THE COLLECTION OF FISHES
=How to Secure Fishes.=--In collecting fishes three things are vitally
necessary--a keen eye, some skill in adapting means to ends, and some
willingness to take pains in the preservation of material.
In coming into a new district the collector should try to preserve the
first specimen of every species he sees. It may not come up again.
He should watch carefully for specimens which look just a little
different from their fellows, especially for those which are duller,
less striking, or with lower fins. Many species have remained unnoticed
through generations of collectors who have chosen the handsomest or
most ornate specimens. In some groups with striking peculiarities, as
the trunkfishes, practically all the species were known to Linnæus.
No collector could pass them by. On the other hand, new gobies or
blennies can be picked up almost every day in the lesser known parts of
the world. For these overlooked forms--herrings, anchovies, sculpins,
blennies, gobies, scorpion-fishes--the competent collector should be
always on the watch. If any specimen looks different from the rest,
take it at once and find out the reason why.
In most regions the chief dependence of the collector is on the markets
and these should be watched most critically. By paying a little more
for unusual, neglected, or useless fish, the supply of these will rise
to the demand. The word passed along among the people of Onomichi in
Japan, that "Ebisu the fish-god was in the village" and would pay more
for okose (poison scorpion-fishes) and umiuma (sea-horses) than real
fishes were worth soon brought (in 1900) all sorts of okose and umiuma
into the market when they were formerly left neglected on the beach.
Thus with a little ingenuity the markets in any country can be greatly
extended.
The collector can, if he thinks best, use all kinds of fishing tackle
for himself. In Japan he can use the "dabonawa" long lines, and secure
the fishes which were otherwise dredged by the _Challenger_ and
_Albatross_. If dredges or trawls are at his hand he can hire them and
use them for scientific purposes. He should neglect no kind of bottom,
no conditions of fish life which he can reach.
Especially important is the fauna of the tide-pools, neglected by
almost all collectors. As the tide goes down, especially on rocky
capes which project into the sea, myriads of little fishes will remain
in the rock-pools, the algæ, and the clefts of rock. In regions like
California, where the rocks are buried with kelp, blennies will lie in
the kelp as quiescent as the branches of the algæ themselves until the
flow of water returns.
A sharp three-tined fork will help in spearing them. The water in
pools can be poisoned on the coast of Mexico with the milky juice of
the "hava" tree, a tree which yields strychnine. In default of this,
pools can be poisoned by chloride of lime, sulphate of copper, or, if
small enough, by formaline. Of all poisons the commercial chloride of
lime seems to be most effective. By such means the contents of the pool
can be secured and the next tide carries away the poison. The water in
pools can be bailed out, or, better, emptied by a siphon made of small
garden-hose or rubber tubing. On rocky shores, dynamite can be used to
advantage if the collector or his assistant dare risk it and if the
laws of the country do not prevent.
Most effective in rock-pool work is the help of the small boy. In
all lands the collector will do well to take him into his pay and
confidence. Of the hundred or more new species of rock-pool fishes
lately secured by the writer in Japan, fully two-thirds were obtained
by the Japanese boys. Equally effective is the "muchacho" on the coasts
of Mexico.
Masses of coral, sponges, tunicates, and other porous or hollow
organisms often contain small fishes and should be carefully examined.
On the coral reefs the breaking up of large masses is often most
remunerative.
The importance of securing the young of pelagic fishes by tow-nets and
otherwise cannot be too strongly emphasized.
=How to Preserve Fishes.=--Fishes must be permanently preserved in
alcohol. Dried skins are far from satisfactory, except as a choice of
difficulties in the case of large species.
Dr. Günther thus describes the process of skinning fishes:
"Scaly fishes are skinned thus: With a strong pair of scissors an
incision is made along the median line of the abdomen from the foremost
part of the throat, passing on one side of the base of the ventral
and anal fins to the root of the caudal fin, the cut, being continued
upward to the back of the tail close to the base of the caudal. The
skin of one side of the fish is then severed with the scalpel from
the underlying muscles to the median line of the back; the bones
which support the dorsal and caudal are cut through, so that these
fins remain attached to the skin. The removal of the skin of the
opposite side is easy. More difficult is the preparation of the head
and scapulary region. The two halves of the scapular arch which have
been severed from each other by the first incision are pressed toward
the right and left, and the spine is severed behind the head, so that
now only the head and shoulder bones remain attached to the skin.
These parts have to be cleaned from the inside, all soft parts, the
branchial and hyoid apparatus, and all smaller bones being cut away
with the scissors or scraped off with the scalpel. In many fishes which
are provided with a characteristic dental apparatus in the pharynx
(Labroids, Cyprinoids), the pharyngeal bones ought to be preserved and
tied with a thread to their specimen. The skin being now prepared so
far, its entire inner surface as well as the inner side of the head are
rubbed with arsenical soap; cotton-wool or some other soft material is
inserted into any cavities or hollows, and finally a thin layer of the
same material is placed between the two flaps of the skin. The specimen
is then dried under a slight weight to keep it from shrinking.
"The scales of some fishes, as for instance of many kinds of herrings,
are so delicate and deciduous that the mere handling causes them to rub
off easily. Such fishes may be covered with thin-paper (tissue paper
is the best) which is allowed to dry on them before skinning. There
is no need for removing the paper before the specimen has reached its
destination.
"Scaleless fishes, as siluroids and sturgeons, are skinned in the same
manner, but the skin can be rolled up over the head; such skins can
also be preserved in spirits, in which case the traveler may save to
himself the trouble of cleaning the head.
"Some sharks are known to attain to a length of thirty feet, and some
rays to a width of twenty feet. The preservation of such gigantic
specimens is much to be recommended, and although the difficulties
of preserving fishes increase with their size, the operation is
facilitated, because the skins of all sharks and rays can easily be
preserved in salt and strong brine. Sharks are skinned much in the
same way as ordinary fishes. In rays an incision is made not only from
the snout to the end of the fleshy part of the tail, but also a second
across the widest part of the body. When the skin is removed from the
fish, it is placed into a cask with strong brine mixed with alum, the
head occupying the upper part of the cask; this is necessary, because
this part is most likely to show signs of decomposition, and therefore
most requires supervision. When the preserving fluid has become
decidedly weaker from the extracted blood and water, it is thrown away
and replaced by fresh brine. After a week's or fortnight's soaking the
skin is taken out of the cask to allow the fluid to drain off; its
inner side is covered with a thin layer of salt, and after being rolled
up (the head being inside) it is packed in a cask the bottom of which
is covered with salt; all the interstices and the top are likewise
filled with salt. The cask must be perfectly water-tight."
=Value of Formalin.=--In the field it is much better to use formalin
(formaldehyde) in preference to alcohol. This is an antiseptic fluid
dissolved in water, and it at once arrests decay, leaving the specimen
as though preserved in water. If left too long in formalin fishes
swell, the bones are softened, and the specimens become brittle or even
worthless. But for ordinary purposes (except use as skeleton) no harm
arises from two or three months' saturation in formalin. The commercial
formalin can be mixed with about twenty parts of water. On the whole
it is better to have the solution too weak rather than too strong. Too
much formalin makes the specimens stiff, swollen, and intractable,
besides too soon destroying the color.
Formalin has the advantage, in collecting, of cheapness and of ease in
transportation, as a single small bottle will make a large amount of
the fluid. The specimens also require much less attention. An incision
should be made in the (right) side of the abdomen to let in the fluid.
The specimen can then be placed in formalin. When saturated, in the
course of the day, it can be wrapped in a cloth, packed in an empty
petroleum can, and at once shipped. The wide use of petroleum in all
parts of the world is a great boon to the naturalist.
Before preservation, the fishes should be washed, to remove slime and
dirt. They should have an incision to let the fluid into the body
cavity and an injection with a syringe is a useful help to saturation,
especially with large fishes. Even decaying fishes can be saved with
formalin.
=Records of Fishes.=--The collector should mark localities most
carefully with tin tags and note-book records if possible. He should,
so far as possible, keep records of life colors, and water-color
sketches are of great assistance in this matter. In spirits or formalin
the life colors soon fade, although the pattern of marking is usually
preserved or at least indicated. A mixture of formalin and alcohol is
favorable to the preservation of markings.
In the museum all specimens should be removed at once from formalin
to alcohol. No substitute for alcohol as a permanent preservative has
been found. The spirits derived from wine, grain, or sugar is much
preferable to the poisonous methyl or wood alcohol.
In placing specimens directly into alcohol, care should be taken not to
crowd them too much. The fish yields water which dilutes the spirit.
For the same reason, spirits too dilute are ineffective. On the other
hand, delicate fishes put into very strong alcohol are likely to
shrivel, a condition which may prevent an accurate study of their fins
or other structures. It is usually necessary to change a fish from
the first alcohol used as a bath into stronger alcohol in the course
of a few days, the time depending on the closeness with which fishes
are packed. In the tropics, fishes in alcohol often require attention
within a few hours. In formalin there is much less difficulty with
tropical fishes.
Fishes intended for skeletons should never be placed in formalin.
A softening of the bones which prevents future exact studies of
the bones is sure to take place. Generally alcohol or other spirits
(arrack, brandy, cognac, rum, sake "vino") can be tested with a match.
If sufficiently concentrated to be ignited, they can be safely used
for preservation of fishes. The best test is that of the hydrometer.
Spirits for permanent use should show on the hydrometer 40 to 60 above
proof. Decaying specimens show it by color and smell and the collector
should be alive to their condition. One rotting fish may endanger
many others. With alcohol it is necessary to take especial pains to
ensure immediate saturation. Deep cuts should be made into the muscles
of large fishes as well as into the body cavity. Sometimes a small
distilling apparatus is useful to redistil impure or dilute alcohol.
The use of formalin avoids this necessity.
Small fishes should not be packed with large ones; small bottles are
very desirable for their preservation. All spinous or scaly fishes
should be so wrapped in cotton muslin as to prevent all friction.
=Eternal Vigilance.=--The methods of treating individual groups
of fishes and of handling them under different climatic and other
conditions are matters to be learned by experience. Eternal vigilance
is the price of a good collection, as it is said to be of some other
good things. Mechanical collecting--picking up the thing got without
effort and putting it in alcohol without further thought--rarely serves
any useful end in science. The best collectors are usually the best
naturalists. The collections made by the men who are to study them and
who are competent to do so are the ones which most help the progress
of ichthyology. The student of a group of fishes misses half the
collection teaches if he has made no part of it himself.