AN AERATING DEVICE FOR SALT WELL WATER 



By Donald W. Strasburg, Fishery Research Biologist 



Biological Laboratory, Bureau of Commercial Fisheries, Fish and Wildlife Service, 

 U.S. Department of the Interior, Honolulu, Hawaii 



Abstract. — Salt well water appeared to be a suitable medium for captive oceanic skip- 

 jack tuna except that the available supply was devoid of dissolved oxygen. A model 

 aerating device, whose characteristics could be varied, was used to determine the features 

 of a definitive aerator. The aerator was a tower containing 16 perforated horizontal 

 trays spaced 2 inches apart ; the well water was pumped to the uppermost tray, from 

 which it showered successively through those beneath, becoming 95 to 100 percent saturated 

 with oxygen when it reached the bottom. Skipjack were later maintained in this water. 



A desire to increase the efficiency of cap- 

 turing oceanic skipjack {Katsuwonus pel- 

 a7nls) has led the Bureau of Commercial 

 Fisheries Biological Laboratory at Hono- 

 lulu into a study of skipjack behavior. 

 In addition to a high-seas investigation, 

 the study has a shore phase in which skip- 

 jack are confined in ponds under controlled 

 conditions. Because earlier attempts to 

 establish skipjack in ponds were unsuccess- 

 ful (Tester, 1952), a large amount of pre- 

 liminary planning was undertaken in 

 order to avoid what were regarded as pit- 

 falls in the capture, handling, and main- 

 tenance of these sensitive fish. 



Of utmost importance was the need for 

 an abundant supply of clean, circulating 

 sea w^ater, preferably water of an oceanic 

 rather than a littoral character. The Lab- 

 oratory's dock and pond facilities are lo- 

 cated in Kewalo, a Honolulu district with 

 three sources of salt water : Kewalo Basin, 

 the Pacific Ocean, and salt ground w^ater 

 (fig. 1). Although Kewalo Basin is im- 

 mediately adjacent to the Laboratory 

 ponds, its water was eliminated from con- 



Editor's note : Later developments of this system are 

 described in the paper by Eugene L. Nakamura, which 

 follows this one. 



Figure 1. — Bureau of Commercial Fisheries dock 

 facilities at Kewalo Basin, Honolulu, with the 

 Pacific Ocean in the background. 



sideration because of a variable contami- 

 nation from industrial and maritime 

 sources, and also because the small size 

 of its water body might result in a drastic 

 salinity drop during heavy rains. In addi- 

 tion, Kewalo Basin water is rather turbid, 

 a condition deemed unsuitable for ecologi- 

 cal and observational reasons. The cost of 

 pumping Pacific Ocean water across 300 

 to 700 yards of reef and shore seemed pro- 

 hibitive; also tending to eliminate ocean 

 water were similar, if lesser, problems of 

 contamination and dilution. 



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