Animal Intelligence / The International Scientific Series, Vol. XLIV.

CHAPTER VIII.

FISH.

Although we here pass into the sub-kingdom of animals the intelligence of which immeasurably surpasses that of the other sub-kingdoms, it is remarkable that these lowest representatives of the higher group are psychologically inferior to some of the higher members of the lower groups. Neither in its instincts nor in general intelligence can any fish be compared with an ant or a bee—a fact which shows how slightly a psychological classification of animals depends upon zoological affinity, or even morphological organisation. For although a highly competent authority, namely Van Baer, has said that a bee is as highly organised an animal as a fish, though on a different type,[110] no one would be found to assert that an ant or a bee is so much more highly organised than a fish as its higher intelligence would require, supposing degrees of intelligence to stand in necessary relation to degree of organic development. And this consideration is not materially altered if, instead of regarding the whole organism, we look to the nervous system alone. There is no doubt that the cerebral hemispheres of a fish, although small as compared with these organs in the higher Vertebrata, are, bulk for bulk, enormous as compared with the oesophageal ganglia or 'brain' of an insect; while the disproportion becomes still greater if the cerebral hemispheres of a fish are compared with their supposed analogues in the brain of an ant, viz., the pedunculated and convoluted lobes which surmount the cephalic ganglion. But here the relative smallness of the ant as a whole must be taken into consideration, and also the fact that its brain is relatively much more massive as well as more highly organised than that which occurs in any other order of invertebrated animals, except, perhaps, the octopus and his allies. Therefore, although the brain of a fish is formed upon a type which by increase of size and complexity is destined in function far to eclipse all other types of nerve-centre, we have to observe that in its lowest stage of evolution as presented to science in the fishes, this type is functionally inferior to the invertebrate type, where this reaches its highest stage of evolution in the Hymenoptera.

Emotions.

Fish display emotions of fear, pugnacity; social, sexual, and parental feelings; anger, jealousy, play, and curiosity. So far the class of emotions is the same as that with which we have met in ants, and corresponds with that which is distinctive of the psychology of a child about four months old. I have not, however, any evidence of sympathy, which would be required to make the list of emotions identical; but sympathy may nevertheless be present.

Fear and pugnacity are too apparent in fish to require special proof. The social or gregarious feelings are strongly shown by the numberless species which swim in shoals, the sexual feelings are proved by courtships, and the parental by those species which build nests and guard their young. Schneider saw several species of fish at the Naples Aquarium protecting their eggs. In one case the male mounted guard over a rock where the eggs were deposited, and swam with open mouth against intruders. The following accounts of the nidification of certain species of fish show that the parental instincts are not unlike those which obtain in birds, and are comparable in point of strength with the same instincts as they occur in ants, bees, and spiders.

Agassiz remarks[111] that while examining the marine products of the Sargasso Sea, Mr. Mansfield picked up and brought to him a round mass of sargassum, about the size of the two fists placed together. The whole consisted, to all appearance, of nothing but gulf-weed, the branches and leaves of which were, however, evidently knit together, and not merely balled into a roundish mass. The elastic threads which held the gulf-weed together were beaded at intervals, sometimes two or three beads being close together, or a branch of them hanging from the cluster of threads. This nest was full of eggs scattered throughout the mass, and not placed together in a cavity. It was evidently the work of the Chironectes. This rocking fish-cradle is carried along as an undying arbour, affording at the same time protection and afterwards food for its living freight. It is suggested that the fish must have used their peculiar pectoral fins when constructing this elaborate nest.

The well-known tinker or ten-spined stickleback (Gasterosteus pungitius) is one of our indigenous fish which constructs a nest. On May 1, 1864, a male[112] was placed in a well-established aquarium of moderate size, to which, after three days, two ripe females were added. Their presence at once roused him into activity, and he soon began to build a nest of bits of dirt and dead fibre, and of growing confervoid filaments, upon a jutting point of rock among some interlacing branches of Myriophyllum spicatum—all the time, however, frequently interrupting his labours to pay his addresses to the females. This was done in most vigorous fashion, he swimming, by a series of little jerks, near and about the female, even pushing against her with open mouth, but usually not biting. After a little coquetting she responds and follows him, swimming just above him as he leads the way to the nest. When there, the male commences to flirt—he seems unaware of its situation, will not swim to the right spot, and the female, after a few ineffectual attempts to find the proper passage into it, turns tail to swim away, but is then viciously pursued by the male. When he first courts the female, if she, not being ready, does not soon respond, he seems quickly to lose his temper, and, attacking her with great apparent fury, drives her to seek shelter in some crevice or dark corner. The coquetting of the male near the nest, which seems due to the fact that he really has not quite finished it, at length terminates by his pushing his head well into the entrance of the nest, while the female closely follows him, placing herself above him, and apparently much excited. As he withdraws she passes into the nest, and pushes quite through it, after a very brief delay, during which she deposits her ova. The male now fertilises the eggs, and drives the female away to a safe distance; then, after patting down the nest, he proceeds in search of another female. The nest is built and the ova deposited in about twenty-four hours. The male continued to watch it day and night, and during the light hours he also continually added to the nest.

The marine fifteen-spined stickleback (Gasterosteus spinachia) affords another instance of nest-constructing fishes. The places selected for their nests are usually harbours, or some sheltered spots to where pure sea water reaches. The fish either find growing, or even collect some of the softer kinds of green or red seaweed, and join them with so much of the coralline tufts (JaniÆ) growing on the rock as will serve the purpose of affording firmness to the structure, and constitute a pear-shaped mass five or six inches long, and about as stout as a man's fist. A thread, which is elastic and resembles silk, is employed for the purpose of binding the materials together: under a magnifier it appears to consist of several strands connected by a gluey substance, which hardens by exposure to the water.[113]

M. Carbonnier, who has studied the habits of the Chinese butterfly-fish (Macropodus) in his private aquarium in Paris, where he had some in confinement, observed that the male constructs a nest of froth of considerable size, 15 to 18 centimetres horizontal diameter, and 10 to 12 high. He prepares the bubbles in the air (which he sucks in and then expels), strengthening them with mucous matter from his mouth, and brings them into the nest. Sometimes the buccal secretion will fail him, whereupon he goes to the bottom in search of confervÆ, which he sucks and bites for a little in order to stimulate the act of secretion. The nest prepared, the female is induced to enter. Not less curious is the way in which the male brings the eggs from the bottom into the nest. He appears unable to carry them up in his mouth; instead of this, he first swallows an abundant supply of air, then descending, he places himself beneath the eggs, and suddenly, by a violent contraction of the muscles in the interior of his mouth and pharynx, he exhales the air which he had accumulated by the gills. This air, finely divided by the lamellÆ and fringes of the gills, escapes in the form of two jets of veritable gaseous powder, which envelopes the eggs and raises them to the surface. In this manoeuvre the Macropodus entirely disappeared in a kind of air-mist, and when this had dissipated he reappeared with a multitude of air-bubbles like little pearls clinging all over his body.[114]

Again, in detailing Mr. Baker's observations on the three-spined stickleback, published in the Philosophical Transactions, this author says:—

It has been remarked that after the deposition of the eggs the nest was opened more to the action of the water, and the vibratory motion of the body of the male fish, hovering over its surface, caused a current of water to be propelled across the surface of the ova, which action was repeated almost continuously. After about ten days the nest was destroyed and the materials removed; and now were seen the minute fry fluttering upwards here and there, by a movement half swimming, half leaping, and then falling rapidly again upon or between the clear pebbles of the shingle bottom. This arose from their having the remainder of the yelk still attached to their body, which, acting as a weight, caused them to sink the moment the swimming effort had ceased. Around, across, and in every direction the male fish, as the guardian, continually moved. Now his labours became more arduous, and his vigilance was taxed to the utmost extreme, for the other fish (two tench and a gold carp), some twenty times larger than himself, as soon as they perceived the young fry in motion, continuously used their utmost endeavours to snap them up. The courage of the little stickleback was now put to its severest test; but, nothing daunted, he drove them all off, seizing their fins and striking with all his strength at their heads and at their eyes. His care of the young brood when encumbered with the yelk was very extraordinary; and as this was gradually absorbed and they gained strength, their attempts to swim carried them to a greater distance from the parent fish; his vigilance, however, seemed everywhere, and if they rose by the action of their fins above a certain height from the shingle bottom, or flitted beyond a given distance from the nest, they were immediately seized in his mouth, brought back, and gently puffed or jetted into their place again. The same care of the young, bringing them back to then nest up till about the sixth day after hatching, has been remarked by Dr. Ransom in the ten-spined stickleback (G. pungitius).[114]

The well-known habit of the lophobranchiate fish, of incubating their eggs in their pouches, also displays highly elaborated parental feeling.[115] M. Risso says that when the young of the pipe-fish are hatched out, the parents show them marked attachment, and that the pouch then serves them as a place of shelter or retreat from danger.[116]

M. Carbonnier has recorded how the male of the curiously grotesque telescope-fish, a variety of Carassius auratus (Linn.), acts as accoucheur to the female. Three males pursued one female which was heavy with spawn, and rolled her like a ball upon the ground for a distance of several metres, and continued this process without rest or relaxation for two days, until the exhausted female, who had been unable to recover her equilibrium for a moment, had at last evacuated all her ova.[117]

That adult fish are capable of feeling affection for one another would seem to be well established: thus Jesse relates how he once captured a female pike (Esox lucius) during the breeding season, and that nothing could drive away the male from the spot at which he had perceived his partner slowly disappear, and whom he had followed to the edge of the water.

Mr. Arderon[118] gave an account of how he tamed a dace, which would lie close to the glass watching its master; and subsequently how he kept two ruffs (Acerina cernua) in an aquarium, where they became very much attached to one another. He gave one away, when the other became so miserable that it would not eat, and this continued for nearly three weeks. Fearing his remaining fish might die, he sent for its former companion, and on the two meeting they became quite happy again. Jesse gives a similar account of two gold carp.[119]

Anger is strikingly shown by many fish, and notoriously by sticklebacks when their territory is invaded by a neighbour. These animals display a strange instinct of appropriating to themselves a certain part of the tank in which they may be confined, and furiously attacking any other stickleback which may presume to cross the imaginary frontier. Under such circumstances of provocation I have seen the whole animal change colour, and, darting at the trespasser, show rage and fury in every movement. Of course, here, as elsewhere, it is impossible to be sure how far apparent expression of an emotion is due to the presence of that mental state which we recognise as the emotion in ourselves; but still the best guide we have to follow is that of apparent expression.

Following this principle, we are also entitled to attribute to fish the emotions conducive to play; for nothing can well be more expressive of sportive glee than many of their movements. As for jealousy, the fights of many male fish for the possession of females constitutes evidence of emotion which would be called by this name in the higher animals. Schneider, in his recent work already often quoted, says that he has observed a male fish (Labrus) show jealousy only towards other individual males of his own species—chasing these away from the neighbourhood of his female, but not objecting to the approach of fish of other species.

Curiosity is shown by the readiness, or even eagerness, with which fish will approach to examine any unfamiliar object. So much is this the case that fishermen, like hunters, sometimes trade upon this faculty:—

And the fisher, with his lamp
And spear, about the low rocks damp
Crept, and struck the fish which came
To worship the delusive flame.[120]

Stephenson, the engineer, on sinking lighted lanterns in the water, also found that fish were attracted to them.[121]

Special Habits.

As curious instances of special instincts in fish we may notice the well-known habit of the angler (Lophius piscator), which conceals itself in mud and seaweed, while waving in the water certain filaments with which it is provided above its snout. Other fish, attracted by these moving objects, approach, and are thereupon seized by the angler. We must also allude to the Chelmon rostratus, which shoots its prey by means of a drop of water projected from the mouth with considerable force and unerring aim. The mark thus shot at is always some small object, such as a fly, at rest above the surface of the water, so that when suddenly hit it falls into the water.[122] This remarkable instinct can only, I think, have originated as a primordially intentional adjustment, and as such shows a high degree of intelligence on the part of these fishes' ancestors. Moreover, the wonderful co-ordination of sight and muscular movements required to judge the distance, to make due allowance for refraction, and to aim correctly, shows that the existing representatives are not unworthy of their ancestors.

Several species of fish in different parts of the world have the habit of quitting pools which are about to dry up, and taking excursions across country in search of more abundant water. Eels have this habit, and perform their migrations by night. Dr. Hancock, in the 'Zoological Journal,' gives an account of a species of Doras, the individuals of which are about a foot in length, and travel by night in large shoals, or 'droves,' when thus searching for water. A strong serrated arm constitutes the first ray of the pectoral fin; and, using this as a kind of foot, the animal pushes itself forward by means of its tail, thus moving nearly as fast as a man can walk. Another migrating fish (Hydrargzra) was found by thousands in the fresh waters of Carolina by Bosc. It travels by leaps, and, according to Bosc, always directs itself towards the nearest water, although he purposely placed them so that they could not see it.

But perhaps the strangest among this class of habits is that of the climbing perch (Perca scandens), first discovered by Daldorff in Tranquebar; for this animal not only creeps over land, but even climbs the fan palm in search of certain Crustacea which form its food. In climbing it uses its open gill-covers as hands wherewith to suspend itself, while it deflects its tail laterally upwards so as to bring to bear upon the bark certain little spines with which its anal fin is provided; it then pushes itself upwards by straightening the tail, while it closes the gill-covers not to prevent progress, and so on. Sir E. Tennent, however, without disputing the evidence that these fish do climb trees, says,—

The probability is, as suggested by Buchanan, that the ascent which was witnessed by Daldorff was accidental, and ought not to be regarded as the habit of the animal.[123]

A great number of species of fish perform migrations. In relation to intelligence, the most interesting of these is the migration of salmon, which annually leave the sea to spawn in rivers, though there is some doubt whether the same individuals spawn every year. There is no doubt, however, that the same individuals frequently, though not invariably, revisit the same rivers for their successive spawnings. This fact may be due either to the remembrance of locality, similar to that which is unquestionably manifested by birds, or to the salmon not swimming far along the coast during other seasons of the year, and therefore in the spawning season when seeking a river happening to hit upon the same one. The latter hypothesis is one which Mr. Herbert Spencer tells me he is inclined to adopt, and, being a salmon-fisher, he has paid attention to the subject. He informs me of an observation by a friend of his own, who saw a salmon, when about to spawn, swimming along the coast-line, and all round a boathouse, apparently seeking any stream that it might first encounter.

The distances up rivers to which salmon will swim in the spawning season is no less surprising than the energy with which they perform the feat, and the determination with which they overcome all obstacles. They reach Bohemia by the Elbe, Switzerland by the Rhine, and, which is much more wonderful, the Cordilleras of America by the Maragnon.

They employ only three months in ascending to the sources of the Maragnon (a journey of 3,000 miles), the current of which is remarkably rapid, which is at the rate of nearly forty miles a day; in a smooth stream or lake their progress would increase in a fourfold ratio. Their tail is a very powerful organ, and its muscles have wonderful energy; by placing it in their mouths they make of it a very elastic spring, for letting it go with violence they raise themselves in the air to the height of from twelve to fifteen feet, and so clear the cataract that impedes their course: if they fail in their first attempt, they continue their efforts till they have accomplished it.[124]

General Intelligence.

With reference to the general intelligence of fish, allusion may first be made to their marked increase of wariness in waters which are much fished. This shows no small degree of intelligence, for the caution is proved to be the result of observation by the fact that young trout under such circumstances are less wary than old ones. Moreover, many fish will abandon old haunts when much disturbed. Again, according to Kirby, the carp thrusts itself into the mud in order that the net may pass over it, or, if the bottom be stony, makes great leaps to clear it.

At the Andaman Islands fish are captured by the convicts by means of weirs fixed across the openings of creeks. After existing a week or so, it is observed that captures invariably cease; and it is believed that such is due to barnacles, &c., clustering on to the wood of which they are composed. It does not seem improbable that the fish have learned to avoid a locality out of terror at those which enter but do not again return.[125]

LacepÈde[126] relates that some fish, which had been kept for many years in a basin of the Tuileries, would come when called by their names. Probably it was the sound of the voice and not the articulate words to which they responded; for LacepÈde also relates that in many parts of Germany trout, carp, and tench were summoned to their food by the sound of a bell; and the same thing has been recorded of various fish in various localities, notably by Sir Joseph Banks, who used to collect his fish by sounding a bell.[127]

In 'Nature' (vol. xi., p. 48) Mr. Mitchell gives the following instance of intelligence on the part of a small perch. Having one day disturbed its nest full of young fry, Mr. Mitchell next day went to look for the nest; 'but we searched in vain for the fish and her young. At length, a few yards further up stream, we discovered the parent guarding her fry with jealous care in a cavity scooped out of the coarse sand..... This is the first and only instance that has come under my notice of a fish watching over her young, and conveying them, when threatened with danger, to some other place.'

In 'Nature' (December 19, 1878) there is also published a communication which was made by Mr. J. Faraday to the Manchester Anglers' Association, concerning a skate which he observed in the aquarium of that town:—

A morsel of food thrown into the tank fell directly in an angle formed by the glass front and the bottom. The skate, a large example, made several vain attempts to seize the food, owing to its mouth being on the underside of its head and the food being close to the glass. He lay quite still for a while as though thinking, then suddenly raised himself into a slanting posture, the head inclined upwards, and the under surface of the body towards the food, when he waved his broad expanse of fins, thus creating an upward current or wave in the water, which lifted the food from its position and carried it straight to his mouth.

It will be observed, however, that this observation is practically worthless, from the observer having neglected to repeat the conditions in order to show that the movements of the fish were not, in their adaptation to these circumstances, purely accidental. Therefore I should not have alluded to this observation, had I not found that it has been quoted by several writers as a remarkable display of intelligence on the part of the fish.

I must not take leave of this class without making some allusion to the alleged habits of the so-called 'pilot-fish,' and also to those of 'thresher' and 'sword-fish.' I class these widely different habits together because they are alike in being dubious; different observers give different accounts, and therefore, until more information is forthcoming, we must suspend our judgment with regard to the habits in question. The following describes what these habits are believed by many observers to be.

Captain Richards, R.N., says that he saw a blue shark following a bait which was thrown out to him from the ship. The shark, which was attended by four pilot-fish, repeatedly approached the bait; but every time he did so one of the latter rushed in and prevented him. After a time the shark swam away; but when he had gone a considerable distance, he turned back again, swam quickly after the vessel, and before the pilot-fish could overtake him, seized the bait and was caught. While hoisting him on board, one of the pilots was seen to cling to his side until above water, when it dropped off. All the pilots then swam about for a time, as if searching for their friend, 'with every apparent mark of anxiety and distress.'[128] Colonel Smith fully corroborates this observation; but Mr. Geoffrey, on the other hand, saw a pilot-fish take great pains to bring a shark to the bait.[129] Probably the truth is that the pilot-fish attend the shark in order to obtain the crumbs that fall from his feasts, and that the cases in which they appear to prevent his taking the bait are without any psychological significance.

With regard to the alleged co-operation of the threshing and sword-fish in the destruction of whales, all that can be said is that the statements, although antecedently improbable, are sufficient in number not to be ignored. Mr. Day appears to accept the evidence as adequate, and gives the following cases:—

Captain Arn, in a voyage to Memel in the Baltic, gives the following interesting narrative:—One morning during a calm, when near the Hebrides, all hands were called up at 2 A.M. to witness a battle between several of the fish called threshers or fox-sharks (Alopecias vulpes), and some sword-fish on one side, and an enormous whale on the other. It was in the middle of the summer; and the weather being clear, and the fish close to the vessel, we had a fine opportunity of witnessing the contest. As soon as the whale's back appeared above the water, the threshers springing several yards into the air descended with great violence upon the object of their rancour, and inflicted upon him the most severe slaps with their long tails, the sounds of which resembled the reports of muskets fired at a distance. The sword-fish in their turn attacked the distressed whale, stabbing from below: and thus beset on all sides and wounded, when the poor creature appeared, the water around him was dyed with blood. In this manner they continued tormenting and wounding him for many hours, until we lost sight of him; and I have no doubt they in the end completed his destruction.

The master of a fishing-boat has recently observed that the thresher-shark serves out the whales, the sea sometimes being all blood. One whale, attacked by these fish, once took refuge under his vessel, where it lay an hour and a half without moving a fin. He also remarked having seen the threshers jump out of the water as high as the mast-head and down upon the whale, while the sword fish was wounding him from beneath, the two sorts of fish evidently acting in concert.

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