FISHERY BULLETIN; VOL. 86, NO. 2 



0.62. This ratio did not change between years (x^ 

 = 7.92, P < 0.01) and was significantly less than 

 1.0 (binomial test: z = -5.37, P < 0.001). There 

 was no trend between sex ratio and smolt age in 

 1982 (x^ = 1.21, P = 0.75), but the percentage of 

 males tended to increase with smolt age in 1983 

 (X^ - 12.67, P - 0.002). 



Length at Smoltification 



The mean length at smoltification was esti- 

 mated by back-calculation at 135 ± 15 mm for 

 postsmolts collected in 1982 and 1983. Scale ra- 

 dius was linearly related to body length both in 



1982 (4 scales measured per fish, P < 0.0001) and 

 in 1983 (1 scale measured per fish, P < 0.0001); 

 probability values are those of F-tests from anal- 

 ysis of variance. Back-calculated smolt lengths 

 were normally distributed (P = 0.80): 75% of the 

 postsmolts ranged between 120 and 150 mm at 

 smoltification. There were also 7% individuals in 

 the 160-200 mm range. Differences in mean 

 smolt length were not significant between the 

 ages and the sexes both in 1982 (F = 1.84, 

 P = 0.08) and in 1983 (F = 1.05, P = 0.39), and, 

 pooling the ages and the sexes, between 1982 and 



1983 (^ = 1.32, P >0.15). 



Rate of Increase in Size 



The rate of increase in size of postsmolts was 

 very rapid in summer both in 1982 and 1983. 

 Postsmolts collected in 1982 between mid-August 

 and mid-October in = 383; mean date is 1 Sep- 

 tember) averaged 265 ± 25 mm (range 195-328) 

 and 212 ± 58 g (range 92-389). In 1983, 

 postsmolts collected between mid-September and 

 mid-October (n = 155, mean date is 30 Septem- 

 ber) averaged 306 ± 17 mm (range 258-362) and 

 320 ± 57 g (range 192-565). There was no differ- 

 ence in mean size between males and females and 

 between age-classes in 1982 (P > 0.40) and 1983 

 (P > 0.20); probability values are those of F-tests 

 from 2-way analysis of variance. From a mean 

 smolt length of 135 mm and assuming smolts mi- 

 grated to estuaries 15 June, postsmolts grew at a 

 rate of 1.65 mm/day during a 2.5-mo (15 June — 

 1 September) and a 3.5-mo (15 June-30 Septem- 

 ber) period in 1982 and 1983, respectively. 



This estimate is conservative because the rate 

 of increase in length tended to decrease late in the 

 sampling period. Postsmolts steadily increased in 

 length and weight in the period mid-August to 

 mid-September 1982 (Figs. 2, 3). From mid- 



September, the rate tended to slow down. The 

 inclusion of data for 1983, collected later in the 

 autumn, corroborates this observation indicating 

 that conditions changed in late-September in 

 1982 and 1983. 



Length-weight relationships were examined 

 for 1982 and 1983 separately. The analysis of co- 

 variance showed that males and females exhib- 

 ited the same length-weight relationship, both in 



1982 (P - 0.53) and 1983 (P - 0.42). Similarly, 

 length-weight relationship did not change be- 

 tween age groups in 1982 (P - 0.06) and 1983 

 (P = 0.49). The covariance for 1982 was nearly 

 significant because the slope for 5-yr-old 

 postsmolts, based on 15 individuals, was larger 

 than for other age groups. However, mean condi- 

 tion index values by age revealed no significant 

 difference between age groups in 1982 (P = 0.11) 

 or 1983 (P = 0.28). 



Since there was also no significant difference in 

 the length- weight relationship between 1982 and 



1983 (P = 0.14), the data were pooled. Thus the 

 length-weight relationship for postsmolts col- 

 lected in this study can be described as a single 

 regression: 



log W = (2.8280 • log L) - 4.5336 



P < 0.001, n = 539 



where W = weight (g); L = length (mm). 



Maturation of Gonads 



Postsmolts were all immature both in 1982 and 

 1983, but differences were observed between 

 males and females in 1982. Testes averaged 

 48 ± 6 mg (95% C.L., n = 124) for a mean male 

 gonadosomatic index value of 0.025% ± 0.003% 

 (95% C.L., n = 124). There was no significant dif- 

 ference in the mean value of either parameter 

 between age groups (P > 0.52). Testis weight in- 

 creased in time and as body length and body 

 weight increased, but again there was no differ- 

 ence between age groups (Table 2). However, the 

 gonadosomatic index did not change in time 

 (P = 0.10) or as postsmolts' size increased 

 (P = 0.16 for body length and P = 0.10 for body 

 weight), suggesting that changes in size of the 

 testes were not allometric in male postsmolts in 

 the autumn period. Regressions were tested and 

 compared following Snedecor and Cochran (1967) 

 and Sokal and Rohlf (1969). 



There was more variability in the data for fe- 



200 



