Once a Week (magazine)/Series 1/Volume 8/Fish growth

FISH GROWTH.

 

 

The old adage, which holds good under so many varied circumstances, of truth being stranger than fiction, was never better exemplified than in the numerous controversies that have arisen about the growth of fish, and which have been carried on with great vigour by the learned in such matters. The wars of the naturalists have been as bitter and prolonged as those other wars promoted by kings for the purpose of conquest or the acquisition of territory; and great or small as uninterested people may deem these intellectual battles, some of them are of more than common interest—particularly those fought under the sign of Pisces. There have been the parr, the grilse, and the salmon growth controversies in connection with the Salmonidæ; and there has been a fierce sprat and herring controversy, as well as a hot contest about the transformation of crabs, the natural history of eels, the food of salmon; while the loves of the Gadidæ have also afforded matter for disputation. There is so little known concerning the natural history of fish and crustacea, our naturalists (from want of opportunity, we presume) have told us so little about these inhabitants of the great world of water—especially as regards the question of growth—that we must cease to wonder at the learned wrangling which has taken place, the ignorance of the subject betrayed by people of considerable learning, or the length of time many of the controversies have lasted.

The disputes connected with the fishes of the salmon family have, for instance, been raging for about a century and a half. Parr, smelt, grilse, and salmon have each in turn supplied a theme for discussion, and as Salmo Salar is the acknowledged King of Fishes—the venison of the waters, as the great stag is the monarch of the British forests—it will be only a grateful concession to the throne to consider first what has been said about his birth, breeding, and growth, as his biography is far from being uneventful.

Between its cradle and its grave, a period averaging four years, the salmon undergoes no end of adventure. It is usually born in the rippling waters of some tributary to a large river. The parent fish in the early winter-time plough up the gravel with their snouts and tails till a suitable trench for the deposition of their spawn is formed. The eggs, being duly deposited by the female fish and fructified by the milter, are left to their fate; and whether the river foam in flood, or be frozen over, or dried up at its source, the eggs remain. But they are not hatched in forty-eight hours, as was once asserted by a wise salesman of Billingsgate! nor even in twice forty-eight days are they certain to be in life. The sharp winds of February must toss about the water, and the suns of March and April require to light up the river, before the eggs come to maturity, and the young fish bursts from its fragile prison. A very small number of salmon eggs are hatched, so that the quantity deposited is usually out of all proportion to the fish which are born; the percentage of loss being enormous. It was long a disputed point with naturalists how fish eggs were rendered fruitful; and notwithstanding what has been so well demonstrated at the Stormontfield breeding-ponds, some folks will not believe that the fructification of salmon or other ova is a purely external act.

One of the most prolonged controversies about fish-growth, has been in connection with the infant salmon: it is known as the parr controversy, and has been carried on for a great number of years by a succession of clever disputants. The young of Salmo Salar are best known as parr, although on some rivers they are called samlets, salmon-fry, branlin, fingerling, &c. The dispute regarding the parr arose from its being set down by naturalists as a distinct animal, perfect and complete in itself, and not the young of any other fish. This delusion lasted for a century, till at last there arose infidels and heretics, observing men, looking and thinking for themselves, who came to the conclusion that parr were salmon in their most infantile stage. This was at once set down by the naturalists of the old school as “flat blasphemy;” but the idea moved for all that, as did the earth in the time of Galileo. Proof was demanded, and in good time proof was forthcoming—and, strange to say, Mr. Robert Buist, the conservator of the river Tay, and the moving spirit of the Stormontfield salmon-breeding experiments, who has recently witnessed over and over again the transformation of the parr into salmon, was the Pope of the old school, whose one fixed idea was that parr were parr, and parr only. He was encountered in those days by the Ettrick Shepherd, one of the very earliest to doubt “the distinct fish” theory. Hogg, while wandering about in the quiet pastoral districts of the South of Scotland, saw, as he tells us in one of his egotistical essays, “the bits o’ things changing their skin before his ain twa e’en;” he saw the finger’d bars of the parr melt away only to reveal the silver scales of the smelt; and seeing this year after year, he became perfectly certain that parr were young salmon. How to convince the old sceptics of this fact was the great difficulty with Hogg. However, as he used to say, “necessity is the mother of invention;” and from necessity he invented a plan of marking the fish, and in the country smithies he advertised his plan, described his marks, and offered handsome rewards, in the shape of gills of whisky, to all who would bring him the fish he had marked in their next stage of growth. By this plan he procured abundant proof of the correctness of his theory; but the naturalists were still sceptical. “No doubt,” said they, “this smelt is the young of the salmon, but then it is the young salmon you have marked, and not the true parr.” Hogg was quite convinced himself of the thoroughness of his experiments, but as for “they asses of naturalists,” as he called the savans who took part with him in the dispute, “there is no convincing them except by mathematics, an’ ye canna mak’ diagrams and figures out o’ the parr question.”

Although the Shepherd of Ettrick died without making a great many converts to what was called by scientific people his “mad theory,” yet he left a disciple who carried out his ideas and proved his case. Mr. Shaw, forester to the Duke of Buccleuch at Drumlanrig, the re-discoverer of pisciculture, was determined to have the question set at rest; and in order that there might be no doubt about his facts, he commenced by gathering the eggs of the salmon from the spawning beds and placing them in water where they could be hatched under his own eye. These eggs in due season quickened into life, and as duly in process of time they became salmon, changing from the parr to the smelt state, and in Mr. Shaw’s opinion his experiment was triumphant. “Oh dear, no,” said the old theorists, “you have proved nothing; the whole process is a mistake; you have not obtained the eggs of the real parr at all; it is salmon eggs you have taken, and there is no merit in growing salmon from their own eggs.”

Mr. Shaw’s enthusiasm was a little cooled, no doubt, by this attempt to put him down; but, by and by, he returned to his experiments with renewed vigour, and speedily carried out a plan which was destined to settle peremptorily one phase of the parr question. He caught the male and female fish, and depriving them of their spawn, placed it in his pond to hatch. Again he was successful. The eggs at the proper time disclosed their fish; these in a short time were seen to be unmistakeable parr: after a period becoming smelts, and so growing through all the grilse stages into undoubted salmon. Curiously enough, another practical man had engaged in similar experiments, almost simultaneously with Mr. Shaw. Mr. Young, of Invershin, manager of fisheries to the Duke of Sutherland, by a similar process had also convinced himself that the parr was the young of the salmon. The experiments of these gentlemen, however, originated a new branch of controversy. Granting that the parr had been proved to be the young of Salmo Salar, the question now was—At what time did it become a smelt? In one year, said Mr. Shaw. “Nay,” said Mr. Young, “it is two years before the change takes place.” Both gentlemen have been found, by means of the experiments at Stormontfield, to be right. One-half of the parr of any year’s hatching undergo their metamorphosis into smelts and depart for the sea at the end of twelve months from the date of their being hatched; the other moiety does not depart for the sea till a space of two years has elapsed!

This curious anomaly in the growth of the salmon has never been explained. Up till the experiments of Shaw and Young, the smelt was always considered to be the fry of the salmon in its most infantile stage—in fact, the fishmonger who asserted that the spawn of that valuable fish was hatched in forty-eight hours, was not worse informed than the men who supposed that the fish within a few days of its breaking the shell grew to be a smelt six or seven inches Jong and of corresponding girth. It is impossible to account for the young fish being thus divided—one half changing the one year, and the other half in the year following. Before these various experiments were made, no one, of course, had noticed this remarkable circumstance in the history of the salmon. The parr being thought a distinct fish, attention was centred in the smelt, and, as has been stated, it was thought to be the young salmon grown magically large within a few weeks of its birth. The little fry, the parr, are on most salmon rivers captured in thousands. At some places they used to be advertised, just like whitebait, as a rare fish delicacy, nobody taking into account that in every female parr which they placed in their fryingpan they were killing a countless number of future salmon. As a matter of course, a considerable percentage of fish are still spared (out of the large number of eggs which are annually hatched) to become smelts; these, again, have their own particular enemies. On their way to the sea they become the prey of innumerable anglers, and on their arrival at the salt water they are waited upon by a horde of sea cannibals, who straightway begin to feast upon them, decimating the arriving shoals with the greatest possible industry. A twenty-pound female salmon will yield twenty thousand eggs, but about half of that number only will come to life; as many of them will waste for want of fructification; others will be devoured by the yellow trout or other fishes, and many more by the wild fowl. Again, a few thousands of the parr will be lost long before they become smelts; and these latter will, from various causes, be reduced in the river and sea to about a third of their original number; these again changed into grilse, will gradually be seized upon by fishermen and anglers, till only a very few of the original fish are left to become salmon and perpetuate their kind.

Before discussing one or two other interesting features of salmon-growth, it may be as well to allude to a dispute which is yet going on, very similar to the parr controversy. It has already been shaped into a pertinent question, and “What is a sprat?” is ever and anon being asked by both the ignorant and the learned. Well, as in the case of the parr, and the two cases are very similar, there are people who believe a sprat to be just a sprat, and nothing more. But there are others, equally learned, who say that a sprat is a young herring. There has been some fighting over these two propositions—the sprat-and-nothing-but-a-sprat men assert that their fish is a totally distinct individual, and neither the son nor the daughter of old Clupea harengus. “The sprat has a different shape.” “The sprat has a serrated abdomen.” “The sprat has a larger number of vertebrata.” “The sprat is very oily.” “The sprat has its fins differently placed from the herring.” “The sprat is—in fact, the sprat is a distinct fish, and that’s all about it,” say the “old fogies.” “All the differences you mention,” reply the other side, “are of no consequence, the serrated belly is a mere provision for growth; the oiliness of the sprat cannot be greater than that of the pilchard; the fins will be adjusted as the animal grows, and so will the shape; depend upon it we are correct, and that sprats are young herring.”

So the dispute stands for the present, and there is no pond for breeding herring where the question might be solved. Some of the objectors to the young of the herring being thought sprats, say that they have specimens with spawn in them, and that were they not a separate fish it could not be charged with spawn. But this argument must fail, because plenty of young parr have been taken in the Tay and elsewhere with spawn. Indeed, at the Stormontfield ponds the milt from a male parr was used to impregnate the ova of a full-grown female salmon! It is certain, too, that as a general rule the sprat is not found with either roe or milt developed in it; it is likewise certain that sprats and young herring are found in the same shoals, they are sold indiscriminately as sprats, and millions of them are annually consumed in London and elsewhere. After the dogmatic way in which the parr question was argued, it would be unsafe to assert that the sprat may not some day be proved to be the young of the herring (Clupea harengus), or of the pilchard (Clupea pilchardus). The French, we believe, are taking steps to solve the question by means of their large salt-water aquarium. M. Coste, who is great in all questions connected with pisciculture, will add another laurel to his brows if he succeed in determining the question of What is a sprat?

A case in point as regards fish-growth, although the crustaceans are not exactly fish, has been much disputed in reference to the natural history of the crab. The young crab in its earlier stages was gravely described by various naturalists as a distinct animal. Naturalists are so ignorant of how the work of growth is carried on in the fish world—in fact, it is so difficult to investigate points of natural history in the depths of the sea—that we cannot wonder at less being known about marine animals than about any other class of living things. Pisciculture has settled the parr controversy, and to the system of artificial cultivation we must look ultimately for the solution of others of our fish mysteries. As to the crab dispute, it is only of late years that the various metamorphoses undergone by that popular crustacean have come to be understood. The crab yields a great number of eggs, and these, when hatched, yield an animal not in the remotest degree like the parent; hence the mistakes which have been so frequently made about the time necessary to mature a crab for table purposes. It was Slabber, a Dutch naturalist, who first started the idea of this crustacean metamorphosis; and, as in the case of Shaw and the parr, he was taunted with having made a blunder. He kept a zoea in water, in order that it might grow into one of the higher crustacea under his own eye; and so it was said that “Slabber lost his zoea in changing the sea water, and that another animal came with the added portion.” It was thought by all scientific men to be a wonderful discovery when Mr. Vaughan Thompson announced, in corroboration of Slabber, the remarkable fact of the genus zoea, founded by Box, being nothing else but the higher crustacea, in an early stage of their development. We know the kind of worms that our butterflies grow from, and most people are convinced that these crawling animals do get themselves changed into winged insects, and flutter out a brief life in the sunbeams; but the rule of belief in the changes of marine animals seems to be different, and so we have still people who cannot believe that a parr will some day become a salmon, or that the zoea will assuredly change into the highest order of crustacean life.

Perhaps, as we are now on the subject of crustacea, we may just remind the reader of the wonderful conditions of growth which are common to the greater number of our shell fish. Lobsters, crabs, shrimps, prawns, crayfish,—in fact, the crustaceans generally, have to change their shelly covering in order that they may increase in size. During the first year of their age the crab and lobster must change their suit of clothes more than once, they grow with such rapidity; but, as a rule, they have a new suit once a-year, and a wonderful power has been given them to throw off their old covering at the time of moulting. Crabs and lobsters have also the privilege of growing a new limb, whenever it is necessary for them to dispense with an old one, which they sometimes do in cases of fright or from accident. When from either cause a limb is destroyed, nature supplies a new one with great rapidity, either at once, or on the first occasion of exuviation.

Returning to the Salmonidæ, there are several interesting points in the biography of Salmo Salar that deserve mention, because every phase in the life of that king of fishes has been productive of controversy. Where does the salmon go to when it reaches the salt water? What is the cause of its going to the sea at all? What does it find to feed upon, and how quick does it grow? are slight samples of the questions which have been asked in reference to salmon growth. At one time wise people abounded who could answer these and similar queries off-hand, as it were; and one of the gravest assertions of the old writers about the salmon was, that the smelt, on arriving at the salt water, went off direct, and at lightning speed to the North Pole; a place where the common herring was also supposed to be a constant visitor. The real truth, however, is, that no one knows where the salmon goes to when it reaches the sea;—whether it proceeds to a great distance, or finds a luxuriant feeding-ground in the nearest deep water, has never been properly ascertained, but that it grows rapidly under the influence of the brine is certain. The curious instinct which leads the salmon, at certain seasons, to seek the salt water, and then to return to its native stream in order to perpetuate its kind, is another of the mysteries of salmon growth upon which different ideas prevail. It is said, that while in the salt water the salmon becomes infested with parasites of the crustacean kind, which it cannot get quit of till it reaches its native streams, or at least the fresh-water. Then, again, a kind of fresh-water louse fastens upon the animal in the river that is supposed to force it seaward; doubtless, however, these are but weak inventions of man to account for phases of life which are the nature of the animal, and which it was created to undergo. The sea seems to provide a rich feeding-ground for the salmon, for it returns home improved in condition and increased in size. Many of the smelts liberated from the breeding ponds at Stormontfield were marked, in order to ascertain how long they would be absent, and at what rate they increased in size. These points have been from time to time pretty satisfactorily detailed. It will be found, for instance, that a moiety of the salmon born in March of the present year (1863) will go off to sea as smelts in the months of April and May, 1864; and that in the autumn of that year they will come back as pretty sizeable grilses, whilst the half of their brothers and sisters will be still in the breeding-ponds as parr! Smelts a few ounces in weight, when liberated, or marked in April (we speak now of the river Shin experiments), have been recaptured in the month of July, after having attained a weight of from four to seven pounds. It was thought at one time that grilses never became salmon; indeed, the assertion was very recently reiterated; but the point was firmly settled years ago by the Duke of Athole marking a great number of fish while in their grilse stage; and as salmon almost invariably return to their parent stream, it became an easy matter to note the capture of the marked animals, and observe the rate of growth, which was in every case found to be remarkable. A specimen marked on February 18th of a particular year, and then weighing four pounds, was recaptured on June 28th, when it had increased in weight as much as five pounds, its total weight being, when recaptured, nine pounds. Another specimen increased eight pounds in a period of five months and a half. Whilst the salmon grows rapidly enough in its earlier stages, it is not thought that that fish grows now to the same size as in former years; a consequence, no doubt, of the increasing demand which has told so severely on some of our English streams as totally to impoverish them. Salmon of eighty pounds weight were known to exist fifty years ago, and salmon of fifty pounds were not at all rare, while fish of forty pounds were quite common; but now the usual run of salmon weigh from twelve to twenty-five pounds; and there are fishermen who assert, that the system of over-fishing, so long persevered in, is deteriorating the quality as well as diminishing the weight of the fish.

The salmon is not the only fish which migrates. The eel is also a great traveller, but in a way quite opposite to the salmon—that is to say, the eel spawns in the sea; and, at the proper season, the young fish ascend to the river, where they remain till they in turn are seized with the instinct to visit the salt water. The land crabs do the same, they proceed annually to the sea-shore in a great procession, travelling in a body from the far interior; they remain at the edge of the water for a few days, during which time they deposit their spawn, and then they return home to undergo their annual moult.

The migration of the common herring is an old story now, but is still occasionally revived by ignorant writers; and it is curious as showing the growth of knowledge in matters relating to the natural history of fish. The supposition was, that the herring was a native of the Polar regions, and that it annually came to the British coasts in a vast horde, in order to spawn, the young departing for the same icy region as soon as ever they were able to swim so far. It is a pity that this fine old myth has been submitted to the laws of logic: it was so imaginative, so poetic. The grand shoal, moved by certain weather influences, was depicted as setting out for Britain at an early period of the year. The body of fish was so immense as to defy enumeration. A space equal to all the parks of London, covered with herrings as close as they could lie together, and at least half a mile in depth, would not be anything like equal to a tenth part of this great herring “heer!” which annually came to us from the high latitudes of the north. This gigantic host of fish came in one great body as far as Iceland, where it was broken into two divisions, each of which took, by a marvellous instinct, its own proper route. The great army destined by its invasion to give wealth to the people of Britain, subdivided itself at the Shetland Islands, and with the precision of regularly disciplined soldiers, brigades departed to all the points of the compass; these again broke up into other squads, each finding out the particular bay or frith in which it was destined to pass the summer months, and perpetuate its kind, and at the same time yield food and wealth to thousands of the population. At the proper season, instinct taught the various divisions of the herring army to unite for the homeward passage; and it is needless to state that the parties who invented the story took care that each division should join at the precise spot where it had separated, so that the body might reach its Polar home in the exact order of its departure. The young fish, after luxuriating for a time in the shallow waters, where they had come to life, gradually followed the example of their parents, and left for the far north, there to feed on the thousands of minute crustaceans which are known to inhabit those icy regions.

As regards the sprat, an ingenious “old voyager,” who takes an interest in such questions, has informed the world, through a local newspaper, that it also is a migratory fish, but that its habits are in every respect the opposite of the herring; in other words, the sprat, he says, goes to the North Pole to spawn, and the young fish kindly come here in the winter months—to afford employment to the costermongers perhaps, and a dish for the Lord Mayor’s feast. Of course, this idea is sheer nonsense, and is only worthy of citation, as showing the absurdities which people invent, in order to have a royal road to learning.

The sprat and the herring are as local to Britain and some other countries, as the whale is to Greenland. They breed and grow all along our coasts, all the year round, as do most kinds of British fish and Crustacea. We have seen the herring in all its stages of growth, from the minute ova to the sizeable summer fish. A jar with herrings newly hatched was lately in our possession, the young fish swimming about like bits of feather or cotton thread, but it is impossible to keep them alive for any length of time, they are so fragile. It would be interesting, however, if herrings could be grown from the egg in presence of our naturalists, as indeed it would be in the case of all other kinds of fish; and there need be no despair on the subject, after what has been achieved in the case of the salmon at Stormontfield, and after what has been done in constructing oyster-beds in the seas, and breeding fresh-water fishes in the rivers of France. Although we are yet but groping, as it were, in the rudiments of sea-science, a time is rapidly approaching when we may hope to have the wonders of the deep revealed to us, of which we are now ignorant, so that we may know much more accurately than we do now the conditions which regulate the vast stores of food-wealth that lie at our command when we choose to do business in the great deep.