326 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



an area (approximately 40 ft. long by 15 ft. wide) 

 in the outlet in which several males and a few fe- 

 males were spawning. Three pairs of fish spawned 

 from 3 to 40 feet above the net while it was in 

 position. The current velocity was about 3 feet 

 per second. Only 6 eggs were recovered by the 

 net (4 dead and 2 fertile) and these could have 

 been eggs from a previous spawning which were 

 dislodged from the bottom by the spawners. 

 Brown (1938b) also failed to collect eggs in a screen 

 placed directly behind spawning grayling. One 

 male and one female grayling were examined from 

 those spawning in this area. The male's stomach 

 contained no eggs, only caddis cases and amphi- 

 pods. The female had recently swallowed a 

 single egg and was full of dipteran larvae. 



The grayling in Sweden (Fabricius and Gustaf- 

 son, 1955) is mostly polygamous. Three females 

 under observation spawned 19, 27, and 34 times, 

 respectively, in 1 day, the first 2 with 2 different 

 males; the third was with only a single male. The 

 daily peak of spawning activity of these Swedish 

 grayling was in the afternoon. Males left their 

 territories about midnight and did not start return- 

 ing until between 9 and 11 a. m. Grayling were 

 seen spawning in Grebe Lake tributaries at all 

 hours of the day, but no observations were made 

 at night. 



Males attempted to spawn with all females 

 entering their territories and sometimes with other 

 males. No females were seen to be attacked (as 

 was noted by Fabricius and Gustafson, 1955). 

 However, if the female was not ready to spawn, 

 she kept moving away, and took refuge under a 

 bank or among other fish. Often the male fol- 

 lowed for as much as 8 feet, exhibiting courtship 

 behavior. The male drifted repeatedly toward 

 the female, inclining his dorsal side (particularly 

 his extended dorsal fin) toward her. When the 

 female was ready to spawn, the male moved closely 

 against her to fold his dorsal fin over her back. 

 The male then vibrated his entire body while 

 maintaining a rigid form. The female, after 1 or 

 2 seconds, began to shiver. The two fish with 

 backs arched, headed into the current, and with 

 mouths gaping, sank to the bottom. A cloud of 

 silt and gravel was swept upward as the vibrating 

 caudal fins came near the bottom; eggs and milt 

 were extruded at this time. Grayling eggs are 

 adhesive and when first released stick to the par- 



ticles that are stirred up, and also adhere to the 

 bottom. Fabricius and Gustafson (1955) found 

 that in Thymallus thymallus the male also bends 

 his tail across that of the female. The female of 

 T. thymallus curves her body and with vigorous 

 vibrating movements works her genital opening 

 deep into the gravel before extruding her eggs. 



Brown (1938b) observed one female that 

 spawned twice within 45 minutes (each time with 

 a different male). He suggested that the egg 

 laying interval lasts from 2 to 4 days per individual. 

 I found that females placed within fenced 

 enclosures appeared to have completely spawned 

 on the fifth day. After completion of spawning, 

 the grayling moved back into Grebe Lake or Wolf 

 Lake. 



Mortality 



To investigate distribution of fish and natural 

 mortality, many spawning-run individuals were 

 marked and released in 1953 and returns sought 

 in 1954. In 1953, plastic streamer tags were 

 placed on 142 grayling (artificially spawned the 

 preceding day). These fish were then released 

 below Hatchery Creek trap. In addition, 153 

 individuals were similarly tagged and placed above 

 the trap to spawn naturally. Of the 295 grayling 

 tagged during 1953, 62 were recovered during the 

 1954 spawning migrations. Nineteen of these 

 had lost their tags. Of the 43 returns still carrying 

 their tags, 23 belonged to the naturally spawned 

 group and 20 to the group that had been artificially 

 spawned. It would appear that artificial spawn- 

 taking incurred no greater mortality than natural 

 reproduction. 



Both during 1953 and 1954, fish migrating into 

 streams other than Hatchery Creek were fin- 

 clipped distinctively in each waterway, not only 

 to avoid counting individuals twice, but also to 

 identify further movements (table 15). In the 

 outlet, fish traveling upstream (into Grebe Lake) 

 had their right pectoral fins removed. The 

 adipose was clipped from downstream migrants. 

 During the 1953 population study, 1,032 grayling 

 were further distinctively fin-clipped (left pectoral) 

 and released. 



Spawners marked in 1953 tended to return to 

 the streams in which they had been marked the 

 previous year, but some straving occurred (table 

 15). 



