ert SEE Nr TED +] Fr TU ene
i:

RR
ease,

ere anede tern It et man
TEE SEE RE REE ere Ear EL TErr DR
ears SEE SER
£

mr Br er are meg rsrer 684550 seg rr 50 DS Er SE 7 Den — z - == av me CERES —e—0—a0
ESSEN meeen
SLS EET Eee RR Eee SISSE SEES ERR ERR EKE RES ker

ere rer ad SER SS SEE RE See Te SES TTV SES BSN SPRE SENDES NESS LEE ENES SS BE Snes

er unike sne adam unike Shen =s
gane ae ken neg, Page ane nen dl era ln MED Annan den aben ene nn et Aon dd anne elnettet me = > = mm i
mn KS RØN 1 Cr REr

From

The danish biological Station.

Kjøbenhavn.

Centraltrykkeriet.

1896.

ie Eg
le B S åd KU
;x SØGE
il ll

sr

orig te dgsafooford rn ml
IR

SED fy)
; ,
Re VASE rr 1548 7
Sa Ø
I Sr LIGE
i BERO NU EG 5
&o ers dg pE A
DN gs Joh i q =
”z NEN MT
Ar eN SMAGE
VENN PASSIES: . "3
SØ RE 3 NE Ø
EPJ SEE FALDE SER XR
2 be AM An

7
NS

ng
VE

Gorm tents

Page.
The Common Eel (Anguilla vulgaris, Turton) gets a particular breeding-dress k
before its emigration to the sea. The bearings of this fact on the classifica-
tion and on the practical eel-fisheries. By C. G. Joh. Petersen. With 2 litho-
ERE SEES SEE ES ESF EEG EEN EN EO ED HEE SE ER 5—39
On the species of fishes living at Stege and in the neighhouring inshore
seas, with notes on their occurrence, breeding-time, etc. By C. G. Jol.
ES SEE SUE DD EEN EEN ES ENE CTS ET SNIT En 37—40.
On the species of fishes observed at Frederikssund in the Roskilde Fjord, i
Heth mOLERr eter ETIK PEFEF SEN og Ree Fede EEN ER 42—42
Cruise in the »Havørn« from the Issefjord to the Limfjord and the northern
GCattegat: 2:13. October 1894; By CC. G.. Joh. Petersen 2. sum unemmeeene 45—47

On the labelling of living Plaice: By C. G. Joh. Petersen... æn
Continued researches on the occurrence of the fry of Plaice in the Baltic

Sen SIS OS and DE Br DR MARTENSEN re ne are Ser e EE TS] TE En Te ER

— Ek K ARR. ver
z 6 ed - SÅ K Fi w-

ma HOT ”d ea
SE, ip

AS (2
Sy se UDE 9% %,

Ar

« sp

SYGE Xe5 KS DÅ
z Jar HERR SD i:
gs) UEGOGNe GE
z [og 320 å K [RA ; E -
Be! "MAD SAS
EAN ESS i
3 ZAR . BÆR

% & AU GUTNYTG UN GK

>; i SÅ IN R+ w i

Em

I. The Common Eel (Anguilla vulgarts, Turton) gets a parti-

cular breeding-dress before its emigration to the sea. —

The bearings of this fact on the classification and on
the practical eel-fisheries.

Jy C. G. Joh. Petersen.

With 2 lithographie plates.

E common eel gets a breeding-dress which in many, and m part
very essential, features differs from the growing-dress. Ås the systematists
have hitherto not understood this correctly, and the various forms of eels,
therefore, have been misconstrued in many ways, I shall here render a some-
what closer account of the various forms within this species of the eel (An-
guilla vulgaris, Turton) and show their mutual relations and hearings, as

far as my investigations into this matter go.

The Yellow Eels.

When in summer time we examine the eels caught hy our fishermen in
the salt waters with seines or on hooks, or when we take the eels in hand asthey
are speared in our fjords in winter-time, we may be pretty sure that almost
all of them belong to the category of eels which the fishermen and fish-
mongers call the yellow eels (»gule Aal«, in Jutland »Vesaal«), i. e. eels in their
growing-dress. — In certain fjords, however, towards autumn, particularly in
the month of August, we may among the yellow eels get others which the
fishermen call si/ver eels (»blanke Aal«, in Jutland »Gaardaal«) i. e. eels in their

breeding-dress; but if we ask a skillful fisherman to sort out the latter we

may also at this time get a number of eels in growing-dress to examine. —-
These yellow eels are generally distinguished by rather light colours; the
back, for instance, is gray or brownish, often with a shade of a greenish
colour (Green Eels), the sides are pale lemon, the hbelly either like the sides
or of a pure white. The large eels of more than 2 lbs. will often vary
from this — about which later on.

On the heads of these yellow eels (see fig. 1, 2, 5, & 10) the snout (in
front of the eyes) is much flattened, while the width differs very much; the
interorbital space, i. e. the distance between the upper edges of the eyes, is,
I dare say, always considerably larger than the horizontal diameter of the

eyes (i. e. of the transparent membrane which covers the eyes), and in lar-

ger eels (25—30 inches long) generally about double that size. When we
look at the head from above (fig. 1, 2, 5, & 10 (b)), we see the eyes turned
more upwards than sidewards, and the corners of the mouth with the
lips can, particularly on the large eels, almost always be seen indistincetly
outside the eyes; sometimes the corners of the mouth reach so far to the
sides that the head gets some resemblance to that of certain frogs (»the
frog-mouthed eel«); this, however, is applicable only to the /arger, lean females
(see plate I, fig. 1b). The muscles of the occiput m such females åre very
prominent at the nape on åccount of the lean, lank body (plate I, fig. 1),
and the body is very slim (plate I, fig. 10), while the stomach, however,
when it is filled, can he expanded very much by the food. The fact is
that these eels are very voracious, and they are caught, particularly im the
summer-time, im great numbers on hooks baited with small living fishes:
(zobiideæ (Gobius niger) or young hurbots in their first year; im fresh water
other little fishes are used to catch them, for instance the perch. Ås the
head does not dwindle down in the same degree as the body when an eel
grows thin, and as the ecel in this period, in which it eats much, makes
great use of its mandibulary muscles, the head of these thin eels becomes
strikingly large, and seems still larger than it is. Analogies to this are well
known, from codfish as well as from human beings, whose heads hecome
strikingly large when they grow thin. The fishermen then say that »the
cels have heads«, and they know very well that this is no recommendation
with the fish-mongers; but ås these eels are always large, generally ”/,—
1—2—3 Ibs. a piece, they are paid, nevertheless, far better than the little
vellow seine-eels, which often on an average weigh only Y,—/, lb.

It seems to be the winter, particularly, which produces these lean eels;
for they occur in the greatest number ås soon as the water is growing warm

in the early summer, and are then very voracious. Later m the year they

become gradually rarer, probably because a great many of them have been
fished, and the rest are not so thin any more.

These large, yellow, »hbroad-nosed« eels have among the fishermen at
various places particular names, such ås »X/æpaal«, »Bredpander«, »Bred-
hoveder«, Prokuratorer« (i. e. »lawyers«). Also outside Denmark the fishermen
give them special names, in Sweden for instance »$/ukål«, in Germany
»Dickkopf«, »Ramskopf«, ov »Tanzmeister«, the latter evidently on account of

ther thin, lean body, m England »frog-mouthed eels«, »yrig«, or »glut«, etc.

These eels have by several, especially earlier, authors been raised to the
honour of being a particular species or at least a variety (Yarrell and Krøyer,
ete.), but as the bulk of them is only represented by females it will be seen
from this reason already that this view is untenable. Though I have seen
many hundreds of these large-headed and thin eels, I never succeeded
more than anyhbody else in finding males among them, so numerous or so
strongly marked »frog-mouthed« eels that they together might be supposed to
represent the males of this species. Also other characters speak very distinctly
against the above-mentioned view, and particularly the fact that the ovaries
of these frog-mouthed eels as a rule are but little developed, heing at about
the same stage of development as those of all other yellow eels. To this mat-

ter, however, I shall return later on.

The frog-mouthed eels are found in great numbers both in salt and m
fresh water; the value of those taken in our little fjords durimg the summer
is certainly considerably above 100,000 Kroner, so that they are exceedingly

common at certain seasons, hoth in fresh and in salt water.

By comparing the figures 1 & 2, plate I, we shall see that the large yel-
low female eel is very like the smaller female eel; the characteristic flat snout,
the small upturned eyes, the inconsiderable height of the body over the pectorals,
the light-coloured pectorals rounded behind, are common to both of them, and
im these characters they resemble all other yellow eels. The latter may be
recognized also by their thin skin in which the scales are but slightly visible;
nor do we find, in the skin, many of those small silvery particles (guanin cery-
stals) which are so exceedingly prominent in the silver eels, so that the princi-
pal colours of the skin are only dully-white, yellow, or, where these colours
are covered with the black pigment-cells, more or less dark, always without
any noticeable metallie lustre. — The lateral line and its ramifications are vi-
sible, but not by far so distinct as on the silver eels.

The appearance of the male yellow eels (plate II, fg. 5) is m all essen-
tials like that of the females. I have been unable to find any good external
characters except in the size, which can serve to distinguish yellow males
from yellow females. When authors as Møbius and Heincke (»Die PFische der
Ostsee«) speak of a difference in the size of the eyes of males and females,
this holds good of silver eels only, and these only seem also to have been the
hasis of their pictures. Robin (»Journ. de VAnat. et de la Phys. 5. Ser. 1881«)
also seems to know males in breeding-dress only (»pimpenaux«). L. Jacoby:
»Der Fischfang in der Lagune von Comacchio. 1880. (Berlim.)« mentions, p.
40, several external differences between males and females, among which
however he particularly lays the stress on the difference in size as the most
important one. (More of this under »The Silver Eels«). He then mentions that
the tip of the snout is broader im the females than im the males; that this
character is quite unreliable will be seen immediately when we look at fig. 6,
plate II, nor have I ever found it confirmed by my investigations; to be sure
the males may sometimes be very sharp-nosed (fig. 7, plate II), but as to the
form of the snout and the interorbital space there is so great variation within
both sexes, that it can scarcely afford any reliable character. — Jacoby then
mentions that the females at Comacchio differ from the males in their colour,
and that »ich fand zuweilen vållig broncefarbene Aale, stets mit dem

Syrskyschen Organ«; I have the impression of his description, loc. cit. p. 50,

where he says »der vollståndig ausgebildete weibliche Aal . .. Bauch
weisslich-gelb, wenig oder kein Metallglanz . . .«, that the emigrating female

eels he has seen are not fully developed silver eels, but that on the other
hand, the males may be so. In our seas the fully developed female eels
have a strong metallic lustre, and åre not im the least inferior to the males
in this regard.

His next distinctive mark hetween male and female is the height
of the dorsal fin. It is very possible that there is a slight difference here;
it seems so. Whether Jacoby has here compared yellow males to yellow
females, or whether there may possibly be any difference in this regard
between the Italian and the Danish eel, I do not know; but to this exter-
nal character I have been unable to attach much importance, especially
as it is not easy to measure accurately.

At last, and as least applicable as a distmetive mark between the sexes,
he mentions the size of the eyes; the reason of this is evidently that he
has had both yellow males and silver males hefore him, the former with

small eyes the latter with large ones.

Many other authors have mentioned the male and female eels, but
none of them, as far as I know, has pointed out any other external di-
stinetive marks than those mentioned hy Jacoby; of these (with respect to
the yellow eels) I have only been able to use 7/e size: I never found any
males larger than c. 48 ctm. in total length, while the females can grow
much larger and are, when full-grown, between 0,5 and 1 meter. As already
mentioned before the broad head (not the broad front (large interorbital space|)
with the expanded jaws and the upturned eyes is, moreover, characteristic
of the large, yellow thim females.

Ås I have said, the yellow males agree, externally, very closely with
the yellow females of the same size, so closely that it is quite impossible to
distimguish between them with certainty, when they are so young that we cannot
distinguish between them by an examination of their sexual organs. On the other
hand, when the eels have reached a somewhat considerable size, we need
only cut them open and with naked eyes look at the sexual organs in
order to decide the question: male or female; hut when they are only 10—11
inches this will often already be difficult; a drop of spirit dropped in the
eel just as it is cut open will then, as vet, frequently be able to help, hut
with smaller specimens this will be of no avail any more. By careful
microscopical investigations F. Trybom, however, has been able to point
out unquestionable eggs in eels of 207 mm (c. 8 inches) in length. (»Fisket
i Halland 1893, Bilag I«, p. 42). Under this size it must be looked upon
as impossible with any certamty to distmguish between the male and the
female by means of either external or internal characters.

At about this length, c. 200 mm, the eels are getting their scales, till
then they have been naked. The scales appear first near the lateral line;
they are rather longish and have streaks showing later additions, which in
number correspond pretty closely perhaps to the years gone by; this, how-
ever, needs further investigation. Already before the scales appear, the eels
have the yellow colour on the sides, and the scales, which lie deep in the
skin, do not change the appearance of the fish very much.

Ås it is well known /he fry of the eel occurs on our shores when very
young, but though I have made careful researches I never was able to find
fry smaller than c. 2!/, inches (c. 6 ctm.) m length; I must suppose, and
have done so long, that all former statements of eels as thin as »a string«,
»a darning needle«, etc. rest on a mistaken estimate. When Jacoby, loc.
cit. p. 61, mentions fry of eels in the Italian rivers only 6—S8 mm long, this

statement evidently arises from Coste: »V'oyage dexploration sur le littoral

SGICÆRN
SELER
> 40 ip

Åre
z (LIBRARY)
- - SS
A Sg

10

de la France et de VItalze 1855«, where, p. 58, is mentioned fry of eels

imm long and, p. 60, fry of 1 centimeter. Strange to say this mistake,
which I think originally arises from confounding 6—7 ctm. with 6—7 mm
has not been corrected till quite lately by Grassi and Calandruecio im
»Boll. del” Accademia (zioemia de Serenze Naturah in Catania. — Fase.
37. Marzo 1894«, im which we are mformed that their explorations at
Comacchio as well as at Pisa and m Sicily have proved »che non esi-
stono anguilline di montata di lunghezza inferiore ai cinque centimetri«.F)
— They have consequently among the ascending eels heen unable to
find any under 5 ctm., c. 2 inches, in length; our eels then are nearly
as small. — The Italian authors no doubt are right in this, and
we hope soon to get further information as to their explanation of
this" fact, viz. that: the .eel has pelagic eggs which are shed m the
sea, where the voung ones undergo a metamorphosis (the larvæ are
Leptocephalus brevirostris) which is mot concluded till they have grown
Bb ctm. long.

The pelagic eggs and fry of eels are not known here in the north; on
the other hand the immigrating young ceels of 2!/,—2!/, inches in length are
very common. Before they appear at the mouths of our rivulets m spring, we
mav sometimes meet them im the deeper, northern parts of the Sound where,
personally, I have once got one in a scraper, and whence P. Willumsen,
the fisherman, has got me some from the stomachs of fishes. At first
when they arrive at the shores they are without any pigment im the skin,
later on the pigment appears, and already in the course of the first sum-
mer the y jook very much like the larger yellow eels.

The sexual organs of the yellow eels are but very little developed;
the festicles particularly are very small, though the formation of the lobes is
distinct im those over 12 inches im length. — The ovarres are somewhat more
developed, and Jacoby's description of the »sterile Weibchen« (loc. cit. p. 46)
is in the main very characteristic of them, when he says that the ovaries
are thin ligaments, without any fat, slightly folded up, not rarely transparent
like glass, and of the same length and breadth”) as in the other eels (viz. the

silver eels). But he is quite wrong when, following the supposition of

+) After this was written I have scen in »Mittheil. des Deutschen Seefischereivereins«
No. 1. 1895, p. 24, that Dr. Seligo has noticed the same erroneous, old statement
of the length of the young cels.

ÆV

). The breadth of the ovaries in the little yellow females, on the other hand, is con-
siderably smaller than in the silver eels,

ilt

r. Siebold, he calls these large vellow ecls slerile; they are no more sterile
than all other yellow eels that have not spawned before, and it is amusing
to see his scientific indignation against the lagoon-fishermen, who have
the same word »Pasciuti« for the large, frog-mouthed vellow eels as well as
for all the little yellow eels, males ås well as females. »Pasciuti«, in the
mouth of a lagoon-fisherman, is (according to Jacoby) exactly the same as »yel-
low eels« in the mouth of a Danish fisherman. The scientific justice of this
appellation has long been overlocked, and Jacoby overlooked it completely. —
I shall not decide whether Jacoby's translation of the word Pasciuti is correct,
but if the fishermen at Comacchio really have a common name for the eels
»which do not migrate, which im autumn do not go to the fishing-gear, but
which eat all the year round«, then this name suits very well the eels in
growing-dress. Jacoby has not imagimed the possibility that the »sterile
Weibchen« should be able to change their outer,appearance, as he did not
know that also the eel has a particular breeding-dress; as a matter of course,
therefore, he could not agree to using the same appellation for these large females
and for the young »normal« eels, which also comprise all the later on mi-
grating ones). t

It still remains to mention the very peculiarity which has been

”y The above view of the frog-mouthed eels as large, normal, vellow females,

which quite naturally presents itself when we compare their sexual organs
with those of other yellow eels, and when we see that the yellow eels change into
silver eels, I have set forth for the first time in a preliminary note in >»Dansk
Fiskeriforenings Medlemsblad«, November 1893. In a way we might certainly call
these eels (as on the whole all yellow eels) »sterile« since they have never bred, but
this use of the word, nevertheless, is not allowable.

In >»Zeitschrift f. Fischerei« 1893. No.4 (which I know only from an extract
in »Svensk Fiskeritidsskrift«. 1893. 153—156) E. Sennebogen-Comisa mentions an
experiment he has made with the breeding of female eels; he thinks he has seen
that large, vellow-coloured, broad-nosed, small-eyed female eels have changed their outer
appearance, and that their ovaries took the appearance of those which we find in
common eels.

He himself scems to doubt, however, whether the experiment has been made
under sufficient control.

After the above has been printed I see that the Italian ingeneer G. $. Bullo in his
Previsioni sulla Laguna di Comacchio 1894, which he has sent me, and which chiefly turns
upon the solution of practical questions attached to this great >»embanking-undertaking«,
has observed (p. 7) that »Le anguille discendono spontaneamente al mare quando abbiano
vestita un'apposita divisa di colore piu lucido con... Gli empirici coltivatori le chiamano
allora anguilla femenali o meglia bisati femenali.« — consequently that the eels get a
particular dress when they emigrate to the sea, i. eé€. become silver eels; and p. 62
Bullo says »mentre quelle che non andavano al mare (pasciuti) vennero trovate, secondo
V Jacoby con ovaia abortita e secondo quanto io credo, sono anguille con ovaia embrionale«.
He supposes then correctly in contradistinetion to Jacoby that pasciuti (the yellow
eels) åre eels with embryonal (youthful) sexual organs,

2

pointed out by the lagoon-fishermen, viz. that the yellow eels eat so much:
for in this they distinguish themselves from the silver eels, and it is such
an important thing that it has a great mfluence on the digestive organs of
the eel, and through those on its whole outer appearance. — It has been men-
tioned already that the yellow eels can be caught on hooks, but that the
silver eels comparatively rarely are caught on them; already this fact tells
of a different appetite in the two forms. When many thousand hooks, haited
with living small fish or dead sticklebacks, pieces of various fishes, prawns
(Palæmon), shrimps (Crangon), or worms, are set out daily (or rather
nightly) and the yellow eels always form the great majority of the catch,
this must be explained by the much greater voracity of the yellow eels, a
fact which is fully borne out when we examine the contents of the sto-
machs of eels which have been caught im other ways; the silver eels gene-
rally contain nothing, though it may happen, particularly when the eel has
perhaps not quite finished the change of its dress. When it is migrating,
and in its full, characteristic dress, I never saw any lood in its stomach.
The vellow eels, on the other hand, can often be so crammed with food,
consisting of small fish, or (when they are younger) little snails, crustacea,
annelida etc. that them stomachs are dilated so much that they are quite
shapeless. This however is seen only in the warmer season; im winter the
eels do not eat so much. —

We can also directly see that the digestive organs of the yellow eels
work powerfully; for they take up much more room than in the silver eels,
even though the stomach and intestmes are empty of food. This slight size
of the liver, stomach, and intestines m the silver eels makes the eels feel hard,
they are more difficult to hold, and the anus is never dilated hut
»closed« as the fishermen say. — The following table of weighings is
given, partly to point out this shrinking of the digestive organs of the
silver eels, and partly to show that the sexual organs on the other hand
(particularly the ovaries) are somewhat stronger developed in the silver eels
than in the yellow ones.

Yellow females. | Yellow males.
Total weight. Digestive organs Sexual organs. | Total weight. Digestive organs Sexual organs.
and air-bladder. and air-bladder.
385 gram. 40 gram. 2,5, gram. | 125 gram. c. 10 gram. Lessthan 1 gram.
250 — PE 2 — | 110 — - 10 — Se LA St
235 — OFRE DEERE TODT. SE: SR MES SABES ARE DSE oe
17å — 24 — Less than 1 — |
1l6å — 17,, — il — |
160 — 20 — 1 — |

Silver females. Silver males.
Total weight. Digestive organs Sexual organs. Total weight. Digestive organs Sexual organs.
and air-bladder. | and air-bladder.
340 gram. c, 11 gram. 6, gram. 121 gram. c. 5 gram. Less than 1 gram.
245 — - 88 — i. — | 106 — - 8, — lm ==
PB EE RG 38 — (fore REESE
180 — Så "Gak VS 3 — 92 — då, — SE KARSAN 3 AK —
160 — by — 2. — 86. — - få — - SEE
83 == syne (HUL SSRNERR

I have mentioned several distmetive marks, both external and internal,
which distinguish the yellow eels from the silver eels, but it must be said also
that these marks pretty often åre insufficient, and that we are therefore some-
times left im doubt whether we are to place an eel in the former or the latter
of these categories. "This is oftenest the case with large female eels; we can
here easily find all transition-forms from yellow frog-mouthed eels to shining
fully characterized silver eels: to this I shall return later on. But also
among the smaller eels transition-forms can he pointed out, particularly in
salt water in after-summer.

The Silver Eels.

What before all characterizes the silver eels is the form of their snout
and the situation of the eyes on this (fig. 3, 4, 6, 7, plates I & IN). The
snout before the eyes is not quite flattened mm the silver eels as im the
yellow ones, but it is high and a little compressed, probably owing to the
considerable development of the olfactory organ and the size of the eyes.
Among the males (fig. 6 & 7, plate II) this height of the snout is exceedingly
striking, but a comparison between the large yellow females and the large
silver females shows something similar.

This, evidently, is the basis of C. U. El:strøm's 2 species: Muræna oxyrhina
and Muræna plathyrhina, of which the former corresponds to the silver eels,
the latter to the yellow ones; the former, moreover, has a small, the latter a
larger anus. They are evidently rather based on the fishermen's knowledge than
on El:strøm's own investigations, and the fishermen always distinguish (in all
countries) between the yellow and the silver eels. The zoological view on the spe-
cies, on the other hand, is all the same to them. That many other authors have
looked upon this different form of the snout as a specific character will he
mentioned afterwards.

The situation of the eyes of the silver eels is such that they, when
we look at the head vertically from above (fig. 3, 4, 6, & 7 (b), plates I & II),

14

generally protrude hefore the lips, so that the latter cannot be seen outside
the eye, but this forms å part of the outlineF); this can be expressed also by
saying that the eyes of the silver eels look more to the sides than those of
the yellow ones, which look more upwards. The eyes of the silver eels,
moreover, åre much larger than those of the yellow ones, the largest diameter
of the eye, the horizontal one, oftenest exceeding half the interorbital space,
and in the males even very nearly equalling the whole interorbital space, and
sometimes (fig. 6 a) being longer than the snout before the eyes. Among the
females, however, there is much variation in the latter measure, so that the
eyes are the larger in proportion to the breadth of the front the smaller the
eels are; this evidently is nearly connected with the fact that the interorbital
space is greatest in the large eels. Im order to show the extremes among the
large eels, two such of 30"/, and 352/, inches m length are represented (fig. 3 & 4,
plate 1), the latter with a broad front, the former with a narrow one. Though
the difference in the size of the eyes in proportion to the interorbital space
here is very distinct, such a difference is not very striking when the diameter
of the eyes is compared to the length of the snout. The form with a narrow
interorb. space, however, has decidedly somewhat larger eyes than that with
a large interorb. space.

Among the males of the silver eels there is, as shown in fig. 6 & 7, plate II,
great difference in the form of the head; but the diameter of the eves is al-
ways nearly or exactly as large as the interorbital space; the tip of the snout,
on the other hand, is now pointed, now snubbed, and there can, upon the
whole, be a very considerable difference in the size of the head; butin no case
of which I know can we find an appearance which, like that of the females,
resembles the appearance of the frog-mouthed eels (fig. 1, plate I).

There is no doubt that fig. 4, plate I, represents a female eel whose head
when it was younger has looked something like that of the frog-mouthed eel
represented in fig. 1, plate I. She changes which have taken place in it since
then are chiefly the following: The head before the eyes, where the olfactory
organ lies, has grown higher; the eyes have become several times larger in
volume, and have turned in such a way that they look more to the sides; the
head, upon the whole, has become fatter and plumper. The lower jaw seems
to have grown a little longer by the formation of a soft point at its foremost

end; the occipital muscles are no longer protruding, for the whole body of the

This is still more conspicuous before the eels are placed in spirit; all the figures,
nevertheless, show the same, though they have been drawn from eels which are

kept in spirit

15

eel has become round, fat, fleshy, and much higher than before; compare
particularly the height above the pectorals m order to have a basis for the
comparison; the profile of the oeciput has thus hecome quite another. It
scems that the lips generally become a little smaller while these changes take
place, but it is difficult to decide this question "on account of the great
individual variation; one thing however has remained unaltered: the inter-
orbital space. On the whole, I do not believe that this transformation of the
head extends to the bony cranium; it is certainly the soft parts only which
produce the whole transformation from frog-mouthed eel to silver cel.

It will surely be granted that this transformation from an appearance
like fig. 1 to another appearance like fig. 4 is striking, and it will easily be
understood that the fishermen have noticed these two forms, or more cor-
rectly, the former of them; for they do not distinguish the latter from other
silver eels with a narrow interorbital space; thev all go by the name of
sharp-nosed eels; for between fig. 3 and 4, plate 1, there is neither habitually
nor gastronomically the difference as hetween these and the frog mouthed eel, fig. 1.

If we look at the heads of the smaller eels which are represented (also the
males), we shall observe that some similar changes have taken place; it is here
particularly the enormous eyes which tend so much to change the appearance.

We must not imagine, however, that it is only the membrane covering
the eyes which grows larger in the silver eels; already fig. 6 a, plate II,
shows that the profile has directly changed its form by an enlargement of
the apple of the eye, and by taking out the eyes I have seen, moreover, that
the very apple of the eye really grows larger. By weighing the eyes after
they were taken out and, as well as possible, cleared of the appendant
muscles and nerves, I found in avyellow and a silver female eel of respectively
20”/, and 20 inches that the eyes of the vellow eel weighed 75 mgr. (and
measured 5!/, "), and that those of the silver one weighed 170 mgr. (and mea-
sured 7//, mm. and in a yellow and a silver male eel, both 14"/, inches in length,
that the eyes of the yellow one weighed 40 gr. (and measured 5 mm”), and that
those of the silver eel weighed 80 mgr. (and measured 6 »m). These were far
from representing extreme cases, rather below the average.

On the said figures representing heads of yellow and silver eels we can
further see that he ramifications of the lateral line are more distinct on the
silver eels than on the yellow ones, and that the pectorals of all silver eels,
though somewhat varied in form, undoubtedly are more pointed behind than
those of the yellow ones, and that they, compared to the length of the head,
are longer on the former than on the latter; further, the pectorals of the
yellow ones are bright-coloured, those of the silver eels dark, even black.

16

This difference between the pectorals is a very constantly returning distinctive
mark between silver eels and yellow ones, and the fishermen im the Limfjord
know, for instance, very well how to distinguish »bluefins« from the yellow
eels; they know that m years when there are many »bluefins« there will be
a good weel-fishery of silver eels.

The 3 figures 8, 9, & 10, plate II, are intented to illustrate the difference
m the form of the hody of a silver eel with large interorbital space, a smaller
silver eel with narrow interorbital space, and a lean yellow cel. The thick
fleshy, frm body, which is much higher than the head at the occiput, charac-
terizes the two silver eels at first sight; the thin and lamnk body with the
proportionally large head of the yellow one differs considerably from them;
the yellow eels, however, are fortunately not always so lean as this. The
specimen represented in the figure has a large interorb. space.

With some practice it is easy when we take hold of an cel, even with
our eyes shut, to perceive whether we feel the hard, powerful body of the
silver eel or the soft, lean, often lank body of the yellow one, in which as
above mentioned the intestines take up a proportionally large room, while the
muscles are hut of slight importance.

Of other characters which mark silver eels in general, but which cannot
be seen from the figures, must be mentioned that the colours on the back of
these eels ås a rule are very dark, nearly black; then follows on the side a
bronze-coloured streak, broader or narrower, which stretches along the fish in
nearly its whole length; it may be very little developed, but when it is there,
it is verv strikmg on account of its bright metallic lustre. The rest of the
sides, as also the whole of the belly, is, I dare say, im all eels when they are
just caught, of a pure silver white with the brightest metallic lustre. The dor-
sal and the caudal fins are dark, the greater part of the anal fin on the
other hand light-coloured, often with a red flesh-coloured tone. The fins have
no metallie lustre.

Under special circumstances, however, other colours than the above men-
tioned may occur, the eels, like most other fishes, bemg able to change colour
quickly.

In the Lesser Belt for instance I have seen many eels whose back was ol a
paåle bluish-gray (nearly like dry clay), but this colour I have seen only on eels
which had lived in a weel for some time, and it disappeared in the course of
a day when the eels were placed in a well. The light colour is produced hy a
contraction of the pigment.-cells im the skin, which on the back quite cover
the scales, but which are found also in numbers down the sides and on the

belly. On eels which have long been imprisoned I have often seen these pig-

17

ment-cells spread into dark spots on the helly and sides, and the phenomenon
can expand over the whole of the belly and sides so that they become quite
dark-gray: »der graue Aal« of the German smoking-places. (See Møbius
and Leth later on.) When the eels are fully developed silver eels there is
not the slightest yellow on them.

The outlines of the scales are more distinct than on the yellow eels,
though they are quite covered hy the »silver lay«.

The tubes of the /ateral line and its round openings show distinctly
along the whole body, dark on a light ground; also on the head its rami-
fications, as above mentioned, are more distinct than on the yellow eels.

The skin itself is thick and firm, owing particularly to a strong develop-

ment of the bluish fibrous tissue of the corium.

While we have »yellow« eels of all sizes, from the eels have any colours
at all and upwards, there are known m Denmark no silver eels under 29 ctm.
in length, and silver eels of such small size, moreover, åre very rare; besides
they are all of them males. The smallest females I have found are 42 ctm.,
and they are rare too; it is always easy to see, even without any microscopi-
al examination, whether these eels are males or females, and their sexual
organs are stronger developed than those of yellow eels of the same size. No
doubt, however, much is wanting before eggs and spermatozoa are ripe, nay
the latter have never been seen in testes as yet; hut the eggs are unmistak-
ably present.

The testes of the silver eels are always distinctly lobated, though the
lobes, as I think, never exceed 3 ”” in breadth, if they are so broad as that;
also the testes of the yellow eels are often distmetly lobated, but it is certain
that the formation of the lobes of the silver eels as a rule is more advanced
than in the yellow ones.

The ovaries are never half-clear, or half-transparent, in fully developed |
silver eels, as they generally are in all genuine, yellow eels; on the contrary, |
they are whitish, opaque, with a yellowish or reddish tinge; they are to a
high degree filled with fat, and the diameter of the egøs often reaches 0, m",
or even more, 0,,, (Lilljeborg), a size I never saw in yellow eels. The ovaries,
moreover, are plumper, more folded, hroader, and doubtless nearer ripeness
than those of the yellow eels, though, certamly, they are still far from being

3

18

ripe”). As to the size of the eggs in the ovary of the eel I shall refer the
reader to the above quoted work by Trybom.

Which isthe Relation between the Yellow Eels and the Silver ones?

Having pointed out the differences between the yellow and the silver
eels, and shown that these two forms of eels as a rule really do appear pretty
well distinguished in nature, and that the specimens within either group are
closely connected by similarity in several essential anatomical characters,
in which they differ from the specimens within the other group, I shall
state the reason why these two groups ought not to he looked upon as
different varieties or species, and show that they are much more closely
connected.

”) Note: In the literature, from both earlier and later times, we find accounts of eels
with almost ripe ovaries. H. Rathke, for instance, in »Miilllers Archiv 1850«, p. 20%
seq., mentions an eel whose length was 16 inches 6 lines, whose circumference
was 4 inches 6 lines, whose ovaries were very plump and 1, inch broad, but whose
eggs were only at most 0,948 inch (consequently but a little more than 0,,m14) in
diameter. Though Ratø/ike in other eels has seen eggs of double that size, without
the ovaries being plumper than usual, he looks upon the above mentioned eels as
>»hochtriichtig», and says of it: »Ohne Zweifel wiirde sich bei dem Thiere, wenn es
am Leben geblieben wire, die Eier nach kurzer Zeit von den Eierstocken abgelåst
haben«. Well, what is »kurzer Zeit«? And are the eels with the large eggs not
still nearer spawning than this? That Rathke found one of the lobes of the ovary
pressed out through the genital opening does not seem to me to indicate that the
breeding time is near; the size (the smallness) of the eggs indicates that it is far
off, as far off as in a great number of common eels. Rathke does not inform us
whether the eel was silver or yellow, but its inconsiderable total length, just like
that of the exceedingly rare silver females of the very smallest size, indicates that
it was yellow. The eel was brought to Rathke dead, in May (the 24th).

I should have been rather doubtful as-to this eel, if I had not a few years
ago, among a number of eels which had been speared in spring, found a specimen
which in many ways agrees with it. IÉ was a yellow eel, c. 16 inches long, c. 3
inches in circumference, with thickly folded and very plump ovaries, whose greatest
breadth is c. 1 inch, and whose eggs vary in diameter between 0,, and 0, mm,
an eel, consequently, which in many respects reminds us of Rathike's. As this eel
is yellow, its breeding time, of course, is still far off, which is also very clearly
indicated by the small size of the eggs; as the eggs are much smaller than in
most silver eels, I must look upon the strongly developed folds in its ovaries and the
accompanying great mumber of eggs, as an abnormal development. Such eels are rare;
besides the two above mentioned I have seen only one more, an eel from the
Lesser Belt, caught in a weel in December 1888 (cp. »Fiskeritidende« 1888, No. 51,
p. 406); it was 23 inches long, and the eggs at most 0,,,, mm, This scarcity, I think,
ugrees very well with my supposition that these eels with thickly folded ovaries
are abnormal specimens.

19

Though I have carried on my investigations through several years, and
had the most ready help from fishermen and fishmongers, I have, as ahove
mentioned, not succeeded in finding males of silver eels under c. 29 ctm., and
none larger than c. 48 ctm.; I have seen no yellow males larger than c. 44
etm., hut I have seen them so small that it has barely been just possible to

decide the male sex.

How it is in this regard with the »Freshwater Eel in a Ripe Condition«
caught 12 English miles south of Eddystone, and mentioned by W. L. Calderwood
>2Ann. Mag. Nat. Hist (6)12 1893«, p. 35, I cannot tell, as the diameter of the eggs
is not stated; we are only told that the eggs are »apparently quite ready to drop«

. »however« . . . »the nuclear membrane was still distinctly visible«.

I must therefore remain doubtful as to these breeding eels, mentioned by
Ratlike and Calderwood, as also with respect to a number of other cases in which,
for instance, the breeding of the eels has been observed in fresh water, etc., and
which I think it unnecessary to mention any further here.

An eel which is mentioned by Å. Feddersen in »Dansk Fiskeriforenings Med-
lemsblad« 1894, p. 466, and of which it is said that »it lies near to look upon it
as a spent female« I shall here mention somewhat closer, as Mr. 4. Feddersen at
my request has been kind enough to permit me to examine it.

Its remarkably emaciated appearance is evidently the most striking thing in
this eel; for its bones are not brittle, as Mr. F. mentions; it is only the loosening
of two vertebræ by the bending together of the thin tail, which made Mr. F. think
so, and as to the »emptiness« of the ovaries, a microscopical examination of them
showed that they contain many eggs, chiefly of the same size and outer appearance
as those of other frog-mouthed eels of this size (6å ctm.). It cannot be denied,
however, that the fatty substance in the ovaries, and in the whole eel, was re-
duced to a minimum, which, together with the bad state of preservation, gave the
interior parts a somewhat uncommon appearance. If the eel had spawned, we
might either have expected to see the ovaries quite empty of eggs, or among the
remaining ones have been able to point out larger eggs which were not dropped,
as it is common to see in spent fish; but of this I found no trace. I must say,
therefore, that I think we had better stick to the second possibility which Mr. F.
mentions: that the cel is a »starved or sick specimen«, much the more so, as I
have observed that the skin has been scraped off, and most of the scales lost, at
a certain place round its body, which might tend to show that the eel has some-
how been squeezed, perhaps kept so for a long while. This hurt is quite different
from those which, in the form of streaks or scratches, may be seen on many of
the large silver eels, which towards the end of the fishing-season are caught in
the Lesser and the Great Belt. Whence these »scratched« eels come, and how the
scratches arise, I cannot tell; but it is a phenomenon which returns yearly
with great regularity, and which is looked upon as indicating the approaching
end of the fishing-season; these scratched eels are not lean as the Ringkjøbing-
eel. It lies near to ask whether the said eel is »silver« or »yellow«, and we
might be tempted then to answer, that it is black, i. e. it is neither yellow-
coloured or of a metallic lustre, and its whole appearance makes it impossible to
decide by means of the usual characters, whether it is to be referred to one or the
other of these categories,

920

Silver females I have not seen under c. 42 ctm, hut probably thev may
be found a little smaller, though but rarely; the largest eels, on the whole,
which I have seen, have been silver eels. Yellow females I have seen so
small that it was just possible to decide the sex; more difficult is it to state
their limits upwards, as I have already mentioned, because the larger
female eels, over c. 78 ctm., as a rule, form the transition between yellow and
silver eels.

It will be seen that these size limits for the sexes agree in such a way
that the supposition that the yellow eels are »the young ones« of the silver
eels lies very near, and the fact that no silver eels are found here under the
said lengths is, I think, sufficient to warrant our looking upon this supposition
as the only possible; there are several other circumstances, however, which
as decidedly point at the same solution of the question, and which I shall set
forth here for further confirmation, viz.: ]

1) The greater development of the sexual organs in the silver eels.

2) The smaller desire for food among the silver eels and the whole state

of their digestive organ during the migration.

3) The periodical occurrence of the silver eels in the waters, their
emigration to the sea in summer and, particularly, in autumn, and
the fact that the stock of eels in our fjords i» winter almost exclu-
sively consists of yellow eels. i

4) The conclusiox of the development from yellow eel with commencing
metallic lustre to the fully developed silver eel without any yellow
colours I have repeatedly witnessed in caufs im which I kept yellow
eels; some of these grew in a few weeks into fully developed. sil-
ver 'eels.

5) We find, in nature, eels which in all characters that distinguish silver
eels from yellow ones (except the size limits downwards) form transi-
tion stages between both.

6) Great numbers of .silver eels emigrate every year from fresh waters
whose mouth is an artifical lock, where we know, therefore, that sil-
ver eels never immigrate, fresh waters that always swarm with yellow
cels in all sizes which while they åre yellow only emigrate in very
small numbers.

From the above reasons I must consider it an undoubted fact that the
»silver« eels are eels which have formerly been »yellow«, but now before the

propagation get a peculiar breeding-dress,

1 7] re

21

Such a thing has not yet been pointed out withim the family of the
Murænidæ, except with respect to the Conger vulgaris by Cunningham (J. Mar.
Biol. Ass. vol. II, 1891—92, p. 16) who showed that the eyes of the male by
commencing maturity grow very large; other external characters do not seem
to have been observed in the Conger which might indicate their getting a
peculiar breeding-dress, and such a one cannot be said therefore to have
been observed.

The peculiarities which have been observed in the Conger by the com-
mencing ripeness of its eggs and sperm, make it probable that both males and
females die soon after the first spawning-season; this seems to be indicated
especially by the peculiarly soft condition of the bones in the crania of the
mature fish. Also the considerable size of the eyes of the mature males indi-
cate the same; for we do not see large eyes in immature males, and it is un-
likely that they can have dwindled in after the propagation.

Cunningham says of the mature female Conger that »all the eggs are of
about the same size«, viz. about 1—0,5""; must not this also indicate that
each specimen has in its life but one spawning-season ?

I have formerly, without further elucidation of the matter, spoken of the
breeding-dress of the eel, as though it quite corresponded to what we call
breeding-dress when we speak for instance of salmon, trout, and other fishes;
but, indeed, it does not do so at all. For the salmon gets 1) a new breeding-
dress before each spawning-season, and 2) it does not get it till its eggs and sperm
are nearly ripe. But now there is every reason to believe that the eel only
once in its life gets -the said dress, and it gets it at any rate long before eggs
and sperm are ripe. lf, therefore, we will compare the transition of the eel
from yellow to silver with anything in the salmon, the nearest thing to think
of is the transition of the salmon from »Parr« to »Smolt« and »Grilse« (from
a young fish to a grown-up one); for this change occurs but once in the life
of the fish, at the same time as the migration instinct awakes, and it is ac-
companied by a similar transformation, for instance of the skin and its colours,
as in the eel. This »dress«, or whatever we now may call it, is never lostin such
a way that the skin of the fish again becomes as it was when it was a »Parr«,
but during the spawning-seasons it may be further developed into a breeding-
dress of rather a perishable condition; for this breeding-dress disappears after
every spawning-season. I mean therefore that (he transition of the eel from
yellow to silver eel must be compared to the transition of the salmon from au young
fish to & grown-up (afterwards ripe) one, and not to the changes in the colours of
the salmon and other transformations of it during the spawning-season. When,
nevertheless, I call the dress of the silver eel its breeding-dress, it is because

Ro

I suppose that fhe time for the eel's transition to a grown-up fish is identie with
the transition to its only breeding-season.… Whether the silver cel is more
strongly coloured or further transformed before the propagation I cannot
tell; but the two things: the transition of the eel to a grown-up fish and the
transition to its only spawning-season occur at the same time, therefore it can
be defended to call the silver eel the eel in breeding-dress. I suppose that the eel
has only one spawning-period in its life, partly in analogy with what we know
of the Conger, partly because nobody as yet has ever met with a spent eel; if a
scientific man got hold of such a one it would surely be proved immediately by
the state of the ovaries and, as far as the males are concerned, hy the large eyes.

Till this day this has not happened, not even a fully mature eel has been
observed more closely (cp. ante). The silver eels on our shores are the most ma-
ture eels that are known; and they do not, as the Conger, develop their sexual or-
gans, even when they are kept in captivity for a long time. I have kept them in
»aufs for more than half a year, and have not been able to trace the slightest devel-
opment. On our shores, as well as on the German shores of the Baltic, ten thou-

. sands of living silver eels are wintered yearly in reservoirs of running fresh water,
because the price of them rises iu the course of winter. These eels often go
from September—October of one year till April—May of the next, always with-
out taking any food and without losing more than a few per cent in weight du-
ring that time. If the sexual organs could be developed under these circum-
stances, it must certainly be observed now and then; but in spring, after half
a year's. captivity, there is no alteration to be seen worth noticing.

That we know of no eels so near the spawning-season as the Congers ob-
served by Cunningham, agrees also with the fact that the eggs of the eel, even in
the most developed specimens, are still small (0,,—0,,,””), and that the eggs
in the same ovary are not all of the same size. After all, it seems to me how-
ever, that there is nothing in what we know about the construction of the
ovary of the eel, which really does prove that the eel has but one spawning-
season in its life, but, on the other hand, there is nothing against it neither
(cp. Trybom). As yet the facts seem capable of being explained in both ways.

Ås to the gwickness with which the eel gets its breeding-dress I shall say
only that while the last stages of the latter, the changes of colour, may pro-
ceed very quickly, in a few weeks, as I have said already, I cannot tell from
immediate observations how long time the whole transformation takes; as however
almost all the silver eels disappear from our fjords in winter and reappear to-
wards the end of next summer, the transformation cannot last more than c.

;/[,—1 year in general. When the silver eels have gone away in autumn, we

23
may see already among the smaller eels some which evidently begin to get
the dress, though they will not finish it quite till next year. Among the large
female eels, on the other hand, we find at any season specimens which are in
transition hetween yellow and silver eels. I have got the impression that
these large eels are a much longer time in getting their hreeding-dress than
the small ones; perhaps it lasts even several years.

It would be interesting to examine this by placing eels in ponds, where
there are no eels previously, as also to examine what becomes of the silver
eels when we prevent their migration to the sea, whether they will commence
eating again, or whether they will die. The latter is suggested perhaps in a
note in »Ann. Scot. Nat. Hist. 1894, p. 183«. I know the note only from an
extract; it is said to treat of sick and old eels from a warm lake which has
no (?) connection with the sea.

E. Blanchard, im »Les poissons d'eaux douces de la France« 1866, pp.
498—501, mentions an eel which for 37 years has belonged to the Desmarests.
1. Desmarest, who was a naturalist at Paris, informed B/anchard that this
eel was bought in 1328; it measured, in 1865, 1,,,—1,,, meter, and had since
1828 grown about "/,. It goes on eating, though not much and not at all sea-
sons; in the foresummer it generally gets migrating propensities and wants
to jump out of its reservoir.

In 1828 then this eel has already been c. 30 inches long, a very consi-
derable eel; it has for many years been but little voracious, and must certainly
have been å silver eel, what its migrating propensities seem also to imply.
It appears then that such silver eels, when they are prevented from emi-
grating to the sea, can continue fo eat and to grow, and it will be difficult
perhaps also in any other way to explain the occurrence of very considerable
silver eels (all females of course) in basins of fresh water often of slight extent.
At all places where the fishery is carried on very intensely these large eels
seem to become rarer, and at last quite to disappear; simply, I suppose, be-

cause they are not permitted to grow old and large before they are fished.

On the Opinions of earlier Authors.

It is quite a remarkable thing indeed that is has notlong ago been point-

ed out that the eel gets such a breeding-dress, particularly when we remember

24

how eagerly the classification of the eel has been studied, or at any rate how
much there has been written on it.

On the one hand the fishermen have always known that there were two
very different forms of eels, the yellow and the silver eels, but we cannot ex-
pect them to give a further explanation of this fact; on the other hand most
skillful systematists have seen that all our forms of eels doubtless helong to
one species, and this I think is also correct; therefore they have not cared to
enter into a study of the two forms of eels; other authors have not seen this
and have uncritically set up the forms they have got from the fishermen as
species, and have thus got 2, 3, or even more species. In our own literature,
for instance, H. Krøyer, im »Danmarks Fiske«, has set up 3 species: I. Am-
guilla migratoria, Krøyer, which evidently corresponds to the large, silver eels
with a broad interocular space; II. Angwilla acutirostris? Yarrell, correspond-
ing to the middle-sized, half silver, still yellow-tinted eels (the figure is tåken
from Yarrell and is evidently a picture of a silver eel),, and finally UL An-
guilla latirostris, Yarrell? corresponding to the meager, yellow eels (the figure
from Yarrell and representing a frog-mouthed eel).

The latest great Scandinavian work on the fishes, Lilljeborg: »Sveriges
och Norges Fiskar«, makes one species out of Krøyer's three, and justly so, but
without explaining what then is the reason why these forms exist. In Eng-
land where Yarrell m his time in »British Fishes« also set up 3 species:
Anguilla acutirostris, A. lattrostris, and A. mediorostris, corresponding to Blank-
aal, Klæpaal og alm. gule Aal or Silver eels, Frog-mouthed eels, and Yellow eels,
later authors, as Fr. Day: »British Fishes«, 1880-—84, have also looked upon
these forms as belonging to one species, but without giving sufficient reasons
for it; his statements vol. II, p. 242, are partly wrong, partly insufficient.
England's well-known ichthyologist Å. Grinther, on the other hand, has, 1870,
in his »Catalogue of the Fishes im the British Museum«, vol. VIII, tried to dis-
tinguish between the two species: A. vulgaris and latwrostris; the latter, evi-
dently, is founded only on yellow females and corresponds exactly'to the » frog-
mouthed eel«, (»Glut« or »Grig«). Neither the position of the fins, the length
of the head, the size of the lips or the eyes, nor the breadth and length of the
snout can be used as specific characters, for all transition-forms are found be.
tween the extremes. — In France and Germany the authors rather agree in
believing in one species of eels in Europe, and Camille Dareste: »Résumé d'une
Monogr. des Poissons Angwuilliformes.. Arch. de Zool. exper. etc. Tom. IV.

1875« has arrived at the same result, viz. that the form of the head

25

and snout is a quite useless character to distinguish between ÅA. vulgaris
and A. latirostris.

Though skillful systematists have thus for a long time held the opinion
that there is in Europe only one species of Anguilla, it wil! easily be under-
stood that this question could not be finally settled till we got an explanation
of the reciprocal relations between the different forms of the eels, and this of
course could not he done till the question of sex had been solved, i. e. till
both females and males could be pointed out. It is well known that this was
done first, in 1874, through the investigations of Syrski; what could be done
before that time (except the pointing out, or the more correct explanation,
of the breeding-dress) seems to me to have been done by v. Siehold m »Die
Stisswasserfische von Mitteleuropa«, 1863.

v. Siebold says for instance, p. 343: »Der Aal nimmt in seinen verschie-
denen Alters und Lebenszustinden mancherlei Formen und Farben an, welche
zur ÅAufstellung von mehbreren Aalarten Veranlassung gegeben haben. Eine
grosse Verschiedenheit bietet die Långe und Form der Schnauze des Aales,
worauf Risso und Yarrell die drei Species Anguilla acutirostris, latirostris
und mediorostris grundeten. Elstroém gab der Vermuthung Raum=), dass
sich zwei Aalarten unterscheiden lassen, die er als spitznasigen und platt-
nasigen Aal (Muræna oxyrrhina und platyrrhina) bezeichnete. Es verstehen
sich gewohnlich die Fischer sehr gut darauf, diese verschiedenen Aalformen
herauszufinden. Nach Cwuvier's Angaben scheinen es hierin die Fischer in
Frankreich am weitesten gebracht zu haben, indem sie sogar vier ver-
schiedene Aalarten unterscheiden. Ich muss aus weiter unten anzuftihrenden
Grinden die Art-Berechtigung dieser verschiedenen Aalformen durchaus in
Zweifel ziehen.«

His view on the matter agrees here quite with mine.

Page 352 v. Siehold says further: »Von der einen dieser Åalformen

wird behauptet, dass derselbe, wenn sie auch ausgewachsen sei niemals

wandere« . . . »so liegt alsdann die Frage nahe, ob diese niemals wandern-
den Aale nicht steril gebliebene Individuen sein kånnen« . .. v. Srebold

has here the yellow eels in view; but he has not thought that they could change
their appearance or that their »sterility« is their normal condition.

How far v. Siebold is from acknowledging the existence of a breeding-
dress is shown by his statement p. 353: »Dass zur Herbstzeit in das Meer
hinausgewanderten Aale wirklich dort ihren Fortpflanzungsgeschåtft vollziehen,

”) See ante p. 13.

daruber kann kem Zweifel mehr herrschen«, . . . in connection with his state-
ment p. 352: »Es ist ein Beweis mehr, dass die Aale nicht im geringsten fir
das Fortpflanzungsgeschiåft vorbereitet im das Meer hinaustreten«. If besides
being an intelligent naturalist he had also been a little more of a fisherman,
he would soon have seen that the emigrating eels all had a pecular appear-
ance, i. e. that they were silver eels, eels in breeding-dress.

The author, after 1874, who seems to me to have been nearest to obtain
a clue to the difference m the outer appearance between males and females
as well as between yellow and silver eels, is Jacoby. In »Der Fischfang in
der Lagune von Comacchio 1880«, p. 50, (3), he thus gives a very correct
description of the little males with a metallie lustre which emigrate to the
sea. He says however here »Augen nieist gross« though they are always large
in the silver males; the reason of this, I dare say, is that at Comacchio he has
also seen yellow males.

Loc. cit. p. 50, (2), he describes the frog-mouthed eels which he cannot
look upon as normal eels.

Loc. cit p. 50, (1), finally, he describes the females, but he says of them:
»Wandert im Herbst ins Meer und hårt auf zu fressen wåhrend dieser Zeit« ;
they are consequently in autumn strongly marked silver eels, and yet he says
of them: »Ricken braun-grin, niemals intensiv schwarz, Bauch weisslich-gelb,
wenig oder kein Metallglanz«, and he does not mention the eyes. Evidently
he has here had more yellow females than silver ones to look at, and to distin-
guish between these and unite the yellow ones with the frog-mouthed eels
has not occurred to him for one moment, though as above mentioned the
fishermen down there so to speak call upon him to do so. Loc. cit. pp. 4£7—48
he says: »Aus diesem Gebrauch desselben Namens Pasciuto fir zwei ganz
verschiedene Kategorien, von dessen die eine simmtliche noch nicht reife,
also auch die spiter wandernden normalen Weibchen und die Aale mit dem

Lappenorgan umfasst, die andere sich aber allein auf die sterilen Weibchen

bezieht, welche niemals wandern ..... ergiebt sich eine Verwirrung, .....
die dem Forscher anfangs .... Schwierigkeiten hereitet.« This, however, is

the way in which all skillful fishermen all over the world have looked upon
the eels, and will look upon them also in future; but I think it will no lon-
ger cause the naturalists any »Schwierigkeiten«. —

It might seem perhaps that Møbius and Heincke: »Die Fische der Ost-
see 1883«, pp. 144—145, are still nearer the full understanding; for they know
that the fishermen distinguish between »zwei Sorten Aale; den granen und

den gelhen Aal«; they know, finally, that Letn has éxpressed the opinion that

2
die graue Farve des Wanderauls dessen Paarungsfarbe ist«. They do not
try, however, to connect these statements with the forms or species of eels set
up by the authors, they do not try to find out how »the frog-mouthed eel«
is to be understood, and they do not know that the yellow and silver (gelbe
und graue) eels differ in many other regards than the colour. Still in 1887
when Mølius in his essay on the sexual organs of the eels in »åter Bericht
Komm. Wissensch. Unters. deutsch. Meere«, p. p. 127—157, again returns
to the same thing, he speaks but very briefly of Paarungsfarbe, and seems,
like Leth, to mean that just the gray colour is characteristic in this respect
(cp. ante), and he even mentions that this colour appears in dots.

Though our various forms of eels have thus for many years already
been looked upon as belonging to one species, and though the migrating form
only (the fishermen's »silver eel«) was supposed to take part in the propagation,
while the yellow eel on the other hand was stationary, nobody has directly
written that it is so before Mr. F. H. T. Leth, the lawyer,") (see »Fiskeri-
tidende« 1882 p. 393 seq.); he has, more than Jacoby, represented the fisher-
men's view of the matter, and he has, moreover, got the idea that one of the
forms they have adopted represents the eel in growing-dress, the other the
eel in breeding-dress, though certainly without any further satisfactory ex-
planation. I hope that the above statements may be regarded as such.

If therefore in future any one will set up more than one European
species of the eel, he must take care that it embraces both males and females,
both yellow and silver eels, and that it is founded on something else than the
breadth of the interocular space; for this latter character is in discredit; —
specimens with a /arge interocular space are to be found, as above mentioned,
among the yellow eels as well as among the silver ones; hut this is not at
all what the authors call and have called 4. latirostris (frog-mouthed eels), for

the sharp-headed silver eels with a large interocular space have, as far as I

know, never been placed in that category — and as yet no one has success-
fully tried to distinguish between the silver eels with a small and those with
a large interocular space; to do so it is necessary to have other characters.
— Nor does there seem to be any difference in the life of these forms of eels,
for we meet with the yellow specimens with a large interocular space both
in fresh and in salt water, and it is just the same with the corresponding
silver eels with a large interocular space; of course, only the silver ones take
part in the breeding-migration. But it is a great mistake to believe, as many

=) Consequently 9 years before Bullo, the engineer; see note p. 11.

IS

authors do, that the vellow ecls do not migratc at ull; they emigrate from
our fjords and fresh waters and immigrate into them, hut often at other times
and in other directions than the silver eels; several considerable weel-fisheries
have lately been "developed on the hasis of these formerly hut little heeded
migrations of the yellow eels.

There has been considerable doubt for some years after the discovery
of the male eels (1874), whether they were found in numbers in fresh water or
whether the females were nearly sole masters here, a question, after all, of no
very great interest, which had got some scientific importance only because
their scarcity in fresh water was supposed to be a proof of their inability to
breed there; they could do so only in salt water.

Already im 1880, however, O. Hermes proved the occurrence of a num
ber of male eels a long way up the'Elbe, but as this did not seem to have
convinced v. Siebold that male eels really and ordinarily do occur in fresh
water Hermes further (in »Sitzungs-Berichte der Gesellschaft naturforschender
zu Berlin 1882« pp. 37—38) set forth a statement of finds of male eels in
the Elbe at Wittenberg, i. e. more than 20 German miles from the sea-shore;
he found among 600 eels on an average 5,”/, males, and in order to further
remove all doubt he adds: »Dieses Ergebniss ist nicht etwa ein zufålliges, son-
dern wurde durch die im nåchsten Jahre fortgesetzten Untersuchungen von
Neuem als richtig beståtigt«.

Afterwards several others have shown the occurrence of male eels in fresh
water, and they are known also in our waters. -—— The places, however, where
the males are most frequent, are certainly our little brackish fjords, as for
instance Roskildefjord, where I have found them hy far to exceed the fe-
males in numbers. (See later on.)

On Classification and Foreign Species of Eels (Angulla).

Of course it is not our northern eels only which get such a breeding-
dress as that described above; I have seen also at the Zoological Museum a
specimen of Anguilla vulgaris from Egypt, which was a fully developed silver
eel, and the breeding-dress, of course, is found at all places where the species
occurs; it is not known for certain whether it is found also in the other spe-
cies of Anguilla, represented by such distinct types as Anguilla sidat and An-
guilla labiata, but it can scarcely be doubted.

Authors as Bleeker and Kaup have set up a number of species
of Angwilla, which Grwinther has afterwards partly united, without giving

29

any other reason than the, after all, very good one, that they were con-
nected with one another by all possible transitions; Kaup's European species
of Anguilla, particularly, have been much reduced in number, from c. 20 to
2 or 1. But though we must agree with Gynther in this reduction, we want
a little more explanation, and the above statements give us some help that
way. — It will easily be understood that the size of the eyes and the form of
the head can scarcely be good specific characters, as they are dependent upon
the breeding-dress of the eel; but in Dr. Kaup: »Catalogue of Apodal Fish
1856«, p. 32, these very characters are used to mark out the first group of
species, consisting of 4. Of these 4. Kreneri is a questionable Anguilla which
I shall here leave quite out of consideration (Fr. Day has thought to recog-
nise in it a Lycodes); the 3 others are little silver (or half-siiver) eels, all of
them males I dare say, of sizes between 18,, and 13,, English inches.

Kaup's second group of species is characterized by a more longish
snout and a taller dorsal fin, and will thus particularly embrace yellow eels
and females; Å. marginata, A. ancidda? A. altirostris, and A. platycephala
must thus he looked upon as little yellow eels, Å. /atirostris and Å. capitone
as frog-mouthed eels, Å. morena? and A. melanochir? as silver eels.

It would be a good tbing, no doubt, if all the species within the whole
family of Murænida could be subject to a revision where there were the ma-
terials for it; for as long as net the slightest attention is paid to the sex or
the breeding-dress of the eels in the descriptions of the species, we cannot ex-
pect the latter to satisfy our just demands. This has not been done in any
of the more comprehensive works, nor could it be done as these things have
not been more closely elucidated till after they were written. In his »Cata-
logue of the Fishes m the British Museum, Vol. VIII. 1870« Gzønther, in
grouping the species within the genus Anguilla, tries to avoid such characters
as the form of the snout, the size of the eyes, etc., which are known to be
subject to great individual variation, but he supposes nevertheless that the
groups a »Eye considerably shorter than the snout« and / »Eye not shorter
than the snout« can be maintained. Among / he counts only Å. hieneri; but
many of our common male silver eels must belong to /, while the females and
a number of the males must be classified under a. See for instance plate II,
fig. 6 a; the snout of the specimen which is represented is even shorter than
the diameter of the eye.

30

On the Size of the Eels in our various waters, and on our
Eel-Fisheries.

Everybody who has had anything to do with the echolesale trade in
eels, knows that the eels which are fished in our Danish waters are not of the
same size; that, for instance, the eels we may buy of the fishermen in the
Lesser Belt are, on an average, much larger than those which we get from
Roskildefjord. This cireumstance is the same every year. From the Lesser
Belt we can get for instance yellow eels caught in seines in great numbers,
of which, on an average, 2—3 go to 1 lb.; in Roskildefjord, on the other hand,
6—8 go to 1 lb. — Something like this applies to the silver eels from these
two waters; of the silver eels from the Lesser Belt, south of Middelfart, there
generally go 20 to the »Lispund« (— 16 Danish Ilhs.), of those from Roskilde
and Frederikssund (from the fjord) there go 60—80. As the size has a great
influence on the value of the eel pr. lb., this is a matter with which the Ger-
mans who buy up the eels are very well acquainted, and they have indeed a
set price per lb. of silver eels which are bought, depending on whether they
are fished at one place or the other. These prices were in 1888 as follows:
48 Øre for silver eels from Klakringen (off Vejlefjord).

45 Øre for silver eels from Fredericia, Middelfart, Assens, Boiden, Horne-Mark,
Dyreborg, Faaborg, Svendborg, Thurø, and the neighbouring districts.
43 Øre for silver eels from Ærø, Langeland, and all islands south of the north-
most point of Ærø, Nyborg, Kjerteminde, and the interjacent districts.

For silver eels from Kallundborg, Korsør, Skjelskør, Karrebæksminde,
and the interjacent districts:

in the first dark of the moon 40 Øre,

im the 2nd and ård dark 42 Øre.

These prices were offered hefore the eels were fished, based on the know-
ledge which the fish-salesmen had of the quality of the take from former years, and
their knowledge is very trustworthy. It will be seen that the whole emporium
embraces only the Lesser and the Great Belt, as the trade on the northern
shores of Jutland and in the Sound was on other hands. Within this said
emporium it is the Lesser Belt which produces the dearest goods, i. e. the
largest silver eels.

Such a difference in the average size is found also among other species
of fish, for instance among plaice and cod, and it can depend on various

circumstances; in certain waters, for instance, there live chiefly fish that are

31

one or two years old, while the older ones emigrate to deeper places; in
other waters there are dwarf-races that become adult at a proportionally
small size.

It was clear to me heforehand, however, that these two circumstances
could scarcely be the main cause of the different sizes of the eels; for all sizes,
to the very largest, are found in fresh water as well as in salt water, and at
certain seasons very large eels are found on shallow water near the shore.
This very fact that the eel is independent of the salimity, made it improbable
that strongly marked dwarf-races of this fish would be found in our seas, and
a direct examination of this question gave also another explanation of the
phenomenon. The male eels were found to be so rare in the Lesser Belt that
only 2797, of the males were caught there in the first dark of the moon
which generally gives most male eels there, as at other places, while I got
94 0, in Roskildefjord in the first dark and 85%, m the last darks; m
these latter darks, into the bargain, there were not by far caught so many eels
as in the former, so that the male eels, from this reason also, play a still more
dominant part here. As the males, on an average, do not weigh more than
c. 1/, Ib. a piece, while the females, as a rule, weigh 3/,—1 lb. and more, it
will easily be understood that the average size becomes smaller where the males
are numerous, than chere there is but a little number of them. The numerical rela-
tion between the sexes is the main cause of the various average sizes of the silver
eels in our waters, for a comparison between the eels of either sex from different
waters does not show such a difference in size; c. 18 inches is everywhere the
maximum size of the males, and very large females are found in all seas and
fresh waters, though certainly not im equally great numbers everywhere. In
certain smaller brackish waters, to be sure, it seems that some few eels, both
males and females, can hecome silver eels with a total length which is some-
what smaller than that which is the minimum in more open waters; this,
however, seems but slightly to affect the average size.

To get the exact measures here is very difficult, as the fishermen at the
various places use meshes of very different widths; and as the Biological Sta-
tion, on account of the shortness of the fishing-season, as a rule is unable to
examine the silver eels with its own fishing-tackle at more places than one in
the year, it will last some time before it can get more considerable materials
collected, by its own fishery, from all parts of the country.

From this reason I shall not now enter more closely into this matter,
but only mention that the numerical relation between the sexes differs

very much among the yellow eels also, and that it, to a very high

32

degree, influences the average size of the eels that are caught; as might
be expected, the yellow males are numerously represented in the same
waters where the silver males are found in great numbers, and
vice verså.

In a following report I shall return more closely to the conditions which
affect the different sizes of the eel in our waters, the correct knowledge of
which is of the most vital consequence to our fishery. 30 years ago the size
of the eel (of the yellow eels as well as of the silver ones) was another in the
Issefjord than it is now, /he cause of which, certainly, is to be found in the intense
fishery of later years, when so very few eels can reach any considerable size as
they are fished before this is attaimed. The yellow eels in the fjord are there-
fore, on an average, small now, and the silver eels are almost exclusively
represented hy males.

The above statements, that the yellow eels become silver and emigrate
to the sea, and that the so-called frog-mouthed eels are not for ever sterile but
also at last become silver cels, are of no slight consequence to our cel-fishery
in the more inclosed waters, particularly, consequently, in fresh waters; for,
pursuant to this we must suppose that all adult eels voluntarily leave these
waters in order to go to the sea, and where we have it m our power to catch
all the emigrating eels (for instance in eel-trunks, eel-baskets, etc.), the fishery,
consequently, ought as a rule to be limited to the catching of these, and
'fishery with seine or hook ought not to be carried on in the same water, be-
cause the expenses become heavier by doing so, while the”profit on the fishery
m the long run cannot he supposed to become greater, as also because the
eels which are caught in this way are not yet adult, nor are they so fat as
they will normally become if we waited till they were silver eels. If, at such
places, we catch only a//l the emigrating eels, we get what the water in ques-
tion can give, and, exactly, all that is ripe to be caught. The expensive seines
which in several of these waters are used for catching yellow eels, ought
certainly not to be employed; by this we shall save money for keeping the
fishing-apparatus in repair, or for the crew.

If, on the other hand, we cannot catch all the emigrating eels, but only
a greater or smaller number of them, the use of other methods for catching
them may be recommendable, and in salt water where, I dare say, only a
small number of the emigrating eels are caught, such methods are quite

indispensable.

Emigration from fresh and brackish Water to the Sea for the sake
of spawning is not an exceptional phenomenon among our fishes.

That the eel in its silver dress emigrates to the sea in great numbers has
been known by everybody from time immemorial, and great fisheries and
interests have always been attached to this migration; the silver eel goes out
of our fresh waters as well as along our shores, and the yellow eel does not
Follow it on this migration. These are long-established facts which in them-
selves fully prove that the yellow eels become silver, particularly after it had
been pretty unanimously agreed upon that we had to do with only one species
of eels; nohody, however, had taken the trouble more closely to examine this
circumstance and show what is hidden behind the fishermen's names »yellow «
and »silver«.

The silver eel's great migration has, at least since v. Stebold's time, and
surely most justly, been supposed to be connected with the breeding of the
eel in the salt water, of which, after all, we do not know much; hut the brood
which in spring has immigrated into the inshore seas and fresh waters is
evidence, however, that such a breeding has taken place.

When the direction m which the migration goes has generally been
looked upon as an exception from the breeding-migrations of other fishes, which
from the sea approach the shores or go into fresh water, while the eel 20170
draws from the shores and the fresh water, this is in my opinion quite un-
justified. The breeding-migration of the eel fully agrees with the migrations
of several others of our commonest salt-water fishes, for instance p/aice and
Jlounder.

That fishes as trout, salmon, and various others, which spawn in fresh
water, during the breeding-time go up the rivulets and brooks from the sea
cannot surprise; they must be looked upon as fresh-water fishes which have
accustomed themselves in certain periods of their lives to seeking their food in
the sea; but by their breeding and their tender fry they are firmly attached
to fresh water which, therefore, they cannot at all dispense with.

Equally easy is it to understand that sa/t-water fishes as the herring and
the garfish, whose eggs are deposited on the bottom of the sea on shallow water,
in breeding-time generally approach the shores, as their eggs and fry cannot
live at any other places. i

That fishes whose eggs, on the other hand, float or buoy in the water also must

go to such places as are suitable for the development of their eggs, i. e. places

»

34

where the specific gravity of the water is high enough to bear the eggs, i. e.
where the water is salt enough, is a fact of which we generally do not think,
and it was therefore a surprise to me to see, that both the f/ownder and the
plaice, which at times are common in our small, half-brackish fjords, before
the breeding-time leave these and, consequently, withdraw from the shores and
the fresh water, where they often go up, when little ones, to seek more open
and salt water, just as the eel does.

Such a breeding-migration from the inner fjords to the more open sounds
and shores takes place also among fish without pelagic eggs, for instance
Spinachia vulgaris, which is very fond of staying im the enclosed fjords, but
in breeding time always emigrates to the clearer waters with more rapid cur-
rents at the mouths of the fjords. It is then not at all an exceptional or in-
explicable thing that the eel goes into the enclosed waters during its growth
and leaves them before it becomes mature, it is only the greatness of the
phenomenon which is uncommon, as the eels appear in such great numbers
and many of them not only go up the small brackish waters but even into
the fresh waters which are often at a long distance from the sea. T'he eel
must, no doubt, be looked upon as a salt-water fish, Just as well as the flounder
or the plaice. For them all, considered as species, the salt water is quite
necessary, and only during their growth some specimens go into fresh

water.

Copenhagen, in the spring, 1895.

3D

Explanation of the Plates.

Plate I, fig. 1a-b. Head of a27 inch. long yellow eel with large interorbital space 9

— SU DET == 19

— %3ab. — - - 3527, -

—= - 4ab. — - -30/, -
Platel, fig.dab. — - - 14!/, -

— SMb'aD. 0 — == 16

— ap — 1-5 793], -

— - 8. Sketch of a 31

The figures are drawn by

time been kept in spirit.

sy

that of a normal eel.

n ”, linear size.

3

yellow Q eel in ”/, linear size.

silver eel with small interorbital space 9 in Y, linear size.

0

silver eel with large interorbital space Q in %/, linear size.

yellow & eel in natural size.
silver å - - — -
silver & - - —

silver eel with large interorbital space 9 inc. '/, lin. size").

==" -… small = SE TE
yellow - -… large — — Q—- 15

means of the Camera lucida from eels that have for some

Note: The tip of the candal fin of this eel was a little damaged, but is drawn like

Zåvle 1. (Den danske brol.Station V” (Fiskeri Beretning 189495)

7érnle 11.1 Den danske biol. Station V/ (Fiskeri Beretning 189% 95 +

BEDS Sr serne
=

FYPE= SEES

II. Om de ved Stege og nærliggende indenskærs Farvande
levende Fiskearter med Bemærkninger om deres Forekomst,
Legetid o.s.v.

Af C. G. Joh. Petersen.

Ahborren (Perca fluviatilis) har tidligere været langt almindeligere end nu. Den
leger her i Farvandene, men i 1894 saa jeg det ikke.

Ulken (Cottus scorpius).. Enkelte Individer, men kun voksne; efter Fiskernes
Sigende er der langt fra lige mange hvert Aar, som det andre
Steder plejer at være Tilfældet. Iaar er der kun faa.

Kutlinger (Gobius niger) meget almindelig. Den legede ved Stege midt i
Maj 94.

Gobius sp.

Stenbideren (Cyclopterus lumpus) saas af og til.

Aalekvabben (Zoarces viviparus).. Mange Aalekvabber saas, men megen For-
skel paa de forskellige Aar, sige Fiskerne.

Hundestejlen (Gasterosteus aculeatus og pungitius). Begge Arter ere særdeles
almindelige. G. aculeatus legede midt i Maj.

Tangsnarren (Spinachia vulgaris). Ikke hyppig. Leger her næppe.

Hornfisk (Belone vulgaris). I Efteraaret 93 fangedes i Bundgarn i Stege Nor
en Mængde Hornfiskeunger paa c. 9” Længde.

Torsken (Gadus callarias) fandtes ikke ved Stege i 93—94, til andre Aar kan
den efter Sigende være almindelig der. Geddeperioder og Torske-

perioder siges at afløse hinanden i disse Farvande. Ved Masned-
sund og særlig vestefter optræder Torsken til Stadighed, og her ere
Gedderne kun sjældne. Torsken yngler næppe nogensinde i disse
Farvande, dertil er bl. a. Saltholdigheden for ringe.

Tobisen (Ammodytes).

Pighvarren (Rhomlbus maximus). Et enkelt mindre Individ saas.

Skrubben (Plewronectes flesus) findes her til Stadighed, men ikke i stor
Mængde; den yngler, næppe nogensinde her, og yngre Individer
saas aldeles ikke. I Begyndelsen af Maj saas enkelte Skrubber

med megen Rogn.

38

Rødspætten (Pleuronectes platessa) er endnu sjældnere end Skrubben og leger
her sikkert ikke.

Naalefisken (Syngnathus typhle) hyppig, og leger her som andet Steds, hvor
den findes.

Ørreden (Salmo trutta) almindelig. Den udklækkes kunstig flere Steder i
Bækkene.

Silden (Clupea harengus) fiskes meget i Bundgarn, saavel Foraar som Efteraar.
I de første Dage af April iagttoges Mængder af nylig udklækket
Sildeyngel i Dammene ombord. De forsvandt snart igen. Det maa
antages, at Silden leger i Nærheden, hvilket ogsaa de i Bund-
garnene fangede Silds Kønsorganer kunde tyde paa, men det lykke-
des mig ikke at paavise Legepladserne.

Aalen (Anguilla vulgaris) findes overalt og i stort Antal, men de cre temmelig
smaa. Hanaal ere rigelig repræsenterede.

Aalene fiskes mest med Vaad og ved Blus med Piglyster.
Savlysteren indførtes i Kallehave af Biologisk Station, dog bruge de
der en egen selvlavet Form. Aalekroge og Aaleruser bruges kun
lidt.

Rudskallen (Leuciseus erythropthalmus) er, vet almindelig her. Om dens Legen
iagttoges intet.

2, der fangedes i Stege Nor i Oktober 93, havde Maverne
fyldte med en grønsort Masse, hvis Hovedbestanddel var Dipter-
larver.

Løjeren (Leuciscus alburnus) var særdeles almindelig i Strømmen i Stege
Havn.

Emden (Leuciscus idus).. Enkelte Individer fangedes.

Brasenen (Abramis brama). Yngre Individer fangedes af og til enkeltvis.

Gedden (Esox luctus) er hyppig i disse Vande, og der drives betydeligt
Fiskeri efter den.

Den legede i 1894 fra c. 20de April i Stege Nor og ved
Staureby. (Ogsaa i Præstø Fjord fandtes dens Rogn paa Hav-
bunden.)

De levende, enkeltvis spredte Æg fandtes kun, hvor Bundens
Algetæppe var tæt nok til at forhindre Ægene fra at synke ned i
Mudderet, men ikke hvor der var ren Sandhund, Characer eller
LZostera; de fandtes f. Eks. i de Alger, der vare fulgte med op i et
Aalevaad, som Fiskerne fiskede Aal med. Ægene fandtes kun paa
Dybder af c. 6—10 Fod. Paa den største Legeplads (ved Staureby
i Sandvig) stod mange Gedderuser, og her foregik et stort Fiskeri
af legende og udlegede Gedder.

Gedder fanges desuden i store Vaad, saakaldte Strandgarn, et
Slags Landdragningsvaad, samt i »Tog«, d. v. s. et Drivvaad med
store Masker, der ligner Aaledrivvaad og bruges paa samme Maade.

Med Stangeredskaber fanges desuden en Del Gedder paa Blus, og
endelig tages en Del paa Blink.

Il Vinteren 1894 døde en Mængde Gedder (ogsaa Aborrer og
enkelte andre Ferskvandsfisk) under de stærke Storme i Midten af
Februar Maaned saavel i Stege Nor som i Præstø Fjord og i Bøge-
strømmen ned mod Masnedsund. Vandet blev meget plumret af
Stormen, og Saltholdigheden steg til næsten 1!/, ”/, ved Stege, ende-
lig indtraadte ogsaa stræng Kulde i denne Tid eller umiddelbart
derpaa. Gedderne døde saavel i de udsatte Ruser og i det frie,
som i Hyttefade. Fiskerne vide at fortælle om mange lignende
tidligere Lejligheder med »Bundfrost«, der dræber Gedderne i Masse.
I Aaret 1894 var Geddefiskeriet ifølge Statistiken ikke desto mindre
det bedste, det i flere Aar har været.

Ved Forsøg ombord viste det sig, at en Gedde meget vel
kunde leve i Vand af 1/7, '%, Saltholdighed, hvori der var udrørt
en Mængde Mudder, jeg maa derfor tro, at det enten er Kulden,
der dræbe Gedderne, eller maaske alle tre Ting i Forening, eller,
hvad der vel er det sandsynligste, kun de svageste Individer bukke
under for Stormens uheldige Indvirkninger.

Om Faunaen i Stege Nor skal her, for at give en Forestilling om dens

Karakter af Brakvands-Fauna, nævnes, at Pighude ganske savnes.

Af Orme saas bl. a. en Nerceide.

Af Krebsdyr: Idothea, Sphæroma, Gammarus, Corophium o. s. v.

Insekter:

Bryozoer:
Bløddyr:

I alt 1 eller to Individer af Carcimus mænas.

Palæmon Fabricii (den alm. Reje) er derimod almindelig, men
Fiskeriet efter den er taget overordentlig af.

Af Mysider fandtes flere Arter, bl. a. Mysis fleruosa og Ma-
cropsis Slabberi.
Flere Slags, f. Eks. Nofonecta, og navnlig Larver vare meget al-
mindelige.
En Membranipora.
Cardium edule alm., Card. exiguum alm., Macoma baltica, Mya are-
naria, Hydrobia sp., Littorma tenebrosa, Neritina fluviatilis, og et Par

Arter Limnæus var alt.

Det pelagiske Dyreliv var reduceret til et Mimimum af Arter, nogle faa

Mysider og

Aurelia aurita, af Smaakrebs saa jeg lidet i den Tid, jeg laa der.

I Stege Nor var Bunden dækket paa store Strækninger af Characeer og

forskellige Potamageton-Arter; Bændeltang forekom dog ogsaa.

40

Det skal udtrykkelig omtales, at det med ovenstaaende ikke er Hensigten
at give en Fortegnelse over alle de Fiskearter, der kunne forekomme ved Stege
og nærmeste Omegn; men kun at give et Billede af den der levende Fiske-
bestand og dermed vise dens ejendommelige Karakter af halv Salt- halv
Ferskvandsfauna, af hvis Arter kun faa lege paa Stedet, medens Resten kun
strejfer derind paa mere eller mindre regelmæssige Vandringer.

III, Om de ved Frederikssund i Roskildefjord 1894 iagttagne
Fiskearter med Bemærkninger 0. s. v.

Af C. G. Joh. Petersen.

Søkarudsen (Ctenolabrus rupestris). To Individer saas.

Ulken (Cottus scorpius) almindelig, men kun som voksen.

Kutlingerne. Gobius niger legede i Mængde i Begyndelsen af Juni Maaned.
Den fiskes i et Antal af flere Tusinde daglig, saalænge Aalekrog-
fiskeriet staar paa.

Gobius microps legede i Juni. Almindelig.

Aalekvabben (Zoarces viviparus) meget almindelig.

Tangsnarren (Spinachia vulgaris). Ret hyppig, men legede først ude ved
Lynæs.

Hundestejlerne (Gasterosteus aculeatus og pungitius). Begge almindelige. De
legede begge i Slutningen af Maj.

Hornfisken (Belone vulgaris). Smaa Unger saas i Mængde allerede i Juni
Maaned, i Slutningen af September, før de forlode Fjorden, vare de
71/,—9"/," lange. Legepladserne ere vistnok i den store Issefjords-
bredning, hvor ogsaa Hovedfiskeriet foregaar.

Torsken (Gadus callarias) var meget sjælden. Et Individ fangedes 22. Sep-
tember i en Ruse.

Skrubben (Pleuronectes flesus) er meget almindelig, men leger her ikke. Indi-
vider under 3//,” fandtes ikke. Der drives et ikke ganske ubetyde-
ligt Fiskeri efter den. Den synes som voxen at vandre regelmæssig
ud og ind ad Fjorden.

Isingen (Pleuronectes limanda). Kun et Individ saas.

Tungen (Solea vulgaris). Et Individ saas.

Naalefisken (Syngnathus typhle) almindelig og legede som sædvanlig.

Ørreden (Salmo trutta) hyppig. Leger i-mange af Aaerne. Der drives om
Efteraaret Rusefiskeri efter den.

Smelten (Osmerus eperlanus) fanges ret ofte, men enkeltvis i Sildegarn om
Efteraaret.

Silden (Clupea harengus) fandtes der hele Tiden, men hyppigst Foraar og
Efteraar, til hvilke Tider der drives Fiskeri efter den. Den leger
dog næppe i selve Roskildefjord, men flere Aargange vare til Stede.

Brislingen (Clupea sprattus), enkelte fangedes.

Brasenen (ÅAbramis brama). Et Par Individer fangedes.

Karudsen (Cyprinus carasstus).. Et enkelt Individ fangedes 22de Juni, vel
sagtens nylig udvandret fra et eller andet Ferskvand.

Gedden (Esox lucius).. Et Individ fangedes i Efteraaret.

Aalen (Anguilla vulgaris) er saa at sige den eneste Fiskeart, der drives et
videre indbringende Fiskeri efter. Da dens Biologi andet Steds vil
blive omtalt, skal jeg ikke her gaa nærmere ind paa Sagen.

Roskildefjorden er ved sin Munding ved Lynæs et udpræget Saltvand,
og ved Roskilde et næsten rent Ferskvand, alle Overgange findes mellem disse
to Yderpunkter. Pighude findes saaledes ikke ved Roskilde, men endnu ved
Frederikssund lever AÅstertas rubens. Forskellige andre Saltvandsdyr, saasom
Cardium edule og Mytilus edulis leve helt op til Roskilde.

IV. Togt med ,,Havørnen" fra Issefjorden til Limfjorden og
det nordlige Kattegat. 2.—13. Oktober 1894.

Af C. G, Joh. Petersen.

2den Oktober ankom »Havørnen« Kl. 9 Fm. forsinket af Taage til Frederiks-
sund. Kl. 107/, Fm. afsejlet igen.

Nr. 1. Hesseløen i ONO. 7 Kvartmils Afstand. 12 Favne Vand. Aale-
haandvaad: 4 Isinger, 2 Ulke, Actinier, 1 Echinus Drøbakiensis.. Vaad-
det hoppede over større Sten.

Til Grenaa Aften Kl. 6/.
3die Oktober fra Grenaa Kl. 6 Morgen.
Nr. 2. Rejehov ved Limfjordsbroen gav ingen Flynderyngel. Det grønne
smaamaskede Snurrevaad:
4 Skrubber paa 6, 6, 6!/, og 5%, Tommes Længde.
2 Rødspætter paa 43/, og 43/,”.
Crangon i Masse.
Nr. 3. Syd for Egholm påa Sandet. Det grønne Vaad. 2 Træk.
3 Skrubber paa 38/,, 43/,, 41/4".
1 Pighvar paa 3”.
Crangon i Masse.

Nr. 4. Troldholmene. Grønne Vaad paa Sandet ved Vadning.
4 Skrubber: 453/,, 41//,, 41/,, 41/,7.
i Pizhvar: 2%".
. 1 lille Østers paa Buccinum.
Buccimum i Masse etc.

Nr. 5. Samme Sted. Om Aftenen med Aalehaandvaad paa Kanten af Renden.
1 1Tæk:
2 mislykkedes fordi Ankeret ikke holdt.
TRØSTE o] ars ed KOS ASS ET Ft Fa LY FRE H(0 JAG 7 REG KUSK SET ØSRE EJ Fr ØE SST ØRSR BESET RE
1 Rødspætte 7!//,”,

14

i Ea Nes En fr AR SE Der RE RES Re SEE ET NEDE SES STENE.
VEND FEOT SR OT so Se OL SERGE

1 Motella cimbria.

36 Aal. 18 smaa, 18 store, vejede tilsammen 10 T.

4de Oktober.
Nr. 6. I Trend-Aa nær Ærtebølle.
Masser af Smaaskrubber fra iaar og en enkelt ældre: 7//,, 4//,, 3%,
311, 31/0, 31/,, 3, 3, 231, 28/1, 28/, og flere Hundrede mellem 21/9
oms NE
Udenfor paa Revlen kun en ganske enkelt Skrubbe.

Nr. 7. I Fuur Sund. Søgt 2 Steder paa Revlerne med grønt Vaad og
Rejehov.
ES DN SE TE RDS KO ES ES

KM

1 Pighvar 5

Nr. 8. Flere Træk Øst for Nykjøbing paa 5—6 Fv. Vand. Grønt Vaad.
c. 20 større Rødspætter.
Nogle Isinger.
1 Aal.
Ophiurer i Masse.
Bunden graat, friskt Leer.

Nr. 9. Glyngøre-Hage paa Revlerne. Grønt Vaad.
Rødspætter 6175 5 DID IE SE RS RE SDS] AN

5te Oktober.

Nr. 10. Venø Bugt ved Vrald Odde. Flere Træk med grønt Vaad.
SER gås peer HO ET ET ET] el
1 Slethvar 67/,”.

Nr. 11. Ved Handbjerg paa Revlerne og ude ved Kanten ialt 3 Træk med
grønt Vaad.
Skrub ber 61 GES ET ED SN HEDT] SE DIT SEES SES ERE S ER

Ingen Rødspætter.

6te Oktober.
Nr. 12. Ved den nye Aggerkanal. Flere Træk med grønt Vaad.

8 Skrubben 93 6 GE GT] SNG TEE NED ISTED TER

AP ohne TS EET ”

1 Slethvar 31/,”.

90 Rødspætter 84 BE ETT TT OLE GTI GNIDE I NES ENGE
52/,, 53/,, 51/,, 51/,, d, Eyre 41/2, Ang Er 21% ED 0 4, 4; 384,
SAR AE FEE] PRS PRERG IEG TT ENES EGE ST ERE TT FEE S) TA MESSRESTET STS)
BEN RE BTS DTT DU KOTE SDN TEDE ANES AED NED NED TED RAE

LOD NDA Ts as

45

Nr. 13. Indenfor Fjordgrunden paa 2 Fv. Vand. Grønt Vaad.

Rødspætter 11 631670, 671, 6 6 GS DIT DI,
DE ENE ES SE EA SAN SAT SAT SAD GSAT s
AS AN AS AI ATP Alf 41 8 pas All Ar paa 4.
SU NENS EES TE SEE BESS OBE ONS pe PP MON DRE
4 paa 2"

ENS SEE RE ENE EEN Ha] REE TJ] NERE, (REG IS URNE HESS DRE] FREE SLY DES
ES EDT Ta 2023) paa 12/1"

1 Hvilling (Séé) 41/,”.

Nr. 14. Længere inde paa Fjordgrunden. Grønt Vaad.

Paa 7 Fod Vand c. 140 Fladfisk.

Paa 3 Fod Vand c. 40—50 Fladfisk.

1 lille Knurhane.

Sild.

Tobiser.

2 Slethvarrer 41/,, 31/,”,

Rødspætter 8, 7//,, 62/,, 63/,, 61, ARR 6! [v 6,
BENS SED AA ANSAT SÆL LEES NS AES EYES
4" paa '283/, 21 paa 21/,, 40 paa 2/, , 43 are PAL E)

ISinger ANSE STED KO D ”a ANES NED GE pads RO Spade] ss
nal”

Nr. 15. Øst for Jegindø-Tap paa 8 Fv. Vand. 3 Træk. Grønt Vaad.
Rødspætter "10310, 71016; paa 92/7 paa 955 9106 paa 9,
SAR Daa ER SI NS pas ER NET TT Dr pads, TNT,
GESTEN G TYR 5] ARK GUN ERRS NEED ESATA EB E KOS SE DUS ADA KROLEE
21/1, 2),

FE RS ESRB ES TREN DS] PEGE

7Tde Oktober: Søndag.

8de Oktober.
Nr. 16. Skarre-Odde i Thisted Bredning. Smukt hvidt Sand, men Vadning
saavel som Vaaddræt paa dybere Sandbund gav aldeles ingen Fladfisk.

Nr. 17. Saa i Thisted hos Fiskerne store Rødspætter, fiskede i Bredningen, en
enkelt til '/, & fiskes af og til, alle andre ere større. Mon Bredningen
saavel ved Feggesund som mod Vest skulde være lukket af Bændel-
tang, saa at saavel Indvandring af smaa, som Udvandring af store
Rødspætter er umulig?

9de Oktober.

Nr. 18. Ved Indløbet til Agger-Dyb (Løgstør) fisket med grønt Vaad paa dyb,
ren Sandbund ialt kun:
1 større Skrubbe.

46

Nr. 19. Længere inde ved Løgstør. Flere Træk med grønt Vaad.
1. Pighvar 4”,
1 større Skrubbe.
10de Oktober.
Nr. 20. Ved Hals (Kattegat). Paa Grundene ved Vadning og forskellig Bund
samt Træk paa 1—2 Fv. Vand.
Skrubber UI 68/,, 611, 61, 58/1, 53), SME 51/,, ol, 5%, 43/,
My 4, 23/1, 28.
Rødspætter 8, 67/,, 51/,, 57/,, 470 4) AN, AN, 4, 23/,, 98P
Isinger 10/,, 8”.

1 Tunge 2”.

i:

Aarets Yngel af Rødspætter saaledes kun meget sparsomt repræsen-
teret.

llte Oktober.

Nr. 21. Mellem Sæby og Bangsbo paa Revlerne samt paa 2 Fv. Vand.

Grønt Vaad. Flere Træk.

Sildeyngel, nogle ganske nøgne, andre en Del større, de største
4—5 Tommer.

Tobiser.

Naalefisk.

Gobius Minutus.

5 Pighvar dyse See

Sktub ber Es REST ES SEG EG REE NED REST RL SES PERS

Rødspætte se ET RTR GE NG] RG TNS GT RG TERRE ER

ERE EK SL BRS FR SEES NESS EN ERE EET ES ES ED NE EB,
RESET FEE ERE PRES AR SE 2] GE

Tsnger dl ORSON TE SE ET SES RD LS] BERG NEL] SER
BE

Nr. 22. Udenfor Frederikshavns Havn paa c. 3 Fod Vand. 2 Træk. Grønt

2
Vaad.
<h HEE Te i 91/ / i 2 3 Q 1/ 21/ g ad d
Skrub ber et ENO EDT SOE NERO ESS NES TT SNE BT SNS SEES SES SEES
72/1 —Åo/ -—2/ -=1/ -—1/ / =1(/ - == om rd 2/ 19 / "i a
YDERST ASE PETE ERET ET SETE SERENE EET SET EEN SE TEST SE DT (ST him iD,

BESES ES RES AES RES SES RDS STEDT SED DE Da
53 4, 4, At, Att,
Rødspætter TORE LEE ES STRESS ET SEEST TREE
620, 631, 1631, 6%, 11 paa 67/5, 12"paa6, 15 paa 6) 9 pad sse/g
9 paa 51/5, 4 paa 5, AN SAY 4783 7830 opad ll EPAR
31/4, 3, 3, 3, 281, 21/5, 2 er
ES ER SER SETE) Pr SE SYES (SL REST FSK) AE DE
1 Slethvar 4!/,”.
12te Oktober afrejst fra Frederikshavn.
13åde Oktober i Fréderikssund.

47

Aarets Yngel af Rødspætter repræsenteres paa denne Tid af Aaret
ved Individerne under 3—3!/,”, Som det vil ses, vare disse talrig til Stede
ved Aggerkanalen og paa Fjordgrunden indenfor samme; mellem Aal-
borg og Mors fandtes aldeles ingen, ejheller i Thisted Bredning; ved
Glyngøre i Salling-Sund fandtes 3, ved Jegindø-Tap 6. Ved Udløbet til
Kattegat ved Hals fandtes kun 2 Individer af Aarets Yngel, ved Sæby derimod
10 og ved Frederikshavn en Mængde.

Rødspættens Yngel synes saaledes at indvandre til Limfjorden vestfra,
hvad ogsaa tidligere er antaget. (Se Beretning IV. Biolog. Station.)

Skrubbens Yngel fra iaar fandtes derimod i Mængde ved Trend Aa;
den maa antages repræsenteret ved Individer under c. 3”; saadanne fandtes

ellers ikke ved Limfjordens Kyster i Saltvand (se dog Hals).

V. Om Mærkning af levende Rødspætter.
Af C. G. Joh. Petersen.

396 mærkede Rødspætter udsattes i Mariagerfjord ved Mariager 19. April 1894.

Følgende ere indfangede:

Næs Længde | Fanget hvor. | Dato 1894. | Længde Maalt af hvem.
i Tom. | | i Tom.
831. SÅ Mariagerfjord. 11. August. 8/…. C. G. Joh. Petersen.
|
932 EET 0: | — 112. — 10. —
991.| 107, = | Ko 7uerr 10/,. =
6 Kattegat s
VE LYDER = 28. Se på en
123. 8 (Carl Bang). 8. Septbi re
p 2 | NORGES SOLE SA, Oktober. 2 Vejede "/,, &.. Brønnum.
(Brønnum). |
815.| 9/7,, | … Aalborgbugten za 11. GE GITOR Petersen
z (P. Schou). "
869. | 10. Mariagerfjord. — | Es | 10.
|
810. EEN == = fn Berg —
866. | 9. == z | 10. z
1895.
1000. 9. = Januar. 10778: —
OA | 79] == = | 101/,: z=
744. | 9. z | == 103/,.
| |
878.| 92, = || Marts. | 10%, =
|

49

298 mærkede Rødspætter udsattes i Thisted Bredning d, 28.—29. Marts 1894,

Følgende ere indfangede:

Nr: Længde | Fanget hvor. Dato 1894. | menn Maalt af hvem.
|
408. J | Vilsund. | 27. Juni. id: Agent Tachou.
592. 9 = es 127, -
617 9 = 26. — ib hyæg —
507. | 8%. | Thisted Bredning. BET = 10%.
ma ) | Kirkegaards Hage. ODER 127 er
686. y. | Thisted Bredning. 29. — 1æ —
.Ks TOR NELS TED HS 7 ØR | 29 — 12 —
630. | STS 129 12 —
681. | of Vilsund. Ott | 12. =
649. | g. | Gudnæs Hage. | 28. — 3 Lys —
661. | 9: Vilsund. Ade | 127; —
433. 9. | Øst for Vilsund. Ed KN 12:
LOGE OLE 9TN.- | = oe lg —
(|
502. 9. | Thisted Bredning. | 3. — 12:
585. | 9% = re 12 =:
690. | 9. = Ure 12 —
620. 10. - 2». — 13 —
456. | 9. == SS < 11%. se:
607. 7. | == tor 12. Ey
687. | 9. | Aas Bakker. 5. — LEE —
697. 10. | Thisted Bredning. Tx — 4 AS —
672. SK" er ga) ==. | 12. 2=
569. 9. | — vESARR HV 53 —
448. | 9. == VE 11%. z
|
572. | 94. | Vilsund. EN SED <E

50

Nr. LES | Fanget hvor. | Dato 1894. | vænne Maalt af hvem.
|

EU Se Te
DOSER HR 9270 Thisted Bredning. | 10. Juli. if Agent Tachou.
478 8/, er or ag =

509. y,. == joe 12, 2

505. 9: — 11. — EL —

528 SER - 17. — 122

631. 9 zl yes 1237. er

659. | 9%, 2 URE 12! Ezj

590. 83/1, Øst for Vilsund. | 167 — 12.

511. 8 le Thisted Bredning. 16. - IT —

|

513. BYE = (Fr GE Hos En

551. | 91, re: ig, == 125. El

534. | 8%. = tage 12. Frø

ÆDE ER SEE — | 29, — 1153/16 ==

bb 98 Øst for Vilsund. 21. — 13. =

489, | 9. Thisted Bredning. | 20. — 12 — Uden Hoved.
435. | 8%. Dragsbæk Bugt. 21. — hor tklis —

658. | Se pe Silstrup Hoved. 21. — har =

HOS RR 91 Silstrup. Iel hør 2475 —

437. 1 9%, | Thisted Bredning: | 23) — | 11%, —

492 | 9 — | on e== kile. —

>12 | SK, — 24. — 13 —

506. ak — 23. — he 2 —

547, Byes — 23. — 11578 —

488, SB — 25. — 12. ==

481. | 9, £s For me 133, E

416. 94, = SSR UATOBTE ££

539: DE - | 29. — 13875: —

587.

500.

451?

665.

412,

404,

508.

419.

586,

Længde

som Fanget hvor.
i Tom. :

oh AR Thisted Bredning. 30.

Malle Hage.

ss Thisted Bredning. 6.

9: August.

9. Livø Bredning 21.
817: Thisted Bredning.

Oktober.

10. ? 'Phisted. | ?

Dato 1894.

August.

August.

23. Septbr.

Længde

RS Maalt af hve
org: laalt af hvem.

11 Agent Tachou.

Uden Oplysninger.

12%. Tranum.
is: —
15. Petersen.
13. de! Mærkerne
13 vare vok-
tå: =
sede udaf
12: Fiskene.
9 Ingen. Kun Mærkerne
i indsendte.

Foranstaaende Rødspætter vare mærkede med to Benknapper med et ind-
brændt Nr., fastholdte af-en Sølvtraad, der gaar tvers igennem Fisken mellem
Rygfinnens Straalebærere, ligesom de i Beretning IV, pg. 140 omtalte.

Det vil ses, at Fiskene gennemsnitlig ere voksede mere og hurtigere i
Limfjorden end i Mariagerfjord, dog skal det her bemærkes, at de i Limfjorden
fangede ere maalte i levende Tilstand og ere derfor maalte forholdsvis længere
end de fra Mariager, hvilke jeg selv har maalt i indtørret Tilstand. Om man
nu ogsaa vil regne Fiskens Indskrumpning til en god Tomme, saa ere dog
Limfjordsfiskene alligevel nok saa store, som de fra Mariager; dette maa selv-
følgelig hidrøre fra Naturforholdenes Forskelligheder; thi Fiskene ere alle tagne
i Vesterhavet, saavidt vides paa omtrent de samme Steder.

Det vil endvidere ses, at medens af de i Thisted Bredning udsatte Fisk
ingen er indfanget uden i selve Limfjorden og næsten alle i Thisteds umiddel-
bare Nærhed, ere 3 udvandrede fra Mariagerfjord til Kattegat; af den ene af
disse har jeg dog ikke set Mærket selv”). Ingen af de ogsaa i tidligere Aar i
Limfjorden udsatte Fisk ere genfangede med Mærker paa udenfor Fjorden.
Dette kan dog ikke betragtes som Bevis paa, at de ikke vandre ud af denne
Fjord, men maaske snarere paa, at Mærkerne kun blive siddende i nogle
Maaneder, før de falde, rives eller vokse ud af Fisken; Fisk med År efter
Mærket har jeg flere Gange set. Paa den anden Side sidde de Mærker,
som tilsendtes mig fra Mariager 1 Marts 1895, altsaa efter omtrent et Aars
Forløb, ligesaa fast, som da de bleve udsatte. Mærkværdig er det, at jeg
siden August 1894 modtog saa faa mærkede Fisk, og at jeg iaar aldeles ingen
modtog af de i 1893 udsatte; — skulde det være muligt, at omtrent alle
de mærkede Fisk blive opfiskede i Sommerens Løb, uden at Fiskerne enten
se eller aflevere de påaasiddende Mærker? — Forhaabentlig ville videre Under-
søgelser kunne oplyse dette.

+) En fjerde er senere kommen til: Nr. 830; den modtoges dde Maj 1895, Den maalte

11" og var fanget udenfor Frederikshavns Havn,

VI. Fortsatte Undersøgelser over Rødspætteyngelens
Forekomst i Østersøen i 1894 og 95.

Af Th. Mortensen, Cand. mag.

(Undersøgelserne ere udførte paa Foranledning af og under Ledelse af Forstanderen for
Biologisk Station, for at supplere de fra denne i de sidste Aar gjorte Undersøgelser over
Flynderfiskenes Biologi.)

Det var ved de fra Biologisk Station anstillede Undersøgelser konstateret,
ut der i 1893 næsten ingen Rødspætteunger af Aarets Yngel (0-Gruppen) fandtez=
ved de danske Østersøkyster. Kun 3 vare fiskede ved Snogebæk paa Born-
holm, den 8de September, henholdsvis 2, 2!/, og 27/," lange, og 1 ved Hesnæs
paa Falster; den øde August, der maalte 2”. Paa Grund af denne næsten abso-
lute Mangel paa Rødspætteyngel i Østersøen mente Dr. Petersen at maatte
antage, at de mange større Rødspætter, der findes i Østersøen, ere indvandrede
fra Kattegat. Hans Anskuelser, der findes udtalte paa forskellige Steder i IV.
beretning fra den danske biologiske Station, ere i Korthed følgende:

Rødspættens Æg have ved c. 109 €. en Vægtfylde af omtrent 1,4,;2—1;,94;
og fordre saaledes for at kunne flyde eller svæve i Vandet, at dette maa have
en Vægtfylde, der ikke er ringere, altsaa en Saltholdighed af c. 1,,, 7/4.
Da en såa stor Saltholdighed kun undtagelsesvis findes i Østersøen, maa
Rødspætteæggene altsaa synke til Bunds der, og som Følge deraf udvikles
der ingen Unger af dem. Østersøens talrige Rødspættebestand »maa derfor
fødes andet Steds og senere indvandre til Østersøen« (Op. cit. p. 11). Lig-
nende Forhold gælde Pighvarren, hvis Æg ere endnu tungere end Rød-
spættens; de kræve i Følge Dr. Petersens Maalinger noget over 2 9%/, Salt-
holdighed for at kunne fivde. — Det er særlig den østlige Del af Østersøen, dette
gælder. I den vestlige Del er Vandet noget saltere, og Æggene synes der
undtagelsesvis at kunne komme til Udvikling.

Paa Grundlag af dette ene Aars Erfaringer kunde disse mærkelige For-
hold naturligvis ikke fremstilles som videnskabelig beviste, kun som højst

DÅ

sandsynlige. For at faa Sagen undersøgt paany og yderligere suppleret,
bleve de Undersøgelser foretagne, som her skulle refereres. Hovedformaalet
var at faa konstateret, om der heller ikke i disse Aar fandtes smaa Rød-
spætteunger ved Bornholm og de øvrige danske Østersøkyster. Af Vigtighed
var det ogsaa at faa undersøgt, om der fandtes Rødspætteæg i den østlige
Del af Østersøen. Af Betydning for Afgørelsen af Spørgsmaalet, om Østersø-Rød-
spætterne ere indvandrede eller ej, vilde det være at faa konstateret, om der kan paa-
vises Karakterer, hvori Østersø-Rødspætterne afvige fra Kattegat-Rødspætterne.
Ved de Tællinger af Straaleantallet hos forskellige PFlynderarter, som udførtes
for om muligt derved at paavise bestemte Kendemærker for Ungerne af disse
(se IV. Beretn. fra Biol. Stat. p. 128 f.), viste det sig, at der var nogen For-
skel i Straaleantallet efter de forskellige Lokaliteter. At undersøge dette For-
hold nærmere hos Rødspætten (og såa vidt muligt de andre Flynderarter) var

ogsaa en af Opgaverne.

Før Fremstillingen af Spørgsmaalet, om Rødspætten (og Pighvarren) kan
udvikles i Østersøen celler ej, bliver det nødvendigt at give en kort Fremstilling
af Østersøens Hydrografi paa Grundlag af Ekmans og Petterssons Under-
søgelser”). Ved den store Mængde Vand, der gennem Floderne strømmer ud
i Østersøen, fremkommer der en stadig udadgaacnde Strøm fra Østersøen ud
gennem Sundet og Bælterne. Dette svagt saltholdige” Østersøvand danner
Overstrømmen i Kattegat, den »baltiske Strøm«. Som Reaktionsstrøm danner
det mere saltholdige Kattegatsvand en Understrøm, der gaar gennem Store
Bælt, mellem Lolland og Femern, mellem Møen og Rigen, hen nord om
Bornholm og videre ind i Østersøen, Der findes i Østersøen 5 store, mere
eller mindre vel adskilte Dybdebassiner: Bornholmsdybet (25—50 Fy.), Danziger-
dybet, »Østerdybet« (Øst for Gotland), »Nørredybet« (mellem Nordspidsen af Got-
land og den finske Bugt) og Gotlandsrenden (alle 4 med Dybder paa over 50 Fy.).
Helt adskilte fra disse er Aalandsdybet (50—135 Fyv.), den botniske Bugts to
Dybdebassiner (50—135 Fy.) og den botniske Vigs Dyb (25—65 Fv.). Naar nu
Understrømmen naar hen. til det første Dyb, ved Bornholms Østkyst, synker
dette salte, tunge Vand ned deri og fylder det; kommer der mere af det salte
Vand, end der behøves for at fylde dette Bassin, strømmer det videre til de
næste Dybdehassimer. Paa den Maade blive de større Dybder i Østersøen
fyldte med temmelig saltholdigt Vand. Paa den svenske hydrografiske Expedi-
tion 1877 fandtes der i Bornholmsdybet Vand af 1,,—1,, ”, Saltholdighed, i
de øvrige Bassiner var der kun 0,,—1,, 7/9. I Aalandsdybet og i de botniske
Dybdebassiner er Saltholdigheden aldrig større end 0,,—0,7 0. Ved de i Far-
vandene mellem Møen og Riigen foretagne Maalinger har det vist sig, at den

”)y Ekman och Pettersson: Den svenska hydrografiska expeditionen år 1877. Kgl.

Svenska Vetenskaps Akad.s Handl. Ny Fåljd. Bd. 25, 1892,

Y

salte Understrøm ikke er konstant; til Tider strømmer der intet salt Vand ind
i Østersøen. Enkelte Gange under exceptionelle Forhold kan der ogsaa trænge
salt Vand ind i Østersøen gennem Øresund. Det salte Vand, der er sunket
ned påa Bunden af de store Dybdebassiner, bliver staaende der uforandret
94

foretagne Undersøgelser paa de samme Steder, som undersøgtes i 1877, viste

og blander sig kun meget lidt med de øvre Vandlag. Ved de i 1893

det sig, at Saltmængden endnu vår omtrent den samme, medens derimod Ilt-
mængden var aftagen betydeligt (paa Grund af det organiske Liv).

Som ovenfor omtalt have Rødspætteæggene en Vægtfylde af 1,6;9—1,045
(ved 109 C.), hvilket svarer til sen Saltholdighed af 1,,4,—1,8; 9/96... De kunne

altsaa ikke svæve i de øvre Vandlag i Østersøen), hvis Vægtfylde kun er

1,6066—1,00:: Den Vægtfylde, der kræves, findes derimod i det salte Bundvand;
i Bornholmsdybet fandt den svenske Expedition i 1877 1,644 '/, ved en
Temperatur af 2,9, hvilket svarer til en Vægtfylde af 1,444... Udenfor Born-
holmsdybet fandtes ikke større Saltholdighed end 1,%14 7% ved en Temperatur
af 3," (i Østerdybet), hvilket svarer til en Vægtfylde af omtrent 1,94. Øst
for Bornholmsdybet kan man altsaa ikke vente at finde Rødspætteæg, der maa
de synke til Bunds. Men i Bornholmsdvybet kunne de svæve, der maatte man
kunne vente at finde Rødspætteæg i det salte Bundvand. Det lykkedes ogsaa
at finde Fiskeæg deri. Den 7de og 9de Maj 1894 fiskedes der i Dybet ved
Christiansø og udfor Gudhjem, og begge Steder viste der sig at være. Fiskeæg i
det saltere Bundvand, men ingen i de øvre Lag; der fandtes i det hele taget
ikke Fiskeæg i Overfladevandet i Østersøen paa denne Tid. Den 10de Maj viste
sig samme Forhold 14 Km. N.t. V. for Arkonas Fyr paa en Dybde af 25
Favne. Bundvandet havde her en Vægtfylde af 1,645.

Det er nu Spørgsmaalet, hvad det var for Slags Æg. Nogle af Æggene
vare smaa og indeholdt en Oliedraabe; det kan kun være Motellaæg, den
stærke Pigmentering af Fostret viser det. De andre uden Oliedraaber kunne
være Rødspætteæg eller Torskeæg. Skrubbe- og Isingæg kunde man ganske
vist ogsaa tænke paa; men senere hen, i Juli Maaned, fandtes der mange Æg
af 3 forskellige Slags ved Overfladen i Østersøen, og efter de i Juli Maa-
ned 1894 i Østersøen foretagne Undersøgelser synes det at være Skrubbe-,
Ising- og Brislingeæg.. Hensen angiver ganske vist Isingæggenes Vægt-
fylde til 1:69:
dem (hvor stor angives ikke), og formoder da, at de Æg, han tidligere har |

), men seneref) har han selv fundet en ringere Vægtfylde for

maalt, maaske ikke have været fuldt modne. — Naar Skrubbeæggene senere

”) O. Pettersson: Redogårelse får de svenska hydrografiska undersåkningarne 1893—
94. Bihang till Sv. Vetensk. Åkad. Handl. Bd. 19. Afd. II.

+) Ved zØstersøen« menes stadig den østlige Østersø, begrænset af Linierne Kjøben-
havn—Malmø og Gjedser—Darsserort.

"+%) Vorkommen und Menge der Fier einige Ostseefische. IV. Bericht d. Comm. z.
wiss. Unters. d. deutschen Meere in Kiel. 1877—81, p. 300.

+) Uber die Bestimmung des Planktons. V. Bericht d. Comm. p. 40.

n6

kunne findes ved Overfladen, kan der ikke godt være Tale om dem, «då disse
Æg kun fandtes i det salte Bundvand. Isingæggene ere saa smaa, at man ikke
kan forvexle dem med vore andre Flynderarters Æg. Der bliver altsaa kun
Rødspætte og Torsk tilbage at tænke paa. Aarstiden taler ikke meget for, at
det er Rødspætteæg, da Rødspættens Legetid som bekendt falder i December—
Marts, men der kunne jo være Efternølere; i 1881 fiskede Hensen Rød-
spætteæg i Tiden fra 23. April til 11. Maj”) — der kan altsaa findes Rød-
spætteæg paa denne Tid. Størrelsen af de Æg, der fiskedes, var 1,,5—1,41 "Mm;

lødspætteæg ere i Almindelighed noget større, c. 2mm, de fleste af disse

Æg ere da sikkert Torskeæg — maaske alle), Om Torskeæggenes Vægt-

1

fylde siger Hensen, at ved 1,645 spec. Vægt ved 7,,? C. flød Halvdelen oven-

Det forholder sig
i

paa, men i det frie flød de ved en ringere Vægtfylde"
då rimeligvis ogsaa med Torsken saaledes, at dens Æg kun kunne udvikles
det tunge Vand i Dybderne i Østersøen.

Det maa altsaa siges, at Rødspætteæg ikke med Sikkerhed ere
konstaterede i den østlige Østersø.

I Begyndelsen af Juli 1894 fiskedes der igen i Østersøen omkring Born-
holm. Som omtalt fandtes der paa denne Tid mange Fiskeæg i Overfladevandet,
sandsynligvis Skrubbe-, Ising- og Brislingeæg. I Fald Pighvarreæg kunde svæve
i Østersøvandet, skulde man vente at finde dem nu. Som allerede nævnt,
fordrer de en større Saltholdighed, 2/,, for at kunne flyde, saa det var ikke
påa Forhaand sandsynligt, at de skulde kunne findes der. Pighvarreæggene
ere karakteriserede ved en Oliedraabe og vilde altsaa være lette at kende
sikkert, hvis ikke en anden i Østersøen forekommende Fisk, hvis Æg ligeledes
ere forsynede med en Oliedraabe og cre af omtrent samme Størrelse, netop
ynglede paa samme Tid. Det er den 4-traadede Havkvabbe, Motella cimbria.
Ved Mikroskopets Hjælp kan man dog temmelig sikkert skelne mellem de to
Slags Æg, idet Motellaæggene ere noget mørkere; navnlig er Fostret 1 Motella-
ægget langt stærkere pigmenteret end Fostret i Pighvarreægget. — Der viste
sig nu at være temmelig mange Æg med Oliedraaber i det salte
sundvand. De vare i alle mulige Udviklingsstadier fra første Begyndelse,
indtil Ungerne lige skulde til at forlade Æghinden. (Den Tanke, om muligvis
den ringere Iltmængde i Bundvandet skulde hindre Udviklingen, er dermed
udelukket.) De i Spiritus opbevarede Æg vare ikke alle til at bestemme sikkert,
men i alt Fald vare de fleste Motellaæg. Ved de i 1895 i Juli anstillede
Undersøgelser, der gave samme Resultat med Hensyn til Æggenes Fordeling i
Vandet, viste det sig, at næsten alle de med Oliedraabe forsynede Æg

+) Vorkommen u. Menge d. Eier etc. p. 300.

=%) Det maa bemærkes, at vistnok ikke alle Æggene ere blevne maalte; største Delen
bleve — om jeg husker ret — udtagne af Glassene og foreløbig undersøgte kort
Tid efter, at de vare fangede, og ere da ved en Misforstaaelse ikke blevne op-
bevarede igjen.

sx%) Vorkommen u. Menge d. Eier etc. p. 305. Hensen bruger stadig Udtrykket

>Shwimmen»> om Æggene; jeg har oversat det ved »flyde« eller »svæve«, hvilket

jo er Meningen dermed.

vare Motellaæg, kun ganske enkelte syntes at være Pighvarreæg?
Resultatet bliver altsaa, at Pighvarreæg ikke, eller i alt Fald kun i
meget ringe Antal, ere fundne i den østlige Østersø.

Paa denne Aarstid (Juli) skulde man vente at kunne finde Rødspætte-
ungerne ved Bornholm, i Fald der vare saadanne. Jeg fiskede ivrig derefter,
men uden Held. Dog blev der den Gang ikke fisket i Nærheden af Dueodde,
hvor de bedste Steder for Flyndervngelen findes. Det maatte saa opsættes
til hen i Slutningen af August; paa den Tid maatte man ogsaa vente
at kunne finde Pighvarreunger der. Da jeg ikke selv var om Bord paa den
Tid, paatog Kaptain Trolle og Lieutenant Jessen sig med stor Beredvillighed
at søge efter dem, og deres Søgen kronedes med Held. Den 30te og 3lte Au-
gust fiskedes ved Dueodde og i Bugten Nord for Salthammerrev 26 Rød-
spætter, 24 Pighvarrer og 31 Skrubber af Aarets Yngel og enkelte fra
forrige Aar. I 1895 fangede jeg i Juli Maaned ved Bornholm, trods ivrig
Eftersøgen ialt kun 2 Rødspætter, 1 af Aarets Yngel 1” lang, og 1 fra
. forrige Aar, 21/,” lang. Af Pighvarrer fandtes ingen, derimod var der en
Mængde Skrubber af Aarets Yngel. Der fiskedes meget netop paa de Steder,
hvor Rødspættevngel fandtes i 1894. Jeg skal her give en Oversigt over
Resultatet af Fiskeriet efter 0- og 1-Gruppen af Flyndere ved de danske Østersø-
kyster i 1894 og 95.

1894… 2. Juli. Sandvigbugten. 6 Rødspætter, 21/,, 21/,, VRED DA Van 3

— 5. — … Møllebugt ved Rønne. 1 Pighvar 2!/,”.

— 6. — KFaxebugt ved Sjælland. 1 Rødspætte 2”.

— 30.—31. August. Dueodde og Bugten Nord for Salthammerrev (Lieute-
nant Jessen). 27 Rødspætter, 24 Pighvarrer og 36 Skrubber.

Nedenstaaende Tabeller viser Størrelserne:

Rødspætter. Pighvarrer. Skrubber.
du: BM Sk
o g 00
o 00
. 00 o
2 0 2 0000000000 ER
000000000000 000 000
000000000 00 0000
0000 o 00000000000000
aN2g 1 00 1 00000000
000 00

1895. 22. Juli. Bugten Nord for Salthammerrev. 1 Rødspætte 2!/,”, 105
SE SIE EN NET AT RE STEG] Ain HET OF: Ca (ERR Hr SYV: SI Ass
lor hr ANE

— 238. — Sandvigbugten. 1 Rødspætte 1”, 115 Skrubber (2 paa 3/8”,
Sapa SED par pad).

”) Æggene bleve konserverede i Eddikesyre, hvori de holdt sig næsten fuldstændig

klare.
8

58

1895. 26. Juli. Neden for Allinge. " 12 Skrubber (7 paa "/,7, 5 paa 2/7).

25 i

— 26. — KSnogebæk. 84 Skrubber (1 paa ”/,”, 44 paa %/,”, 34 paa 1”,
Dup

— 29..— Faxebugt ved Sjælland. 3 Rødspætter, 27/,, 21/,, 21/7 DA

Skrubber (1 paa] pande 7 pan SOREN ae

i ;
bp lp anes] Ma SS):

— 29. — … Søhundehavn ved Møen. 3 Skrubber paa 1”.

— 30. — … Præstø Fed. 4 Rødspætter, 2!/,, 21/,, 21/,, 2/,”, 30 Skrub-
LYDER ERE re RE Ea or Cr RE TEEN Ed I Aa beror ILSE is raynen
SEEDEDE ERP DN LSE AE of> ET SED

At udtale noget sikkert om, hvorledes det forholder sig med denne Sag, om
Østersøens Rødspætter (og Pighvarrer) i Almindelighed indvandre eller ej, er endnu
ikke muligt; det foreliggende Materiale er ikke tilstrækkeligt dertil. Der blev i
1895 kun fanget 3 Rødspætter af 0-Gruppen ved Bornholm og 1 ved Palster mod
Hundreder i Kattegat. I 1894 fangedes 26 Rødspætter af 0-Gruppen, 7 af 1-Grup-.
pen (samt 24 Pighvarrer af O-Gruppen, 1 af 1-Gruppen) ved Bornholm samt 1 Rød-
spætte af 1-Gruppen (?) ved Faxe. I 1895 fangedes kun 1 Rødspætte af 0-Grup-
pen og 1 af 1-Gruppen ved Bornholm samt 7 af 1-Gruppen ved Faxe og Præstø.
Æg af Rødspætter og Pighvarrer ere ikke med Sikkerhed konstaterede i den
østlige Østersø. De foreliggende Kendsgerninger tyde maaske paa, at der kun
i visse Aar udvikles Rødspætter af nogen Betydning i Østersøen, saa
at Østersøens Rødspættehestand sandsynligvis for største Delen re-
kruteres ved Indvandring fra Kattegat. Til en sikker Afgørelse af dette
interessante Spørgsmaal ere fortsatte Undersøgelser nødvendige; før de ganske
spæde Unger under !/,—1” (og helst ogsaa Æggene) ere fundne der, kan man
overhovedet ikke vide med Sikkerhed, om Rødspætten i det hele taget for-
planter sig i disse Farvande.

Mine Iagttagelser over Fiskeæggenes Fordeling i Østersøen stemme godt
med, hvad Hensen har fundet. I »Das Plankton der åstlichen Ostsee und
des Stettiner Hafs«F) siger han: »Ejendommelig var Fangsten af Fiskeæg.
Jeg fangede saadanne næsten kun over Dybet mellem Memel og Gotland. Fra
en Dybde af 140 m fik jeg 81, fra en Dybde længere østlig paa 150'm 30, der-
imod ved 2 Træk fra kun 30m Dybde 1 og 2 Æg. Æggene havde et Gennem-
snit af 1,5 mm; til hvilken Fiskeart de hørte, har jeg ikke kunnet udgrunde;
de vare klare og indeholdt ingen Fedtdraaber. Efter dette Fund, og fordi jeg
ellers intet Steds (— ved Bursterort og Scholpin fik Hensen et Æg hvert Sted
fra SOm —) har fundet Æg, synes det mig utvivlsomt, at de væsentlig forekom
i den dybe, tunge Understrøm. Dermed løses et Problem, som frembød sig
for mig ved Undersøgelser over Forekomsten af svævende Æg. Jeg fandt, at
Æggene af Pighvarre og Torsk i den vestli

g ge Østersø endnu kun ved nogen-

”) Sechster Bericht d. Comm. z. wiss. Unters. d. deutsch. Meere in Kiel. Jabrg.
1887—91, p. 108.

59

lunde vægtfyldigt Vand formaar at svæve, at ogsaa Spermatozoerne kun i
dette Vand vedblive at være bevægelige, og maatte forelægge mig det Spørgs-
maal, hvorledes disse Fisk endnu kunde forplante sig i den østlige Østersø.
Resultatet bliver nu, at naar disse Fisk begive sig hen til den kolde Under-
strøm for at lege, ville de finde den Saltholdighed, der fordres til Legningen.«

Det er altsaa Vægtfylden, der spiller saa stor en Rolle, ikke den større
eller mindre Saltholdighed i og for sig, da det jo viser sig, at Fiskene selv
godt kunne leve i Vand, der ikke er salt (vægtfyldigt) nok til at bære deres
Æg — ja, Skrubben gaar jo som bekendt helt op i Ferskvand. Det har der-
for stor Interesse åt vide, hvor stor Vægtfylde de forskellige pelagiske Fiskeæg
have. Hensen, Cunningham og Petersen”) have ydet vigtige Bidrag til dette
Spørgsmaals Løsning. Om det nu er saaledes, at Rødspættens Æg overalt
have gennemsnitlig samme Vægtfylde, kan man paa Forhaand ikke sige noget be-
stemt om; det er jo muligt, at Æggene at Østersø-Rødspætterne ere lettere end
af Kattegat-Rødspætterne. Der har, som det i det følgende skal ses, vist sig at
være en temmelig tydelig Forskel i Antallet af Finnestraaler hos Østersø- og
Kattegat-Rødspætterne, saa det andet kan jo ogsaa tænkes at finde Sted. Det
fortjener i alt Fald at undersøges. I Fald der virkelig er Pighvarreæg blandt
de med Oliedraaber forsynede Æg fra Bornholmsdybet, maa en betydelig For-
ringelse af Vægtfylden have fundet Sted for disses Vedkommende, da Pig-
hvarreæg jo ellers kræve 27, Saltholdighed for at kunne flyde. Hensen har
ogsaa tænkt sig denne Mulighed; i »Uber das Vorkommen und die Menge der
Zier einiger Ostseefische«, p. 305, siger han: »Derimod vil hinsides Riigen i
den østlige Del af Østersøen vel aldrig den Saltholdighed, der er nødvendig for
at Æggene kunne svæve, være til Stede, hvis ikke Æggene der antage en
anden Vægtfylde.

Endnu et Spørgsmaal maa berøres angaaende disse Fiskeæg. Dø de,
naar de synke til Bunds? Hensen synes at mene, at de ogsaa kunne ud-
vikles, naar de ligge paa Bunden, — hvis de då ikke blive fortærede. Han
har ved en særlig dertil indrettet Skrabe fisket levende Æg fra Bunden,
saaledes paa 13—20m Dybde udenfor Mundingen af Kielerbugt, og han siger
senere, at det derved er blevet »vist, at Æggene kunne udvikle sig saavel
sek)

svævende som liggende paa Bunden Jeg kan dog ikke indse, at dette er
bevist, fordi Hensen har fundet levende Æg ved Bunden. Det kan jo være
Æg, der nylig ere sunkne ned, og som maaske snart vilde dø, — eller de
have sandsynligvis slet ikke ligget paa Bunden, men svævet i Vandet lige over
Bunden. Det er meget usandsynligt, at Æg, der normalt flyde frit i Vandet,
ogsaa skulde kunne udvikles, naar de ligge paa Bunden. Direkte Forsøg ere, saa-
vidt jeg ved, hidtil ikke anstillede derover; men de vilde være af stor Interesse. —

Det er en almindelig Mening blandt Fiskerne, at Rødspætten i Østersøen
er en anden »Art« end den i Kattegat — vel nærmest fordi Østersø-Rødspætterne

") IV. Beretn. fra den Biol. Station, p. 28.
”») Vorkommen und Menge der Eier etc., p. 305.

60

ere mindre, magrere og smage anderledes end Kattegat-Rødspætterne. For om muligt
at finde ud af, om der virkelig skulde være nogen egentlig, mere bestemt For-
skel mellem de to Rødspætte-»Arter«, har jeg undersøgt en Mængde i Løbet
af Sommeren 1894. Da jeg ikke har haft begge Slags samtidig, saa jeg di-
rekte har kunnet sammenligne dem, har jeg ikke kunnet finde andet nemt
brugeligt Forhold at holde mig til end Finnestraalernes Antal. Men da dette
jo plejer at være temmelig konstant for hver Art, vilde det netop ogsaa være
af særlig Interesse, om man kunde paavise nogen Forskel heri mellem Rød-
spætterne i Østersøen og i Kattegat, — og dette har netop vist sig at være
Tilfældet. Jeg skal her anføre disse Tællinger i en let overskuelig Form.

Af 137 Rødspætter fra den østlige Østersø fandtes:

75 Straaler i Rygfinnen hos 2 Exempl. | 58 Straaler i Gatfinnen hos 1 Exempl.

(se = = 2 = 55 — == 1 =
(DER = 1 = DA — == 11 =
eEE— — 4 = 53 — — 13 —
71 —= == 8 == bv — 23 —
10£— = 18 — 51 = — 21 =
GO) — 20 = 50. — — 25 ==
68 = 21 — 49 — = 22 —
SEE == 17 — 48 — == 9 —
Go = 18 == 47 == 6 —
oor= = 13 —= 46 —= 2 ==
Ga — 6 — 45 — —= al ==
ba = 6) = 44 — = 2 —
(Re — 1 —

blE— == 1 —

Af 255 Rødspætter fra det nordlige Kattegat (regnet fra Linien Fornæs—
Anholt) fandtes:

80 Straaler i Rygfinnen hos 1 Exempl. | 61 Straaler i Gatfinnen hos 1 Exempl.
18 5 — 4 = 603 — 1 —
RR — 4 = 59 — — 1 —
70 — — 8 = 58 — — 7 —
Tb — — 14 — 57 — == 7 —
74 — — 27 — 56 — — 19 —
73. — — 20 — bd — = 32 =
(PÆRER — 32 — br = 53 —
71 — — 36 — 583 . — — 46 —
((URE— — 30 — 52 — >= 35 ==
69 — — 27 — bl — — 24 —
68 — — 21 — | Non == — 13 —
Buns= — 9 — kon == — 6 —
66 … — — 6 — 1.48. — — 5 —
65 — — 6 — 470 — — 3 —
64 — — 6 — | 46 — — 1 —
63 — 3 — 44 - — 1 =

DY — = 1 == |

61

Det fremgaar heraf bestemt, at der i Almindelighed findes færreStraaler
hos Østersø-Rødspætten end hos Kattegat-Rødspætten. Hos Østersø-
Rødspætten er det hyppigste Straaletal i Rygfinnen 70—65, med Maximum
ved 68, det hyppigste i Gatfinnen 52—49, med Maximum ved 50. Hos
Kattegat-Rødspætterne er det hyppigste Straaletal i Rygfinnen 74—68, med
Maximum ved 71, det hyppigste i Gatfinnen 56—51, med Maximum ved 54).

Mine Undersøgelser over Finnestraalernes Antal strakte sig ogsaa til de
andre Flynderarter, men af ingen af disse har jeg haft tilstrækkeligt Materiale
til at kunne konstatere, om her findes en lignende Forskel mellem Østersø- og
Kattegatsformerne som hos Rødspætten. De Tal, jeg fandt, vare følgende:

Af 179 Skrubber fra den østlige Østersø fandtes:

65 Straaler i Rygfinnen hos 1 Exempl. | 46 Straaler i Gatfinnen hos 1 Exempl.
64 — — 2 — he SAREE — il —
63 — == 10— | MM — — 8 —
62 — — 6 — (45 — = 14 ==
(5) HØRSREE — 17 — Ao — 20 ==
60 — — 22 = ÆRE — — 36 —
59 — — 29 — |40 — — 34 —
58 — — SR EEN VG CEUS == 42 —
57 — — 29 — 38 — — 18 ==
56 — — 17 — SURE == 3 ==
bom — == 15 — sr — 2 =
54 — — 8 —

DE — 7 — |

d2 — — 1 —

&d1 — — 1 —

Af 36 Skrubber fra det sydlige Kattegat og den vestlige Østersø fandtes:

63 Straaler i Rygfinnen hos 1 Exempl. 43 Straaler i Gatfinnen hos 1 Exempl.
62 — — 2 — | 42 — — 1 —
61 — — 1 — | 41 — — 33 —
60 - — 2 — 40 — — 16 —
og — — 3 — Bo == — 7 —
ore = == ZED no u= 38 — == DE
57 — — 8 — 37 — — il —
56 — — 8 — 36 — — 1 —
55 — — 2 — | 34 — — il —
BA — = es |

52 — — 2 — |

æy

I Zoologischer Anzéiger 1895 Nr. 468 har G. Duncker givet en lille foreløbig
Meddelelse om >»Variation und Verwandschaft von Pleuronectes flesus L. und Pl.
platessa L.< Før hans udtørlige Afhandling foreligger, skal jeg ikke komme nær-
mere ind derpaa; men i alt Fald synes Duncker at være den første, der har gjort
opmærksom paa dette Forhold med Finnestraalerne.

Af 24 Skrubber fra det nordlige Kattegat fandtes:

61 Straaler i Rygfinnen hos 1 Exempl. | 41 Straaler i Gatfinnen hos 6 Exempl.
59 — — 2 — | 40 — — 6 —
SEE — = 5 — SPYNUEEL — 4 —
57 — — 3 — 38 — — 4 —
5% — — 6 — 37 — — 2 —
55 — — 3 - 36 — 2 —
54 — = 2 = |

53 — — 2 —

Af 36 Isinger fra den østlige Østersø fandtes:

75 Straaler i Rygfinnen hos 1 Exempl. | 58 Straaler i Gatfinnen hos 1 Exempl.
or k= — 5 — FAD, ASE — 1 —
72. — — 3 — | res — 2 ==
If BERREE = GES ES 50 es =E GER
Ds = REE = IDE
69. = — 4 — | 58 — — 10 —
68: — - ON RDS == 4 0
67 — — 2 — | 51 — — 1 —
65 — — 1 — | 50 — -— 1 —
kan == — 1 =

Af 7 Isinger fra det sydlige Kattegat og den vestlige Østersø fandtes:

72 Straaler i Rygfinnen hos 3 Exempl. | 56 Straaler i Gatfinnen hos 2 Exempl.
70 — — 1 — lose — 2 —
69 — — 1 — 52 — — 2 —
68 — — 1 — 51 — — 1 —
67 — — LERET al]

Af 106 Isinger fra det nordlige Kattegat fandtes:

7d Straaler i Rygfinnen hos 3 Exempl. | 59 Straaler i Gatfinnen hos 3 Exempl.
74 1

— — 5 — 285 — — =
vo = SN gr Sr = Gee
re LE = RER ARR Era = GARE
rå renee = sr Br == = (1954 ge
Tone = Ore TZ Wi == lere=
(fr cz ER 16 Er 53 = Toe
68 RE ze ER GE ze gere
vene —= EM ES ub) Un = ae
Brm= en Ma
65. — — 6 sr

Af 77 Pighvarrer fra den østlige Østersø fandtes:

67 Straaler i Rygfinnen hos 3 Exempl. | 51 Straaler i Gatfinnen hoe 1 Exempl.
66 — — 4 — | 48 — — 3 —
65 z 3 — 47 — — 16 —
64 — — 7 -—- | 46 — — 19.… - —

63

63 Straaler i Rygfinnen hos 18 Exempl. 45 Straaler i Gatfinnen hos 17 Exempl.
62 — - 12 — | 44 - 11 —

61 — — 14 — 43 — — 6 —
(ole rees - 7 — | 42 — — 2 —
59 — - 5 - 41 — — 1 —
58 — — 2 -— | 40 — — 1

oe =, ENE

55 — — 1 —

Af 8 Pighvarrer fra det nordlige Kattegat fandtes:

65 Straaler i Rygfinnen hos 3 Exempl. | 48 Straaler i Gatfinnen hos 1 Exempl.
638 — — 2 — |. 47 — — 1 —
baner = kem e NIGEE = BE a=
60 z — 2 — | 45 = — l ==
er — — 1 —
42 — — 1 —
Af 2 Slethvarrer fra det sydlige Kattegat fandtes:
79 Straaler i Rygfinnen hos 1 Exempl. 57 Straaler i Gatfinnen hos 1 Exempl.

7D — — 1 — 54 — — l —

»
Af 11 Slethvarrer fra det nordlige Kattegat fandtes:

80 Straaler i Rygfinnen hos 2 Exempl. 60 Straaler i Gatfinnen hos 1 Exempl.
19 z — 5; — 58 — — il —
78 — == I — K=57. — — 1 —
77 — — 1 — 55 — — 6 —
76 — — i — 54 — — 1 —
7Tå — — 1 -— 53 — - 1 ==
73 — = 1 et

72 — — 1 ==

Samtidig med at der fiskedes efter pelagiske Fiskeæg, benyttedes Lejlig-
heden til at studere Planktonorganismernes Fordeling i Vandet Undersøgelserne
herover ville blive offentliggjorte andet Steds; her kan kun gives et kort
Resumé af Resultaterne. Det har vist sig, at Vægtfylden spiller en stor
Rolle for adskillige Dyreformers Optræden i forskellige Vandlag. En Del Dyr
ere såa tunge, at de kun kunne svæve i Vand, der har en Vægtfylde af
1,97 eller mere — særlig de fligede Ribbegopler, Bølina og en anden Gople,
en Thaumantias-Art").. Andre have en meget ringere Vægtfylde og kunne derfor

”) Direkte Maalinger af disse Dyrs Vægtfylde ere ikke foretagne, men det Faktum, at
disse Dyr fandtes næsten allevegne, hvor Vandet havde en Vægtfylde af 1,,, eller
mere, lige meget i hvilken Dybde, men aldrig i Vand af ringere Vægtfylde, synes
ikke at kunne tydes paa anden Maade.

64

findes i Vand af en langt ringere Vægtfylde (Saltholdighed). Paa Grund af
de ejendommelige hydrografiske Forhold i vore Farvande kommer Vægttylden
til at spille en meget stor Rolle for disse Dyrs Udbredning. Et Dyr, der
har en Vægtfylde af 1,929, vil jo kun kunne findes, hvor Vandet mindst
har denne Vægtfylde, det vil derfor sjælden komme længere syd paa end i
Kattegat. I Østersøen kan man ikke vente at finde saadanne Dyr, undtagen
naar der en Gang imellem kommer særlig salt Vand derned. Det er ikke blot
Fiskcæggene, men ogsaa mange andre ØOrganismer, der ligesom Fiskecæggene
svæve frit i Vandet, hvis Udbredning er afhængig af Vægtfylden.

Ogsaa for de Dyr, der have frit svømmende Larver, men selv sidde
fast eller kun langsomt bevæge sig langs Bunden, faar Vægtfvlden Betydning.
Kun hvor der findes Vand, vægtfyldigt nok til at bære Larverne, kan
man vente at træffe de voxne Dyr, selv om disse sidste godt kunne leve i
mindre salt Vand. Dette gælder navnlig Echinodermer, Snegle og Muslinger.
Vor almindelige Søstjærne, AÅsfertas rubens, kan leve i Østersøen; helt inde ved
Jershåft (i Nærheden af Danzig) er der fundet nogle faa Exemplarer”). Men
alligevel findes den i Regelen ikke i den østlige Østersø, og Grunden dertil
er vistnok den, at Larvens Vægtfylde er ca. 1,013

Vand af saa stor Vægt-
fylde forekommer kun sjælden i den østlige Østersø, og Larverne kunne altsaa
heller ikke komme derhen. En enkelt Gang sker det, at der kommer usæd-
vanlig saltholdigt Vand ind i Østersøen; ved en saadan Lejlighed ere uden
Tvivl Larverne til de omtalte Exemplarer fra Jershåft komne derind. Der kan
saaledes næppe være Tvivl om, at Grænserne for denne Søstjærnes Ud-
bredning i vore Farvande bestemmes af dens Larves Vægtfylde; og-
sad påa mange andre Dyrs Udbredning har Vægtfylden uden Tvivl
stor Indflydelse.

Kjøbenhavn i December 1895.

+) K. Brandt: Die auf der (> Holsatia«)-Expedition gesammelten Thiere. 6. Bericht
d. Commiss. zur wiss. Unters. etc., p. 145.
23

Heller ikke for dette Dyrs Vedkommende ere direkte Maalinger af Vægtfylden an-

stillede, men jeg har ikke fundet den i Vand af ringere Vægtfylde, hvoraf man
vel kan slutte, at dens Vægtfylde er omtrent af denne Størrelse.

DH: 4423)
AHH

——

SE —
SR vie
= ==