Fishery bulletin of the Fish and Wildlife Service - NOAA

8 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE
Close examination of the available records reveals that the abundance of striped
bass on the Atlantic coast has shown tremendous fluctuations over a long period of
years. As will be shown below (see p. 13), this is because the striped bass is subject
to year-class dominance, a phenomenon which has received increasing attention in
the past quarter century, since it has been found to apply to so many different species.
Briefly explained, year-class dominance may be said to be the production of such
unusuaUy large quantities of any species in a single year that the members of this agegroup
dominate the population for a considerable period, and are noticeably more
abundant than the individuals produced in the preceding and following years. Such
dominant year-classes usually make their appearance only at fairly lengthy intervals.
Year-class dominance in any species does not, of course, insure the maintenance
of the population at a consistently high level. It is also clear that dominant yearclasses
are often produced by a comparatively small parental stock (see p. 14), and
that therefore—at least down to a certain point—their appearance is not correlated
with an unusual abundance of mature and spawning fish. There may even be an
inverse correlation between these two factors—that is, a large production in any season
by a comparatively small population of mature individuals. Such a correlation has
been suggested by Bigelow and Welsh (1925) for the mackerel (Scomber scombrus),
the "years of great production always falling when fish are both scarce and average
very large . . ." This phenomenon is probably most common in particularly prolific
species that produce a large number of eggs. Such a species is the striped bass, and
such a production of a dominant year-class took place in 1934 (see p. 11).
In the case of the striped bass a study of the size of the stock over short-term
periods may, therefore, be most deceptive. Thus the first manifestation of a large
year-class might give the impression of increasing abundance, or, if the study started
shortly after an exceptionally productive year, a sharp decline in the population
would be apparent under the conditions of the existent intensive fishery. To get a
true picture of the trend in abundance, it is therefore essential to study the fluctuations
over long-term periods.
Accurate catch records, which form the most reliable means of studying the relative
size of the population in different periods, are unfortunately not available
farther back than the latter half of the nineteenth century. Bigelow and Welsh
(1925), however, state: ". . . that a decrease was reported as early as the last half
of the eighteenth century." Nor is it surprising that such a decline was noticed so
long ago when it is considered that the striped bass is a strictly coastwise species,
and one that is easily available throughout the year. If haddock (Melanogrammus
aeglefinus) (Herrington, 1935), halibut (Hippoglossus hippoglossus) (Thompson and
Herrmgton, 1930), and other offshore fish.es have become scarcer through the intensity
of fishing, and this is admitted, it is much more likely that a purely coastal
species such as the striped bass, which is far more accessible and therefore unceasingly
the object of fishermen's attention, should soon have shown a marked decrease
in numbers. Also, the availability of the striped bass and the resultant heavy drain
on the stock is not the only factor involved. Since this fish is anadromous, there
has been every chance for civilization to do irreparable damage to valuable spawning
areas. There is abundant evidence to show that such destruction has often
occurred (see p. 16). In view of these facts it was not an unreasonable expectation
that the supply should soon have diminished, and that in spite of the production
of dominant year-classes the stock could not be maintained at its original high
level. Even in the absence of catch records or figures to prove the point, there can be
no question but that the numbers of striped bass along the Atlantic coast have decreased
during at least the past 2 centuries. There have undoubtedly been periods
when the population showed sudden and pronounced increases, presumably due to
the presence of unusually good year-classes. But these peaks have probably been
short-lived, and the general trend over long periods has been downwards.
Two series of accurate catch records going back to the latter half of the nineteenth
century have been made available to the author. Both of these bear out the above
contention and substantiate such a hypothesis. The first record is that of the numbers
of striped bass taken annually from 1865 to 1907, on rod and line, by the members of