of data derived from Chesapeake Bay,^ 

 the dominant peaks in the length- 

 frequency distributions were identical 

 up to about 265 mm., and the slight 

 discrepancies between the sexes are 

 not considered serious. Above this 

 size, however, the difference between 

 the sexes was sufficiently great to 

 indicate that any marked changes in 

 sex ratio could shift the position of the 

 modes in unsexed samples. It is also 

 evident from the curves and appendix 

 tables 1-5 that female Atlantic men- 

 haden not only attained a larger size, 

 but apparently grew faster (since the 

 female curves were displaced to the 

 right of the males) and showed a ten- 

 dency to live longer than the males. 



The predominance of females in 

 the catches with respect to both num- 

 bers and length is shown in tables 7 

 and 8. In table 7 it is seen that the 

 males were more numerous in the 

 South Atlantic summer catches, while 

 in every other area, the females pre- 

 dominated. If, however, the total num- 

 ber of fish in each ^-centimeter length 

 class is considered for the coast as a 

 whole, it may be judged from table 8 

 that the females accounted for a greater 

 proportion of the catch over virtually 

 the entire size range. The unequal 

 representation of sexes in the catch 

 may have resulted from the selec- 

 tivity of purse-seine gear and the 

 apparent differential growth of the 

 females. 



Weight Composition 



Percentage weight-frequency dis- 

 tributions of fish in samples from the 

 purse-seine catches in the different 

 areas in 1957 are shown in figure 8 

 (see also appendix tables 6-10). The 

 most noticeable aspects of the graphs 

 are the marked differences in the shape 

 of the curves and the positions and/ or 

 lack of dominant modes. The curve 

 for the South Atlantic Area shows a 

 range in weight from 20 to 230 g. and 



TABLE 7. — Sex ratio of fish in purse- 

 seine catches, by area and season, 

 1957 



^The irregularities in the length -frequency curves 

 and sex-ratio data (table 7) for Chesapeake Bay in 1957 

 are believed to be the result of the difficulty in sex 

 determinations of immature males in samples taken in 

 late July and August when fish frequently were partially 

 decomposed upon reaching the reduction plant. 



Area and 

 season 



SUMMER FISHERY 



South Atlantic. 

 Chesapeake Bay-"-. 

 Middle Atlantic. 

 North Atlantic. . 



FALL FISHERY 



North Carolina. , 



Males 



1,5^5 

 1,248 

 3,';08 

 1,557 



A96 



Females 



1,519 

 1,72-; 

 3,516 

 1,749 



586 



Ratio of 

 females 

 to males 

 (percent) 



0.98 

 1.38 

 1.03 

 1.12 



1.18 



See footnote 7 in left column. 



a prominent mode at 110 g. which is 

 preceded by a secondary peak at 50 g. 

 In Chesapeake Bay samples, a domi- 

 nant mode occurs between 80 and 90 g., 

 with the suggestion of a secondary 

 peak between 160 and 170 g., while in 

 those from the Middle Atlantic Area, 

 two prominant peaks are evident, one 

 between 130 and 140 g. and the second 

 at 220 g. The latter curve is markedly 

 skewed to the right and emphasizes 

 both the concentration of weights of 

 younger fish at the left and the com- 

 paratively larger sizes of a few fish 

 at the right. With minor variations, 

 the weight curves for the South Atlantic, 

 Chesapeake Bay, and Middle Atlantic 

 Areas are similar in shape to the 

 length-frequency curves shown in fig- 

 ure 6 and, in general, show relatively 

 the same disparity in size of fish of 

 the same age, both within and between 

 the three areas. 



In contrast to other areas, fish 

 taken during the summer in the North 

 Atlantic Area were highly variable in 

 weight, ranging from about 160 to 

 900 g., and the weight curve shows no 

 concentration of fish in any one weight 

 class. This probably was the result of 

 a combination of factors, including a 

 proportionately greater increase in 



13 



