August 26, 1920] 



NATURE 



823 



Uescribed as Lopholatilus chamaeleontic&ps , was dis- 

 covered in 1879 by one of the United States tishing 

 schooners to the south of Nantucket, near the 

 loo-fathom line. Several thousand pounds' weight 

 was caught, and the matter was duly investigated by 

 the United States Fish Commission. For a couple of 

 years after that the fish was brought to market in 

 quantity, and then something unusual happened at 

 the bottom of the sea, and in 1882 millions of dead 

 tile-fish were found floating on the surface over an 

 area of thousands of square miles. The schooner 

 Navarino sailed for two days and a night through at 

 least 150 miles of sea thickly covered, so 'far as the 

 eye could reach, with dead fish, estimated at 256,000 to 

 the square mile. The Fish Commission sent a vessel 

 to fish systematically over the grounds known as the 

 "Gulf Stream slope," where the tile-fish had been 

 so abundant during the two previous years, but she 

 did not catch a single fish, and the associated sub- 

 tropical invertebrate fauna was also practically 

 obliterated. 



This wholesale destruction was attributed by the 

 American oceanographers to a sudden change in the 

 temperature of the water at the bottom, due in all 

 probability to a withdrawal southwards of the warm 

 Gulf Stream water and a flooding of the area by the 

 told Labrador current. 



I am indebted to Dr. C. H. Townsend, director of 

 the celebrated New York Aquarium, for the latest 

 information in regard to the reappearance in quantity 

 of this valuable fish upon the old fishing-grounds of 

 Nantucket and Long Island, at about 100 miles from 

 the coast to the east and south-east of New York. 

 It is believed that the tile-fish • is now abundant 

 enough to maintain an important fishery, which will 

 add an excellent food-fish to the markets of the United 

 States. It is easily caught with lines at all seasons 

 of the year, and reaches a length of more than 3 ft. 

 and a weight of 40-50 lb. During July, 1915, the 

 product of the fishery was about 2,500,000 lb. weight, 

 valued at 55,000 dollars, and in the first few months 

 of 1917 the catch was 4,500,000 lb., for which the 

 fishermen received 247,000 dollars. 



We can scarcely hope in European seas to add new 

 food-fishes to our markets, but much may be done 

 through the co-operation of scientific investigators of 

 the ocean with the administrative departments to 

 bring about a more rational conservation and exploita- 

 tion of the national fisheries. 



Earlier in this address I referred to the pioneer work 

 of the distinguished Manx naturalist. Prof. Edward 

 Forbes. There are many of his writings and of his 

 lectures to which I have no space to refer which have 

 points of oceanographic interest. Take this, for 

 example, in reference to our national sea-fisheries. 

 We find him in 1847 writing to a friend : " On Friday 

 night I lectured at the Royal Institution. The sub- 

 ject was the bearing of submarine researches and dis- 

 tribution matters on the fishery question. I pitched 

 into Government mismanagement pretty strong, and 

 made a fair case of it. It seems to me that at a time 

 when half the country is starving we are utterly neg- 

 lecting or grossly mismanaging great sources of 

 wealth and food. . . . Were I a rich man I would 

 make the subject a hobby for the good of the country 

 and for the better proving that the true interests of 

 Government are those linked with and inseparable 

 from Science." We must still cordially approve of 

 these last words, while recognising that our Govern- 

 ment Department of Fisheries is now being organised 

 on better lines, is itself carrying on scientific work of 

 national importance, and is, I am happy to think, in 

 complete sympathy with the work of independent 

 scientific investigators of the sea and desirous of closer 



NO. 2652, VOL. 105] 



co-operation with university laboratories and biological 1 

 stations. ] 



During recent j^ars one of the most important and 

 most frequently discussed of applications of fisheries i 

 investigation has been the productivity of the trawling ; 

 grounds, and especially those of the North Sea. It 

 has been generally agreed that the enormous increase i 

 of fishing power during the last forty years or so has ^ 

 reduced the number of large plaice, so that the ; 

 average size of that fish caught in our home waters ■ 

 has become smaller, although the total number of 

 plaice landed had continued to increase up to the year 

 of the outbreak of war. Since then, from 19 14 to 

 19 19, there has of necessity been what may be 

 described as the most gigantic experiment ever seen ; 

 in the closing of extensive fishing-grounds. It is still 

 too early to say with any certainty exactly what the 

 results of that experiment have been, although some j 

 indications of an increase of the fish population in ■ 

 certain areas have been recorded. For example, the ' 

 Danes, A. C. Johansen and Kirstine Smith, find that ' 

 large plaice landed in Denmark are now more abun- ' 

 dant, and they attribute this to a reversal of the pre- 

 war tendency, due to less intensive fishing. But Dr. 

 James Johnstone has pointed out that there is some 

 evidence of a natural i)eriodicity in abundance of such 1 

 fish, and that the results noticed may represent phases ! 

 in a cyclic change. If the periodicity noted in Liver- ■ 

 pool Bay^* holds good for other grounds, it will be J 

 necessary in any comparison of pre-war and post-war | 

 statistics to take this natural variation in abundance j 

 into very careful consideration. j 



In the application of oceanographic investigations ; 

 to sea-fisheries problems one ultimate aim, whether 

 frankly admitted or not, must be to obtain some kind 

 of a rough approximation to a census or valuation 

 of the sea — of the fishes that form the food of man, ! 

 of the lower animals of the sea-bottom on which many ; 

 of the fishes feed, and of the planktonic contents of 

 the upper waters which form the ultimate organised 

 food of the sea — and many attempts have been made ■ 

 in different ways to attain the desired end. I 



Our knowledge of the number of animals living in ' 

 different regions of the sea is for the most part rela- 

 tive only. We know that one haul of the dredge is j 

 larger than another, or that one locality seems richer 

 than another, but we have very little information j 

 as to the actual numbers of any kind of animal per '■ 

 square foot or per acre in the sea. Hensen, as we 

 have seen, attempted to estimate the number of food- 

 fishes in the North Sea from the number of their l 

 eggs caught in a comparatively small series of hauls ^ 

 of the tow^-net, but the data were probably quite in- 

 sufficient and the conclusions may be erroneous. It is | 

 an interesting speculation to. which we cannot attach ] 

 any economic importance. Heincke says of it : "This i 

 method apf>ears theoretically feasible, but presents in 

 practice so many serious difficulties that no positive 

 results of real value have as yet been obtained." ; 



All biologists must agree that to determine even ' 

 approximately the number of individuals of any par- 

 ticular species living in a known area is a contribution 

 to knowledge which may be of great economic value 

 in the case of the edible fishes, but it may be doubted ; 

 whether Hensen 's methods, even with greatly in- ' 

 creased data, will ever give us the required informa- ' 

 tion. Petersen's method, of setting free marked plaice 

 and then assuming that the proportion of these re- \ 

 caught is to the total number marked as the fisher- ) 

 men's catch in the same district is to the total popula- j 

 tion, will hold good only in circumscribed areas l 

 where there is practically no migration and the fish ] 



*' See Johnstone, Report Lanoc Seft^FUh. Lab. for 1917, p. 60 ; and 

 Daniel, Report for 1919, p. 51. 



