G. Brown (George Brown) Goode.

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

. (page 109 of 146)
Online LibraryG. Brown (George Brown) GoodeThe fisheries and fishery industries of the United States (Volume 1:1) → online text (page 109 of 146)
Font size
QR-code for this ebook


Eels, on an average, eight females, and two with the supposed male organ; but, if the selection is
made with a careful reference to all these marks of difference, the proportion changes, and out of
every ten examples about eight will be found with the supposed male organ. 1

For another excellent discussion with figures of the characters of male and female Eels, the
reader is referred to a translation of an article by S. Th. Cattie, in the Proceedings of the United
States National Museum, vol. iii, pp. 280-284.

EELS SUPPOSED TO BE VIVIPAROUS. The discovery of the two sexes has not, however, writes
Beuecke, settled the question whether the Eel lays eggs or brings its young alive into the world.
There has always been a strong disposition to adopt the latter hypothesis, and there are many peo-
ple at the present day who claim to have been present at the birth of young Eels, or to have found a
quantity of young Eels in adult Eels which have been cut open. Frequently ichthyologists hear
accounts of occurrences of this kind, and receive specimens of supposed little Eels, from one to two
inches in length, which have been kept alive for several days in a glass of water. These are usually
thread worms, Ascaris labiata, which live by the hundred in the intestinal cavity of the Eel, and
which may be easily distinguished from the Eels of the same size by the sharp ends of the body, the
absence of fins, of eyes and mouth, and by the sluggishness of their motions. The smallest Eels,
less than an inch in length, have already the complete form of the adult, and are also transparent,
so that with a magnifying glass one may perceive the pulsations of the heart, and see behind it the
brownish-red liver; the mouth, the pectoral, dorsal, anal, and caudal fins, are easily seen, and the
black eyes cannot be overlooked. In addition to the intestinal worms, the young of a fish of another
family, Zoarces vivipariut, have given opportunity to the ignorant for many discoveries ; for instance,
Dr. Eberhard, in No. 4 of the "Gartenlaube" for 1874, described and illustrated an "embryo of the
Eel," which, in company with about a thousand similar embryos, had been cut out of the belly of
au Eel. This tolerably good drawing at first sight is seen to represent the embryo of Zoarcea,
which is almost ready for birth, since it still possesses a very minute umbilical sac. It is very
evident that the minute egg of the Eel could hardly produce a great embryo with an umbilical sac
which exceeds by more than a hundred times in size the whole egg. It is also evident that the
imagination of the writer had exaggerated the two or three hundred young in the Zoarces to a
thousand.



'JACOBT: Dor Fiaohfang iu tier Laguno von Comacchio.



YOUNG EELS. 647

Si:.u:< it mi; YI>IN<; i.r.i.s. As might have U-en foreseen, remarks Jucoby, Syrski's disco\ i \
drew attention anew to the solution of the eel problem. In the spring ami summer of 1877 the
German and Austrian papers and journals were full of articles and paragraphs upon this subject.
Among others the following announcement made the rounds of the press: " Hitherto, in spite of all
efforts, science has not succeeded in discovering the secret of the reproduction of the Eel. The
German Fiseherei -Yen-in in Berlin offers a premium of fifty marks to the person who shall first find
a gravid Eel which shall be sufliciently developed to enable Professor Virchow in Berlin to dissipate
the doubts concerning the propagation of the Eel." Heir Dallmer, of Schleswig, inspector of fisheries
in that province, otl'ried to transmit communications to Berlin, and in 1878, in the January number
of the. " German Fishery Gazette," he published a detailed and very interesting report of his proceed-
ings. He wrote, among other things, that it was quite beyond his expectation that this announce-
ment would have found its way into nearly all the German journals between the Ithine and the
Weichsel and from the Alps to the sea. The number of letters which he received first rejoiced
him, then surprised him, finally terrified him, so that at last he was obliged to refuse to attend to
the communications. He had learned at Berlin that an equal number of communications from all
parts of Germany had been received, sent directly to the address of Professor Virchow. Objects
which were said to be young Eels cut out of the parents, but which were really thread-worms,

\\n-e sent to him by dozens; tin- most ineredihle storio, usually from women, al I -icat thii-k

eggs which they had found in Eels, were received by him. A witty Berliner communicated to him
in a packet sent by express the information that the eel problem was now happily solved, since a
lady Eel in Berlin had given birth to twins. Finally Herr Dallmer found himself compelled to
insert the following notice in the "Schleswiger Xachrichten": "Since the German Fischerei-Verein
has offered a premium for the first gravid Eel, the desire to obtain the prize, curiosity, or the
desire for knowledge has created so lively an interest upon this point that it might almost be
called n revolution. I at one time offered, when necessary, to serve as an agent for communica-
tions, but since business has compelled me to be absent from home a great part of the time, I
would urgently request that hereafter packages should be sent direct to Professor Virchow in
Berlin. I feel myself obliged to inform the public upon certain special points. The premium is
offered for a gravid Eel, not for the contents of such an Eel, since if only these were sent it would
be uncertain whether they were actually taken from an Eel. The Eel must always be sent alone;
the majority of senders have hitherto sent me only the intestines or the supposed young of the
Eel, which were generally intestinal worms; the Eel itself they have eaten; nevertheless the prize
of fifty marks has been expected by nearly all senders," etc. By this transfer of the responsibilities
the inspector of fisheries has rendered a very unthankful service to Professor Virchow ; he was
obliged to publish a notice in the papers in which he urgently stated that he wished to be excused
from receiving any more packages, for he would hardly know what to do with them. The comic
papers of Berlin now circulated the suggestion that hereafter the Eel should be sent to the inves-
tigators only in a smoked state. This amusing episode is interesting in showing how remarkable
an interest the whole world was beginning to take in the eel problem. 1

NORMAL REPRODUCTIVE HABITS. "It may be assumed with the greatest safety," writes
Benecke, " that the Eel lays its eggs like most other fish, and that, like the Lamprey, it only spawns
once and then dies. All the eggs of a female Eel show the same degree of maturity, while in tin-
fish which spawn every year, besides the large eggs which are ready to be deposited at the next
spawning period, there exist very many of much smaller size, which are destined to mature here-



1 Zoologischer Auzoigur, No. 26, p. 193; Amriou Naturalwt, xiii, p. 125; and Jeol>.v, p. 44.



(548 NATURAL HISTORY OF AQUATIC ANIMALS.

after, and to be deposited in other years. It is very hard to understand how young Eels could
find room in the body of their mother if they were retained until they had gained any considera-
ble size. The eel embryo can live and grow for a very long time supported by the little yolk, but
when this is gone it can only obtain food outside of the body of its mother. The following circum-
stances lead us to believe that the spawning of the Eel takes place only in the sea: (1) that the
male Eel is found only in the sea or brackish water, while female Eels yearly undertake a pilgrim-
age from the inland waters to the sea, a circumstance which has been known since the time of
Aristotle, and upon the knowledge of which the principal capture of Eels by the use of fixed
apparatus is dependent; (2) that the young Eels with the greatest regularity ascend from the sea
into the rivers and lakes.

All statements in opposition to this theory are untenable, since the young Eels never find
their way into land locked ponds in the course of their wanderings, while Eels planted in such
isolated bodies of water thrive and grow rapidly but never increase in numbers. Another still
more convincing argument is the fact that in lakes which formerly contained many Eels, but
which by the erection of impassable weirs have been cut off from the sea, the supply of Eels
has diminished, and after a time only scattering individuals, old and of great size, are taken in
them. An instance of this sort occurred in Lake Miiskeudorf, in West Prussia. If an instance
of the reproduction of the Eel in fresh water could be found, such occurrences as these would be
quite inexplicable.

In the upper stretches of long rivers the migration of the Eels begins in April or May; in their
lower stretches and shorter streams later in the season. In all running waters the eel fishery
depends upon the downward migrations. The Eels press up the streams with occasional halts,
remaining here and there for short periods, but always make their way above. They appear to
make the most progress during dark nights when the water is troubled and stormy, for at this
time they are captured in the greatest numbers. It is probable that after the Eels have once
returned to the sea, and there deposited their spawn, they never can return into fresh water, but
remain there to die. A great migration of grown Eels in spring or summer has never been reported,
and it appears certain that all the female Eels which have once found their way to the sea are
lost to the fisherman. In No. 8 of the German " Fischerei Zeitung" for 1878, Dr. Schock published
certain statements sent to him by Dr. Jacoby. It is remarked in this paper, among other things,
that after the deposition of the spawn the female Eel dies a physiological death, and that occasion-
ally the sea in the neighborhood of the mouths of rivers has been found covered with deaa Eels
whose ovaries were empty. When, where, and by whom this observation was made, and ,vho
pronounced upon the empty ovaries in these dead fish, is unfortunately not mentioned.

A great number of the Eels remain in inland waters while others proceed to the sea, either
because their eggs are at this time not sufficiently ripe, or perhaps because they are sterile. It
would seem probable that the increase in the size of the eggs in the wandering Eels begins to be
very rapid after August and September, while in the earlier months of the year, in all Eels of
moderate size, the eggs were at the utmost but about 0.09 millimeters in diameter. In Septem-
ber of the same year, I found (as an average of numerous measurements) a diameter of 0.10; in
October, 0.16; in November, 0.18 to 0.23, while the eggs showed other characters connected with
approaching maturity which earlier in the season were not to be seen. All the Eels which were
captured later in December and in January part of which came from rivers and harbors, part
from the harbor of Putzig (Putziger Wiek), had eggs measuring from 0.09 to 0.16 millimeters,
although among the fish examined were some which measured three feet in length.



MIGRATIONS OF THE EEL. f, I'.l

Do MALE KKI.S t.r.Avr. mi. SKA AND I;MT.I; FUESH WATEEt This problem is one of great
interest, lint h to the biologist and tin- lish cnlturist; it is, in fact, the one disputed i mint still remain-
ing to be solved. Upon its solution appears to depend the final decision of the question, still so
warmly debated both in Europe and America, "Do Eels breed in fresh water only, in salt water
only, or in both fresh and salt water t" As has already been stated, the theory for a long time
generally accepted is that the Eels are "catadromous," descending to the sea to spawn. This
theory is, however, sharply contested by many observers, chief among whom on this side of the
Atlantic is Hon. Robert B. Roosevelt, president of the American Fish Cultural Association. It
appears probable to the writer that the truth lies somewhere between these two extremes, and
that it will bo hereafter ascertained that the Eel, like a majority of other animals, has flexible
habits, sometimes deviating from its ordinary custom, which appears to be to spawn in salt or
brackish water.

Male Eels have been found in the following localities:

(1) In 1874, by Syrski, in the fish markets of Trieste, these markets being supplied with Eels
from Chioggia on the Adriatic, and to a lesser extent from the lagoons of Gomacchio.

(2) In 1875, on the coasts of France, by Dareste.

(3) In 1875, among specimens of Anguilla marmorata from India.

(4) In 1875, in the Baltic, at Wismar on the Danish coast, by Professor von Siebold.

(5) In 1877, in the lagoons of Comacchio, by Jacoby. Among twelve hundred specimens, five
per cent, were males; while among those less than fifteen inches in length twenty per cent, were
males. This was in brackish water.

(6) In 1879, at Trieste, by Dr. Hermes, who found fifteen males among twenty Eels selected
by Dr. Syrski.

(7) In 1880, on the Baltic coasts of Denmark, by Dr. Hermes. Out of one lot of thirty-six
from Wismar, he obtained eight males, thus repeating von Siebold's observation.

(8) In 1880, from the Baltic between Zealand and Salaud, Denmark. Out of one lot of thirty-
six, Dr. Hermes obtained eight males.

(9) In 1880, in France, by Robin.

(10) In 1880, by Cattle.

(11) In 1880, by Dr. Hermes, at Cumlosen, on the Elbe, about one hundred and twenty miles
from the German Ocean.

(12) In 1880, at Riigers on the Baltic, by Dr. Hermes, who found forty-four and one-half per
cent, males in one lot of 137.

(13) By Dr. Pauly, among Eels planted at Hiiniugen, in Alsace-Lorraine.

It has been shown by Dr. Pauly that among the very young Eels [Montte] taken near the
mouths of rivers is a considerable percentage of males, which, when transplanted to fresh water,
will there retain their masculine characters and develop into perfect adult males. This discovery
is, of course, of the utmost importance to fish-culturists making the attempt to introduce Eels into
new waters. Its importance has already been pointed out by Director Haack.

The practical lesson to be learned is simply this, that young Eels, for introduction into
strange waters, must be taken from very near the mouths of rivers, in order that both males and
females may be secured. The interest to zoologists lies in the fact that Pauly's discovery renders
the theory of von Siebold less plausible, indicating that the sexes of the young Eels are differ-
entiated before they begin to mount the rivers and that the males do not ascend beyond the limits
of brackish water.



650 NATURAL HISTORY OF AQUATIC ANIMALS.

Dr. Pauly's discovery is so interesting that I propose to translate his own account of it. The
investigation was made, I believe, in Munich, and the report from which I quote was published in
the ''Austro-Hungarian Fishery Gazette," of Vienna, December 23, 1880. Dr. Pauly writes:

"During the past year I have received from Court-fisherman Knffer a large number of Eels,
which I have used in my investigations. The large individuals, all of which came from the lakes
of Northern Italy, were females. I received, however, from the same individual, another lot of
Eels, consisting of much smaller individuals, weighing from twenty to ninety grams (two- thirds
of an ounce to three ounces), also taken in fresh water. At the request of Professor von Siebold,
I had paid particular attention to the sexes of the Eels which I was engaged in investigating,
and to my great astonishment I found that a large majority of these small Eels (nineteen out of
twenty-seven) were males, possessing, instead of the familiar ovaries, the 'Lappenorgan' described
by Dr. Syrski. A histological examination of these organs convinced me that the structure of
these tissues agreed with that described by Freud. . . .

" My next inquiry was very naturally concerning the locality whence these Eels had been ob-
tained. I learned that Kuffer had received them two years before from Director Ilaack at Hiinin-
gen, and, upon questioning Director Haack, learned that they had been brought from a French river,
the Sevre nantaise, where they were caught as young fry [montee] at a distance of ten or twelve
miles from its mouth, and furthermore were at the time of examination about four years old. The
small size of these fish, their age being taken into consideration, satisfied me that they had been
reared in captivity, since uncultivated Eels would have been much heavier. The females in this
lot of Eels exceeded the males in length and weight, and also exhibited those external characters
described by Jacoby as indicating sex.

"The locality iu the Sevre niortaise where these fish were taken may easily, especially at flood
tide, have been within the limits of brackish water ; my observations do not prove, therefore, that
male Eels enter fresh water.

"Dr. Jacoby found male Eels in the lagoons of Comacchio, where the water is brackish. These
males must have ascended in the 'mounting' as fry, and probably at the approach of sexual
maturity descend with the females to the sea. My investigations and those of Jacoby prove only
this: that the young female Eels do not necessarily break away from their parents and from their
birthplaces at sea, and entirely alone proceed upon their migrations, while the males scatter through
the sea, but that their brothers seem to accompany them part of the way upon their journey. But
how far ! Do the males know where pure fresh water begins, and are the fry of different sexes found
mingled together only at the river mouths t If we bear iu mind the fact that the male organs had
so long escaped discovery, that, on account of their crystal-like transparency, their detection in a
fresh Eel is so difficult, etc., may we not admit that past conclusions are probably erroneous, and
that although thousands of fresh- water Eels have been studied by different investigators, male Eels
may yet be found in our streams, especially when more of the smaller individuals have been
examined t"

Dr. Pauly then discusses the observations of Dr. Hermes, who found eleven per cent, of males
among Eels taken at Wittenberge, on the Elbe, about one hundred and twenty miles from the Ger-
man Ocean, and no males whatever at Havelberg, twenty or thirty miles higher up the stream, and
closes his essay with the following conclusions : " Male Eels undoubtedly ascend the rivers, but the
numerical percentage of males to females appears to diminish as one proceeds up the streams." This fact
is opposed to the theory proposed by some one that young Eels are at first of undifferentiated sex,
and have the tendency under the influence of fresh water to become females, under that of salt
water to develop male characters.



MOVEMENTS OF YOUNG EELS. 051

BENECKE ON THE MOVEMENTS OF YOUNG EELS. Benocke gives the following thorough
discussion of the movements of young Eels:

The young Eels, hatched out of the eggs at sea, doubtless live at the bottom until they grow,
through consumption of rieli fowl substances there to be found, to a size from one to three cen-
timeters. When they have attained this size they begin their wanderings in immense schools,
proceeding to ascend into the rivers and lakes. These wanderings of the young Eels have been
known for a very long time; for instance, in the lagoons of Comacchio, in which they may be found,
for the. most part, after they have gained the length of from six to eight millimeters, and in France,
later also in England, Denmark, Sweden, and, more recently, in Germany they have also been
observed.

According to the French reports young Eels are hatched out early in the winter, and in Feb-
ruary, having attained the length of four or five centimeters, they appear in the brackish water
at the mouth of the Loire in immense numbers, soon to begin their wanderings up the stream.
They swim in crowded schools at the surface of the river right up to the banks, and little detach-
ments of the army deploy at the mouth of each tributary and pursue their wanderings along its
course. These swarms of young Eels are called in France "Montee," in Italy, "Montata." The
number of the young fish is, as might be expected from the number of the eggs in the ovary of the
Eel, wonderfully large. Kedi has recounted that, from the end of January to the end of April the
young fish continue wandering up the Arno, and that in 1867 over three million pounds of them
were taken in five hours. Into the lagoons of the Comacchio the Eels pour from February to
April. In March and April they have been noticed in many French rivers, in which the migra-
tion continues for from eight to fourteen days. The first account of these wanderings in Germany
was that given by von Ehlers. In 1863 he wrote to von Siebold: "This took place about ten
years ago, in the village of Drenuhausen, in the province of Wesen, in the Kingdom of Hanover.
As we were walking, towards the end of June or the beginning of July, on a dike, which at that
plae projects out into the Elbe, we noticed that along the entire shore there might be seen a
moving band of a dark color. Since everything which takes place in the Elbe is of interest to the
inhabitants of that region, this phenomenon immediately attracted attention, and it soon became
apparent that this dark baud was composed of an innumerable body of young Eels, which were
pressing against each other, as, at the surface of the stream, they were forcing their way upwards
towards its source, while they kept themselves so close to the shore that they followed all its
bendings and curves. The width of this band of fish at the place where it was observed (where
the Elbe has a considerable depth) was perhaps a foot, but how deep it was could not be observed,
so thickly crowded together were the young Eels. As they swam a great number could be taken
in a bucket, and it was very annoying to the people who lived along the Elbe that, so long as the
procession of fish lasted, no water could be taken out of the river which was not full of the little
fish. The length of the young Eels was, on an average, from three to four inches; the thickness
of the body was about equal to that of a goose-quill. By themselves might here and there be seen
swimming Eels of greater size, but none of them were probably more than eight inches in length.
All of them, even the smallest, were dark colored. This wonderful procession of fishes continued
unbroken and of the same density throughout the whole of the day on which it was first observed,
and continued .also upon the following day. On the morning of the third day, however, not one
of the young Eels was to be seen."

Similar observations have been made at Wittenberge, on the Elbe. KuflVr observed great
quantities of young Eels, of about three centimeters in length, in the brackish water of the Eider
at Fried richsstadt; so also did von Stemann.



652 NATURAL HISTORY OF AQUATIC ANIMALS.

" Every year," writes the latter, " from April to the end of June, there appear great masses of
young Eels, which are present in large schools towards the Upper Eider, seeking in every way to
pass each other. In April the first Eels show themselves generally singly; cold weather has
evidently kept them back up to this time; since this year, until to-day, no ascent whatever has
taken place, and now the approach of the great schools is beginning. Where the current is feeble
the procession is broad; but where the Eels encounter a strong current near a mill it becomes
small, and presses close to the shore, in order to overcome the currents. The little animals swim
eagerly and rapidly along near the banks until they find a place over which they decide to climb.
Here they lie in great heaps, and appear to await the rising of the tide, which makes their ascent
easier. The tide having risen, the whole mass begins to separate without delay ; Eel after Eel
climbs up on the steep wall of rock, determined to reach the little pools, at the height of fifteen
or twenty inches, into which some of the water from the Upper Eider has found its way. Into
these holes the little animals creep, and have yet to travel a distance of forty or fifty feet under
the roadway before they can reach the Upper Eider. Another detachment betakes itself to the
sluiceways, and clings to the cracks in the wood; also around the mills their ascent may be
observed, especially about sunrise." 1

Davy sends a similar account from Ireland. He was a witness of the ascent of young Eels, or
" Elvas," at Ballyshannon, at the end of July, 1823 ; he speaks of the mouth of the river under the



Online LibraryG. Brown (George Brown) GoodeThe fisheries and fishery industries of the United States (Volume 1:1) → online text (page 109 of 146)