ABSTRACT 



In connection with investigations of potential albacore tuna fishing grounds, the distribution 

 of chaetognaths and pteropods in the North Pacific was examined to determine whether any represen- 

 tatives of these groups could serve as biological indicators. The results indicated that the species 

 of these groups, especially of the chaetognaths. segregated themselves into three "zones" which were 

 termed the Subtropic, the Transition, and the Subarctic. Examination of the temperature-salinity 

 relations coincident with the plankton tows showed the presence of three types of water with boundaries 

 corresponding closely to t h e "zones". Higher catches, as number per unit of water strained, of 

 chaetognaths and pteropods were obtained in the shallow (0 - 40 m. ) hauls than in the deeper (0 - 140 

 m. ) hauls both during the day and at night. Indications are that surface albacore are not confined to 

 a particular type of water as defined by the faunal zones and the temperature-salinity characteristics. 



