EXPERIMENTAL FISH 



The experiments on chemical, light j and sound reactions were 

 conducted on two species of tuna? the yellowfin or ahi ( Neothunnus 

 macropterus ) and the little tunny (henceforth called "tunny") or 

 kawakawa ( Euthynnus yaito), which were established in captivity in a 

 concrete tank at the Hawaii Marine Laboratory, Coconut Island^ Oahu^ 

 over a 7-nionth periodo The experiments on electrical reaction were 

 performed on the "mountain bass" or aholehole (Kuhlia sandvicensis)^, 

 for reasons which /vvill be discussed elsewherso 



The concrete tank in, which the tuna were confined (fig.. 1, repro- 

 duced, from figo ^s Tester 1952) is partially sunk m the ground^ it 

 has smooth 6-inch concrete walls and bottomj it is 3hc7 feet longj 

 10,8 feet widej and 3<,8 feet deep at the north end and UoO feet deep 

 at the south end^ its volume is 10 j 663 gallons;^ the rate of flow of 

 the saltwater supply is about 25 gallons per minute^ the inletj near 

 the northwest corner, is directed horizontally (towards the south) 

 at a depth of about 2^ feet^ the outlet is a notch cut in the top of 

 the south wall at its center o Baffles consisting of 3 x U-foot galva- 

 nized iron sheets^ painted white, are placed across three comers^ a 

 larger baffle, 3 x 10 feetj also painted white is placed across the 

 fourth or northeast comer for the purpose of housing equipment for 

 light reaction studies^ A ^=foot fence, with ipright posts and 

 horizontal, spaced plank bars, surrounds the tank at its upper edgeo 

 Towards the end of the summer the fence was lined with chicken wire 

 to keep the fish from jumping through, and the top was similarly 

 covered to keep visitors from throwing stones at the fisho Two 60- 

 watt bulbs were suspended above the tank and were lit from dusk to 

 daybreak o 



During the experimental work varying numbers of tuna (from one 

 to seven) were present in the tank, as shown in tdole 1= As their 

 reactions to stimuli were dependent on their I'state of healths" 

 their history is briefly reviewedo 



Yellowfin No, 1, the subject of most of the experiments, was 

 introduced to the tank on June 20^ 1951 .. started feeding on July 2<, 

 195ls and was in excellent condition until about October 31 j 1951 o 

 Following that date it took less and less food.^ and finally ceased 

 feedingo The normally shiny, black skin became whitish and dis- 

 tended, as if the body were swolleno The swelling around the eyes 

 made the eyeballs appear to sink within the sockets, and interfered 

 with the tuna*s vision » During late December and early January the 

 yellowfin resumed a desire to feed^ although it would snap at the 

 food, it would invariably misso It died on January 13,, 1952. and 

 in addition to being puffy and swollen, was found to have been blind 

 in one eyeo Its initial weight was estimated at about 5 pounds, its 

 weight at death was 11 pounds o 



