Fishery bulletin of the Fish and Wildlife Service - NOAA

STUDIES ON THE STRIPED BASS OF THE ATLANTIC COAST 43
season in such a place as the Niantic River, where striped bass are caught so consistently
at approximately the same temperature in the spring and fall, are mainly
winter residents, but it is also known that migratory individuals are present at the
times of the earliest and latest catches. It is of interest to note that during October
and November 1936, a time which was characterized by sudden drops in temperature,
it was plainly indicated that with each cold snap, and resultant decline in temperature
of the water, some of the striped bass in the Niantic River moved out and their place
was almost immediately taken by fish that presumably came from farther up the
coast. Such changes in the population were definitely observed on at least two
occasions, both immediately following sharp drops in temperature. Strong winds
and storms in the fall also play a part in causing the fish to undertake their migrations.
The maximum temperatures for this species appear to be in the neignborhood of
25°-27° C. (77.0°-80.6° F.), for in New England waters in the latter part of August
and early September 1937 when there was a protracted period of exceptionally warm
weather (see fig. 30), dead bass in considerable numbers were reported simultaneously
in Connecticut and Massachusetts. Such mortality occurred chiefly in shallowwater
estuaries where the water temperatures reached especially high levels. A
number of dead bass were observed by the author in the Niantic and Thames Rivers
at this time, and an examination of them disclosed no parasites or injuries that might
possibly have been fatal. The water analyses of the Connecticut State Water Commission
taken at various intervals in the Thames River near New London, Conn.—an area
where many dead bass were found—showed nothing unusual nor the presence of any
toxic substances during this period (see table 21). There also was a marked migration
of bass that normally spend the entire summer in the Niantic and Thames Rivers
out to the cooler coastal waters at the time the water temperatures were so high.
This was shown by the recapture of tagged fish outside, and by the almost complete
absence of bass in the rivers where they are usually found at this time of year. In
view of such facts, the evidence is strong that a temperature of 25°-27° C. (77.0°-
80.6° F.) marks the maximum tolerance limit. This is a water temperature which
is seldom exceeded over the entire range of the striped bass.
It is of some interest to note that although a considerable number of striped bass
weighing from 5 to 25 pounds were marked by external disc tags, there have been no
returns from these fish save in the immediate locality at which they were released
and within a short time after marking took place. Returns of tagged fish from any
other area then the general point of release have been confined to individuals not
more than 4 years old. It is difficult to account for this circumstance, and, although
it may be that the larger bass did not take such a great part in the migrations as the
younger individuals, information as to the size-categories appearing m commercial
catches in previous years does not make it seem likely that this is an adequate explanation.
By the same token, it is improbable that the larger fish migrate in waters
farther offshore, thus reducing the chances of their being caught along the coast.
It is possible that the larger individuals do not carry the external disc tags as well as
the smaller fish, and that the tags are not retained for more than a short while. It is
true that the larger the bass the nearer the top of the back the pin bearing the tags
must be inserted, because the breadth of the fish makes it impossible for pins only
1% inches long to penetrate to the other side far below the dorsal contour. Other
reasons for the lack of returns of the larger tagged fish are, first, the overwhelming
abundance of the members of the dominant 1934 year-class, and second, the tendency
of the smaller size-categories—2- and 3-year-olds—to school heavily. This schooling
instinct, or schooling "synaprokrisis" (Parr, 1937), tends to make them much more
available to commercial fishermen than the larger individuals which are not so strongly
inclined to congregate together. The heavy schooling of the smaller fish of definite
size-categories was observed countless times in the course of seining for tagging
purposes in 1936 and 1937. That these schools tend to travel considerable distances
without breaking up is suggested by the recapture in several instances at the same
time and in the same area some distance away from the original point of release of
two or three fish that had previously been tagged in a single seme haul in the Niantic
River.