of two or more fish occupying adjacent hooks than if the tuna were 

 randomly distributed in space, thus reducing the number of runs„ 

 A "t" test is used to estimate whether the actual number of runs 

 is significantly different from the most probable number. 



The distribution of hooked yellowfin along the line was 

 studied for one cruise (Smith cruise 11)4/^ selected because the 

 mean catch rate was high and also nearly identical in all portions of 

 the line, whereas during most cruises the portion of the line remov- 

 ed from the water last had a higher catch rate than those portions 

 removed earlier. There were 28 fishing stations during Smith cruise 

 11, but only 15 of these could be used for the anlysis (table 1) because 

 the technique required a minimum catch of 1 1 yellowfin. Nine of the 

 15 stations had fewer runs than expected, and 6 had more runs than 

 expected. Of the 9 with fewer runs, 5 had significantly fewer, and 

 in 3 of the 5 the numbers were highly significantly less than was to 

 be expected from a random distribution. In contrastj none of the 6 

 positive deviations were significant. There is, then, considerable 

 evidence that there were fewer runs than would be expected from a 

 non- schooling population. 



The tendency to school is probably greater than this evidence 

 indicates, because the following four factors tended to obscure the 

 manifestation of schooling: (1) About 15 percent of the hooks were 

 occupied by fish other than yellowfin, and if a hook were occupied 

 by some other species before a school of yellowfin chanced on the 

 line, a potential single run might be split into three runs, thus increas- 

 ing the number of runs by two. (2) There were 60 fathoms between 

 adjacent hooks of two consecutive baskets, whereas hooks within a 



47 The line used on this cruise was made up of 40 baskets or "skates" 

 of gear essentially as described by Niska (1953), and fished in a 

 manner described by Murphy and Shomura (1953). Briefly, each 

 set consisted of a connected series of 40 main lines supported in 

 the water by a buoy at each connectiono Attached to each main 

 line were six evenly spaced hooks. In effect the set of gear in 

 the water resembled a series of 40 catenaries, and since the hook 

 lines were equal in length, the hooks within each basket were 

 fishing at different levels. 



