CONSERVATION OF THE HALIBUT — THOMPSON 377 



or fifth month, color began to form, and the left eye began its 

 migration to the other side. As development proceeded, the left eye 

 assumed its usual place beside the other, and one side became densely 

 pigmented. The young fish then settled in shallow waters or even 

 in tide pools along the coast and became a replica of its parent, lying 

 on its blind uncolored side. 



Because of its long floating life, 5 or more months, water currents 

 were the most important feature in the life of this young fish, and 

 the Commission necessarily undertook studies of these currents, 

 because in this remote corner of the Pacific very little had been done. 



On the coasts of British Columbia and Alaska a great many glass 

 floats or net buoys are found bearing Japanese characters. These, 

 used by Japanese fishermen, are frequently lost and are carried by 

 the Japanese current across the Pacific. The Japanese current on 

 reaching our coast divides into two branches, one eddying to the 

 north through the Gulf of Alaska, the other passing to the south 

 and offshore into the influence of the California trades, which carry 

 it to the Hawaiian Islands. The separation of the Japanese current 

 into its two branches takes place at about the northern end of Van- 

 couver Island in summer, south of the Washington coast in winter. 

 It was studied by two methods. 



One of these methods was by means of drift bottles, which car- 

 ried within them a numbered card asking for their return to the 

 commission. They were liberated off the coasts of Washington and 

 British Columbia at the point where the Japanese current was ex- 

 pected to divide, and at various points in the Gulf of Alaska. An 

 astonishing number of these bottles were recovered both from the 

 Washington coasts and from the sparsely inhabited coasts of Alaska, 

 showing clearly the currents and the great eddy that sweeps to the 

 westward through the Gulf of Alaska in both summer and winter. 



These indicated the surface currents only. Some other method had 

 to be found that would prove that the deeper layers in which the 

 young halibut were found were also moving. A method had been 

 worked out by the Norwegians and applied by the International Ice 

 Patrol over the Grand Banks in the Atlantic whereby the direction 

 and speed of a current could be determined from a knowledge of 

 the temperature, salinity, and depth of the waters. The use of this 

 method depends upon the fact that a current is deflected to the right 

 by influence of the earth's rotation. Its speed and direction can 

 therefore be determined by the internal distortion of the natural 

 levels that the layers of more or less dense water would otherwise 

 attain. These methods were applied in the Gulf of Alaska confirm- 

 ing the evidence of the surface currents as to the point of division of 

 the Japanese Stream and the formation of a great eddy flowing west- 

 ward through the Gulf of Alaska. 



