SEASONAL VARIATIONS AND 

 SEX DIFFERENCES 



The regression equations, based on com- 

 mercial and research^vessel samples, for 

 estimating log weight (Y) from log length (X) 

 in each calendar quarter are given in table Z. 

 The regression constants varied slightly from 

 quarter to quarter. The constants for the 

 research vessel and commercial catches in the 

 second quarter also differed. 



The standard deviation from regression, 

 Sy X. (table 2) was similar in all quarters. 

 The last column of table 2 gives values of Sy 

 at mean X. Sy is the standard deviation of 

 Y estimated from a single X observation, and 

 it is needed for computing confidence limits 

 for Y. 



Table 3 gives by calendar quarter the calcu- 

 lated weights for each centimeter of length, and 

 the length-frequency distributions of fish used 

 to obtain the regression equations. The equation 



for the pooled commercial and research- 

 vessel samples was used for the second quarter. 



A length- weight table for 118 summer 

 flounder from Chesapeake Bay collected in 

 both summer and winter (Hildebrand and 

 Schroeder, 1928) agreed closely with data of 

 the second and third quarters in the present 

 study (table 3), 



We used analysis of covariance to examine 

 possible differences between length- weight 

 relations of male s and females for the 

 research- vessel catch of 346 summer flounder. 

 The slopes of the curves were the same 

 (F = 0.07), but the elevations (logarithm of 

 adjusted mean weight) differed significantly 

 (F = 9.39). We concluded, therefore, that in 

 this sample, which consisted largely of fish 

 less than 45 cm. (centimeters) long, males 

 were slightly heavier for a given length than 

 were fen-iales. Further study is needed to es- 

 tablish whether the difference between sexes 

 holds for all sizes and seasons. 



Table 2. — Regression equations for estimating log weight (Y) from log length (X) of summer 



flounder, values of the constant (c), standard deviations from regression (Sy.x), and standard 

 deviations at mean X for Y estimated from a single X observation (S ), by calendar quarter for 

 catches of 1956-62 



