LIST OF ILLUSTRATIONS 



FIGURE Page 



Frontispiece. --Bird flock over skipjack school in Hawaiian waters 



1. Scouting plan for GILBERT cruises 1 1 and 13 4 



2. Track chart, GILBERT cruise 7 5 



3. Scouting plan for cruises 22, 23, and 24 of the HUGH M. SMITH 6 



4. Tracks of airplane scouting flights 7 



5. Flocks seen in concentric segments of the scanning area on GILBERT 



cruises 11 and 13 9 



6. Diurnal variation in the frequency of sightings of bird flocks on GILBERT 



cruises 1 1 and 13 and SMITH cruises 22-24 14 



7. Numbers of schools seen during systematic scouting on the April and June 



cruises of the CHARLES H. GILBERT 17 



8. Direction and distance moved in 10 minutes by schools seen on runs where 



a Doppler effect was suspected during the April and June cruises 19 



9. Location of the average year's catch of skipjack from 1948 to 1952 20 



10. Nunaber of schools sighted on the autumn cruises of the HUGH M. SMITH. • 23 



11. Seasonal distribution of skipjack school sightings on POFI cruises compared 



with nnonthly landings of the commercial fishery. -. . . 24 



