FISHERY BULLETIN: VOL. 73, NO. 4 



Table 3.- Values required to calculate 95^ limits for values of X or 1' predicted from regression 

 equations in Table 2. The ^95 value is based on the number of observations for each regression. 

 For comparison abbreviations see Table 2 caption. 



'Calculated values based on biomass data which was not standardized to per cubic meter. 



regressions based solely on our data reveals two 

 notable features. First, the slopes of the regres- 

 sions based on the same biomass estimators; i.e., 

 displacement volume versus dry weight, wet 

 weight versus dry weight, and displacement 

 volume versus wet weight, are significantly 

 different (P<0.05). This was tested by calculating 

 approximately 95% limits for the difference in 

 slopes using standard normal distribution theory: 



{i\r Vq^)±1 .96/Var v^, + V ar /'g^ . As was true in our 

 cases, if A/' ± 95% limit does not cross 0, the slopes 

 are significantly different. In all cases, slopes of 

 the regressions derived from our data are closer to 

 1.0. 



The second feature is that there is a significant 

 difference (P<0.005) in the variance of observa- 

 tions from the regression lines. The Be et al. (1971) 

 and Be (footnote 5) variance for displacement 

 volume versus dry weight is 4.9 times larger than 

 that calculated for our data; for wet weight versus 

 dry weight, it is 7.4 times larger; for displacement 

 volume versus wet weight it is 2.3 times larger. 



These differences are probably due in large part 

 to the differences in methods used to determine 

 displacement volume and wet weight. The mer- 



cury immersion method Be et al. (1971) and Be 

 (footnote 5) used to measure displacement volume 

 provides estimates substantially more variable 

 than the technique used by us (Grice and Wiebe 

 unpubl. data). The increased variability of their 

 wet weights may have resulted from their use of a 

 vacuum to remove some of the interstitial water. 



One implication of the lower slopes for the Be et 

 al. (1971) and Be (footnote 5) data is that it appears 

 the percentage of interstitial water in their 

 samples may change more radically with increasing 

 biomass than in our samples. This inference is 

 drawn from the calculated values relating dry 

 weight to wet weight and displacement volume in 

 percent (Table 4). The alternate explanation is 

 that as biomass per cubic meter increases, the 

 percentage of wet weight or displacement volume 

 that constitutes dry weight increases as a result of 

 a decrease in intracellular water. It seems unlikely 

 that this accounts for the differences between the 

 two sets of data. Seasonal effects have been 

 minimized by collection of samples at various 

 times of the year and geographical effects should 

 be similar since both studies covered wide 

 geographical ranges. 



Table 4.-Regression ecjuation prediction of the percentage of displacement volume (DV) or 

 wet weight (WW) that is dry weight (DW) for selected dry weight concentrations. 



'Calculated values based on biomass data which were not standardized to per cubic meter. 



784 



