PART 11 



RESPONSE OF TUNA TO VISUAL 

 AND VISUAL -CHEMICAL STIMULI 



BY 



Sidney C. Hsiao and Albert L, Tester 

 University of Hawaii 



During September 1952 a few experiments were con- 

 ducted on a population of 12 little tunny 1/ (Euthynnus yaitoli established 

 in Pond Noo 5 at Coconut islands Oahuj, to determine {1} whether visual 

 lures would promote a tropistic response^ fZi whether the response 

 was heightened when combined with chemical stimulip io e^^ an ex- 

 tract of tuna fleshj, and (V whether the response varied with lures of 

 different colors o It was hoped that the results would be< of interest 

 and value in devising lures which, either alone or in combination 

 with extracts^ would assist in attracting tuna to the stern of fishing 

 vessels at sea, 



METHODS 



The lures consisted of 2-inch sections of l/2»inch rubber 

 tubing of different colors which were suspended from a cross bar 

 attached to the tip of a 25=foot bamboo polej pivoted near the point 

 of balance ffigo 17)o By means of a cordj, a counterweight^ and a 

 System' of pulleys, two lures^ one suspended from each end of the 

 cross bar^ could be momentarily dipped into the water^ When an 

 experiment was in progress the lures were lo^wered about once every 

 2 secondso 



The lure array was fastened near the base of a 20^foot 

 observation tower and could be manipulated from the platform on top. 

 Observations of the fish were made when they entered the 39 x 75-foot 

 attraction area {the same area that was used in chemical stimulation 

 studies) marked off by two pieces of cord stretching across the pond. 



Note; Contribution NOo 48 of the Hawaii Marine Laboratory, 

 University of Hawaii, Honolulu, To Ho 



\/ The activity of one "sick" tunny was not recordedo 



63 



