HARVEST OF THE SEA

Evening Post, Volume CXI, Issue 36, 11 February 1926, Page 10

HARVEST OF THE SEA

VISIT OF FISH EXPERT

DANISH SCIENTIST'S INQUIRIES

IN NEW ZEALAND

MYSTERY OF THE EEL,

r It ia only in recent years that the importance of correct under- ' standing of the life history of fishes has been recognised. Such • knowledge: is necessary for the rational exploitation and administration of the commercial sea fisheries. Of recent years, great progress has been made by the 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 ". en the science of life in the sea ■is Dr. J. Schmidt, of Denmark,who . is-now visiting Wellington. 1 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 npt perhaps with the same skill and assiduity as in the old days. SOLVING A MYSTERY. ! To scientists, however, the eel is above all a problem. For a long time it was a mystery, and the efforts of the older ichthyologists to shed light on its occurrence only served to obicure the facts of its natural history. The mystery of its .life history was cleared up and the problem of the eel was very largely solved by a monumental 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 for Hie 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 out 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 physical conditions in sea water, especil--ally 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 th& 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 Now Zealand at the same time. Of considerable interest to the Fisheries Pepartment and Government of Denmark, therefore, was the question as to the origin of the stocks of eels which oe-; eurred 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 from 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 months of rivers, and'if this were the case it'was obviously unwise to catch too great number of the parent fish in their downward passage. SOME CURIOUS FACTS. Tit. Schmidt's special investigations saving for their object the tracking of the fresh-water eels to their spawning grounds were commenced in 1904, and 5i 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 came to the conclusion that in order to be able to propagate, the species, demands certain external conditions, chiefly great depths, with.high temperature a.nd 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 capture of hundreds of specimens at different stages of development, to the elver stage, at which point the eel fry enter the rivers of Western Europe. i TOST TO NEW ZEALAND. ' Having cleared up the question of tho identity of the two species of AtUntie eels, Dr. Schmidt has extended his investigations to the Pacific Ocean, where- mere species are known. Two species, at least, are common in NewZealand and Eastern Australia, and it is with the object of gathering furthes information about these that Dr. Schmidt has made his present visit. His next objective is Tahiti, where there are as many as five species known.

Dr. Schmidt, who ig accompanied by his wife and Miss Gertrud Ostenfeld, daughter of Dr. C. E. H. Ostenfeld, a •well-known marine biologist of Copenhagen, were met on arrival here ■by-Mr. A. E. Hefford, Fisheries Expert, Marine Department, and Mr. J. Anderttn. Dr. Schmidt will sperd about a week in Wellington, and then goes on to Auckland to pursue his inquiries.