YELLOWFIN TUNA 



CATCH-TOTAL EASTERN PACIFIC 

 CAT CM W OAT-S FlSMIM«-a.lW«ir 

 STANDARDIZES TO CLASS 4 



TOTAL CATCH IN MILLIONS OF 



Figure 5. — Catch, catch-per-day*s fishing, 

 and fishing intensity, yellowfin tuna. 

 1934-57. 



effort, apparent abun- 

 dance, and total catch, 

 with the aid of some 

 mathematical theory 

 which is outlined in 

 detail in the research 

 papers published in our 

 Bulletin series. In 

 figure 6, the data for 

 the yellowfin fishery 

 are presented in a form 

 somewhat more compli- 

 cated than in figure 5, 

 but more suitable for 

 illustrating these re- 

 lationships. In this 

 figure we show, along 

 the axis of the abscis- 

 sae, fishing intensity, 

 and, along the axis of 

 ordinates, catch-per- 

 day's fishing. The pro- 

 duct of the two is, of 

 course, the total catch, 

 isopleths of which are 

 the equilateral hyperbo- 

 lae on the figure. In 

 this figure are shown 

 the actual values for 

 the years 193h-57. Also 

 shown on the figure, 

 by the dotted line, la- 

 belled "Estimated line 



of equilibrium," is our best estimate from 

 these data of the average relationship 

 among the three variables. From this it 

 may be seen that, as the fishing intensity 

 increases, the average catch-per-unit-of- 

 effort continuously decreases, but that the 

 average total catch continues to increase 

 up to about 36,000 standard days' fishing, 

 (Class k clipper units) with a total catch 

 in the neighborhood of 195 million pounds 

 per year. As fishing effort increases 

 beyond this level, it is anticipated that 

 the total catch will also decrease. We 

 require, however, more data at high levels 

 of fishing intensity to substantiate this 

 estimate. The preliminary data for 1958 

 indicate that there was a considerable in- 

 crease in fishing intensity over 1957, due 

 to full operation of the fishing fleets 

 during the later year, and due to extraor- 

 dinarily high availability to the purse- 

 seine fleet. The total intensity did not, 

 however, reach 36,000 standard days. 



FISHING EFFORT, ABUNDANCE AND CATCH 

 YELLOWFIN TUNA 

 TOTAL E. PACIFIC 



eSTIMATEO LINE 

 OF CQUILISRI 



f. eioMsnuAe-iri 



12 14 16 18 20 22 24 26 26 JO 



FISHING INTENSITY -1000'S OF STANDARD OATS (CLASS 4 ) 



Figure 6. — Fishing effort, abundance, and catch, 

 yellowfin tuna. 



40 



