MOYLE ET AL.: NONCOEVOLVED ASSEMBLAGE OF ESTUARINE FISHES 



Table 4.— Spearman rank correlation among species ranked by month (lower matrix) by numbers and among environmental and other 

 variables ranked by month (upper matrix). Underlined values are significant at P > 0.05. 



1 



8 



10 



11 



12 



13. Striped bass 



14. Splittail 

 15 Tule perch 



16. Sacramento sucker 



17. Yellowfin goby 



18. Carp 



19. Prickly sculpin 



20. Stickleback 



21. Delta smelt 



22. Longfin smelt 



23. Threadfin shad 



24. Staghorn sculpin 



25. Starry flounder 



0.19 



0.68 



0.46 



-0.14 



- 0.41 



-0.11 



-0.07 

 -0.17 

 -0.24 

 -0.09 



0.15 - 



0.50 



0.44 0.38 



0.51 

 0.58 



0.53 



0.13 



■0.09 



0.08 



•0.01 



 0.02 



■0.13 



0.30 



0.54 

 0.27 



0.54 

 0.32 

 0.38 

 •0.13 

 0.05 

 0.21 



0.09 

 0.38 

 0.05 

 0.03 



■0.10 

 0.19 

 0.46 



0.22 

 0.46 

 0.34 

 0.07 

 0.03 



0.12 

 0.00 

 0.06 

 0.30 



- 0.64 



0.05 



0.07 



-0.19 



-0.06 



0.16 



0.01 



-0.05 



-0.08 



0.51 

 0.74 



0.07 



1. 

 2. 

 3. 

 4. 

 5. 

 6. 

 7. 

 8. 

 9. 



10. 

 11. 

 12. 



Month series 



Temperature 



Salinity 



Secchi depth 



Outflow 



Neomysis 



Crangon 



Palaemon 



Numbers/ 



trawl 



Grams/trawl 



Species/trawl 



Diversity (H) 



13 



14 



15 



16 



17 



18 



19 



20 



21 



22 



23 



24 



1O0O 



500 



MEAN BI0MASS PER TRAUL 



MEAN NUMBER OF FISH PER TRAWL 



I 979 



I 98 1 



I 982 



I 983 



Figure 3.— Trends in mean numbers and grams of fish per trawl. 



mer progressed although the two introduced species, 

 striped bass and yellowfin goby, tended to peak later 

 than the other species. Consequently, they all showed 

 significant (P < 0.05) negative correlations with 

 outflow. All except Sacramento sucker and tule perch 

 had significant positive correlations with salinity and 

 temperature. There was a general decline in fish 

 abundance throughout the 5-yr period. This was 

 reflected in that four of the six species showed a 

 positive correlation with species diversity, and all had 

 a negative correlation with month series. 



Prickly sculpin seemed to peak in abundance 

 earlier in the year than the first six species (Fig. 4) 

 but the pattern was obscured by the considerable 

 year-to-year variation in abundance of young-of-year 

 fish. Adults were resident in the marsh but appeared 

 in the trawls on an irregular basis because of their 

 tendency to hide under logs and other objects (Moyle 

 1976). Overall, prickly sculpin had negative corre- 

 lations with salinity and Secchi depth, but positive 

 correlations with temperature, N. mercedis abun- 

 dance, and species diversity (Table 3). Threespine 

 stickleback abundance had a negative correlation 

 only with temperature, presumably because their 

 reproductive behavior obscured our ability to catch 

 them. They were most abundant in the trawls in 

 February through May, and the catch consisted 

 primarily of gravid females and schools of young- 

 of-year fish. The males were apparently defending 

 their nesting territories in emergent vegetation. By 

 late summer sticklebacks were rare in the trawls but 

 could be taken in seine hauls made through weedy 

 areas. 



The "winter seasonals" were three plankton- 



Ill 



