stages B and C, and all gonads classified as immature 

 represented stage A. The HM-positivc individuals 

 with stage A gonads from the November samples 

 might have matured later in the spawning season. 

 It is unlikely, however, that the two HM-positive 

 fish with immature gonads from the February sample 

 would have spawned during that season, since all 

 ovaries collected subsecjuently, through the July 

 sample, were immature or spawned out. 



Preliminary results of histological studies being 

 carried out on h^nglish sole gonads by Kathleen 

 Ladue, of our staff, were available for the lower 

 two fish from the February sample listed in table 5. 

 Although both were HM positive, only the ovarj" of 

 the last individual showed atretic follicles as evi- 

 dence of having spawned ; the ovary of the other gave 

 no histological evidence of maturing ova. This 

 evidence supports the previous implications that 

 the 11 M factor occurs in certain female English sole 

 during the spawning season or seasons preceding 

 that in which they are destined to spawn initially. 



Table 5. — HM-jmsitit'e female English sole from November, 

 December, and February samples that had gonads weighing 

 less than 1 g., Port Orchard, Wash. 



Table 6 lists the frequency of the HIM factor in 

 the various samples by age. The samples are 

 grouped by age to follow the ovaries from the devel- 

 oping stage through the resting stage. Samples 

 taken after the height of the spawning season 

 (December and January) through July are assigned 

 to the age they had during the spawning season, 

 because up to July the ovaries are progressing to- 

 wards the resting stage. The October and Novem- 

 ber samples are assigned to the age that they would 

 have had at the next spawning season, because the 



ovaries are maluring during these months. Thus 

 a fish entering its fourth year of life in January would 

 be included in age-group III if taken in July, and 

 age-group IV if taken in October. 



The HM factor occurred initially in age-group II 

 in the fish sampled in this study. The possibility 

 of its presence in group-I fish is not ruled out 

 because insufficient numbers of the group were 

 sampled. 



At a given age the highest frequency of tlu; HM 

 factor appears in the December sample at the peak 

 of the spawning season. Frequency generally de- 

 creases through July but increases again in October 

 and November. The occurrence of a lower II M 

 frequency in II- and Ill-group fish for the March 

 sample than for either the June or July samples is 

 very likely the result of the bias described under 

 Methods and Materials regarding the collection of 

 that sample. 



Table 6. — Frequency of the UM factor in the various 

 groups of female English sole, Port Orchard, Wash. 



age 



.\ge-group V and older. 



Figure 3 is a plot of the seasonal fluctuation of 

 the HM factor with body length. Fish 22 to 25 

 cm. long were combined in the December sam()le 

 because the separate groups had few individuals. 



U.S. FISH AND WILDLIFE SERVICE 



