There are known at the present about twenty thousand species of fishes,
which are distributed throughout the creeks, rivers, lakes, seas and
oceans of the world. A few species of the open sea are cosmopolitan;
the others are more or less restricted in their range. Northern Asia,
Europe and North America have in common a few species of fresh water
fishes. There are many others of close relationship, which indicates a
somewhat common origin of the fish faunas. The same is largely true of
the salt water shore fishes, which live well to the north. The fresh
water fishes of South America, Africa and Australia are all different
from each other, none being even closely related as are those we find
in the countries of the northern hemisphere.
The fishes of our Atlantic coast are different from those of the
Pacific, very few species being common to both coasts. The fishes of
the Ohio river are entirely different from those of the Columbia, not a
single species being common to both streams. The fishes of the Missouri
river are very different from the Ohio, many of the larger species, as
catfishes, buffalo fishes, black basses, and some of the sun fishes are
common to both rivers. The difference between the fishes of these two
rivers is chiefly in the smaller kinds, which do not migrate to any
great extent, and is greater as you go toward their sources, or confine
yourself to their smaller tributaries.
There are many reasons why the fishes of one region are not the same as
those we find in another. Some of these reasons we may learn by making
a careful study of the fishes of each region, and their environment.
In addition we must learn all we can about the past history of the
country, finding which streams were formed first, and how they became
inhabited from the old ancient fish faunas of our earlier geological
periods. If you visit streams in the Alleghanies, the Ozarks and the
Black Hills you will find them much alike. All have clear, cool water,
flowing over sand or gravel. The black bass, speckled trout, channel
cat, and the eastern pickerel will live quite as well in streams of
each locality. If you spend a day at each place collecting fishes all
your catch will not be the same species. In the Alleghany region you
will obtain about forty species, and a like number in the Ozarks. Of
these quite one-fourth, or one-fifth, will be the same species, and
the others closely related. A large portion will consist of sunfishes
and very small, perch-like fishes, which are called darters. These are
spiny-rayed fishes; that is, nearly all of the fins are made partly of
strong, sharp spines, such as you find on the back of sunfishes, black
bass and the like. In the streams of the Black Hills you will not find
more than fifteen species, and not more than one or two, if any, will
be the same as in either of the other two catches. There are none of
the spiny-rayed fishes in the Black Hills, and no trout, though the
streams seem in every way well suited for them. The fishes of the Black
Hills consist of two catfishes, four suckers, eight minnows, and one
member of the cod family. Why are there no spiny-rayed fishes? If you
examine a map you will find that the Black Hills is an isolated region,
about seventy-five by one hundred miles in extent. It is covered with
heavy pine forests and drained by a dozen or more good-sized creeks,
which find, through the north and south forks of the Cheyenne, an
outlet into the Missouri river. Surrounding the Black Hills is a broad
plain one hundred or two hundred miles in width. It has no forests, and
only a scant vegetation. Its streams are alkali and contain much solid
matter in suspension. None of these streams flow over rocky or gravelly
beds. Like all the streams of the great plains they are overloaded
with sediment. All the streams can do with this sediment is to deposit
it in places during falling or low water, and in time of freshets,
pick it up, shift it about and redeposit it farther down the stream.
Such streams are like the Platte, narrow and deep in a few places,
but mostly wide and shallow, with a bottom of quicksand. The streams
of the plains have in them but few species of fishes; especially is
this true of the upper Missouri, and these are such species as we find
in the Black Hills. It is thus evident that the fishes of this region
migrated there, and only such fishes as were able or willing to live
in the muddy, alkaline streams of the great plains could have ever
reached the Black Hills. The minnows and suckers are ever preyed upon
by sunfishes, bass and the like, and to escape them evidently sought
retreat in the alkaline water, which was too much disliked by their
enemies for them to follow. Once there and accustomed to such water
they would migrate farther up stream until they reached the clear, cool
streams of the Black Hills. If we compare the fishes of two rivers
whose mouths are near each other, as the Ohio and the Missouri, those
fishes found near the mouths will be the same species and the two river
faunas will differ most as you go toward their sources. On the other
hand, if you select two rivers whose sources are near each other, as
the James and tributaries of the Ohio, then the fish faunas will differ
most as you go towards their mouths. The same is true of the Missouri
and the Columbia. In such cases it often happens that during high water
some fishes are able to pass from the head waters of one river basin to
the other, just as we see the trout from the Columbia at the present
time colonizing the upper Yellowstone through the Two Ocean Pass. Near
the head waters of many mountain streams there is usually a pass, which
contains a strip of meadow land where the small streams from mountains
unite, forming the sources of two great rivers flowing in opposite
directions. This is the case both at the Two Ocean Pass, the source
of the Missouri and the Columbia, and at the point where the Canadian
Pacific Railroad crosses the divide, forming the source of the Frazier
and Saskatchewan rivers.
Many mountain streams whose sources are at present in no way connected
may have been so at no very remote period. All of our streams which
have their sources within the glaciated area were no doubt connected
as the ice receded. The drainage of Lake Champlain and the lakes in
central New York was southward at the close of the glacial epoch. It
is said that in times of high water one may pass in a skiff from the
head waters of the Mississippi to the Red River of the North. With such
facts before us we can easily understand why the fishes of two rivers
whose sources are near each other should be most nearly alike nearest
the divide. If the two rivers were formed about the same time, as no
doubt were the James and the Ohio, they would naturally have several
species in common. In other words, the two fish faunas will resemble
each other throughout their whole extent. In the case of the Missouri
and the Columbia, the former is much the older stream, and while their
sources have fishes common to both streams, in the lower parts of the
rivers the fish faunas are entirely different. The upper Missouri river
and its tributaries are for the most part inhabited by Rocky Mountain
fishes, practically the same fauna as we find in the Columbia, but few
species characteristic of the Mississippi valley have been able to even
cross the great plains and none have ever passed the Rocky Mountain
divide.
In the study of the geographical distribution of our fresh water
fishes, we are able to make a few generalizations as follows: Two
rivers in the same latitude, and belonging to the same great drainage
basin, and draining similar areas, will have similar fish faunas.
Thus we find a great similarity in the fishes of the Washita and the
Tennessee rivers, a much greater similarity than we do in the fishes
of the Washita and the Cedar rivers. If the stream is a large one,
the fishes near its source will be much unlike those near its mouth.
The fishes of Minnesota differ greatly from those of Louisiana,
though the drainage of these two States is in the Mississippi river
basin. Limestone streams have in them more species of fishes than do
sandstone. All things being equal, the larger of two or more streams
will contain the most species of fishes. There are few, if any, rivers
as rich in species as the Mississippi river and its tributaries. It
drains one slope of each of our two great mountain systems, besides
an immense area of wood-land and prairie, and numerous swamps and
marshes. Its upper course and many of its upper tributaries lie in
the region once covered by glaciers, though now traversed by great
moraines. Its fishes are as diversified as the area it drains. In its
mountain streams we find such fishes as the trout, darters, minnows
and suckers. In the upland streams are darters, shiners, suckers,
sunfishes and small-mouthed black bass. In the channels of the larger
tributaries are found the large suckers, buffalo fishes, gar pike,
channel catfish, drum, pike and pickerel. The lowland streams contain
the dogfish, pirate perch, some sunfishes, the large-mouthed black
bass, some suckers, catfishes and other species. Minnows, darters,
suckers and sunfishes are found in lowland, upland and mountain
streams, though not the same species in each. These fishes belong to
families which are made up of many species, some being strictly upland,
others strictly lowland, each having a limited range. In the same way
we have fresh water fishes and salt water fishes; some fishes, as the
trout and salmon and eel, live in both salt and fresh water. Many
other fishes, as the killifishes, thrive best in brackish water. Each
species of fishes is best fitted for a particular region into which it
has been forced to live, either to escape its enemies or to be able to
get a living easiest. In its migrations it has moved along lines of
least resistance, and has colonized those streams where Mother Nature
has been able to do the most for it. The darters are small, perch-like
fishes, which seldom exceed a length of six inches, the average being
about three. All are active and swift swimmers and well suited for
a life among the rocks and swift water of our smaller streams. All
countries have small, swift, rocky streams, but few have darters. In
their stead we find loaches, gobies, characins, sculpins, and the like.
These fishes have "become dwarfed and concentrated, taking the place in
their respective habitats which the darters occupy in the waters of the
Mississippi valley. By the same process of 'analogous variation' the
cichlids of South America parallel the sunfishes of the United States,
although in structure and in origin the two groups are diverse."
Dr. Jordan tells us that the trout of the Pacific coast came to America
from Asia, and gradually spread eastward and southward until now it is
found in all the streams of the Rocky Mountains, the Sierra Nevada, the
Cascades and the Coast range. It is but a short distance from Kamchatka
to Alaska, and this distance is traveled by trout to this day; once
over, a fish able to spend much of its time in salt water could easily
colonize all our coast streams. Whether or not all of our Pacific trout
are descendants of one species, the cut-throat trout, is more or less
uncertain, though it is quite certain that all have descended from not
more than two or three species. In many places they have been able to
pass from the head waters of one river to that of another, just as they
now pass from the head waters of the Columbia to the Missouri by the
way of Two Ocean Pass. The ancient lakes, Lahontan and Bonneville, no
doubt assisted them in their migrations. Since these have disappeared
each colony has had to remain more or less isolated. In time they
have become somewhat changed, to better adapt themselves to their new
environment. These changes have developed certain peculiar characters,
by means of which we can distinguish one kind of trout from another,
just as the farmer distinguishes his Berkshire from his Poland China.
Spread, as the trout are, over such a large area, in such an immense
variety of streams and lakes, and with a vertical range of over one
thousand feet, we would certainly expect as large a number of species
and varieties of trout to be developed as we find at present in the
streams of our west coast.
Fishes are found in the deepest parts of the ocean. Some of these
are peculiar to the deep waters, none of the shore fishes resembling
them. On the other hand, many deep sea fishes belong to families well
represented in the shallow water. The flounders are found in water at
all depths, and the same is true of the bat fishes, rock fishes and
other shore fishes. It is easy to understand how these fishes have
found their way to the deep water. It was either to escape their
enemies or to extend their range for some reason; as Mr. Garman puts
it, "They have slid down," as it were to the bottom of the ocean.
In general, animals migrating will always move along lines of least
resistance. Some deep-sea fishes have a considerable vertical range. It
is thought that some move into shallower water to deposit their eggs or
place their young in warmer water, and where the peculiar kind of food
they need early in life is the most abundant. To study deep sea fishes
is difficult, and so little has been done that we not only know them
imperfectly but also know very little concerning their life histories.
In February, March and April of 1891 the United States Fish Commission
steamer Albatross explored a portion of the region between the
coasts of Mexico and Central America and the Galapagos Archipelago.
Besides obtaining a large number of shore fishes, about nine hundred
specimens of fishes were secured, ranging from a depth of one hundred
to twenty-two hundred and twenty-three fathoms. This collection was
carefully studied by Professor Garman, of Harvard. He found the
collection to contain one hundred and eighty species, eighty-five
per cent. of which were new to science. The bottoms of the oceans
are far from level, and each deep basin has its own peculiar fauna.
The shallower parts of the sea prevent migration of the deep water
forms and no doubt living as they do in eternal darkness and in a
temperature near the freezing point, there is little to induce them
to much activity. The fact that they are easily captured in nets of
comparatively small size would indicate that they move about slowly.
Dr. Jenkins, who has lately studied the fishes of the Sandwich Islands,
informs me that less than five per cent. are found on our American
coast, while a large per cent. is found all the way to the Red sea.
In other words, the fishes of the Sandwich Islands are East Indian
rather than American. This is no doubt caused from the fact that the
deep water between the islands of the American coast forms a barrier
which has always prevented the two fish faunas from mingling with each
other. Between Africa and the Sandwich Islands this has not been the
case. A recent study of the fishes of the Galapagos Archipelago shows
its fauna to be American, though in what respect its fishes differ from
those of our west coast they resemble all the more the fishes of the
Sandwich Islands. Two fish faunas will usually differ from each other
if separated by an impassable barrier; especially is this true if the
barrier be older than the two faunas.
Any barrier which prevents or hinders fishes in their movements from
one body of water to another will separate two more or less well-marked
fish faunas. These barriers may be mountains, or shallow water, as in
the case of deep sea fishes; deep water, as in case of shore fishes;
muddy or alkaline water, or water of different temperature. Temperature
no doubt has far more influence in governing the movement of fishes
than is generally believed. It plays an important part in guiding
salmon up stream to their spawning beds. It explains why they reach the
head waters of some streams and spawn earlier than in similar streams
not far distant, but of different temperature. If you would know to
what extent fishes of one region differ from those of another, study
well the barriers between the two regions, learn to what extent and
how long they have existed, consider the age geologically of the two
regions, and how fishes may have migrated to one or the other, and in
a general way you will have the key to the situation, which a careful
study of the fishes is quite sure to verify.
Seth E. Meek.
[Illustration: LOUISIANA TANAGER.
(Piranga ludoviciana.)
Life-size.
FROM COL. CHI. ACAD. SCIENCES.
COPYRIGHT 1900, BY
A. W. MUMFORD, CHICAGO.]