school. This suggests that considerable numbers of fish schools are connpletely escaping atten- 

 tion because they are neither visible on the surface nor accompanied by birds. If this is the 

 case, then our estimates of efficiency are maximal. 



Suspecting that schools were being missed, we instructed the fishermen to take special 

 pains to watch all parts of the horizon - astern as well as ahead. Soon after these instructions 

 were issued a large school was located only about a half-miile behind the vessel--directly in its 

 wake--which emphasized the need for looking astern. Consequently, during the fall scouting 

 with the SMITH, 17 of 94 schools were seen off the quarter, and if we assume that these would 

 have been missed by our previous technique, then we saw 22 percent more schools. We note 

 also that the distribution of schools in the forward -section is nearly uniform, which is gratifying 

 because vision from the bridge of the SMITH is unobstructed forward and therefore the distribu- 

 tion is approxinnately as expected. 



Size of Flocks 



If we consider that the flocks accompanying the skipjack schools vary in size from less 

 than 10 to several hundred birds, it appears probable that the size of the flock will affect the 

 efficiency of sighting it. Our data support this probability. In table 6 we have tabulated the num- 

 ber of flocks seen at each distance according to whether they were large (n-iore than 100 birds), 

 medium (50 to 100 birds), or small (less than 50 birds). The data indicate that large flocks were 

 seen farther from the vessel and much more efficiently at distances from 1 to 2 miles. Medium- 

 sized flocks were seen at medium efficiencies, but perhaps most striking is the comparatively 

 large proportion of small flocks (47.9 percent) which were first seen within a half-mile or less 

 from the vessel. 



Table 6. --Compairison of numbers of flocks of various sizes seen on GILBERT cruises 11 and 13— 



1/ 



— Three flocks omitted from table because of incomplete data. 



Weather and Sea 



In Hawaiian waters visibility and sea conditions are remarkably uniform. Visibility is 

 almost always excellent, though reduced occasionally by haze, which is troublesome at distances 

 of more than 8 to 10 miles, and by rain squalls, which are almost always temporary. Neither 

 of these troubles had any important effect on scouting conditions, and it is possible to consider 

 that visibility is essentially constant. The sea conditions, however, are usually choppy and 

 affect vision according to the amount of spray thrown over the vessel. This, of course, also 

 depends on the vessel's course in relation to the wind and sea, and since the wind is usually 

 from the northeast quadrant, certain compass courses are habituailly affected more than others. 



11 



