capement fish passed from the fishway into the 

 lake. During 1977 and 1978, a stratified random 

 sampling plan was used to estimate total numbers 

 entering the lake. The total duration of the run 

 was divided into successive 5-d strata with 2 d 

 randomly selected out of each stratum. All fish 

 entering the trap during a 24-h period were visu- 

 ally counted and released. During each day sam- 

 pled, approximately 25 alewives were measured 

 for total length and sex was determined by strip- 

 ping. 



In 1979 a Smith-Root^ 602A electronic fish 

 counter was installed in the trap. Saila et al. ( 1972) 

 used the system 602 counter with two separate 

 tunnels for counting direction movement, whereas 

 the 602A has one tunnel for counting upstream 

 and downstream passage. The tunnel was 20 cm in 

 diameter and 35 cm long. During most of the run, 

 alewives that passed through the tunnel were held 

 in the trap and later counted to discover any errors 

 and to make necessary adjustments to the instru- 

 ment. 



A separate sampling plan was used at the bot- 

 tom of the fishway for the commercial catch. On 

 randomly selected days during the run, 9 d in 1977 

 and 15 d in 1978, 50-100 fish were taken from the 

 catch. In 1979 the number of days sampled was 31, 

 with 50 fish taken each day. Total length, weight, 

 sex, and scales were taken from these alewives. In 

 1979, otoliths were also removed for aging. 



Mean lengths and weights were computed for 

 each day sampled and for each sex. Length mea- 

 surements were taken from the total length of the 

 fish. Each mean length and weight was weighted 



^Reference to trade names does not imply endorsement by the 

 Maine Department of Marine Resources or by the National 

 Marine Fisheries Service, NOAA. 



by the number of fish caught or counted on that 

 day for total mean length and weight results. The 

 number offish harvested each year was estimated 

 by dividing total weight by the mean weight per 

 fish. 



Results 



Each year the alewife run began in early May 

 and ended in early June. The commercial har- 

 vest contained 1,277,642 fish in 1977, 999,484 in 

 1978, and 777,941 in 1979. The respective escape- 

 ments into Damariscotta Lake (±SE) were 

 26,813 ±2,624, 53,180 ±9,147, and 20,313 ±4,145 

 ripe alewives. The resulting escapement was 

 2.0% , 5.0%, and 2.6% of the commercial catches for 

 1977, 1978,and 1979, respectively 



Sex ratios in the commercial catch samples 

 showed no significant differences from the begin- 

 ning of the run to the end in all but a few samples 

 each season. The overall combined samples for 

 each year showed no significant difference on x^ 

 tests (P&0.05) between numbers of males to 

 females (Table 1). 



Early immigrants into Damariscotta Lake had 

 significantly different sex ratios in which males 

 always outnumbered females and as the run pro- 

 gressed these ratios had a tendency toward a 

 nonsignificant ratio of 1:1 (Figure 1). This persis- 

 tency in male dominance was evidenced by sig- 

 nificant (x^ P<0.05) totals in the ratios of 2.1:1 

 for 1977, 1.9:1 for 1978, and 2.6:1 for 1979 (Table 1). 



Age distribution of commercial and escapement 

 runs ranged from 3 to 9 jrr old. The age distribu- 

 tion for each sex in the commercial catch displayed 

 greater percentages of younger males than 

 younger females; conversely, there were greater 

 percentages of females at older ages than males in 



Table l. — Sex ratios (M:F) and number of alewives sampled in 5-d consecutive periods for the commercial and escapement runs at the 

 Damariscotta Lake fishway, Maine, 1977-79. The samples columns refer to the number of combined samples in the 5-d consecutive 

 periods. 



'x significance atP«0.05. 



208 



