STUDIES ON THE STRIPED BASS OF THE ATLANTIC COAST 47 



The question of how much the areas to the south of Chesapeake Bay contribute 

 to the population in the north, and whether or not the dominant year-class of 1934 

 was produced simultaneously in Albemarle and Pamlico Sounds as well as in Chesa- 

 peake Bay, is of further interest. The author has found no evidence from talking 

 with commercial fishermen in the Albemarle Sound region in 1937 and 1938 that there 

 was an unusually large quantity of yearling bass in 1935 in these waters, as was the 

 case in Chesapeake Bay. Further than this, tagging experiments in March and April 

 in 1938 on the outer coast of North Carolina and in the eastern end of Albemarle 

 Sound tend to show that the bass from this area do not undertake such an intensive 

 migration to the north in the spring, and that they do not contribute a large amount 

 to the summer population in northern waters. It has been pointed out tbat these 

 tagged fish did not show an intensive one-way migration at this time, but rather a 

 diffusion from the point of release with only a small percentage of the fish making 

 definite movements of considerable distance to the north. This was in spite of the 

 fact that these fish were released at exactly the time they would be expected to under- 

 take the spring migration northward, and was in direct contrast to the one-way mass 

 migration southward as shown by tagging hi the north in the fall (see pp. 36-39 and 

 44-46). It is clear from this information that the stock in North Carolina waters 

 probably contributes only a relatively small percentage directly to the populations 

 summering in the north. 



There is further evidence from the results of scale analysis that the main source 

 of supply for the summer populations in northern waters is in the Chesapeake Bay 

 area — or at least that general latitude (which includes Delaware Bay), and not from 

 farther south. Unfortunately vertebral counts are of no value in showing the general 

 point of origin of individual striped bass or for racial analysis, for this is a species with 

 a virtually constant number (25) of vertebrae (see p. 3), and therefore the counts 

 show no variation with latitude such as has been shown to occur in other forms (e. g., 

 Hubbs, 1922). Scale and fin-ray counts may possibly be of some use in this respect, 

 but they have not been used in this study because of the impracticably of making 

 such counts, especially where the material was limited and it was desirable to tag a 

 large proportion of the fish that were taken in northern waters. But whereas scale 

 and fin-ray counts were not feasible in conjunction with tagging work, it was perfectly 

 practicable to take scale samples from live fish. For these reasons, and because the 

 scale method has given such successful results in determining points of origin in other 

 species, scale analysis was used throughout for this purpose. 



The assumption on which such a method rests in a species that spawns over a 

 considerable latitude is that since there are likely to be different environmental factors 

 over the entire range of spawning, there are also likely to be different growth rates 

 which should be reflected in the scales. The problem is, then, to detect these differ- 

 ences in the scales from fish of different latitudes, and to establish that they arc con- 

 stant and therefore good criteria for determining the points of origin of the individuals 

 from which the samples are taken. The striped bass is known to spawn over a wide 

 latitude, and apparently does not migrate along the coast until it becomes approxi- 

 mately 2 j'ears old. Thus, if there are any differences in the growth rate of this species 

 in various localities along the coast, those that are to be used in determining points of 

 origin must be found within that part of the scale bounded by the second annulus. 

 With this in mind, as well as the fact that scale growth is proportional to body growth 

 (see p. 31), the widths of the first and second growth zones of scales from striped 

 bass of known and unknown origin were measured by the method described in the 

 section on age and rate of growth (see fig. 15). 



Figure 32 shows the length-frequencies of the widths of the growth zones in 

 millimeters on scales from striped bass taken in different localities along the Atlantic 

 coast in 1937. The top three series of length-frequency curves (those from scales 

 from fish taken at (1) Cape Cod Bay, Mass., (2) Harkness Point, Conn., and (3) Mon- 

 tauk, Long Island, N. Y.) are from members of the 1934 dominant year-class — 

 that group of fish whose origin is of especial interest. The samplings of fish from 

 which these three sets of curves come, were made in the summer and fall of 1937 in 

 northern waters. In the three sets of measurements, the widths of the first and of the 

 second growth zones are strikingly alike throughout — a fact which at least suggests 



277589 — 41 i 



