CONSERVATION OF THE HALIBUT — THOMPSON 365 



an area of 500 miles was stretched over 2,000 miles of coast from 

 Oregon to Bering Sea. 



Such a process of continued expansion did not have any limit in 

 the early days. It seemed as though the fisherman could count on a 

 continual increase in the efficiency of the vessels and on the existence 

 of new banks to which he could resort as long as this efficiency per- 

 mitted him. Depletion could be continually balanced by expansion. 

 The industry was dependent not on what machinery it possessed but 

 upon the constant addition to that machinery. 



But the fisheries of the sea are not inexhaustible in extent, and in 

 none of the great fisheries has this recently been so clear as in th^ 

 case of the halibut. It is possible to show that the commercial fishery 

 has extended into almost every extreme of the distribution of the 

 halibut. 



One of the steps taken by the Commission was to study the occur- 

 rence of halibut throughout the world in correlation with its environ- 

 ment, because this seemed to define the distribution.^ 



For many years scientists had been collecting data on the currents 

 of the ocean and the temperatures of the waters; indeed, better 

 records were available for such things and for the distribution of 

 many smaller animals and plants than were available for the halibut. 

 Nevertheless, by careful inquiry the distribution of halibut was 

 plotted with sufficient exactness to show that it was taken in waters 

 where the temperature was largely between 3° and 8° C. Whether 

 temperature is the important factor is not yet known, but at all 

 events it is either temperature or associated ph^^^sical conditions. 



The distribution of waters of these particular temperatures, and 

 hence of the halibut banks, is a rather remarkable one. In the At- 

 lantic the cold Arctic water meets the warm Atlantic water in 

 the passages lying between North America and Greenland, between 

 Greenland and Iceland, and between Iceland and the Faroes. And 

 the warmer water follows the right-hand, eastern, side of the Nor- 



*The halibut had until 1904 been regarded as a circumpolnr species, common to Atlantic 

 and Pacific. In that year P. Schmidt described the halibut of the OI<hotsk Sea (speci- 

 mens from Aniva Bay, Salchalin Island) as a distinct species, Hippoglossns stenolepis, 

 distinguished from the Atlantic halibut, H. Jiippof/lossus (Linnaeus), by narrower scales, 

 the manner in which they are set in the skin, the number of fin-rays, and general shape 

 of the body. In 1929 he (U. S. S. R., Acad. Sci., C. R., ser. A, vol. 8, pp. 202-208, 1930) 

 compared specimens from Japan, P.ering Sea, and Vancouver Island, and stated that they 

 ■were identical with H. stenolepis and distinct from the Atlantic form. 



Somewhat more recently Ilialmar Renslahl (Ark. Zool., vol. 22, no. 18, pp. 17-65, 

 Stockholm, 1931), examining a specimen from Petropawlowsk, Kamchatka, in comparison 

 with four specimens from Bohusliin, Sweden, expressed the opinion that it was Inter- 

 mediate between the Atlantic halibut, Hippoc/lossus hippoylossus (Linnaeus) and H. 

 stenolepis Schmidt, and he termed it " H. hippoglossus camtchaticus." 



In view of the existence of races of halibut in the Pacific, and presumably in the 

 Atlantic, which vary greatly in body proportions and other characters, it is not sur- 

 prising that halibut from the two oceans differ. The exact significance of these differences 

 and their magnitude as compared to the variation within either ocean Is a subject 

 deserving of further investigation. 



