FISHERY BULLETIN; VOL 76, NO. 2 



see footnote 4) suggest that the bass we examined 

 for back calculation of length were from both 

 Maryland and Virginia rivers, which could ex- 

 plain the differences in the results of the back calcu- 

 lations and the observed lengths. These data 

 suggest that the size-frequency distribution of age 

 II striped bass on Long Island could be bimodal 

 rather than unimodal. The fact that they were not 

 may be due to striped bass migrating by size 

 rather than by age. Two observations of prerecruit 

 striped bass near Long Island lend support to this 

 theory: 1) lOO'/r of the small 454 sublegal fish 

 tagged in 1972 were age-group II, and 2 1 only 28'7( 

 of the 696 sublegal fish tagged in 1974 were age- 

 group II (year class 1972), the remaining 72*7^ 

 were age-groups III (659<^ ) and IV {T7( ). Those fish 

 probably were the larger 1972 and the smaller 

 1971 and 1970 fish. This large overlap in length 

 ranges permitted an intermingling of the age- 

 classes during the migration of 1974. 



Management Implications 



The size increments between different year 

 classes at the same age, and the size differences of 

 individuals within the same year class have sev- 

 eral implications: 



1) Faster growing large individuals of any given 

 year class or a less abundant year class of 

 larger individuals are subject to earlier exploi- 

 tation in Chesapeake Bay and along the entire 

 Atlantic seaboard; 



2) Slower growing individuals or small individu- 

 als of a large year class may be recruited sev- 

 eral months later than normal in Chesapeake 

 Bay, but perhaps not until a full year later 

 among the northern Atlantic States; a late re- 

 cruitment in the Chesapeake area might result 

 in more available fish to the fisheries in the 

 other coastal states when the fish migrate out 

 of the bay; 



3) Projecting sizes offish on the basis of age or vice 

 versa may be invalid, e.g., age II fish in 1972 

 compared with age II fish of Merriman ( 1941 ) or 

 Mansueti (1961). 



The use of a mean 4- or 5-yr modal function for 

 prediction of landings treats all year classes 

 equally. A weighted mean providing greater rep- 

 resentation to more abundant year classes might 

 result in more accurate predictions of landings. 

 Such a method could be used by any State simply 



472 



by monitoring the spring catches of age 11+ pre- 

 recruit fish taken by commercial fishermen. This 

 would require, in New York for example, annual 

 monitoring of the spring run with measurements 

 of sublegal fish. The use of observed modes rather 

 than computed modes for prediction of landings 

 will probably result in more accurate estimates, as 

 suggested in Table 3. 



Table 3. — Comparison of actual New York commercial landings 

 of striped bass with those calculated using computed and observed 

 age II modal values, for years in which sufficient empirical data 

 exist.' 



'Computed and observed age II modal values are those on Table 1. 



The eastern New York commercial harvest of 

 striped bass is primarily dependent upon the year 

 class abundance of the Chesapeake Bay stock. The 

 harvest is influenced not only by the larger and 

 older individuals, but also by the annual recruit- 

 ment of age III fish, especially when dominant 

 year classes are present. 



Knowledge of Chesapeake Bay year class 

 strength or age 11+ modal sizes in New York wa- 

 ters offers a means of forecasting the New York 

 commercial harvest, and thus the apparent abun- 

 dance of striped bass in New York waters. 



If, as suggested, the level of the New York har- 

 vest is primarily related to the Chesapeake Bay 

 stock of fish, than the former can be used as a 

 qualitative measure of the latter. 



Such predictive tools as those discussed should 

 be flexible to allow for the occurrence of more than 

 four age-groups of fish in the catch. This may be 

 especially important when dominant year classes 

 are present for several years. Necessary, then, is 

 the annual monitoring of the prerecruit fish in the 

 commercial catch by age or year class, length, and 

 weight. Age- weight data are especially important 

 as commercial landings are recorded by weight of 

 catch and not by numbers offish. Differences noted 

 between calculated and observed landings may be 

 due to environmental variability, changes in 

 fishing effort, the dominance of a particular year 

 class in the fishery, and the fluctuation in the 

 relative contributions offish from the several At- 



