FISllKKV Kl'LLETIN: VOL. Hti. NO. 4 



METHODS AND MATERIALS 



Age and Morphology 



Chum salmon were collected with gill nets. After 

 capture in 1984, postorbital-hypural length (Vlady- 

 kov 1962), caudal peduncle depth, and length of the 

 base and height of the anal and dorsal fins were all 

 recorded on the left side in the field to the nearest 

 millimeter. The number of gill rakers on the left 

 anterior arch was recorded, as well as the number 

 of branchiostegal rays on the left side. Five scales 

 and two otoliths were collected from each individual 

 for age determination, and the sex of an individual 

 was confirmed by internal inspection. When the age 

 of an individual estimated from scales and from 

 otoliths disagreed, the age determined from scales 

 was assigned. In 1985, only postorbital-hypural 

 length and sex were recorded for individuals, and 

 only scales were collected for age determination. 



Population differences and sexual dimorphism in 

 the meristic characters were examined by two-way 

 analysis of variance, with population and sex as the 

 indices. Population is used in the manner as de- 

 scribed by Ricker (1972), as a group of fish spawn- 

 ing in a particular river at a particular season, and 

 there is no substantial interbreeding with another 

 group spawning in a different river. Morphometric 

 measurements of both males and females were stan- 

 dardized to a postorbital-hypural length of 520 mm 

 by the method outlined by Beacham and Murray 

 (1983): 



M, = M„ 



L.. 



L = 



L = 



where M, = size of standardized morphometric 

 character, 

 M„ = observed character size, 



length that characters are standard- 

 ized to (520 mm), 



observed postorbital-hypural length, 

 and b is the regression coefficient of 

 log^ M„ on logp Lj, (stocks and sexes 

 separate). 



Two-way analysis of variance was again used to ex- 

 amine population differences and sexual dimorphism 

 in the morphometric characters. 



Developmental Biology 



We estimated fecundity of Yukon River chum 

 664 



salmon by collecting and freezing both ovaries from 

 14 females in the Dawson City commercial fishery 

 in 1985 (we also collected length and scales); we 

 subsequently thawed both ovaries and made tot;vl egg 

 counts for each female. The methodology of the 

 survey of developmental biology was similar to that 

 outlined by Beacham and Murray (1987). Gametes 

 were collected from five male and five female Kluane 

 River chum salmon on 17 October 1985. The gametes 

 were then shipped to the laboratory on ice, the eggs 

 fertilized at 8°C, and then subsequently reared in 

 controlled water temperatures of 4°, 8°, and 12°C 

 in vertical stack incubators. Five full-sib families 

 were obtained from the crosses, with each family 

 replicated in each incubator. Water temperatures 

 were recorded daily, and mean temperatures in the 

 incubators during the study were 4.1° (SD = 0.29), 

 8.0° (SD = 0.44), and 12°C (SD = 0.40), respectively. 



Egg diameter (millimeters) and weight (milli- 

 grams) for each female were determined from 30 

 water-hardened eggs preserved for at least 3 months 

 in 10% formalin. During incubation, dead eggs were 

 removed from each family, stored in Stockard's solu- 

 tion, and later inspected to remove unfertilized eggs. 

 Egg survival rates were then calculated based upon 

 the number of eggs initially fertilized. Once hatch- 

 ing began in each family, we recorded the number 

 of newly hatched alevins daily, and within 1 day of 

 50% hatching we anesthetized and preserved 30 per 

 family in 10% formalin for subsequent determina- 

 tion of alevin length and weight. Fork length was 

 recorded to the nearest 0.1 mm, total weight re- 

 corded to the nearest milligram, the yolk separated 

 from the rest of the body and weighed (milligrams), 

 and then tissue weight (milligrams) determined by 

 subtraction. Dead alevins were also removed and 

 counted in order to determine alevin survival rates. 

 The timing of fry emergence (swim-up) for each 

 family was determined by placing the alevins in an 

 emergence trap modified from Mason (1976), where 

 the alevins were classified as newly emergent fry 

 only when they became neutrally buoyant and 

 positively phototactic When 50% of the fry from a 

 particular family had emerged, all of the family re- 

 maining in the incubator was anesthetized and then 

 preserved in 10% formalin, and 30 fry were random- 

 ly drawn from the preserved samples and fry length 

 and weight determined as for alevins. 



Variation in egg size was analyzed with a one-way 

 (female was the index) analysis of variance. Varia- 

 tion in survival rates was analyzed by first determin- 

 ing survival rates for each group as proportions and 

 then transforming them to radians with the arcsine 



