into the lake to spawn. This particular fishery is 

 one of about 30 commercially harvested alewife 

 runs on the Maine coast and produces between 

 20 and 30% of the state's landings. 



Materials and Methods 



The method of harvesting was not considered 

 selective of size, sex, or age of the alewives, and 

 the catch presumably represented the true com- 

 position of the migrating stock. From previous 

 work it was known that the size and age composi- 

 tion was not homogeneous throughout the run 

 (Libby 1981), so a catch sample of fish was taken 

 on alternate days to gain an equal representation 

 of the total run. 



Each sample consisted of 50 fish scooped from 

 the catch in the holding trough. The sample was 

 then brought to the laboratory and processed as 

 soon as possible to minimize shrinkage or weight 

 loss. Total length and weight were measured to 

 the nearest millimeter and 0.1 g, respectively. 

 The alewives were sexed by visual inspection of 

 the gonads. 



Otoliths were removed, cleaned, dried, and set 

 into labeled black Plexiglas 2 trays. Watson (1965) 

 described this procedure for mounting otoliths 

 with the use of ethylene dichloride to fix the 

 otoliths permanently in the trays. I prefer Per- 

 mount, a histological medium that is poured over 

 the otoliths and left to harden. If an otolith has to 

 be repositioned, a drop of xylene will dissolve the 

 Permount back to a liquid state. The otoliths 

 were read with the use of a binocular microscope 

 at a 30X-60X magnification. 



Results and Discussion 



Table 1.— Sex ratios and mean length of 15 alewife samples 

 taken from the 1980 Damariscotta River commercial fishery. 



ferences between mean lengths. Using the 1980 

 data as an example, females were shown to be 

 larger than males at a given age (Table 1). A co- 

 variance analysis (Table 2) revealed no signifi- 

 cant differences between slopes of the lines for 

 the two sexes at the 5% level. Even though the 



Table 2. — Analysis of covariance of length by time regres- 

 sion for male and female alewives and test for nonzero pooled 

 slope. Damariscotta River, 1980. 



'F test, ratio of mean square of difference between slopes to mean 

 square of difference within slopes. 

 Calculated probability, not significant at the 5% level. 

 3 Pooled slope coefficient. 



The 1980 commercial harvest for the Damari- 

 scotta River lasted for 34 d, starting 4 May and 

 ending 6 June. Fifteen daily samples were taken, 

 each sample containing about 50 alewives total- 

 ing 365 males and 346 females. In each sample 

 the sex ratio did not deviate significantly (P> 

 0.05) based on a x 2 test from a 1 : 1 ratio (Table 1 ). 

 This ratio had been previously shown to be con- 

 sistent from 1977 to 1979 in the Damariscotta 

 River (Libby 1981). 



In analyzing length with time, I was more con- 

 cerned with similarities between the slopes of 

 lines comparing males and females than in dif- 



-Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



mean length varied daily, the compared length 

 distribution in each sample was less variable. 

 Bartlett's test of homogeneity demonstrated no 

 significant differences between the residual var- 

 iances ( x 2 = 3.59, df = 1 , P>0.05). A t-test of sig- 

 nificance of slope (t equals a ratio of the slope to 

 its standard error) applied to the pooled regres- 

 sion coefficient showed that the slope (—0.36) was 

 significantly different from zero (t = 9.36, df = 

 707, P<0.05). The influx of male and female 

 alewives into the river follows a similar pattern 

 regardless of their size differences. Ages through- 

 out the 1979 and 1980 samples ranged from 3 to 8 

 yr for 234 males and 3 to 9 yr for 259 females and 

 from 4 to 7 yr for 361 males and 3 to 7 yr for 344 

 females, respectively. 



903 



