CLIMATIC TRENDS AND THE DISTRIBUTION OF MARINE ANIMALS IN 



NEW ENGLAND 



By Clyde C. Taylor, Fishery Research Biologist, Henry B. Bigelow, Oceanographer, and Herbert W. Graham, 



Fishery Research Biologist 



For many years Americans have commented on 

 an apparent warming of their climate; older people 

 have referred to the "old-fashioned winters" they 

 once knew. Climatologists long shrugged off the 

 idea as unfounded, but a melioration in climate is 

 no longer confined to the popular mind : a decided 

 trend toward warmer winters during the past 50 

 years is now well-documented. Air temperatures 

 in winter, particularly since 1910, are definitely 

 higher in higher latitudes of the Northern Hemi- 

 sphere and probably throughout the world gen- 

 erally. Glaciers have been receding and in far 

 northern latitudes, plants and land animals fol- 

 lowing the retreating ice have extended their 

 ranges northward and to higher altitudes. P'or a 

 bibliography dealing with responses of plants and 

 animals to climatic changes, the reader is referred 

 to Rapports et Proces-Verbaux des Reunions, 

 vol. 125, pp. 42-52, C'onseil Permanent Inter- 

 national I'Exploration de la Aler, Part 1, 1949. 



Warming of the oceans during periods of higher 

 air temperatures is difficult to demonstrate 

 because of the paucity of observations of sea-water 

 temperatures. Evidence shows, however, as Smed 

 (1949, 1953b) points out, that the Arctic Ocean 

 has warmed appreciably since 1921. This author 

 also presents evidence of increased water temper- 

 atures beginning in the 1920's in the North Sea 

 and in the North Atlantic from the British Isles 

 to the west coast of Greeidand. 



The warming of northern waters has been ac- 

 companied by the northward extension of many 

 marine vertebrates to the region of Iceland 

 (Fridriksson 1949) and by profound changes in the 

 fish populations around Greeidand (T;\ning 1949). 

 The development of tlie cod fisliery on tlie west 

 coast of Gicenland has been spectacular. As the 



Note.- Clyde C. Taylor ami llcrbiTl W. Graham, United States Fish 

 and Wildlite Service, Woods Hole. Mass.; Henry B. BiRelow, Museum of 

 Compi',rativ<' Zoology, Harvard I'niversity. 



Approved for publication, November 1, 1956. 



waters warmed in this area, an offshoot from the 

 Icelandic stock of cod became established and 

 now supports a substantial fishery (Jensen and 

 Hansen, 1931). In the years 1911 to 1921, the 

 West Greenland cod fishery produced less than 

 500 tons a year. In 1925, the catch doubled and 

 thereafter continued to increase. In 1952, some 

 252,758 metric tons of cod were landed from the 

 West Greenland area (International Gommission 

 for the Northwest Atlantic Fisheries, 1954, 

 table 2, p. 28). The fishery now reaches 300 

 nautical miles farther north than formerly. The 

 Eskimos in some areas who had never seen a cod 

 in 1924 are now busily occupied in the cod fishery, 

 whereas they formerly were seal hunters. 



Although temperature is only one factor in the 

 ecological complex determining the presence or 

 abundance of a species, in high latitudes temper- 

 ature may in some instances be the sole limiting 

 factor and have a direct effect on distribution. 

 Thus, cod show a definite response to low tempera- 

 tures and their northward extension is probably 

 determined by temperature alone. The abundance 

 of cod in the Greenland area may be related to 

 temperature in a somewhat less-direct manner. 

 Hermann (1953) has shown that the strength of 

 cod year-classes in Greenlaiul waters has a very 

 high correlation witli bottom temperatures in 

 June. Thus, temperature in some way affects 

 survival of whole populations of young fish, per- 

 liaps through affecting their food supply or rate of 

 growth and, conseciuently, their resistance to 

 adverse enviromnental conditions. 



The warming of arctic areas and the accompany- 

 ing ecological changes have been so marked and 

 so well-documented tliat it seems reasonable to 

 suppose that similar changes liave taken place, 

 although perliaps on a smaller scale, in more 

 southern latitudes. It is the purpose of this paper 

 to examine temperature fluctuations in recent 

 years, and to explore the relations which may 



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