HOME and IIORTON: BIOLOGY OF REX SOLE 



about ages 3 and 5 for males and 5 and 9 for 

 females (Table 4). 



The only maturity data on rex sole available 

 from other areas is that of Villadolid (1927). He 

 found that both males and females off San 

 Francisco, Calif., were fully mature at age 4, 

 which corresponded to about 21.8 cm for males and 

 22.8 cm for females. Possibly rex sole mature 

 earlier in the southern portion of their range. 



Spawning 



Duration of the spawning period was from 

 January through June, with a peak in March- 

 April (Figure 7). Although samples were not 

 obtained during August and December, the 

 percentage offish in each reproductive phase gives 

 a good indication of the spawning time. 



The 6-mo spawning period we found is longer 

 than the January through April spawning re- 

 ported by Villadolid ( 1927) for rex sole collected off 

 central California in 1925 and 1926. Paul Reed 

 (FCO, pers. commun.) found a prolonged spawning 

 from January through August for 3,189 rex sole 

 collected off northern California in 1949-54 and 



100 



50 



(20) (77) (16) (64) (60) (37) (84) (33) (55) (50) 



RIPENING 



_□_ 



2 ioo r 



UJ 



=3 



o 



UJ 



a. 



u. 

 50 



o 



UJ 



RIPE AND SPAWNING 



n 



n 



XL 



I00r (—1 r^ 



50 



SPENT AND RECOVERY 



nil 



SONDJFMAMJJA 

 1969 1970 



MONTH 



FIGURE 7. — Annual cycle of reproduction in 496 rex sole (274 

 males and 222 females) collected off northern Oregon, Sep- 

 tember 1969-July 1970. The number in each monthly sample is 

 shown in parentheses. 



1962-63. This suggests the duration of rex sole 

 spawning varies by area and year. 



Fecundity 



Examination of 13 mature females ranging 

 from 240 to 590 mm TL yielded fecundity esti- 

 mates of 3,900 and 238,100 ova, respectively. The 

 numbers of ova generally increased with size of 

 the female. In 11 of 13 fish, the right ovary con- 

 tained more ova than the left ( 100 to 12,700 more). 

 A linear regression fitted to the fecundity-length 

 data gave a correlation coefficient of 0.9620 (Fig- 

 ure 8). The formula for the regression line was 

 F = 5.3797 x 10" 7 L 422667 , where F is fecundity in 

 number of ova and L is fish TL in millimeters. 



300 



200 300 400 500 

 TOTAL LENGTH (mm) 



600 



FIGURE 8. — Fecundity-length relationship for 13 rex sole col- 

 lected off northern Oregon, February 1970. 



Stock Identification 

 Tagging Experiment 



A total of 2,537 rex sole were tagged and re- 

 leased off the northern Oregon coast in April (200) 

 and June 1970 (2,337). There were 15 recaptures 

 (0.59% recovery) by July 1974, all from the June 

 1970 tagging (Table 7). Maximum movement was 

 53.9 km, and 788 days was the longest time at 

 liberty. There was little change in the depth range 

 occupied by recaptured fish, which were released 

 in 42-154 m and recovered by trawls in 51-101 m. 



These results suggest only limited movement by 

 rex sole. However, tag returns were too few to 

 justify definite conclusions. This low recovery is 

 similar to reports of rex sole tagged off British 

 Columbia (Manzer 1952 [90 tagged]) and Oregon 

 (Harry 1956 [19 tagged]) from which no fish were 

 recovered. 



57 



