252 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



for the month to give an estimate of total monthly 

 egg abundance {Cm)- 



ESTIMATES OF EGG ABUNDANCE AND SEASONAL- 

 REGIONAL DISTRIBUTION OF SPAWNERS 



Using the method of Ahlstrom (1954b) pre- 

 viously described, the monthly estimates by region 

 were obtained for the 4-year period, 1951-54 

 (tables 2-5). Spawning does not occur uniformly 

 over the area throughout the spawning season and 

 the seasonal-regional variation is discussed in the 

 following section. 



The estimates of egg abundance revealed that 

 during this 4-year period, the highest annual esti- 



mate (1951) was less than twice that of the lowest 

 (1954). Furthermore, no trend was apparent 

 from 1951 through 1954. Spawning averaged 666 

 trillion eggs per year, with a range of 873 trillion 

 to 462 trillion. 



The seasonal distribution of spawners was in- 

 ferred from the monthly estimates of egg abun- 

 dance and the number of eggs spawned per month 

 expressed as a percent of the annual total for each 

 year. Although the percentages have been car- 

 ried to hundredths, no statistical significance 

 should be attached to these postdecimal places 

 which merely serve to indicate trace amounts of 

 spawning. These figures are given in the last row 

 in tables 2 through 5. 



Table 2. — Estimated number (in billions) of jack mackerel eggs in survey area, 1951 

 [Cruise numbers in parentheses. No eggs taken during cruises 6101 and 5U0 to 6112] 



' Hundredths of a percent are used so that trace amounts of spawning may be Indicated (see text above) . 



