Page and Ricard' Food availability and Mytilus eclulis growth in California coastal waters 



683 



Figure 8 



Estimates of monthly scupe-for-growth of a 0.05-g 

 dry weight (~20 mm shell length) MiilHus edidift at 

 Avila Beach ( • ) and Platform Holly (O). Mean values 

 ±1SE. 



Figure 8 shows the monthly SFG of a 0.05 g dry 

 weight M. eduli>i (~20 mm shell length) at Holly and 

 at Avila, calculated using the seston concentration and 

 percent POM data from these localities and the equa- 

 tions in Table 1. There was a significant effect of 

 month, but not location, on scope for growth (2-way 

 ANOVA, Table 5). An a posteriori test for significant 



Table 5 



Results of two-way ANOVA evaluating the influence of month 

 and location of estimated scope for growth oi Mytilus edulis. 

 ***P<0.001. 



Source 



Sum of 

 square 



df 



Mean 

 square 



F ratio 



Location 



Month 



Month  Location 



Error 



16.09 

 557.95 

 190.31 

 640.51 



1 



7 



7 



33 



16.09 

 79.71 

 27.19 

 19.41 



0.83 



4.11*" 



1.40 



differences among months revealed that the low SFG 

 values of November- February differed significantly 

 from the higher SFG values of March- June (F = 4.11, 

 df=l, 33, P<0.001). 



To evaluate the relationship between shell growth 

 rate and theoretical SFG, we calculated linear corre- 

 lation coefficients between growth rate (Fig. 6) and 

 scope for growth for the combined Avila and Holly data 

 at time lags of 0-4 weeks. Growth was not correlated 

 with SFG at a time lag of weeks (/• = 0.56, P>0.05). 

 However, growth rate correlated with SFG at time lags 

 of 1-4 weeks with strongest correlations at time lags 

 of 2 and 3 weeks {>■ = 0.70 and 0.75, P<0.05, u = 10; 

 Fig. 9). 



