Art. XVI.—Effect of Cold on Fishes.

Transactions and Proceedings of the Royal Society of New Zealand, Volume 16, 1883, Page 275

Art. XVI.—Effect of Cold on Fishes. By Neil Heath. [Read before the Auckland Institute, 2nd July, 1883.] It is asserted by many people that, though shallow rivers and fish-ponds have been occasionally converted into solid ice in countries where the winters are protracted and severe, all the imprisoned fish have not been destroyed, but that, when the ice had completely thawed, many of them have been found to be in possession of their usual health. Imprisonment in their ice-bound home had thus done them no harm. Dead to all appearance they might have been, but they were only asleep—hybernating, and, like many animals that pass the long winters in a state of lethargy, they would, when freed from life-suspending causes, recover their usual animation. It is not an easy matter to ascertain that, in such rivers and ponds, the whole of the water is unquestionably frozen, and, obviously, the acceptance of the truth of such an assertion must be held over until we can prove to demonstration that the waters were completely frozen, and that the fish, which are said to have come again to life, had actually been imprisoned in the solid ice. It struck me that as the “Mataura,” with her freezing chamber, was lying at the wharf, an effort might be made to procure a few facts that would help us to arrive at a satisfactory conclusion as to the truth or otherwise of the assertion. The “Mataura” lay here freezing her cargo of sheep

for the London market, and why should she not, if intense and continuous cold only suspended the life of the fish, bear away to old England slabs of ice holding in their rigid embrace numerous specimens of fish hitherto unknown in that land, which only required to be thawed in its rivers that there they might live and thrive! Why put ourselves to the great trouble, anxiety and expense, of bringing out to our New Zealand home ova that have hitherto proved to be dainty morsels for the discriminating natives of our waters! Could life be suspended, then fish of all kinds, and from all countries, and arrived at a vigorous maturity, could, when allowed to recover from their prolonged sleep, do successful battle with eels and other foes in asserting their rightful claim to a fair share of all the good things in our rivers. It would be good for us, if experience could demonstrate that such a procedure must necessarily prove successful if conducted with ordinary care. Our fish markets, that are at present distinguished by their absence, would then become realities and sources of comfortable incomes for energetic and enterprising men, and the gentle disciples of Izaak Walton would find abundant employment for their rods and tackle that are at present laid regretfully aside. It is my duty to place before you a very brief statement of the steps that have been taken to prove, or to disprove, that fishes can return to life and energy after imprisonment in ice. Captain Greenstreet, of the Mataura, and his enthusiastic chief officer, cordially helped me to make the best use I could of the freezing chamber in their vessel, and in it were placed two pannikins, the one containing a saltwater fish in salt water, the other a goldfish in fresh. At the same time (10 a.m.) two other pannikins were placed in the “shoot,” the coldest part of the freezing apparatus, the one containing a salt-water fish, and the other not a gold- but a silverfish. The water in these vessels was at the ordinary temperature. The cold in the shoot being many degrees below zero. F., it did not take long to convert the water into ice, and at the end of an hour and a half, I was satisfied that all the water—the salt and the fresh—had become solid, and that the two fishes were as hard and firm as the sheep that were hanging in the freezing chamber. Both pannikins were then removed and placed in two tubs filled with water at the ordinary temperature—the one containing salt water for the salt-water fish, the other fresh for the silver one. In a short time the heat of the water in the tubs found its way to the surface of the ice in contact with the interior of the pannikins, and the blocks becoming in consequence reduced in bulk the two parted, the former finding its way to the bottom, the latter remaining at the surface. On examining these blocks of ice it was observed that both fishes must have retired from the surface of the

water towards the bottom during the process of congelation, and that about half an inch of the lower part of the silver fish had actually rested on the bottom of the vessel, and must therefore have been outside the ice. The other fish was entirely surrounded. The appearance of each was identical, they both lay on their side, the head was higher than the tail, the distended gills were filled with ice, and the iris of the eyes had neither dilated nor contracted but the aqueous humour was apparently frozen. The rays of light no longer penetrated to the retinæ, and the eyes presented the appearance of balls of opaque ice. It was an anxious time to those gentlemen who joined me in watching the interesting prisoners as they came out from their icy shroud. The silver fish was the first to be free, and it was observed that at the moment when the fin near the gill was freed from all restraint the little organ commenced to move gently, very gently, so much so that it was impossible to say whether the movement motion was due to the parting of the ice, or to the action of the muscles of the animal. A few moments afterwards, however, there was no mistake about the matter, the fish was alive. The tail awoke to its usual activity, and, as soon as the ice had disappeared from the gills, they began to open and close, and the little fish moved about in the water languidly, dreamily, and to all appearance groping its way. Up to this time the aqueous humour of the eyes had not thawed, all was darkness to the fish, which seemed to be literally feeling its way, but soon the ice was dissolved, light entered, and the silverfish in a very short time was swimming as easily and nimbly as it now does in a glass globe in my house. Meantime, the salt-water fish was being steadily detached from the encircling ice, but the most watchful attention failed to notice any signs of returning life. When entirely free it sank to the bottom—dead. Perhaps the sudden contraction of the water at freezing point following so rapidly upon the expansion had in some way injured the fish, obviously the air-bladder had burst, for all buoyancy had departed. I cannot answer the question, “Why did the animal, which had been taken from the sunny waters of the Pacific but a few weeks previously survive an ordeal that proved fatal to one fresh from the cooler waters of the Waitemata?” A more extended and more efficient series of experiments may yet prove that, after all, the fish, which is usually classed among the cold-blooded animals, may survive imprisonment in ice. It has been suggested that even the slight injury caused by the fishing hook to the salt-water fish may have contributed to its death, but hypothesis is of small value in a case of this kind, unless it leads us to absolutely indisputable facts. During the day I paid frequent visits to the freezing chamber to see how the other prisoners were faring. The former two had been placed in the “shoot,” and consequently I had had no opportunity of observing how they

behaved as the ice gradually closed around them, but in the freezing chamber there was every facility for doing so. At 11.10 a.m. the increasing coldness of the water in the pannikins was rendering their movements less active. They glided from one side to the other, and from the surface to the bottom, but in such a manner as to leave in one's mind the impression that they anticipated something. Their attidude was that of expectancy. An hour afterwards they were apparently going to sleep, the goldfish on its side, the other in its ordinary position. The fins kept moving in a lazy manner, there was no twitching, no abrupt action. The motion reminded one of the vibration of a wire that is slowly but surely coming to rest. The eyes were clear, and to all appearances a deep and placid sleep was falling stealthily upon them. Two hours afterwards they were in the same position, but now there was no movement, the ice was seen advancing upon them like an attacking army with bayonets in front. Some of the spikes of ice had already reached parts of the bodies, and catching the light from the candle produced a strikingly beautiful combination of colour. In fact the two creatures were sleeping in the light of a gorgeous sunset. After eight hours' exposure to the temperature of the freezing chamber, and two more to the much lower temperature of the snow-box, another part of the freezing apparatus, and feeling convinced that the ice was solid throughout, I removed the pannikins to the thawing tubs and sat down to watch for any indication of life. But, alas for this experiment, there were no signs of returning vitality. When freed from the ice, the salt-water fish kept floating about for a short time in the same position as that it occupied when inside the block of ice, and then slowly sank to the bottom, while the goldfish on being freed continued to float for upwards of an hour during which I sat watching it. Next morning it was still floating, not erect like the other, but on its side with the tail slightly depressed. The fish was apparently dead. At night it maintained the same position, and I concluded that life had gone from my goldfish for ever. Such is a brief statement of what was done in a few hours of leisure. I have made it in the hope that others who have more time at their disposal and more enlarged facilities for carrying out a series of experiments will proceed with the investigation, and perhaps some new and valuable information regarding the conditions of life may crown their efforts. The deeply-pathetic words that so briefly told the fate of the brave men who accompanied Franklin are, with some slight modification, applicable to my two fishes:—“When they lay, they slept; and when they slept, then they died.”