In the sample of June 5, 1962, which gave the best 

 representation of different ages within a gi\-en length 

 interval, no indication of an age dependency was 

 detectable. In spite of the small sample sizes, the 

 fre(|uency of the HM factor seems to increase in 

 length in all samples but that of February 23, 1963. 

 This exceptional situation is discussed lielow. 



Tahi.e 7. — IIM frequencies in female hatibiil iiecnrding to 

 lenijlh 



Note. — Sampling areas shown in table 2. 



As pointed out previously, we detected the HM 

 factor during the spawning season in tlie serum of 

 certain indi\'idual English .sole with immature ova- 

 ries; apparently a similar condition exists in halibut. 

 Two 76-cm. females taken in the February 23, 1963, 

 sample at the peak of the spawning season were HM 

 positive. [Thompson (1915) defined the spawning 

 season for halibut as extending from December to 

 April with the peak in February.] These fish were 

 smaller than the minimum length reported by 

 Thompson for mature females captured from areas 

 included in this study, and the small ovaries diil not 

 give external indications of development. The rec- 

 ords of scrum titers of the HM-positive females in 

 the sample of February 23, 1963, show that the two 

 HM-positive females which were judged immature 

 had very low titers whereas the mature individuals 

 had titers exceeding a serum dilution of 1/250 

 (table 8). These findings suggest that a quantita- 

 tive means may lie used to distinguish maturing and 

 mature females from immature females in which 

 the HM factor may also be present. 



In the discu.ssion of table 4 in a preceding section, 

 serum titers were comjiared with (lualitative reac- 

 tions of kidney-tissue fluids from the halibut sample 

 taken on June 6, 1962. The only failures of parallel 

 reactions were in individuals lia\'ing .serum dilution 



titers of one-eighth or less. This information indi- 

 cates that kidney-fragment fluids may l)e useful in 

 researchers' obtaining data relative to maturity and 

 sex by sampling the eviscerated fish in the commer- 

 cial catch upon arrival in port. 



Tahi-E S. — Serum tilerx mid iiinliiritji eslimales of IIM- 

 posilive fernalea from hiilihut soiiipir of February 2.-i, 1!)6S, 

 taken at Cape Flattery, Wash. 



' Reciprocal of last positive diltition. 



PRODUCTION OF HM FACTOR BY MALES 



The link connecting estrogen with the i)roduction 

 of .serum components related to maturity has been 

 determined by a numi)cr of investigators of birds, 

 through the production of these components in 

 males and immature iemales after artificial stimula- 

 tion with estrogenic hormones (McDonald and Rid- 

 dle, 1945: Frist and Schjeide, 1961). Bailey (1957), 

 Frist and Schjeide (19()1), and Ho and Vanstone 

 (1961) have likewise demonstrated that artificial 

 stimulation with estrogenic hormones produces a 

 blooil serum situation similar to that of the mature 

 female in the teleosts Carassius aiiratus, Paralabrax 

 clalhratus, and Oncorhi/nchus ncrka, respectively. 

 We attempted this procedure in this study with 

 four English sole maintained in an aquarium at the 

 Fniversity of Washington College of Fisheries. 

 Each fish was injected intramuscularly with 1 ml. 

 of an aqueous suspension of estrone (5 mg./cc). 

 Two fish survived the initial handling (table 9). 

 Data for the fish firmly establisii the presence of the 

 HM factor as a consequence of introducing the 

 estrogenic hormone. .Mthough a control bleeding 

 was not made for fish Xo. 1, the rise in titer between 

 the first and second bleeding establishes beyond 

 doubt the efTect of the estrone injection. 



The HM factor was in low concentration in two 

 male halibut taken during the spawning season. 

 The possibility of coiitaniinat ion cannot be excluded 

 becau.se both were taken immediately following the 

 collection of a sample from an HM-positive female, 

 although precautions were taken to minimize 

 contamination. 



54 



U.S. FISH .\ND WILDLIFE SKRVICE 



