Fishery bulletin of the Fish and Wildlife Service - NOAA

STUDIES ON THE STRIPED BASS OF THE ATLANTIC COAST 29
ments of fish from any one region at any one time, and that the samples from different
areas may have been composed of stocks from widely separated localities which showed
different growth rates. Nevertheless, scale analysis (see Origin of the dominant 1934
year-class, pp. 46-52) points to the fact that the striped bass on which studies were
made in northern waters in the summer of 1936 and 1937, were mainly of essentially
the same origin and with similar growth rates in their first and second years. Figure 19
shows length-frequency curves for 2- and 3-year-old striped bass taken north and
south of Cape Cod in 1937. Those taken north of Cape Cod were from Massachusetts,
and those south of Cape Cod from Connecticut. The striking difference
in the striped bass of the same ages from these two areafe is at once apparent. The
2-year-olds north of Cape Cod show a peak at approximately 40 cm., while those
south of Cape Cod have a peak near 34 cm. The 3-year-olds from the same areas
present peaks at 45 and 40 cm., respectively. It is almost certain that all these fish
were of southern origin (see Origin of the dominant 1934 year-class, p. 51), and that
they first migrated to northern waters as 2-year-olds in the spring (see Migrations,
p. 44). It is possible that the difference hi size can be accounted for by differential
LENGTH FREQUENCY CURVES OF TWO- AND
THREE-YEAR-OLD STRIPED BASS TAKEN
NORTH AND SOUTH OF CAPE COO, JUNE-
SEPTEMBER, 1937 г YEARS OLD
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10
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NORTH OF CAPE COD
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10 INCHES
3 YEARS OLD
39 40 49 90 59 £0
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15
SOUTH OF CAPE COD
PIQUEZ 19.—Length-frequency curves of 2- and 3-year-old striped bass taken north and south of Cape Cod from June through
September 1937. Data smoothed by a moving average of threes throughout (see Table 13 for original measurements).
migration—that is, that the larger fish of the age-categories concerned migrated farther
north than the smaller individuals. This is unlikely, however, and the difference
in size is probably best explained by differential growth rates in the spring, summer,
and early fall in the areas under consideration. The samples from these areas are
perhaps poor, in that they are composed of rod-and-line caught fish in order that they
might be comparable, for it was impossible to get samplings of the population north
of Cape Cod over this entire period by any other method. The differences in size
may be slightly exaggerated, owing to the fact that the sampling in the early summer
south of Cape Cod was somewhat more intensive than that oi the middle and late
summer, while the sampling north of Cape Cod was evenly distributed throughout
the entire period from June through September 1937. There can be little doubt,
however, that in 1937 the 2- and 3-year-old striped bass north of Cape Cod grew much
faster than those in Connecticut waters from June through September.
The average length attained by striped bass each year from the first to the
tenth, year has been calculated by two different methods, and is shown in figure 20.
It is of some interest that these lengths of striped bass at different ages compare
almost exactly with those given by Scofield (1931) and Clark (1938) for striped bass
on the Pacific coast. Since bass 2 years old and older were available in Connecticut
waters in large numbers, it was possible to calculate the average lengths of the different
age groups simply by making age determinations from the scale samples of fish
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