MARINE NATURE NOTES

Otago Daily Times, Issue 23221, 19 June 1937, Page 3

MARINE NATURE NOTES

Written for the Otago Daily Times By David H. Graham, F.R.M.S., F.Z.S. COLLECTORS’ SPECIMENS Some time ago Mr J. Ballard sent me a specimen of a fish caught in Blueskin Bay by a trawler and asked for some information as to its habits. He added that it is seldom seen on the market. This fish is known as the lamprey and is often found in freshwater creeks and rivers, but to catch one in the sea is uncommon, although it is well known in scientific circles that the lamprey spends part of its life in the ocean. It may be that it is not caught in the sea because it does not take bait and is too small to be caught in the trawl net. One specimen was caught oil WicklifTe Bay in 1931 and sent to me, and one other was taken from the stomach of a ling by me.

The specimen forwarded to me Is 19 inches in length and is in what is known as the velasia or middle stage of its life. It is in this stage that most of its growth takes place. It is shaped somewhat like an eel; the back and top parts are decidedly bluish, while the lower parts are silvery white. There are no distinct jaws in the lamprey as in other fish, but a cartilaginous ring supports the lips oL the suctorial mouth,-which contains a rasping muscular tongue. Nor is there a true backbone as in ordinary fish, and on this account it is not a true fish, but is known to scientists as a fishlike animal, and we pay it a compliment by including it among our list of fishes. The skeleton is cartilaginous, the skull imperfectly roofed, the spinal cord flattened._ The roots of the nerves do not unite, and there is no nervous system. From the floor of the throat a groove is seen which apparently agrees with the thyroid of higher vertebrates. The gut is straight and simple, but with a liver without a pancreas. For the respiratory system there are seven gill pouches which open directly with the exterior of each side and also communicate indirectly with the gullet. The eyes are well developed but there is some doubt as to whether the eyeball moves. There is one single nostril immediately above and between the eyes. The most curious feature is the mouth in that in life it is round, but once the fish is preserved it assumes a slit-shaped appearance. There is no bottom jaw, the creature relying on its power of suction to obtain its food, from any fish to which it can adhere. The so-called mouth is studded with horny teeth, but the tongue also has teeth and works them to and fro like a piston and thus boires its way through the skin and flesh of its victim to obtain its meal of blood and juices. It is this power of suction that often causes the loss of its life for not only does it adhere to fish but it will suck on to stones and other objects, and observers in England have been known to catch hold of a lamprey while it was attached to a stone and lift it out of the water. A lamprey caught in a seine or trawl net usually lets go and escapes through the meshes. Lampreys allowed to attach themselves to a person’s arm could not be separated until they were lifted from the water without breaking the person’s skin. With its sucking mouth it often anchors itself to stones in the water, holding itself against the strongest current; it can climb over waterfalls and has been known to carry stones to build its nest. These habits of attaching itself to stones and fish gave it its popular name, which is from lambre (to lick), and petra (a stone). A lamprey, while attached to its victim, will have free trips to any part of the sea its host visits.

The nesting habit of lampreys 'is most interesting and entails a good deal of labour. When the lamprey arrives at a suitable place in a shoal for a spawning nest, a beginning is made to, move stones with the mouth from the centre to the margin of an area one or two feet in diameter. A great many stones are moved and placed in this way, more especially at the upper edge. They are cleaned free ot dirt or sediment by being moved and by being fanned with the tail When the proper condition of sand is found at the bottom of the basin formed, it is ready to be used as a spawning nest. For some unknown reason many spawning nests are begun and abandoned. It may be that the lampreys do not find that the requisite conditions supply all their needs and fulfil all conditions for ideal sites. There are three distinct stages in the life of the lamprey. The young are hatched in rivers and creeks where they can be found in wet, sandy patches several inches below the surface. After reaching a certain stage these young lampreys descend the river to the sea and begin a life of feeding on fish. After some unknown period of time in which they develop and grow to maturity, they ascend the rivers to spawn and afterwards die. The Maori is very fond of lamprey flesh, and the fate of an early English king, who was a worthy son of William the Conqueror and a valiant warrior, but died ingloriously of a surfeit of lampreys, is sufficient evidence that they arc palatable. Mrs Wilson, ot Stewart Island, nas sent a specimen of one of our several species of shellfish commonly known as pawa, but correctly called paua. It is not the true pawa or mutton fish of the early colonists, being much smaller, and in my opinion much prettier than its larger sister from which so many trinkets and ornaments are now being made This species of “ sea ear,” or paua can be distinguished from the large species by its peristome winding its way into the interior of the shell. This species does not become so covered by barnacles, limpets, and other crustaceans. The interior is very iridescent and silvery, red, blue, and green in colour, the red or pink being most noticeable. The fact of the inner surface being sculptured by the corrugations, crossed by spiral, cords, or rather the impressions from the outside, adds considerably to the play of colours This specimen received is nearly four inches in length, which is the maximum reached by this species, although the true paua grows to nearly seven inches in length. The animal of this silvery species has a yellow undersurface or foot, in distinction to the black foot of the paua It is this foot that enables it to attach itself to rocks and also to move its quarters. Mrs Wilson asks how to clean the paua. To instruct my readers how to clean these shells as seen in the jewellers’ shops is beyond the limits of this column, but the method of cleaning them for ordinary ornaments or for a shell collector’s cabinet is quite simple. To remove barnacles and calcareous incrustaceans, the best implement is a piece of sharpened wood or a penknife; but the knife requires gentle manipulation lest it damage either the shell or one’s hand. After the worst of the growths are removed, the rest can be attacked by using spirits of salts diluted with equal parts of water. Be sure to have a bowl of water handy in which to dip the shell from time to time before the acid proceeds too far Keep on giving the obstinate spots touches of acid, but always with extreme caution Then with a piece of flannel rubbed on sandstone or bath brick or even fine sand, rub the surface till the whole of the incrustaceans are gone. After this nothing else but “ elbow grease ” is required, until finally when the paua is smooth and polished a mixture of sperm oil and liquid chloroform should be used to bring up the colour. But do not expect to get the same results from this crude method as experts achieve with machinery.