30 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



of measured length. This has been done on 2,500 fish, and the results are shown by 

 the solid line in figure 20. The average lengths of striped bass from 1 to 4 years old 

 have been calculated from the scales of 4-year-old bass of measured length (see below). 

 This is indicated in figure 20 by the dot-and-dash line. There is every reason to 

 believe from the available samplings of fish of the ages covered by this part of the 

 graph that the lengths derived by this method are accurate estimates. Further 

 than this, it will be noticed that in the center part of the growth curve in figure 20, 

 where the lengths at different ages calculated by both the above-mentioned methods 

 overlap, there is an almost perfect correspondence in the estimated lengths as derived 

 by the two different procedures. It should be emphasized again, in connection 



Figure 20. — The growth of the striped bass, as calculated from scales and the average lengths of different age groups. 

 14 for average lengths of striped bass at the time they become 1 year old, 2 years old, etc., to 9 years old. 



See Table 



with figure 20, that the lengths represented on this graph are averages, and that 

 there is a wide variation about the mean in the lengths at any age. This is of 

 course particularly true among the larger sizes, as is indicated by the broken line at 

 the upper end of the growth curve. In general, fish 100 cm. (nearly 40 inches) 

 long average about 25 pounds and are about 11 or 12 years old; those 125 cm. (nearly 

 50 inches) long weigh approximately 50 pounds and are roughly 20 to 25 years old. 

 The largest striped bass taken in recent years (caught in Rhode Island on rod and 

 line in October 1936) weighed 65 pounds and measured 137 cm. (54 inches); examina- 

 tion of several scales leads the author to believe that this fish was 29, 30, or 31 years 

 old. 10 



In calculating the growth of striped bass up to 4 years old by the scale method, 

 the following formula was used: 



L^C+^iL- 



■O 



L x equals the length of the fish at the end of year "x," \\ the length of the scale in- 

 cluded in the annulus of year "x," V the total length of the scale, L the length of the 

 fish from which the scale is taken, and C the length of the fish when scales first appear. 

 (The use of the factor C has various limitations, see pp. 31-32). The measurements 

 on striped bass scales were made from the focus to the anterior edge of the scale and to 

 the annuli along a line that bisected the angle formed by the junction of the two 



10 In connection with the age of striped bass, Bigelow and Welsh (1925) write, 

 in the New York Aquarium lived to an age of about twenty-three years." 



they are certainly long-lived, for one kept 



