OPISTHOMI AND ANACANTHINI
=ORDER Opisthomi.=—The order _Opisthomi_ (ὄπισθη, behind; ὤμος,
shoulder) is characterized by the general traits of the blennies and
other elongate, spiny-rayed fishes, but the shoulder-girdle, as in the
Apodes and the _Heteromi_, is inserted on the vertebral column well
behind the skull.
The single family, _Mastacembelidæ_, is composed of eel-shaped fishes
with a large mouth and projecting lower jaw, inhabiting the waters of
India, Africa, and the East Indies. They are small in size and of no
economic importance. The dorsal is long, with free spines in front and
there are no ventral fins. Were these fins developed, they should in
theory be jugular in position. There is no air-duct in _Mastacembelus_
and it seems to be a true spiny-rayed fish, having no special relation
to either _Notacanthus_ or to the eels. Except for the separation of the
shoulder-girdle from the skull, there seems to be no reason for
separating them far from the Blennioid forms, and the resemblance to
_Notacanthus_ seems wholly fallacious.
[Illustration:
FIG. 484.—_Mastacembelus ellipsifer_ Boulenger. Congo River. (After
Boulenger.)
]
_Mastacembelus armatus_ is a common species of India and China. In
_Rhynchobdella_ the nasal appendage or proboscis, conspicuous in
_Mastacembelus_, is still more developed. _Rhynchobdella aculeata_ is
common in India.
=Order Anacanthini.=—We may separate from the other jugular fishes the
great group of codfishes and their allies, retaining the name
Anacanthini (ἄνακανθος, without spine) suggested by Johannes Müller. In
this group the hypercoracoid is without foramen, the fenestra lying
between this bone and the hypocoracoid below it. The tail is isocercal,
the vertebræ in a right line and progressively smaller backward,
sometimes degenerate or whip-like (leptocercal) at tip. Other characters
are shown in the structure of the skull. There are no spines in any of
the fins; the ventrals are jugular, the scales generally small, and the
coloration dull or brownish. The numerous species live chiefly in the
northern seas, some of them descending to great depths. The resemblance
of these fishes to some of the Blennioid group is very strongly marked,
but these likenesses seem analogical only and not indicative of true
affinity. The codfishes probably represent an early offshoot from the
ancestors of the spiny-rayed fishes, and their line of evolution is
unknown, possibly from Ganoid types. Among recent fishes there is
nothing structurally nearer than the _Nototheniidæ_ and _Brotulidæ_, but
the line of descent must branch off much farther back than either of
these. For the present, therefore, we may regard the codfishes and their
allies (_Anacanthini_) as a distinct order.
[Illustration:
FIG. 485.—Codfish, _Gadus callarias_ L. Eastport, Me.
]
=The Codfishes: Gadidæ.=—The chief family is that of the _Gadidæ_, or
codfishes. These are characterized by a general resemblance to the
common codfish, _Gadus callarias_. This is one of the best known of
fishes, found everywhere on the shores of the North Atlantic, and the
subject of economic fisheries of the greatest importance. Its flesh is
white, flaky, rather tasteless, but takes salt readily, and is
peculiarly well adapted for drying. The average size of the codfish is
about ten pounds, but Captain Nathaniel Atwood of Provincetown records
one with the weight of 160 pounds.
According to Dr. Goode:
"In the western Atlantic the species occurs in the winter in
considerable abundance as far south as the mouth of the Chesapeake Bay,
latitude 37°, and stragglers have been observed about Ocracoke Inlet.
The southern limits of the species may be safely considered to be Cape
Hatteras, in latitude 35° 10´. Along the coast of New England, the
Middle States, and British North America, and upon all the off-shore
banks of this region, cod are found usually in great abundance, during
part of the year at least. They have been observed also in the Gulf of
Bothnia, latitude 70° to 75°, and in the southeastern part of Baffin's
Land to the northward of Cumberland Sound, and it is more than probable
that they occur in the waters of the Arctic Sea to the north of the
American continent, or away around to Bering Strait."
Dr. Gill says:
"The ocean banks of moderate depths are the favorite resorts of the cod,
but it is by no means confined to those localities. The fish, indeed,
occasionally enters into fresh, or at least brackish, water. According
to Canadian authorities, it is found 'well up the estuary of the St.
Lawrence, though how far up is not definitely stated, probably not
beyond the limits of brackish water.' Even as far south as the Delaware
River it has been known to enter the streams. Dr. C. C. Abbott records
that in January, 1876, 'a healthy, strong, active codfish, weighing
nearly four pounds, was taken in a draw-net in the Delaware River near
Trenton, New Jersey; the stomach of the fish showed that it had been in
river-water several days. Many of them had been taken about Philadelphia
between 1856 and 1869.'
"The cod ranks among the most voracious of ordinary fishes, and almost
everything that is eatable, and some that is not, may find its way into
its capacious maw. Years ago, before naturalists had the facilities that
the dredge now affords, cods' stomachs were the favorite resort for rare
shells, and some species had never been obtained otherwise than through
such a medium, while many filled the cabinet that would not otherwise
have been represented. In the words of Mr. Goode, 'codfish swallow
bivalve fish of the largest size, like the great sea-clams, which are a
favorite article of food on certain portions of the coast'; further,
'these shells are nested, the smaller inside of the larger, sometimes
six or seven in a set, having been packed together in this compact
manner in the stomachs of the codfish after the soft parts have been
digested out. Some of them had shreds of the muscles remaining in them
and were quite fresh, having evidently been but recently ejected by the
fish.' Even banks of dead shells have been found in various regions,
which are supposed to be the remains of mollusks taken by the cod.
Shell-fishes, however, form probably but the smaller portion of its
diet, and fishes of its own class contribute materially to its food,—
such as the herring family, the capelin, etc.
"The codfish in its mode of reproduction exhibits some interesting
peculiarities. It does not come on the coast to spawn, as was once
supposed, but its eggs are deposited in mid-sea and float to the
surface, although it does really, in many cases, approach the land to do
so. Prof. C. O. Sars, who has discovered its peculiarities, 'found cod
at a distance of twenty to thirty Norwegian miles from the shore and at
a depth of from one hundred to one hundred and fifty fathoms.' The eggs
thus confided to the mercy of the waves are very numerous; as many as
9,100,000 have been calculated in a seventy-five-pound fish. 'When the
eggs are first seen in the fish they are so small as to be hardly
distinguishable; but they continue to increase in size until maturity,
and after impregnation have a diameter depending upon the size of the
parent, varying from one-nineteenth to one-seventeenth of an inch. A
five- to eight-pound fish has eggs of the smaller size, while a
twenty-five-pound one has them between an eighteenth and a seventeenth.'
There are about 190,000 eggs of the smaller size to a pound avoirdupois.
They are matured and ejected from September to November."
Unlike most fishes, the cod spawns in cooling water, a trait also found
in the salmon family.
The liver of the cod yields an easily digested oil of great value in the
medical treatment of diseases causing emaciation.
The Alaska cod, _Gadus macrocephalus_, is equally abundant with the
Atlantic species, from which it differs very slightly, the air-bladder
or sounds being smaller, according to the fishermen, and the head being
somewhat larger. This species is found from Cape Flattery to Hakodate in
Japan, and is very abundant about the Aleutian Islands and especially in
the Okhotsk Sea. With equal markets it would be as important
commercially as the Atlantic cod. In the codfish (_Gadus_) and related
genera there are three dorsal and two anal fins. In the codfish the
lateral line is pale and the lower jaw shorter than the upper.
[Illustration:
FIG. 486.—Skull of Haddock, _Melanogrammus æglifinus_.
]
[Illustration:
FIG. 487.—Haddock, _Melanogrammus æglifinus_ (L.). Eastport, Me.
]
The haddock (_Melanogrammus æglifinus_) closely resembles the cod and is
of similar quality as food. It is known at sight by the black lateral
line. It is found on both shores of the Atlantic and when smoked is the
"finnan haddie" of commerce.
The pollack, coalfish, or green cod (_Pollachius carbonarius_) is also
common on both shores of the north Atlantic. It is darker than the cod
and more lustrous, and the lower jaw is longer, with a smaller barbel at
tip. It is especially excellent when fresh.
[Illustration:
FIG. 488.—Pollock, _Theragra chalcogramma_ (Pallas). Shumagin I.,
Alaska.
]
The whiting (_Merlangus merlangus_) is a pollack-like fish common on the
British coasts, but not reaching the American shores. It is found in
large schools in sandy bays. The Alaska pollack (_Theragra
chalcogramma_) is a large fish with projecting lower jaw, widely
diffused in the north Pacific and useful as a food-fish to the Aleutian
peoples. It furnishes a large part of the food of the fur-seal
(_Callorhinus alascanus_ and _C. ursinus_) during its migrations. The
fur-seal rarely catches the true codfish, which swims near the bottom.
The wall-eyed pollack (_Theragra fucensis_) is found about Puget Sound.
Smaller codfishes of this type are the wachna cod (_Eleginus navaga_) of
Siberia and the Arctic codling (_Boreogadus saida_), both common about
Kamchatka, the latter crossing to Greenland.
Several dwarf codfishes having, like the true cod, three dorsal fins and
a barbel at the chin are also recorded. Among these are the tomcod, or
frostfish, of the Atlantic (_Microgadus tomcod_), the California tomcod
(_Microgadus proximus_), and _Micromesistius poutassou_ of the
Mediterranean. These little cods are valued as pan fishes, but the flesh
is soft and without much flavor.
[Illustration:
FIG. 489.—Tomcod, _Microgadus tomcod_ (Walbaum). Wood's Hole, Mass.
]
Other cod-like fishes have but two dorsals and one anal fin. Many of
these occur in deep water. Among those living near shore, and therefore
having economic value, we may mention a few of the more prominent. The
codlings (_Urophycis_) are represented by numerous species on both
shores of the Atlantic. _Urophycis blennoides_ is common in the
Mediterranean. _Urophycis regius_, on our South Atlantic coast, is said
to exhibit electric powers in life, a statement that needs verification.
In the Gulf of Mexico _Urophycis floridanus_ is common. Farther north
are the more important species _Urophycis tenuis_, called the white
hake, and _Urophycis chuss_, the squirrel-hake. The ling (_Molva molva_)
is found in deep water about the North Sea.
A related genus, _Lota_, the burbot, called also ling and, in America,
the lawyer, is found in fresh waters. This genus contains the only
fresh-water members of the group of _Anacanthini_.
The European burbot, _Lota lota_, is common in the streams and lakes of
northern Europe and Siberia. It is a bottom fish, coarse in flesh and
rather tasteless, eaten sometimes when boiled and soaked in vinegar or
made into salad. It is dark olive in color, thickly marbled with
blackish.
The American burbot, or lawyer (_Lota maculosa_), is very much like the
European species. It is found from New England throughout the Great
Lakes to the Yukon. It reaches a length of usually two or three feet and
is little valued as food in the United States, but rises much in esteem
farther north. The liver and roe are said to be delicious. In Siberia
its skin is used instead of glass for windows. In Alaska, according to
Dr. Dall, it reaches a length of six feet and a weight of sixty pounds.
[Illustration:
FIG. 490.—Burbot, _Lota maculosa_ (Le Sueur). New York.
]
[Illustration:
FIG. 491.—Four-bearded Rockling, _Enchelyopus cimbrius_ (Linnæus).
Nahant, Mass.
]
The rocklings (_Gaidropsarus_ and _Enchelyopus_) have the first dorsal
composed of a band of fringes preceded by a single ray. The species are
small and slender, abounding chiefly in the Mediterranean and the North
Atlantic. The young have been called "mackerel-midges." Our commonest
species is _Enchelyopus cimbrius_, found also in Great Britain.
The cusk, or torsk, _Brosme brosme_, has a single dorsal fin only. It is
a large fish found on both shores of the North Atlantic, but rather rare
on our coasts.
Fossil codfishes are not numerous. Fragments thought to belong to this
family are found in English Eocene rocks.
_Nemopteryx troscheli_, from the Oligocene of Glarus, has three dorsal
fins and a lunate caudal fin. Other forms have been referred with more
or less doubt to _Gadus_, _Brosmius_, _Strinsia_, and _Melanogrammus_.
Gill separates the "three-forked hake" (_Raniceps trifurcus_) of
northern Europe as a distinct family, _Ranicipitidæ_. In this species
the head is very large, broad and depressed, differing in this regard
from the codlings and hakes, which have also two dorsal fins. The
deep-water genus, _Bathyonus_, is also regarded as a distinct family,
_Bathyonidæ_.
=The Hakes: Merluciidæ.=—Better defined than these families is the
family of hakes, _Merluciidæ_. These pike-like codfishes have the skull
peculiarly formed, the frontal bones being paired, excavated above, with
diverging crests continuous forward from the forked occipital crest. The
species are large fishes, very voracious, without barbels, with the
skeleton papery and the flesh generally soft. The various species are
all very much alike, large, ill-favored fishes with strong teeth and a
ragged appearance, the flesh of fair quality. _Merluccius merluccius_,
the hake or stock-fish, is common in Europe; _Merluccius bilinearis_,
the silver hake, is common in New England, _Merluccius productus_ in
California, and _Merluccius gayi_ in Chile.
[Illustration:
FIG. 492.—California Hake, _Merluccius productus_ (Ayres). Seattle.
]
[Illustration:
FIG. 493.—_Coryphænoides carapinus_ (Goode & Bean), showing leptoceral
tail. Gulf Stream.
]
=The Grenadiers: Macrouridæ.=—The large family of grenadiers, or
rat-tails, _Macrouridæ_, is confined entirely to the oceanic depths,
especially of the north Atlantic and Pacific. The head is formed much as
in the codfishes, with usually a barbel at the chin. There are two
dorsals, the second like the anal being low, but the leptocercal tail is
very long and tapering, ending in a filament without caudal fin. The
scales are usually rough and spinous. The species are usually large in
size, and dull gray or black in color.
[Illustration:
FIG. 494.—Grenadier, _Cœlorhynchus carminatus_ Goode & Bean. Martha's
Vineyard.
]
The best-known genus is _Macrourus_. _Macrourus berglax_ is found on
both shores of the north Atlantic. _Macrourus bairdi_ is abundant in
off-shore dredgings from Cape Cod to Cuba. _Macrourus cinereus_, the
pop-eye grenadier, outnumbers all other fishes in the depths of Bering
Sea. _Cœlorhynchus japonicus_ is often taken by fishermen in Japan.
_Coryphænoides rupestris_ is common in the north Atlantic. _Bogoslovius
clarki_ and _Albatrossia pectoralis_ were dredged by the _Albatross_
about the volcanic island of Bogoslof. _Trachyrhynchus trachyrhynchus_
is characteristic of the Mediterranean. _Nematonurus goodei_ is common
in the Gulf Stream, and _Dolloa longifilis_ is found off Japan. Other
prominent genera are _Bathygadus_, _Gadomus_, _Regania_, and
_Steindachnerella_.
[Illustration:
FIG. 495.—_Steindachnerella argentea_ (Goode & Bean). Gulf Stream.
]
The _Murænolepidæ_ are deep-sea fishes, with minute eel-like scales, and
no caudal fin. The ventrals are five-rayed and there are 10 pterygials.