THE NATURALIST.

Otago Witness, Issue 3662, 20 May 1924, Page 69

THE NATURALIST.

PROBLEMS OF THE SEA.

By the

Hon. G. M. Thomson M.L.C.

XX. What is the biggest problem of the eea? That depends upon one’s outlook and position. To the scientific man there are very many great and important problems all awaiting solution, and specialists to work them out. To the many millions who dwell all round the North Sea in Europe, the biggest problem is how to conserve the fish supply of Northern Europe, so as to get the maximum amount of available fish out of the sea, and at the same time to prevent the depletion of this supply. The problem is one which affects New Zealand directly as well as indirectly. To give one example of the latter statement. Within the last few years the supply of “brisling,” the small clupeid (or sprat) which constitutes the Norwegian sardine, is rapidly diminishing, and those firms in Great Britain which control the Norwegian canneries are looking rounjl for fresh fields to be exploited. New Zealand is attracting their attention. When the investigations now commenced at the Portobello Hatchery have made sufficient progress, it is likely that the question of testing the commercial possibilities of the sprats and pilchards of these southern seas may be undertaken by British capitalists. Of course, at present, even supposing that the fish are available in sufficient quantity and with sufficient regularity of appearance, the cost of labour in this country may prove prohibitive. But all these factors have yet to be ascertained. The enormous importance of the problem to Europe may be gathered from the fact that for many years past an International Council for the Exploration of the Sea has been in existence, and actively carrying on its researches. These consist in making investigations into all matters connected with the fish supply, and as a result of these, in recommending to the different governments concerned what line of action should be adopted. I have before me just now a number of the Fishery Investigations conducted by the British Ministry of Agriculture and Fisheries. Volume five, which was published in 1923, contains the following reports : 1. Report on Market Measurements in relation to the English Cod Fishery during the years 1912-14. 2. The Spawning, of Plaice in the Southern Part of the North Sea in 1913-14. 3. The Plaice Fishery and the War. 4. An Account of the Fishing Gear of England and Wales. 5. Report on Experimental hauls with Small Trawls in certain Inshore Waters off the East Coast of England. 6. Tlie Macroplankton of the Plaice Egg cruises, 1920-21. The price of this single volume, in paper covers is 63s 6d, which makes it prohibitive to most private investigators. But thanks to the good offices of Sir James Allen, High Commissioner for New Zealand, these valuable documents are giesented to the library of the Portobello ateherv. It will be noticed that three of these deal with the plaice, which, though by no means the finest, is from a commercial point of view the most important of the flat-fishes of British seas. There are about twelve species of flat-fishes in New Zealand waters, which are called by the same names as the British fish which they resemble, but they are all different species and belong to different genera. The chief British members of the family are the halibut, dab, turbot, brill, plaice, flounder, and sole. In Scotland the smaller forms of flounders were known as “flukes.” The plaice (Pleuronectes platessa) is not equal, in my opinion, to our common sand flounder as an article of food, but it is in enormous demand in London and in fill the manufacturing districts of England, and is the commonest fish sold in the fried-fish shops. Fifty years ago the average weight of the fish marketed was about three pounds, though fish of seven or eight pounds are sometimes taken. But so great has been the depletion of the sea by the thousands of trawlers which are always after the fish, that by international agreement size-limits have been imposed, and large areas of the North Sea Viave been closed to the trawlers. It would seem to us in New Zealand almost impossible to police the seas sufficiently to enforce these® restrictions, hut they appear to be well kept on the whole. The size limit is itself a difficult problem. The proposal to prohibit the landing of fish below 25ems. (10 inches) in length, would practically destroy the British inshore plaice fishery, while it would not materially protect the North Sea plaice. So close and detailed is the examination, spawning, growth, and marketing of the plaice, that it has been possible, as shown in No. 3 of the papers mentioned above, to ascertain the abundance or diminution in numbers of this species before and after the war. Even an approximate census of estimation of the total number of these fish in the north Sea has been made. During the waryears the quantity of marketable fish greatly increased, and this not only in the North Sea. hut in other fishing regions visited by British trawlers. The' authors of the Beport consider that this points to years of great natural abundance during the war. It may, however, have been largely due to the fact that the fishery could not he fully prosecuted for a period during the war and afterwards. Not only were large, numbers of the fishing fleet employed in naval operations hut considerable areas of the sea. were mined by the Germans, and it was unsafe for two or three years after the war to trawl over the areas, until they had been cleared of all mines. The fish, therefore, had comparative immunity for long

periods, and they increased both in numbers and size. The conditions have now almost reverted to those which prevailed before the war. Among many important results of this piece of research are two recommendations of an international character. One is the transplantation of small fish from coastal grounds to the Dogger Bank, which has already been carried out on a small scale experimentally by Denmark. This is a perfectly practicable measure, and carried out on a big enough scale, it would replenish the depleted stock of plaice on this most important fishing ground. Another is the closure of certain areas periodically to intensive fishing as the only practicable measure of a restrictive character that can he expected to yield effective protection to the plaice. In this connection it is further recommended that the delimitation of areas suitable for closure, in respect both of the gain to the plaice fisheries, and the loss of other fish, should be examined in the light of the observations carried out by Holland, Denmark and Great Britain, and in prewar years by the latter. While the occurrence, migration and growth of plaice have seemed of such importance to the International Council, that it has set up a permanent Plaice Committee to carry out the necessary investigations, and while this fish has received a great amount of attention from the British Ministry of Fisheries, there are many lines of enquiry which have been prosecuted in recent years. The herring fishery is one of great importance to Scotland and the eastern counties of England, and elaborate reports on herring trawling, on age determination from scales of young herring, and on the value of herring as food, have been published. In studies of the age, growth and development of fish, the examination of the scales is found to yield most reliable information. Papers on the subject include a “Review of the Methods of Age and Growth Determination in Fishes by means of Scales,” and a “Report on the scales of some Teleostean fish with special reference to their method of growth.” Other reports deal with market measurements in relation to the cod, and researches in mackerel, pilchards, eels, and oysters. One may gather from these facts in what direction fishery investigations are trending in the older settled parts of the world. The fish supply is. a vital question to many countries, and its investigation is now undertaken by staffs of highly-trained biologists, assisted by numerous practical fishermen. These are provided with large and well-equipped steamers and launches, elaborately furnished laboratories and libraries, and all the latest appliances that science can suggest for conducting their researches. New Zealand, which is destined one day to rank as one of the great fishery countries of the world, has hardly commenced even to know her fishes, much less to know their life-histories. We have not even a complete catalogue of our fishes, and their scientific studv is only beginning. In future, no doubt, the Government and the public will wake up to the importance of developing this great national asset. At the present time both are asleep.