Rickey. Maturity, spawning, and seasonal movement of Atheresthes stomias 



135 



edly over a protracted spawning season, 

 as are Pacific halibut, Hippoglossus 

 stenolepis (St-Pierre, 1984), and Dover 

 sole, Microstomus pacificus (Hunter et 

 al., 1992). Size frequencies of oocyte 

 stages (Fig. 6) show distinct populations 

 of oocytes that indicate a group-synchro- 

 nous pattern of development. Postovu- 

 latory follicles were found in "developing" 

 females, those with no visible translucent 

 oocytes, evidence that these fish had re- 

 cently spawned and that macroscopic 

 examination of ovaries could not separate 

 all spawning from nonspawning fish. In 

 September 1991, early in the spawning 

 season, gravid mean GSI was signifi- 

 cantly greater than developing GSI 

 (Student's t-test, P«0.001), but by No- 

 vember and December there was essen- 

 tially no difference between mean GSI for 

 developing and gravid females (Student's 

 f-test, November P<0.105, December 

 P<0.841); the highest mean GSI was ob- 

 served in December. Under the macroscopic matu- 

 rity definitions used, females progress from imma- 

 ture to the developing stage, then cycle between "de- 

 veloping" and "gravid" as successive batches of oo- 

 cytes ripen and are ovulated. The ripe/running stage 

 corresponds then only to the last and perhaps larg- 

 est batch of oocytes, suggesting that by December 

 spawning was near completion for some females. 



0.25 



0.20 



c 

 o 



■C 0.15 

 o 



Q. 

 O 



CL 0.10 + 



0.05 



0.00 



150 300 450 600 750 900 1050 1200 1350 1500 1650 



Oocyte diameter (microns) 

 Figure 6 



Size-frequency distributions of arrowtooth flounder oocyte developmen- 

 tal stages from ovaries collected late December 1991. Proportions were 

 calculated separately for each oocyte type. 



Spent/resting females were seen year-round, evi- 

 dence that adult arrowtooth flounder may not spawn 

 every year. 



Of particular concern is whether small, resting 

 mature fish were misclassified as immature, and vice 

 versa, since errors will bias estimates of size at ma- 

 turity. Immature male arrowtooth flounder were dif- 

 ficult to identify and errors undoubtedly occurred, 



