Fishery bulletin of the Fish and Wildlife Service - NOAA

STUDIES ON THE STEIPED BASS OF THE ATLANTIC COAST 51
lation summering in northern waters—that is, that they move up into Chesapeake
Bay in the spring as 2-year-olds (e. g., see under the last part of the section on migrations)
and then migrate to northern waters a year or more later. This is added
evidence that the dominant 1934 year-class, which first appeared as 2-year-olds in
northern waters in 1936, came from the general area of Chesapeake and perhaps
Delaware Bays, although evidence of the above type should be obtained for severa 1
successive years before it can be considered conclusive proof of the fact that the
contribution to northern waters in the spring and summer comes essentially from the
latitudes of Chesapeake and Delaware Bays each year.
Measurements of the growth zones of scales from striped bass born in 1936 in
the Delaware Bay and Albemarle Sound regions are shown in figure 34. It will be
noted that the widths of the second growth zones of the scales from the fish of Delaware
Bay origin born in 1936 are slightly below those for the growth zones on the
scales from the fish of Chesapeake Bay origin born in 1935. (Compare upper set of
curves in fig. 34 with middle set of curves in fig. 33.) It is probable that this difference
is at least in part due to the fact that the second growth zones on the scales from
the Delaware Bay fish were not yet quite complete (the fish were taken on November
8, 1937) because the annuli on scales do not appear until spring, although the growth
from November to March is almost negligible. Whether or not there is a constant
difference in the widths of the second growth zones of scales from fish of Delaware
LENGTH FREQUENCIES OF GROWTH ZONES ON SCALES FROM
FROM YEARLING AND TWO-YEAR-OLD. STRIPED BASS IN
1957-1938
FIGDBÏ 34.—The length-frequencies of the growth zones on scales from yearling and 2-year-old striped bass taken In Delaware Bay
and Albem&rle Sound in 1937 and 1938. The measurements making up these curves have been smoothed by threes throughout.
and Chesapeake Bay origin remains to be seen from sampling over a period of years.
It is probable that this method will not provide a good means of distinguishing
between bass born in these two regions, as the environmental differences are apparently
insufficient to cause any constant difference in growth rate during the second
year. The widths of the second growth zones of scales from fish born in 1936 in Albemarle
Sound (see lower set of curves in fig. 34) are interesting because although they
are quite great, they are not so distinctively different from the others as those from
North Carolina collected in 1937 (see bottom set of curves, figs. 32 and 33). They
indicate, in other words, that although a wide second growth zone is apparently 1 a
characteristic of North Carolina fish from the general region of Albemarle Sound,
this characteristic varies from year to year sufficiently so that it can only be used as
a means of distinguishing fish of North Carolina origin from fish of Chesapeake Bay
origin when the scales from fair samplings of bass that are just becoming 2 years old
in the spring, before any coastal migrations have been undertaken, are available
from both areas during any one year.
In conclusion it should be emphasized once more that the available evidence
from general observation, scale analysis, and tagging experiments, gives every indication
that the dominant 1934 year-class originated chiefly in the latitude of Chesapeake
and Delaware Bays; that those fish produced in North Carolina contribute
directly only a relatively small fraction to the population summering in northern
waters; and that the main body of the northern summer population of striped bass
comes from the area bounded on the south by Virginia and on the north by New
Jersey. Further proof that Chesapeake Bay m general contributes a large proportion
of the stock summering in northern waters is seen in figure 35, where the catches