96 SECTIONAL ADDRESSES 



good evidence of long-period fluctuations in fisheries, and though the 

 hydrographical changes to which they may uhimately be traced are not, 

 as it appears, the same as in the Channel, they show that major alterations 

 extending over a long term of years are by no means unusual. 



In 1925 the Norwegians discovered great numbers of cod on the banks 

 surrounding Bear Island, and ever since that year, except in 1929 when 

 ice interfered with the operations, the fishery has been maintained, many 

 trawlers visiting the banks annually to take toll of their wealth. Iverson,^® 

 from whose paper my information on this fishery is derived, states that 

 there was a former occasion when cod were plentiful in this area. That 

 was from 1873 to 1882. Between 1883 and the time when the present 

 fishery began the grounds were examined on a number of occasions, but 

 very few cod were found and the results were unprofitable. It was so 

 in 1924, the year which preceded the present period of abundance. 



Another instance is afforded by the cod fishery in West Greenland. 

 At certain times large concentrations of cod appear on this coast and 

 spread as far north as Disko Bay, affording a profitable fishery ; but after 

 a term of years their numbers suddenly decline and a protracted period 

 of scarcity follows. In 191 7 cod were found in West Greenland in great 

 abundance and the fishery on this coast has been maintained up to the 

 present day. Prior to that, as Jensen and Hansen show in their interest- 

 ing historical account, ^^ the grounds were tested on a number of occasions 

 without finding stocks of cod in marketable quantity ; but early records 

 indicate that there were at least two periods, in 1820 and in 1845-49, when 

 cod were present in great numbers. In recent years it has been found 

 that some of the cod spawn in Greenland waters, while others migrate 

 for this purpose to Iceland. Marking experiments show that there is an 

 interchange of cod across the Denmark Strait, and there is reason to 

 believe that most of the fish found on the Greenland coast during periods 

 of abundance have come from Iceland, either as fry carried in the west- 

 going current or by migration of mature fish.^^ 



To these two instances of large-scale changes in the fish population 

 in northern waters many others could be added and all are apparently 

 due to the same cause — to the fact that in recent years the entire 

 area from Greenland to Bear Island has become appreciably warmer. 

 Berg 1^ has collected much information on the effects of this rise in 

 temperature, Saemundsson ^° has given an interesting account of the 

 alterations which have occurred in the fauna of Iceland, while Stephen ^^ 

 has shown that marked changes have also taken place in the British 

 marine fauna. Berg, quoting from Schischow, gives figures of the very 



"■^ T. Iverson, Rep. Norwegian Fishery and Marine Invest., IV, no. 8 (1934). 



1' S. Jensen and P. M. Hansen, ' Investigations on the Greenland Cod,' Conseil 

 Internal. Rapp. et Proc.-Verb. des Reunions, LXXII, pp. 1-41 (1931). 



1^ E. S. Russell, ' Fish Migrations,' Biol. Reviews, XII, pp. 324-5 (1937). 



1' L. S. Berg, ' Rezente Klimaschwankungen und ihr Einfluss auf die geo- 

 graphische Verbreitung der Seefische,' Zoogeographica, III, Heft i, pp. 1-15 



(1935)- 



2" B. Saemundsson, ' Probable influence of change of temperature on the 

 marine fauna of Iceland,' Conseil Internal. Rapp. et Proc.-Verb. des Rdunions; 

 LXXXyi, no. I, pp. 1-6 (1934)- 



"^ A. C. Stephen, ' Temperature and the incidence of certain species in Western 

 European Waters,' Journ. Animal Ecology, VII, p. 125 (1938). 



