material was usually sensed by the tunny in its first pass into the 

 area,, Usually the fish would become excited immediatelyo It would 

 increase its swimming ratCj, often quickly circling the tank« On re- 

 turning to the area it would swim rapidly in snnall circles „ splashing 

 and swirling at the surfaceo At timies the fish would flex its dorsal 

 fin and snap with its moutho Occasionally it would root uneaten food 

 from the bottom and "pl^y" with it Calthough not eating it cts far as 

 could be observed^. This excitement would usually be prono\inced in 

 the first and second periods (4 nninutes from, start) but woxild grad- 

 ually lessen^ until after the fifth period (10 minutes from staxtj only 

 a more rapid rate of swinnming would be notedo If the reaction con- 

 tinued after the fifth period^ it would usually take place outside of 

 the attraction area along the far wall„ where the material had been 

 cariried by the slowp counterclockwise current in the tanko 



When an attractive substance was introduced into the 

 pondp a reaction would taJce place innmediately if the tunny happened 

 to be near the point of injectioHo Usually^ however „ the material 

 was introduced when the fish were starting to return from the up- 

 stream end of the pond. A reaction usually ensued during the first 

 3-minute period^ as soon as the fish entered the attraction areas 

 When several tunny were present^ they would immediately depart 

 from a linearp follow<= the -leader type of schooling and fan out across 

 the pondj darting into and out of the attraction area at or near the 

 surface;, frequently breaking the surface with their backs and creat- 

 ing a "bow Wave" as they swanio Often individuals would make short 

 circles in the areSp splashing and biting at bubblesp dead leaves^ or 

 other objects which happened to be floating on the surface. This ac- 

 tivity usually lasted for two periods (6 minutes from start) and often 

 persisted with lessening tempo for five periods {lb minutes from 

 start* or more. When darting into and out of the area„ the point at 

 v/hich they turned back seemed to coincide roughly with the disper- 

 sion front of the matertalo the position of which could be inferred 

 from experiments conducted with fluorescein dyeo Usually the re- 

 action was over within 15 minutes and normal swimming up and down 

 the pond was resumedo Thus a typical strong reaction was indicated 

 by (a) increased rale of swimmings (b) surfacingp (cH breaking up of 

 usual school formation; a "f,anning out" of the schoolp often followed 

 by independent circling of individuals^ (d) return to area after passing 

 through the front of the substance^ (e) feeding activity? splashing, 

 lungingj and snapping at objects on the surface,, 



There was considerable variation in both the pattern and 

 strength of the reactiono Sometimes the fish reacted to the material 

 for but a short time within earh period^ in the meantime racing the 

 entire length of the pond ajid quickly returning„ When only two tunny 



15 



