The possibility of exterminating aquatic animals within the restricted limits of a lake or a river cannot be doubted; authorities are decidedly at variance, however, as to the extent of the influence of man upon the abundance of life in the open seas. Distinction must be made between the extermination of a species, even in a restricted locality, and the destruction of a fishery; the former is very unusual, and is seemingly impossible in the case of oceanic species, but the latter, especially for limited regions, is of almost yearly occurrence. Aquatic mammals, such as seals, may be entirely exterminated, especially when, like the fur seal, they forsake the water for a season and resort to the land for breeding purposes. The fur seals of the Pacific and Antarctic are now nearly gone, except in two groups of islands, the Pribylovs in Alaska and the Commander Islands in Siberia, where they enjoy Government protection, the islands being leased to the Alaska Commercial Company by whom only a stated number, all non-breeding males, may be killed each year, the permanence of the fishery being thus perfectly secured. Aquatic mammals also which never leave the water, like whales and sirenians, being conspicuous by reason of their size, and incapable of rapid multiplication, may, especially when they breed near the shore, suffer extermination. As examples may be cited the Arctic sea cow (Rhytina stelleri} and the Pacific grey whale (Rhachianectes glaucus}, the former extinct, the latter having practically become so within the present century. The sperm whale is also rapidly disappearing. In the case of fixed animals like the oyster, the corals, and the sponges, again, the colonies or beds may be swept out of existence exactly as forests are hewn down. The native oyster beds of Europe are for the most part gone, and still more rapid has been the recent destruction of the oyster reefs in Pocomoke Sound, Maryland, a large estuary, formerly very productive—the result being due more directly to the choking up of the beds by the rubbish dragged over them by dredges, and the demolition of ledges suitable for the reception of young spat, than to the removal of all the adult oysters, which could, of course, never have been effected. The preservation of oyster-beds is a matter of vital importance to the United States, for oyster-fishing, unsupported by oyster-culture, will soon destroy the employment of tens of thousands and a cheap and favourite-food of tens of millions of the people. Something may undoubtedly be effected by laws which shall allow each bed to rest for a period of years after each season of fishing upon it. It is, however, the general belief that shell-fish beds must be cultivated as carefully as are garden beds, and that this can be done only by giving to individuals rights in submerged lands, similar to those which may be acquired upon shore. It is probable that the present unregulated methods will prevail until the dredging of the natural beds shall cease to be remunerative, and that the oyster industry will then pass from the improvident fishermen to the painstaking oyster-grower, with a corresponding increase in price and decrease in consumption. Such a change has already taken place in France and Holland, and to a large extent in England, but there appear to be almost unsurmountable difficulties in the way of protecting the property of oyster-culturists from depredations—difficulties apparently as formidable in England as in America.

Fishes in ponds, lakes, or streams are quickly exterminated unless the young be protected, the spawning season undisturbed, and wholesale methods of capture prohibited. Salmon and trout streams are preserved in all countries of northern Europe; and in Canada also a large service of fishery wardens is maintained. In the United States there are in many of the older commonwealths excellent codes of laws for the preservation of fish and game, which are enforced by anglers’ clubs. A river may quickly be emptied of its anadromous visitors, salmon, shad, and alewives, by over-fishing in the spawning season, as well as by dams which cut off the fish from their spawning-grounds. Numerous rivers in Europe and America might be named in which this has occurred. In the same way, sea fishes approaching the coasts to spawn in the bays or upon the shoals may be embarrassed, and the numbers of each school decimated,—particularly if, as in the case of the herring, the eggs are adhesive and become entangled in nets. Sea fishes spawning in estuaries are affected much in the same manner as the salmon in rivers, though in a less degree, by wholesale capture in stationary nets. The shad and alewife fisheries of the United States are protected by an extensive code of laws, varying in the several States and in the different rivers of each State. The most satisfactory laws appear to be those which regulate the dates when fishery must commence and end, and prescribe at least one day in each week, usually Sunday, during which the ascent of the fish may not be interrupted. Migratory, semi-migratory, or wandering fishes, ranging singly or in schools over broad stretches of ocean, the mackerels, the tunnies, the sardines or pilchards, the menhaden, the bluefish, the bonitoes, and the sque-teague, stand apparently beyond the influence of human agency, especially since, so far as is known, they spawn at a distance from the coast, or since the adults, when about to spawn, cannot be reached by any kind of fishery apparatus. Their fecundity is almost beyond comprehension, and in many instances their eggs float free near the surface, and are quickly disseminated over broad areas. The conclusions gained by Prof. Baird, U.S. commissioner of fisheries, agree exactly with those of Prof. Huxley, that the number of any given kind of oceanic fish killed by man is perfectly insignificant when compared with the destruction effected by their natural enemies. Almost any body of water, be it a bay or sound, or be it the covering of a ledge or shoal at sea, may be over-fished to such a degree that fishing becomes unprofitable, especially if fishing be carried on in the spawning season. In this manner, no doubt, have the coasts of England been robbed of the formerly abundant supplies of turbot and sole.

The character of the various destructive influences which man brings to bear upon the inhabitants of the water and their effects having thus been briefly noticed, the student of fish culture is confronted by the question, What can be done to neutralize these destructive tendencies? There are evidently three things to do:—(1) to preserve fish waters, especially those inland, as nearly as it may be possible in their normal condition; (2) to prohibit wasteful or immoderate fishing; and (3) to put into practice the art of fish breeding—(a) to aid in maintaining a natural supply, (δ) to repair the effects of past improvidences, and (c) to increase the supply beyond its natural limits rapidly enough to meet the necessities of a constantly increasing population.

The preservation of normal conditions in inland waters is comparatively -simple. A reasonable system of forestry and water-purification is all that is required; and this is needed not only by the fish in the streams but by the people living on the banks. It has been shown that a river which is too foul for fish to live in is not fit to flow near the habitations of man. Obstructions, such as dams, may, in most instances, be overcome by fish ladders. The salmon has profited much by those devices in Europe, and the immense dams in American rivers will doubtless be passable even for shad and alewives if the new system of fishway construction devised by Col. M i Donald, and now being applied on the Savannah, James, and Potomac, and other large rivers, fulfils its present promises of success.

The protection of fish by law is what legislators have been trying to effect for many centuries, and the success of their efforts must be admitted to have been very slight indeed. Great Britain has at present two schools of fisheryeconomists,—the one headed by Prof. Huxley, opposed to legislation, save for the preservation of fish in inland waters; the other, of which Dr Francis Day is the chief leader, advocating a strenuous legal regulation of sea fisheries also. Continental Europe is by tradition and belief committed to the last-named policy. In the United States, on the contrary, public opinion is generally antagonistic to fishery legislation; and Prof. Baird, the commissioner of fisheries, after carrying on for fourteen years, with the aid of a large staff of scientific specialists, investigations upon this very question, has not yet become satisfied that laws are necessary for the perpetuation of the sea fisheries, nor has he ever recommended to Congress the enactment of any kind of fishery laws

Just here we meet the test problem in fish culture. Many of the most important commercial fisheries of the world, the cod fishery, the herring fishery, the sardine fishery, the shad and alewife fishery, the mullet fishery, the salmon fishery, the whitefish fishery, the smelt fishery, and many others, owe their existence to the fact that once a year these fishes gather together in closely swimming schools, to spawn in shallow water, on shoals, or in estuaries and rivers. There is a large school of quasi economists who clamour for the complete prohibition of fishing during spawning time. Their demand demonstrates their ignorance. Deer, game, birds, and other land animals may easily be protected in the breeding season, and so may trout and other fishes of strictly local habits. Not so the anadromous and pelagic fishes. If they are not caught in the spawning season, they cannot be caught at all.

The writer recently heard a prominent fish-culturist advocating before a committee of the United States Senate the view that shad should not be caught in the rivers because they come into the rivers to spawn. When asked what would become of the immense shad-fisheries if this were done, he ventured the remark that doubtless some ingenious person would invent a means of catching them at sea. The fallacy in the argument of these economists lies, io part, in supposing that it is more destructive to the progeny of a given fish to kill it when its eggs are nearly ripe than to kill the same fish eight or ten months earlier. We must not, however, ignore the counter-argument. Such is the mortality among fish that only an infinitesimal percentage attains to maturity. Professor Möbius has shown that for every grown qy⅛ter upon the beds of Schleswig-Holstein 1,045,000 have died. Only a very small percentage, perhaps not greater than this, of the shad or the smelt ever comes upon the breeding grounds. Some consideration, then, ought to be shown to those individuals which have escaped from their enemies and have come up to deposit the precious burden of eggs. How much must they be protected? Here the fish-culturist comes in with the proposition that “it is cheaper to make fish so plentiful by artificial means that every fisherman may take all he can catch than to enforce a code of protection laws.”

The salmon rivers of the Pacific slope of the United States, the shad rivers of the east, and the whitefish fisheries of the lakes are now so thoroughly under control by the fish-culturist that it is doubtful if any one will venture to contradict his assertion. The question is whether he can extend his domain to other species.

Fish-culture in a restricted sense must sooner or later be resorted to in all densely populated countries, for, with the utmost protection, nature unaided can do but little to meet the natural demand for fish to eat. Pond-culture (Teichwirthschaft'), has been practised for many centuries, and the carp and the gold-fish have become domesticated like poultry and cattle. The culture of carp is an important industry in China and in Germany, though perhaps not more so than it was in England three and four centuries ago; the remains of ancient fish-stews may be seen upon almost every large estate in England, and particularly in the vicinity of old monasteries. Strangely enough, not a single well-conducted carp-pond exists in England to-day to perpetuate the memory of the tens of thousands which were formerly sustained, and the carp, escaping from cultivation, have reverted to a feral state and are of little value. Until improved varieties of carp are introduced from Germany, carp-culture can never be made to succeed in England. Carp-culture is rapidly coming into favour in the United States; a number of young scale carp and leather carp were imported in 1877 for breeding purposes, and the fish commission has since distributed them to at least 30,000 ponds. Two railway cars especially built for the purpose are employed during the autumn months delivering cargoes of carp, often making journeys of over three thousand miles, and special shipments have been made to Mexico and Brazil. The carp is not recommended as a substitute for the salmon, but is especially suited to regions remote from the sea where better-flavoured fish cannot be had in a fresh condition.

A kind of pond-culture appears to have been practised by the ancient Egyptians, though in that country as in ancient Greece and Rome, the practice seems to have been similar to that now employed in the lagoons of the Adriatic and of Greece, and to have consisted in driving the young fish of the sea into artificial enclosures or vivaria, when they were kept until they were large enough to be used.

The discovery of the art of artificially fecundating the ova of fish must apparently be accredited to Stephen Ludwig Jacobi of Hohenhausen in Westphalia, who, as early as 1748, carried on successful experiments in breeding salmon and trout. The importance of this discovery was thoroughly appreciated at the time, and from 1763 to 1800 was a fruitful subject of discussion in England, France, and Germany. George III. of England in 1771 granted to Jacobi a life pension. It has been claimed by many French writers that the process of artificial fecundation was discovered as early as 1420 by Dorn Pinchon, a monk in the abbey of Reome, but this claim is but a feeble one, not having been advanced until 1854, and it is believed by many that the practice of the French monk was simply to collect and transplant the eggs which he had already found naturally fertilized. However interesting to the antiquarian, the proceedings of Dom Pinchon had no influence upon the progress of fish-culture. To Germany, beyond question, belongs the honour of discovering and carrying into practical usefulness the art of fishculture. Upon the estate of Jacobi, by the discoverer and his sons, it was carried on as a branch of agriculture for fully eighty years—from 1741 to 1825—though it was nearly a hundred years before public opinion was ripe for a general acceptance of its usefulness, a period during which its practice was never abandoned by the Germans.

Fish-culture in Britain was inaugurated in 1837 by Mr John Shaw, gamekeeper to the duke of Buccleuch at Drumlanrig, who, in the course of ichthyological investigations, had occasion to fecundate the eggs of salmon and rear the young; and, as regards France, an illiterate fisherman, Joseph Remy, living in the mountains of the Vosges, rediscovered, as it is claimed, or at any rate successfully practised, in association with Antoine Gehin, the culture of trout in 1842. The originality and practical influence of Remy and Gehin’s work appear to have been exaggerated by French writers. On the other hand the establishment in 1850 at Huningue (Hiiningen) in Alsace by the French Government of the first fish-breeding station, or “pisci-factory,” as it was named by Professor Coste, is of great significance, since it marks the beginning of public fishculture. The art discovered in Germany was practised in Italy as early as 1791 by Baufalini, in France in 1820, in Bohemia in 1824, in Great Britain in 1837, in Switzerland in 1842, in Norway under Government patronage in 1850, in Finland in 1852, in the United States in 1853, in Belgium, Holland, and Russia in 1854, in Canada about 1863, in Austria in 1865, in Australasia, by the introduction of English salmon, in 1862, and in Japan in 1877.

Artificial Propagation.—Sponges have been successfully multiplied by cuttings, like plants, in Austria and in Florida. Oysters have long been raised in artificial enclosures from spat naturally deposited upon artificial stools. The eggs of the American and Portuguese oysters have been artificially fecundated and the young hatched, and in July 1883 Mr John A. Ryder, embryologist of the U.S. Fish Commission, solved the most difficult problem in American oyster-culture by completing a mechanical device for preventing the escape of the newly hatched oysters while swimming about prior to fixation. The English oyster, being hermaphrodite, or monoecious, cannot be artificially propagated from the egg like the dioecious American species.

The fertilization of the fish egg is the simplest of processes, consisting, as every one knows, in simply pressing the ripe ova from the female fish into a shallow receptacle and then squeezing out the milt of the male upon them. Formerly a great deal of water was placed in the pan; now the “dry method, with only a little, discovered by the Russian Vrasski in 1854, is preferred. The eggs having been fertilized, the most difficult part of the task remains, namely, the care of the eggs until they are hatched, and the care of the young until they are able to care for themselves.

The apparatus employed is various in principle, to correspond to the physical peculiarities of the eggs. Fish-culturists divide eggs into four classes, viz. :—(1) heavy eggs, non-adhesive, whose specific gravity is so great that they will not float, such as the eggs of the salmon and trout; (2) heavy adhesive eggs, such as those of the herring, smelt, and perch; (3) semi-buoyant eggs, like those of the shad and’whitefish (Coregonus) ; and (4) buoyant eggs, like those of the cod and mackerel. (1) Heavy non-adhesive eggs are placed in thin layers either upon gravel, grilles of glass, or sheets of wire cloth, in receptacles through which a current of water is constantly passing. There are numerous forms of apparatus for eggs of this class, but the most effective are those in which a number of trays of wire cloth, sufficiently deep to carry single layers of eggs, are placed one upon the other in a box or jar into which the water enters from below, passing out at the top. (2) Heavy adhesive eggs are received upon bunches of twigs or frames of glass plates to which they adhere, and which are placed in receptacles through which water is passing. (3) Semi-buoyant eggs, or those whose specific gravity is but slightly greater than that of the water, require altogether different treatment. They are necessarily placed together in large numbers, and to prevent their settling upon the bottom of the receptacle it is necessary to introduce a gentle current from below. For many years these eggs could be hatched only in floating receptacles with wire-cloth bottoms, placed at an angle to the current of the stream in which they were fixed, the motion of which was utilized to keep the eggs in suspension. Later an arrangement of plunging-buckets was invented, cylindrical receptacles with tops and bottoms of wire cloth, which were suspended in rows from beams worked up and down at the surface of the water by machinery. The eggs in the cylinders were thus kept constantly in motion. Finally the device now most in favour was perfected; this is a receptacle, conical, or at least with a constricted termination, placed with its apex downward, through which passes from below a strong current, keeping the eggs constantly suspended and in motion. This form of apparatus, of which the Μ‘Donald and Clark hatching-jars are the most perfect development, may be worked in connexion with any common hydrant. (4) Floating eggs have been hatched only by means of rude contrivances for sustaining a lateral circular eddy of water in the receptacle.

The use of refrigerators, to retard the development of the eggs until such time as it is most convenient to take care of the fry, has been extensively introduced in the United States, and has been experimented upon in Germany.

The distinction between private and public...