Methods of Preservation.—In the field, fishes may be collected and preserved in four different ways, according to circumstances, as follows: 1. Preserved entire in spirits. 2. As skins, preserved in spirits. 3. As skins preserved in brine. 4. As rough skeletons, either preserved dry or in spirits.
For the purposes of scientific study and close investigation, the most valuable fish specimens are those which have been preserved entire in alcohol, or some equally efficient preservative solution. Good alcoholic specimens rank next in scientific value to fishes fresh from their native element. Ordinarily, however, the collector's resources are limited, and it is necessary for him to preserve only the skins of the large and bulky specimens.
Tanks for Alcoholics.—For years past the National Museum and United States Fish Commission have used square, box-like tanks, made of copper and lined with tin, each tank having a large round hole in its top, as large as the width of the top will allow, and which is closed tightly by means of a screw cover. These are known as "Agassiz tanks," for the reason that the design originated with Professor Louis Agassiz. They are light, not very costly, easily managed, and are about as nearly perfect for their purpose as anything can be in this world. They are made of three sizes, to hold four, eight, or sixteen gallons. To protect them during shipment a strong pine chest is used, which is provided with wrought-iron handles, hinged cover, hasp, and padlock. The chests are made to contain one sixteen-gallon tank, two of eight gallons, and either three or four four-gallon tanks. The tanks used by the National Museum are made by W.S. Barker, Seventh and D Streets, S.W., Washington, at the following prices, exclusive of the chests; sixteen-gallon tank, $16.50; eight-gallon, $10; four-gallon, $4.25; pine chests, complete, $3 each.
[a]Fig. 20.]—Agassiz Tank, for Alcoholics.
If Agassiz tanks are not obtainable, the next best and the cheapest course is to have some large round cans made of galvanized iron, with tops that can be soldered on when the time comes to ship specimens. Wooden kegs are not of much use in collecting, but both kegs and barrels are good enough to use in transporting collections. Many a time I have helped myself out of a difficulty afield by falling back upon the immortal American kerosene can, holding five square gallons, and which goes to the uttermost parts of the earth.
Glass Jars.—In the field I have never found any other sort of a glass jar half as useful and safe as a common Mason fruit jar, varying in size from pint to half-gallon. They are infinitely superior to glass-stoppered jars, and far less liable to be broken.
Preserving Fishes Entire in Spirits.—Having taken all the notes on a fresh specimen that you desire, the next thing is to wash it thoroughly. But "before washing the fish," says Dr. T. H. Bean, "look it over for external parasites; examine the gills and the inside of the mouth carefully, as these are favorite situations. These parasites often furnish a clue to the migration of the fish; remove them if they can be taken off entire; if not, let them remain, and call attention to their presence in your shipping notes. Preserve the parasites in vials or bottles, and provide them with labels, stating from what fish they came, and in what situation they were found."
Many fishes when taken from the water have the entire body and gills covered with a coat of persistent mucus that can be removed only by determined effort. If you have any alum at hand, you can in a moment make up a pint or quart of alum water, which will cut the mucus instantly, and clear it off. Use a stiff brush—a large tooth-brush is the best thing—in cleaning off this mucus, and do not forget to cleanse the gills thoroughly.
Open the abdominal region of every fish by making a generous cut from the vent straight forward toward the ventral fins. Usually the length of the opening should be equal to about one-fifth of the entire length of the fish. If the fish be a large one, it has always been my practice to open the fleshy interior still farther by working through this cut, and detaching the skin from the flesh as far up each side as possible. This gives the spirits immediate access to the entire mass of flesh, and the result is very speedy and perfect preservation without any change whatever in the form or weight of the specimen.