HARVEST OF THE SEA

Evening Post, Volume CXI, Issue 36, 11 February 1926, Page 7

HARVEST OF THE SEA

VISIT OF FISH EXPERT DANISH SCIENTIST'S INQUIRIES in new zealand mystek't of the eel. It is only in recent years that the importance of correct understanding of the life history of fishes has been recognised. Such knowledge is necessary for the rational exploitation and administration of the commercial sea fish- . ' cries. Of recent 'years, great progress has been made by tie fishery departments of European countries and of the United States in investigations for the elucidation of the problems connected with the harvests of the sea. One of the foremost of European authorities on the science of life in the sea is Dr. J. Schmidt, of Denmark, who , is now visiting Wellington. \ Freshwater eels to the ordinary angler are merely squirming, slimy undesirables which' sometimes find his line,: and which are guilty of preying upon the eggs and young of the estimable trout species. To the original inhabitants of New Zealand, eels formed a very -valuable and' delectable food supply, and eels are still regarded by the Maoris and sought by 'them, though not perhaps ' with the same skin sad assiduity as in the old days. SOLVING A iIYSTEEY. To scientists, however, the eel is above sJI a problem. For a long time it was a^mystery, and the efforts of j the older ichthyologists to shed light on its occurrence only served to obscure the facts' of its natural history. The mystery of its life history was cleared up and the problem of the oel was very largely solved by a monumraital research on the part of a- Danish biologist, Dr. J. Schmidt, of the Carlsberg Laboratory, Copenhagen, who arrived in Wellington by the Ulimaroa yesterday. When the International Council forthe Investigation of Sea Fisheries was established by the countries of Western Europe, Dr. Scthmidt was one of its foremost.experts, and his earliest work was carried put between 1900 and 1907 in connection with the spawning, growth, and migrations of the, more important food fishes of the Western European seas such as the cod, ling, and plaice. MIGRATIONS OF FISH. Dr. Schmidt was the first to demonstrate the great importance of the phy-' sical conditions in sea water, > especially the depth, temperature, and salinity; in determining the places at which different species of fish congregate to spawn. He showed how the migrations of cod and plaice were governed by the necessity to .move into water of a certain temperature and degree of saltness to ensure proper conditions for the satisfactory hatching of the floating eggs and the, survival -of the fry. In Denmark the fresh-water eel is of considerable commercial importance, the market value of a single year's landings of this species being equal to that of all the fish marketed in New Zealand at the same time. Of considerable interest to the Fisheries Department and Government of Denmark,, therefore, was the question as to the origtyi of the stocks of, eels which occurred in their fresh waters; and especially was it desirable to know how far the fisheries could be exploited without jeopardising the stock necessary for the breeding of supplies for the future. It was known that large mature eels descended the rivers in great numbers at certain seasons,'and that shoals of young eels, commonly termed elvers at this stage, ran up front the mouths to 'the upper waters of river systems with equal regularity. Formerly it was believed thta the adult eels spawned in tidal estuaries or near the mouths of rivers, and if this were the ease it was obviously unwise to catch too great number of the parent fish in their downward passage. SOME CUBIOXTS FACTS. Dr. Schmidt's special investigations having for their object the tracking of the fresh-water eels to their spawning grounds were commenced in 1904, and in the first year by means of voyages in the Danish investigation steamer Thor, he captured specimens of many of the early stages of this species, on their migration towards Europe, from the -mid-Atlantic regions. He cams to the conclusimi that in order to be able to propagate, the species demands certain external conditions, chiefly great depths, with' high temperature and salinity of water. These considerations have been proved to explain the long migrations of European eels to the mid-Atlantic depths to spawn. The return migration of the larval stages has been traced by the eaptore of hundmds of specimens at different stages of development to the elver stage, at which point the eel fry enter the rivers of Western Europe. VIBXT TO.NEW ZEALAND. Having cleared up the question of the identity of the two species of Atlantic eels, Dr. Schmidt has extended his investigations to the Pacific Ocean, where more species, are known. Two species, at least, are common in New Zealand and Eastern Australia, and it is with the object of gathering further information about these that Dr. Schmidt has made his present visit. Hit next objective is Tahiti, where there are as many as five species known. Dr. Schmidt, who is accompanied by his wife and Miss Oertrnd Ostenfeld, daughter of Dr. C. E. H. Ostenf eld, a well-known marine biologist of Copenhagen, were met on arrival here . by Mr. A. E. Hefford, Fisheries Expert, Marine Department, and Mr. J. Andersen. Dr. Schmidt will spend about a week in Wellington, and then goes on to Auckland to pursue his inquiries. ......