G. Brown (George Brown) Goode.

The fisheries and fishery industries of the United States (Volume 1:1) online

. (page 102 of 146)
Online LibraryG. Brown (George Brown) GoodeThe fisheries and fishery industries of the United States (Volume 1:1) → online text (page 102 of 146)
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28







EXTREME AND MEAN TEMPERATURES, BY MONTHS Continued.





Air.


Surface.


Bottom.




Air.


Snriiw.


Bottom.


September:
Maximum
Minimum


OF.

94.0
73.0


OF.
82.0
74.0


OF.

82.0
74.0


I >.!! in Ih-r :
Maximnm
Minimum


OF.
73.0
51.0


OF.

01.0
61.0


OF.
01.0
51.


Mran
October:

M IX'IIIIIITI ..


85.2
84.0


80.1
74


73.9
74


Mean

Jiinn.iry:


62.1


57.4


57.3


Minimum


70.0


70.0


69.0


Minimum


48.0


52.0


M.O


Mran


77.7


70.8


707


MOMI.


60.4


54.8


54.5


NovemlM-r :
Maximum


83


71


71


Febnrirv:


72.0






Minimum


! I.


56.0


56




50


55. 5




















Mean


68.4


(3.6


63 5


iM. ri


83. 3


48. 3






















602 NATURAL HISTORY OF AQUATIC ANIMALS.

Now, in all other streams on the Atlantic coast, the fish appear to wait until the temperature
of the river has risen above that of the salt-water area into which the river empties, before they
ascend in the spring. The migration of the Shad iuto the Saint John's River is clearly not for the
immediate purpose of spawning, as that operation is not performed for mouths, but in order that
they may keep within the limits of the hydro-isothermal area appropriate to them. We must
suppose that the temperature of the ocean waters, on the continental plateau outside the coast
line, is higher than 60 F., and although uncongenial to the fish, yet they must necessarily
remain in that temperature until the waters of the Saint John's, cooling as winter advances, have
fallen below the temperature of the outside waters. As soon, therefore, as water of a lower tern
perature than that in which they are commingles with the ocean water, it serves as an incentive
as it were the signal for their migration into the estuary of the Saint John's.

OBSERVATIONS ON THE POTOMAC RIVER IN 1881. In 1881 the writer, then in charge of the
shad-hatching operations on the Potomac River, collected full statistics of the catch of Shad and
Alewives from four of the seine fisheries occupying that section of the river lying between Indian
Head and Mount Vernon. From these statistics the fluctuations in the run of the Shad up the
river have been closely approximated, and at the close of this paragraph general deductions rela-
tive to the same will be made. Through the courtesy of the Light- House Board and the United
States Signal Office, observations on the water temperature at Winter Quarter Shoals and at
Norfolk, Virginia, have been obtained. The former point is a light-house .in the Atlantic, lying
about fifteen miles from the Virginia coast, and situated, it is believed, on the inner edge of the
cold arctic current that flows down the coast inside of the Gulf Stream. The observations
taken there represent the temperature of the water on the continental plateau between Cape
Charles and Cape Henry. The records taken at Norfolk serve as an index of the temperature
of the waters of the Chesapeake Bay, but are subject to inaccuracies, Elizabeth River being hardly
more than a tidal estuary, and the temperature of its waters being influenced very materially by
local meteorological conditions.

A graphical representation of the temperatures at these two points, as also of the corre-
sponding temperatures at the Potomac hatching station, is given in the accompanying diagram,
which serves to illustrate the influence of hydrothermals in determining the direction of the move-
ments of the Shad and Alewives and in limiting their range. In the diagram are also presented
the fluctuations of the run of these fish in the fishing season, as deduced from the records of
"catch," furnished by the four seine fisheries already alluded to. 1

By reference to the diagram it will be seen that during the first seventeen days of April (1)
the temperature of the water in the Potomac was occasionally lower than at Winter Quarter Shoals
during the same period of time; (2) that the water of the Chesapeake Bay was warmer than that
of the ocean between Cape Charles and Cape Henry, and also warmer than the water in the
Potomac River, and that (3) during that time the temperature was in none of those waters above
60 F. As soon as with the advancing season the water in the river became warmer than in the
bay the Shad commenced to ascend the Potomac, and when the temperature of the river rose to
60 F. the upward run attained its maximum ; the main body of Shad and Herring ascended the
river when its temperature ranged from 56 F. to 66 F.; and, further, that when the temperature
of the river passed above GC F. the run of Shad and Herring rapidly diminished. It may be
seen also that in general the fluctuations in the run of the Herring closely followed that of the

'Although the data obtained from those four shores do not by any means represent the total catch for the whole
river, yet, covering as they do a complete section of the river, they furnish figures from which the fluctuations in the
upward migrations of the Shad and Alewife for the whole river can be approximated.



MOVEMENTS OF YOUNG SHAD. 603

Shad. The run of Alewives indicated by the diagram in the early part of the season at low
temperature was undoubtedly (' rrnmlix, or the 1 '.ranch Herring, which makes its run on a tem-
perature several decrees lower than suitable to the Shad or the (Hut Herring. The fact that the
Shail commence i mmim: into the Potomac when the temperature of the river is 56 F. or less,
does not antagonize the theory here stated, that the hydro-isothermal area which they prefer to
occupy is that having the temperature of about 00 F. If, as is probably the case, there is oeean-
ward.s a limiting wall of low temperature for the Shad occupying the Chesapeake area, 1 then
at all seasons of the year the Shad must be found at some point within that area, be the tempera-
ture exactly what they prefer or not. In other words, the Shad in their migrations travel on
temperature paths, the direction being always towards 60 F.

shad ready to deposit their spawn seem to prefer waters of a warmer temperature than 60 F.
Therefore, when the mature Shad, intent on reproduction, leave the hydrothermal area of 60
V. and ascend the rivers into waters of 65 F. to 70 F. and upwards, they are unaccompanied by
the half-grown Shad, the latter ceasing to ascend as soon as they encounter a temperature of more
than 00 F. In 1882, however, when the temperature of the water was below GO F. for the greater
portion of the season, the spawning had to take place in water colder than the fish would have
preferred, and therefore mature and young Shad were found together on the spawning grounds.

Observations made during that season show that large numbers of young Shad were taken,
which would not have been the case had the temperature of the river waters risen above 00 F.
Inasmuch as the fishing operations are conducted with a view to obtain mature fish, and in most
years the yonng do not accompany the full-grown fish up to the fishing grounds, it would certainly
appear as though this was a special provision of nature to secure the continuance of the species,
providing against the capture of the young Shad during the fishing season.

OBSERVATIONS ON THE MOVEMENTS OF YOUNG SHAD IN THE POTOMAC. The young Shad
which are hatched out during May and June remain in their native streams until the temperature
of the water falls below GO F. They then move down the rivers as the temperature falls, passing
into the salt water as soon as the cooler weather has reduced the river temperature below the
degree congenial to them, and, as a rule, return no more to the fresh waters until they are full-
grown fish. This statement is borne out by observations made in 1881 by Mr. W. E. Stuart and
Mr. Gwynn Harris, inspectors of marine products. These gentlemen, who have been largely
engaged for many years in the Potomac fisheries, whose interest is always manifested in connec-
tion with all matters relating to the fisheries, undertook, at the instance of Professor Baird, United
States Fish Commissioner, to observe the movements of the young Shad in the Potomac in front
of the city of Washington. Their observations show that on November 1C, when the thermometer
showed the temperature of the water to be 68 F., young Shad were present in the Potomac at
Washington in large numbers. From this date the temperature of the water gradually fell, co-
incident with which the numbers of young Shad decreased until on November 23 the fish had
entirely disappeared, the thermometer then showing 58 F. The disappearance of these fish can
be referred only to the fact that the water had fallen "below 60 F., for as long as that temperature
was preserved the fish remained in the portion of the river under observation. The lowering of
the temperature of the water seems to present the only variable factor in the conditions which
surrounded them, and to this we may reasonably refer their disappearance.

THE PERIOD OF RIVEU LIFE. The deposit of the eggs of the mature Shad in fresh waters
seems to be a necessary condition for their development. The idea has prevailed to some

'The Chesapeake area includes the Potomac River, the Chesapeake Bay and its tributary streams, and the
ocean between Cape Henry and Cape Charles.



604 NATURAL HISTORY OF AQUATIC ANIMALS.

extent that the Shad under certain circumstances spawn in salt or brackish waters. Experi-
ments have, however, been made to verify this supposition, but have proved unsuccessful.
Whilst impregnation under such conditions has been shown to be possible, and development has
proceeded to a certain point, yet before the hatching took place the development of the embryo
broke down. The annual migrations .of the Shad into our streams are made apparently for
the sole purpose of reproduction, excepting in the Saint John's River, Florida, where their first
movement into the river seems to be attributable to an influence other than that above mentioned.
The time of these migrations into the rivers varies with the geographical position of the river. As
a general rule, it is usually later as we proceed farther to the north, though we find some excep-
tions. It may be stated generally that this migration takes place as Boon as the continental
waters have become warmer than the salt- water areas into which they discharge. The schools of
fish having entered the streams, ascend until they have reached suitable spawning grounds. The
deposit and fertilization of the eggs having been accomplished, their development commences, and
in a few days, the period varying with the temperature, the young fish, bursting their shells, make
their appearance. These remain in the rivers, feeding and growing all summer, and leave'late in
the fall, at which time they are two or three inches in length. The life history of the Shad from
this time is unknown to us. The young fish, having disappeared, do not again come under our
observation until they return as mature fish to deposit their spawn.

The motive of their movement into the rivers being for purposes of reproduction, we would
expect that with the accomplishment of this desire the mature fish would return to salt water.
This is the general impression among fishermen, and may be true as a general fact, but there are
instances on record where a full-grown Shad in good condition has been taken in our rivers long
after the spawning season is over, and even late in autumn. One of the largest Shad I have ever
seen from the Potomac was taken in the vicinity of the White House in the mouth of November.
In the season of 1880, I believe, several full-grown Shad were taken below Holyoke Dam on the
Connecticut River in the latter part of the summer. These instances would seem to indicate that
under certain conditions the Shad may remain in our rivers during the whole season.

The appearance of the spent fish, or those which have deposited their eggs, enables the fisher-
men to recognize them at once, and various names have been given to them. From the fact that
they are supposed to be moving down the stream when taken, they are called "Down-runners,"
and from their lean, slim appearance, they are also called " Racers."

The Shad make their first appearance in the Saint John's River about the middle of Novem-
ber, the height of their spawning season in that river being about the 1st of April. In the
Savannah River they appear early in January, and in the Neuse River at a period not much later
than in the Savannah. In the Albemarle the important Shad seine-fisheries begin early in March,
but doubtless the fish are in the Sound some time before that date; not, however, in numbers
sufficient to justify the great expenses attendant upon the pperation of these large seines. In the
Chesapeake Bay they make their appearance in February, although the height of the fishing
season in its waters is during April and May, and at a date somewhat later in the more northern
tributaries. In the Delaware, Connecticut, Merrimac, and Saint John (Nova Scotia) Rivers, Shad
are first seen at periods successively later as we proceed farther north. The date of their first
appearance in any of these waters, however, varies from season to season, the limit of such varia-
tion being from three to four weeks.

These irregularities in the time of the run into our rivers, which cause so much perplexity
and discouragement to the fishermen, are, however, readily explained when we keep in view what



I.'KI'KODUCTION OF THE SHAD.

ha* I" -n already said in regard t<> the iiiHiu-nces of temperature in determining the movements of
hcse fishes.

CAISKS IM-I.I i:Nci.N(i Tin: i:\ii; ni MHVI:MKNT rr KIVKKS. The rate and duration of the
movement of Shad in our rivers are intlnenced by various causes. If, in consequence of warm
rains at the river's .-.onice, the temperatiire of the water heroines suitable to the Shad at an earlier
date than usual, then their upward movement takes place very rapidly, and, we may say, tumult-
iiously. the great .-.cliools of fish crowding in and moving up all at once, so as to produce what is
termed a "glut." If, however, the temperature of the river rises by insensible degrees witb the
advance of the season, then the upward movement begins when the water temperature of tbe river
II:IN passed above that of the sea, and takes place gradually, the rate of movement in such cases
iK'ing slow and the period prolonged. Again, when the Shad have entered the rivers, the temper-
ature conditions being such as to dcti-nnine a rapid upward movement, yet should the fish en-
counter floods and consequent muddy waters, their upward movement is arrested, the schools back
down before the flood, and if this condition be prolonged, may be driven entirely out of the river.
In short, fluctuations in the river temperature have corresponding influences upon the shad move-
ments; any sudden change, whether to a higher or lower temperature, apparently arresting their
upward course for a time, and sometimes even determining a retrograde movement.

Many of the anomalies which perplex fishermen in the course of their work may be explained
by the varying movements of the fish, as controlled by the water temperature in the rivers. We
find, for example, that while at a particular seine-shore, during one season, a very large catch
is made, yet in the following season, although the general run of fish in the river has not dimin-
ished, the fishery in the same locality may prove a failure. If we suppose a seine to sweep the
flats at the mouth of such a stream as the Occoquan Creek, 1 and if we further suppose that the
river waters in the channel are colder than, or as cold as, the waters of the Chesapeake Bay, the
Shad in their movement up the river would avoid the main current, and would slowly work their
way up along the shores and over the flats, where the temperature of the waters will be found to
be, under such circumstances, several degrees warmer than in the channel. Such a season would
be profitable to a seine sweeping the flats. Again, if the waters in the main channel of the river
were of suitable temperature, then the upward movement of the Shad would take place in the
channel and not along the flats. Under such circumstances a "channel seine," e. </., that of the
White. House," would make a very large catch, whilst a seine hauled over the flats, as on the
Pamitnkey shore, would probably find very indifferent fishing.

REPRODUCTION. The age at which the Shad reaches maturity and becomes capable of repro-
ducing is not definitely determined ; it is generally held by fish-culturists, however, that the female
Shad attains this condition when three or four years old. The period of maturity for the male, if
the relative size of the two sexes be taken as an indication, is much earlier than for the female.
Males, or " Buck Shad," weighing less than one and a half pounds (numbers of which always accom-
pany the schools of larger fish), are fouud to be milters, and at the shad-hatching stations
especially during the earlier part of the season the spawn-takers are frequently compelled to have
recourse to these fish in order to get the milt necessary for the fertilization of the eggs. These fish
cannot be more than two years of age. It appears that the first part of the run of fish up the rivers
consists almost entirely of males, which precede the females by several days. The records of the
fishing shores agree with this statement, their main catch in the earlier part of the season being
composed of "bucks," with a very sparing intermixture of "roe Shad," which latter, in their turn,

'A tributary of the Potomac River.



606 NATURAL HISTORY OF AQUATIC ANIMALS.

increase in proportion as the season advances. The favorite spawning grounds of the Shad, or
" Shad Wallows," as they are termed by the fishermen, are on the sandy flats which border the
streams, and the sand-bars which are found at intervals higher up the river. When the fish have
reached suitable spawning grounds and are ready to cast their eggs, they move up to the flats
seemingly in pairs. The time of this movement is usually between sundown and 11 p. in. When
in the act of coition they swim close together and near the surface, their back fins projecting above
the water. The rapid, vigorous, spasmodic movements which accompany this operation produce
a splashing in the water which can be plainly heard from the shore, and which the fishermen
characterize as " washing."

The eggs are spun out by the female while in rapid motion. The male, swimming close to
her, ejects his milt at the same time, and the contact of egg and milt, and the consequent impreg-
nation of the egg, is coincident with or immediately subsequent to the ejection of the ova from the
female. The specific gravity of the egg being slightly greater than that of water, it sinks to the
bottom, and, under favorable conditions, develops and hatches out. Large numbers of these eggs
are, of course, destroyed by the predaceous fishes that have learned to frequent the spawning
grounds of the Shad. A sudden lowering in the temperature of the water may, and frequently
does, produce a large destruction of eggs. Floods, too, bring down mud which may smother and
destroy vast numbers. But, escaping these casualties, they hatch out in a period of from three to
eight days. Unlike the Salmonida:, although with a sac relatively as large, the new-born Shad
swim vigorously as soon as they break the shell, and, according to Mr. Seth Green, make their
way immediately to the middle of the stream, where they are too small to be an object of prey to
the larger fishes, and where the smaller ones dare not come after them.

The number of eggs in the ovary of a Shad, as in all other fish, bears a certain relation to the
size and weight of the fish. As the result of experience in the artificial propagation of the Shad we
conclude that a ripe roe Shad weighing four or five pounds contains from 20,000 to 40,000 eggs, the
average number being about 25,000. A much larger number, however, has been obtained from
some individuals. In the season of 1881 we obtained from a single Shad, weighing about six
pounds, over 60,000 impregnated eggs; again, in 1880, on the Potomac River, the yield of eggs from
a single Shad was over 100,000. These were full-sized, thoroughly impregnated, and were hatched
out with a loss of hardly one per cent.

SIZE. A female Shad of a certain age is always larger than a male of corresponding age. A
general average for both sexes along the whole coast would be about four pounds, the extremes
for males being from one and a half to six pounds, and for females from three and a half to eight
pounds, the latter representing a maximum weight for Shad at the present time; although, in the
early history of the fisheries, there are records of the capture of fish weighing eleven, twelve, and
as much as fourteen pounds. These extreme figures, of course, are for fish which, in consequence
of the imperfections of the ordinary kinds of fishery apparatus, the want of skill on the part of the
fishermen, or the accidents of fortune have escaped for a long period the fate which befel their less
happy companions and have returned to the rivers year after year.

FOOD. The shad fry, which spend the first six months iu our rivers, must ot necessity find their
food therein. From examinations made of the stomachs of these young fish, they have been
found to feed upon certain species of crustaccn and insect larva?, common to the IVt-sh waters
of our rivers. During the spring of 1882 some young fry, which were hatched out sit Central
station, were confined by Dr. John A. Ryder in a glass aquarium, through which the circulation
of the water was maintained, and fed with Copepoda, obtained in large quantities I'roin the
United States carp ponds. In about seven days after hatching some of the young fry were




Online LibraryG. Brown (George Brown) GoodeThe fisheries and fishery industries of the United States (Volume 1:1) → online text (page 102 of 146)