FISHERY BULLETIN: VOL. 84, NO. 1 



DELTA OUTFLOW INDEX 



SALINITY 



TEMPERATURE 



UATER TRANSPARENCY 



1979 



Figure 2.— Trends in abiotic factors and Neomysis mercedis abun- 

 dance within Suisun Marsh. Temperature is in °C. Average outflow 

 in 10,000 cubic feet per second of the Sacramento River was 

 calculated by the California Department of Water Resources. Salini- 

 ty is given in parts per thousand. Neomysis mercedis abundance 

 rankings are described in text. 



20- 



1979 



flow, indicating that catches were highest in late sum- 

 mer and lowest in early spring. However, when the 

 patterns of occurrence of the 12 most abundant 

 species were examined, three groups appeared: resi- 

 dent species, winter seasonals, and spring/summer 

 seasonals. 



The "resident species" included the native split- 

 tail, tule perch, Sacramento sucker, prickly sculpin, 

 and threespine stickleback as well as the introduced 

 striped bass, carp, and yellowfin goby. Two additional 



species, native white sturgeon and introduced 

 American shad, probably also belonged in this 

 category, as they were caught at all times of the year 

 but too infrequently to draw any firm conclusions. 

 Splittail, striped bass, tule perch, Sacramento sucker, 

 carp, and yellowfin goby had similar patterns of 

 abundance (Figs. 4, 5) and were correlated (P < 0.05) 

 with each other and with total biomass, numbers, 

 and species (Tables 3, 4). All six species usually 

 became more abundant in our catches as the sum- 



110 



