188 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



33 cm. long. Since the fishery did catch more 

 males in the smaller sizes and was obviously not 

 catching them with full effectiveness, we see no 

 reason to suspect that the sex ratio of the unfished 

 population is other than equal. The unequal rep- 

 resentation in the catch may be due entirely to 

 gear selectivity and the unequal rate of growth 

 of the sexes. 



Table 10. — Length corn-position of yellowlail landed from 

 the southern New England slock, by sex, 1943-47 



Table 11. — Percent length composition, by quarter, of yel- 

 lowlail landed from the southern New England stock, fourth 

 quarter, 1942 through 1947 



The average size composition during each quar- 

 ter of the year (table 11, fig. 8) showed a definite 

 seasonal change, which is in accord with the 

 changes expected in most species of fish. The 

 average length was greatest in the first quarter, 

 January to March (37.40 cm.), least in the third 

 quarter, July to September (34.37 cm.), and in- 

 termediate in the second and fourth quarters. 

 The curves, when plotted on a percentage basis 

 to facilitate comparison, show little change in 

 shape. The changes appear to arise from the en- 

 trance into the fishery of young fish during the 

 spring and summer and their subsequent growth 

 and mortality during the winter. There is also 

 a possibility that some of the differences arose 

 from heterogeneity of the population, since tag- 

 ging experiments indicated some segregation of 



the southern New England stock during the win- 

 ter (p. 180). However, there is no way to distin- 

 guish the two sources of variation with these 

 data. 



Segregating the length data according to 

 statistical area for 1943 through 1947 (table 12, 

 fig. 9) reveals a small geographical gradient in 

 length, with the largest yellowtail coming from 

 the more easterly area. The yellowtail from the 

 Nantucket Shoals area averaged 36.35 cm., from 

 off No Mans Land 35.66 cm., from off Block Is- 

 land 35.23 cm., and from off Long Island 34.27 

 cm. These figures show statistically what is com- 

 mon knowledge among the fishermen, but since 

 the figures are associated with the seasons there 

 is no certainty that the differences are due en- 

 tirely to geography. Table 3, which shows the 

 catch by statistical subarea, indicates that the 

 landings from the Nantucket Shoals area (O) 

 were usually the heaviest when those from off No 

 Mans Land (Q) were light, and vice versa. The 

 landings from the westward, off Khode Island 

 (S) and Long Island (XXIII) run smaller re- 

 gardless of season, but there was no clear-cut sea- 

 sonal pattern in the size changes. It should be 

 noted that in areas from Block Island to Nan- 



