with silversides and sticklebacks; mos- 

 quitofish were planted in some areas for mosquito 

 control. 



Principal Components' Analysis 



The PCA using the numbers per trawl matrix 

 resulted in four components that explained 47% of 

 the variance in the matrix (Table 5). The first com- 

 ponent loaded most heavily on tule perch, Sacra- 

 mento sucker, and splittail, native resident species 

 most abundant in dead-end sloughs, and to a lesser 

 extent on carp and threadfin shad, introduced 

 species common in such sloughs. The second com- 

 ponent loaded heavily on striped bass, yellowfin goby, 

 and carp, three introduced species resident through- 

 out the marsh but most frequently captured in the 

 main sloughs; all reached peaks of abundance in late 

 summer. The third component loaded most heavily 

 on prickly and staghorn sculpins, two benthic species 

 that peaked in abundance during the summer 

 months but were relatively scarce during the last 2 



Table 5.— Loadings (rotated) of major fish species on four com- 

 ponents produced by a principal components analysis of numbers 

 of fish per trawl (n = 1,238). Values over 0.500 are underlined. 



Figure 5.— Capture rates of introduced species within Suisun 

 Marsh. Mean catch per effort is described as percent of the total 

 catch for each species. 



113 



