YELLOWTAIL FLOUNDER OFF NEW ENGLAND 



193 



Table 15. — Reduced length-weight data for yellowtail from the southern A T ew England stock, by quarters, 1943 

 [n=number of specimens; 2 = summation; z=]ogarithm of length in decimeters; y = logarithm of weight in tenths of pounds] 



Table 16. — Length-weight regression formulas for yellowtail 

 from the southern New England stock, by quarter and sex, 

 1943 



'.r = logarithm of length in decimeters; y=estimated logarithm of weight 

 in tenths of pounds. 



Table 17. — Comparison of the weight of male and female 

 yellowtail, by quarter, at the mean length of 35.869 cm. 



[In pounds] 



ence between the sexes at the onset of spawning 

 in early April is probably even greater. 



The differences in the length-weight relation 

 among quarters also are considerable. Yellow- 



tails of the average length of both sexes are 

 heaviest in the first quarter and lightest in the 

 third. This is a little surprising since one would 

 expect the females, at least, to be heaviest during 

 the spawning season. However, as was previously 

 mentioned, 67 percent of the females in the sam- 

 ples were spent, and even in this condition the 

 average weight was only slightly less (0.010 

 pound) than that of the first quarter. Probably 

 the females are their heaviest at the onset of 

 spawning in early April. 



Most of these differences are statistically signif- 

 icant. Covariance analysis (table 18), according 

 to the method used by Kendall (1952, p. 239) in- 

 dicates that the differences between the sexes are 

 highly significant in each quarter except the 

 third, which immediately follows the spawning 

 season. It is not certain whether this lack of a 

 significant difference is due to the small number 

 of males (21) or to the fact that the females are 

 recovering from spawning and have ovaries of 

 minimal size. The differences among quarters 

 for each sex also are highly significant. 



Further consideration of the covariance analysis 

 indicates that the slopes of the regression lines of 

 the males, which are consistently lower than those 

 of the females, are significantly so during the third 

 and fourth quarters. Thus it appears that the 

 males, in addition to being surpassed in numbers 

 and dominated in length by the. females (p. 188), 

 become more slender compared with the females 

 as they grow older. 



These differences between the sexes and among 

 the seasons indicate the necessity of classifying the 

 data by sex and time of capture, if critical com- 

 parisons of condition are to be made and if the data 

 are to be used for transforming the weight of 

 yellowtail to numbers of fish. For the latter pur- 

 pose we have segregated our data by quarters, but 



