FISHERY BULLETIN: VOL. 76, NO. 2 



400-^ 



^1959 



i" 



-I — I — I — I — r- 



STRENGTH OF YEAR CLASS (NO /SEINE HAUL 1 



Figure 3.— Modal size (mm fork length) of age II striped bass 

 from Long Island waters as a function of Chesapeake Bay year 

 class strength. Year classes are indicated. 



number of age 0+ juveniles per standard seine 

 haul near the Maryland shores of Chesapeake 

 Bay. These are the same data used by Schaefer 

 (1972). The relationship (Y = 333 - 3X) yielded a 

 correlation coefficient of -0.95 ir^ = 0.90), 

 suggesting that 909c of the annual variation in 

 modal length at age 11+ for striped bass in New 

 York waters can be explained by annual fluctua- 

 tions in year class abundance in the waters of 

 Chesapeake Bay. 



Modal Size and 

 the New York Commercial Harvest 



The equation described above (Y = 

 333 - 3X) was used to calculate (and thus to esti- 

 mate) modal lengths of age II -I- fish for those 8 yr 

 for which actual modal lengths exist. A ^test com- 

 parison between the observed age II modal sizes 

 and those computed using the correlation formula 

 above showed no significant difference at the 0.001 

 probability level (Table 1). Since no significant 

 difference existed between the observed and calcu- 

 lated modal lengths, the assumption was made 

 that reliable modal lengths could be calculated for 

 years in which no actual measurements exist. The 

 equation described above was, therefore, used to 

 estimate modal lengths of age 11+ striped bass for 

 all years between 1954 and 1972, using the corre- 

 sponding year class abundance data. A correlation 

 analysis was then performed (similar to that done 

 by Schaefer 1972) between the New York land- 

 ings of striped bass ( Y) and a 4-yr mean of the 

 computed modal lengths of age 11+ fish 1 to 4 

 yr prior to harvest (X). The relationship 

 (Y = 15,205,309 - 46,859X) (Figure 4A) yielded 



a correlation coefficient of -0.86 (r^ = 0.74) sig- 

 nificant at the 0.001 probability level it, = 6.06, 

 n = 13). This expression permits the hindcasting 

 of New York landings as well as a forecast 1 yr in 

 advance, with 95'7r confidence limits. The hind- 

 casts and 1-yr forecasts (for 1975) are superim- 

 posed on the actual New York landings in Figure 

 5A. 



As stated by Schaefer (1968, 1972), the New 

 York harvest is predominantly fish of ages III-VI. 

 Close examination of his catch data for 1962, how- 

 ever, revealed that age VII fish, although <27c of 

 the catch in number, could constitute a significant 

 proportion of the catch by weight. Schaefer's 

 (1968) age-frequency distribution shows that in 

 1962 the age III fish outnumbered the age VII by 

 about 10:1. Using the mean age- weight relation- 

 ships of Mansueti (1961) as 1.8 lb at age III and 

 12.5 lb at age VII, the age III fish in Schaefer's 

 ( 1968) 1962 catch thus outweighed the age VII fish 

 by less than 1.5:1. Similarly, the age VI fish ( mean 



295 300 305 



MEAN MODfiL Size I - 5 YEARS PRIOR TO HARVEST 



Figure 4.— Relationship of New York commercial landings of 

 striped bass to the mean modal size at age II; A) 1 to 4 yr prior to 

 harvest; B) 1 to 5 yr prior to harvest. 



470 



