STUDIES ON THE STRIPED BASS OF THE ATLANTIC COAST 



61 



due to the high value estimated for natural mortality each year, for the amount 

 added in total growth by allowing the fish to live until they are 4 years old does not 

 compensate for the numbers lost through natural mortality under these conditions. 



Table 2. — Theoretical treatment of 1,000 striped bass of the 1984 year-class to show the rate of removal 

 by the fishery and natural mortality, the numbers and poundage caught, and the market value, when 

 the fish were caught over a 4-year period from 1987-40. Note that in this treatment the fish were 

 caught for the first time when they were 3-year-olds 



In tables 1 and 2 it was shown that the total market value of striped bass taken 

 from the available stock of 1,000 fish of tbe 1934 year-class from 1936-40 (bass caught 

 for the first time as 2-year-olds) was $57.45, as compared with $64.4S when this same 

 stock was utilized by taking its members for the first time when they were 3-year-olds 

 over the period from 1937-40. It should be pointed out that the gain from allowing 

 the fish to become 3 years old before being caught has been figured in these examples 

 as the least that can result. In the first place, the fishing mortality on the members 

 of the 1934 year-class was estimated from tagging experiments as 40 percent in 1936 

 and 25 percent in 1937. It has been arbitrarily placed at 15 percent in 1938, 10 per- 

 cent in 1939, and 5 percent in 1940, because they are considered the lowest values 

 possible. Whether or not this annual decline in the percentage taken is as steep as 

 indicated above and in tables 1 and 2 is extremely questionable. It is obvious that 

 if this decline is less sharp, the gain from allowing the fish to become 3 years old before 

 being caught is relatively greater. Further than this, the natural mortality of the 

 bass of the 1934 year-class is estimated to be 33 percent of the population (neglecting 

 fishing mortality) in 1936, and it has been arbitrardy placed at 33 percent for the 

 years from 1937 to 1940. Actually, it is extremely unlikely that it remains as high 

 as 33 percent over this period, for it is reasonable to assume that as bass become 

 older than 2 years of age they are less likely to be killed through natural causes. It 

 is possible that when bass become much older the death rate increases, but in the 

 examples in tables 1 and 2 that stage is probably not reached. Thus it is likely that 

 the annual natural mortality of 33 percent from 1937 to 1940 is far too high. If this 

 be so, the gain from allowing the fish to become 3 years old before being caught is 

 again relatively greater than is shown by the total market value in the examples given 

 above. It is evident therefore that the gain from catching striped bass for the first 

 time as 3-year-olds is far more than is shown in tables 1 and 2. Nor should it bp 

 necessary to point out that the figures used in the examples in tables 1 and 2 represent 

 only gross values, and that the net values would be far greater. 



It is also of importance that if the fishery first starts to operate on the striped bass 

 population when its members are 3 years old, a greater proportion of the stock is given 

 a chance to spawn. It has already been shown (see p. 22) that female striped bass first 

 mature at 4 years of age. If the stocks available at this age are compared in tables 1 

 and 2, it will" be seen that of the 1,000 original fish of the 1934 year-class only 200 were 



