(skipjack, yellowfin, or bigeye) or mar lin- -whichever was available- - 

 plus such other scrap fish as came to hando In general they were fed 

 at the rate of about one-half pound of food per fish per feeding, which 

 is probably much less than their normal requiremento This schedule 

 was maintained in order that the fish would be in a constant state of 

 hunger on Tuesdays^ Thursdays^ and Saturdays when tests were usu- 

 ally conducted. Van Weel (1952) showed that this precaution was 

 necessaryo 



Two departures from this diet are worthy of notCo Firstly, 

 the tunny established in the tank on June 16^ 1952, was kept on a non= 

 tuna diet, consisting of squid, anchovy^ and other fish, until about 

 the middle of July when certain tests had been completed. Secondly, 

 following April 25^ 1953, the two tunny in the pond were fed on im- 

 ported (frozen) squid exclusivelyo 



METHODS AND PROCEDURES IN TESTING 



Concrete Tajik 



Tests were run in the concrete tank 2 or 3 times a week 

 from July 1 to August 20, 1952, and occasionally thereafter through- 

 out the remainder of the summer, the fall, and the wintero At first 

 the methods were similar to those used by van Weel (1952)o The ob- 

 server stood by the railings at the side of the tank near the south end 

 until the fish had become used to his presence and had resumed a 

 steady slow circling^ Several successive measurements and counts 

 were made of U) the time (in seconds t for 10 passes past the observ- 

 er, with the fish swimming either up or down the length of the tank, 

 and ^b) the number out of 10 passes made in the half of the tank ad- 

 jacent to the observero Materials were then siphoned into the tank 

 using a rubber hose, and the timing and counting were resumedo Ex- 

 citement induced when the fish sensed the material was indicated by 

 a decrease in the time of 10 passes (increase in rate of swimming) 

 and attraction was indicated by an increase in the number of passes 

 along the near side of the tanko 



Often during attempts to establish control conditions the 

 fish would remain excited for long periods of time by the presence of 

 the observer, whom it could see; during both control and test periods 

 it might also respond to the observer's movements while tirming, in- 

 troducing the materials^ or recording the results o This difficulty was 

 largely overcome on July 23, 1952, (following Test 131 by enclosing 

 the upper railed section of the tank with tarpaper and building an ob- 

 servation booth (figo 2), The three-ply front of the booth overhung 

 the tank at its upper edge to increase the range of visiono It contained 



