FISHERY BULLETIN: VOL. 75, NO. 1 



8 

 6 

 4 

 2 







c 



- 8 



»- 

 x 



< 

 o 



cr 



UJ 



CD o 



3 



8- 

 6- 



4 

 2r 



N = I833 

 r =0.9215 



1971 



1972 



_l I I I I I I I I l_ 



1973 



• N = I926 

 r =0.9558 



_i i i i i i i i i 



8 12 



AGE 



16 



20 



FIGURE 4. — Catch curves of male rex sole collected off Oregon in 

 September 1971, 1972, and 1973. 



I 



< 

 o 



in 

 a. 



UJ 



m 



1971 



N = 2297 

 r =0 9135 



j i i i i i i i ' 



1972 



1973 



FIGURE 5. — Catch curves of female rex sole collected off Oregon 

 in September 1971, 1972, and 1973. 



S = 



Nt + Ns + ... + Nr 

 Ne + Nl + ... + Nr-l 



where N is the number of fish of age group r 

 caught. Annual mortality rate is 1 - S and the 

 corresponding instantaneous rate of total mortal- 

 ity is obtained from the expressions = e z , where e 

 and Z are derived from Ricker (1958). 



The catch curve method probably gives more 

 reliable estimates of Z than those obtained using 

 the Jackson method. In the Jackson method the 

 larger samples of younger fish strongly affect the 

 estimates, with the older age groups weighted 

 less. Thus, the Jackson method substantially 

 underestimates the mean Z for the entire right 

 limb of the catch curve. 



Reproduction 



Size at Maturity 



Some males were mature at 13 cm while no 

 females reached maturity until 19 cm (Figure 6). 



30 

 20 



10 



I 



</> 



u_ 



fe 50 



cr 



iu 40 



CD 



5 



| 30 



20 



10 



— MATURE 



-o IMMATURE 



A LENGTH AT 50% MATURITY 



Q LENGTH AT 100% MATURITY 



VUV^. 



10 14 18 22 26 30 34 38 42 46 50 54 58 62 

 TOTAL LENGTH (Cm) 



FIGURE 6. — Size composition of immature and mature rex sole, 

 by sex, collected off northern Oregon, September 1969-July 

 1970. 



About 50% of the males were mature at 16 cm, and 

 all were mature at 21 cm. For females, 50% were 

 mature at 24 cm and 100% were mature at 30 cm. 

 Lengths at 50% and 100% maturity correspond to 



56 



