RELEASES AND RECOVERIES OF DRIFT BOTTLES AND 

 CARDS IN THE CENTRAL PACIFIC 



By 



Richard A. Barkley, Research Oceanographer, 



Bernard M. Ito, Physical Science Technician (Oceanography), 



and Robert P. Brown, Oceanographer 



Bureau of Commercial Fisheries 



Biological Laboratory 



Honolulu, Hawaii 



ABSTRACT 



Since January 1961, the Bureau of Commercial Fisheries Biological Laboratory in Honolulu has 

 been releasing drift bottles and cards in the central Pacific Ocean. Data are presented on all 

 releases and recoveries through June 1963, together with charts showing the release and recovery 

 points. An analysis of the returns from the Hawaiian Islands shows that there is a seasonal change 

 in the direction and speed of the current system near the Islands which coincides with changes in 

 strength of the trade wind system. During the first half of the year the current moves at speeds of 

 between 6 and 11 nautical miles per day and near Oahu and Kauai it moves toward the northwest, 

 while in the latter half of the year the speed is 6 nautical miles per day or less, and the direction of 

 flow is toward the west or somewhat south of west. 



INTRODUCTION 



In 1961 the Bureau of Commercial Fisheries 

 Biological Laboratory in Honolulu began a series 

 of drift bottle releases designed primarily to 

 obtain more complete and detailed information 

 on the currents near the Hawaiian Islands than 

 was then available. It was clear that such infor- 

 mation was required in order to interpret vari- 

 ous kinds of oceanographic and tifological infor- 

 mation collected by the Laboratory near the 

 Islands, and drift bottle techniques offered a 

 means for obtaining considerable information 

 in an economical way, preliminary to the use 

 of more sophisticated and expensive procedures. 



At that time, the information on surface and 

 near-surface currents near the Hawaiian Islands 

 consisted primarily of oceanographic station data 

 taken by the Laboratory a decade earlier (Mc- 

 Gary, 1955; Seckel, 1955), together with data on 

 surface drift obtained from ship's log books 

 (H. O. Publication nos. 570, 1947; and 569, 1950). 



The dynamic topography of the sea surface 

 near the Hawaiian Islands (McGary, 1955; Seckel, 

 1955) is characterized by an irregular series of 

 eddies which vary considerably in size, number, 

 and location. The eddies tend to obscure the pat- 

 terns of mean flow, and because little is known 

 about the growth and decay of such eddies, or of 

 their movements, the information on mass trans- 

 port which can be derived from the dynamic 

 topography is valid for intervals of time of the 

 order of a few days only. 



Current charts based on ship's drift provide 

 information on a monthly basis, and thus offer 

 some continuity in time. However, the data are 

 averaged over a number of years and over areas 

 of 1 degree of latitude and longitude, so that the 

 details of currents on a scale comparable to that 

 of the individual islands are lost, since even 

 Hawaii, the largest of the islands, is less than 

 60 nautical miles in mean diameter. 



