450 



Fishery Bulletin 89(3), 1991 



JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 

 MONTHS 



30 



25 



? 20 



15 



10 



5 

 3 



JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 

 MONTHS 



Figure 5 



(A) Back-calculated spawning dates for 18 larvae and 77 

 juvenile and young adult/adult Atlantic blue marlin Makaira 

 nigricans. Total increment count on the otolith (sagittae) and 

 date of capture were used to back-calculate spawning month. 



(B) Distribution of capture dates for 18 larvae and 77 juvenile 

 and young adult/adult Atlantic blue marlin collected 1980-88. 



of >0.8 do high levels of spawning shift from the 

 second to the fourth quarter (Fig. 6B). A periodicity 

 of 1 increment per day agrees most closely with the 

 qualitative information available for blue marlin spawn- 

 ing activity. 



To determine whether the lack of information on the 

 time of first increment formation affected our inter- 

 pretation of increment deposition rate, we constructed 

 a contingency table of seasonal spawning versus first 

 increment formation of 1-7 days (using a periodicity 

 of 1.0). The Chi-square statistic (x 2 1.42, df 18, P> 

 0.999) showed that for P= 1.0, a range of 1-7 days for 

 first increment formation does not significantly alter 

 the back-calculated spawning distribution. 



!■ ni.o i i2.o 



PERIODICITY (increments/doy) 



i 



WINTER SPRING SUMMER 



SEASON 



FALL 



WINTER SPRING SUMMER FALL 



SEASON 



Figure 6 



(A) Seasonal distribution of spawning (%) of Atlantic blue 

 marlin Makaira nigricans predicted from chi-square con- 

 tingency table analyses for increment deposition rates of 0.5, 

 1.0, and 2.0 increments per day, and (B) for deposition rates 

 of 0.8, 0.9, and 1.0 increments per day. Summer and fall 

 spawning is most closely predicted in (A) and (B) by a period- 

 icity of 1.0 increments per day. 



Precision 



Average percent error for the aged samples of juvenile 

 and young adult/adult blue marlin (N 77) was 1.6% (Fig. 

 7). This level of precision is either less than or equal 

 to APE values reported for other species and various 

 ageing methods (Table 2). No obvious trends in APE 

 with the increment count or round weight were evident 

 (Fig. 7). Average percent error generally increased 

 with increases in body length (Fig. 7), except for out- 

 liers in the first two lengths of the measured range (4.3 

 and 23.0cm). 



Length-weight relationships 



The length-weight relationship for all immature blue 

 marlin (< 140cm; sexes pooled, Fig. 8A), is represented 

 by the allometric equation 



In W = -11.950 + 2.9921 (In LJFL); tf 2 = 0.98. (5) 



The length-weight relationships for mature adult blue 



