length was measured to the nearest millimeter and 

 sex.was determined by dissection. We determined 

 the sex ratio for each day of the run to observe 

 changes during the migration. In*1982 each sea lam- 

 prey was also weighed to the nearest gram. Chi- 

 square tests were used to compare the sex ratios 

 for differences from a 1:1 frequency. Student's t-test 

 was used to compare the males and females for 

 mean length and weight. We compared males and 

 females for the length-weight relationship by cal- 

 culating a separate regression for each sex using the 

 logarithmic equation: log w = log a + (b) (log 1) 

 (Ricker 1975). 



Results and Discussion 



Abundance 



The numbers of sea lampreys lifted from 1958 to 

 1967 were relatively few, and probably reflected the 

 inefficiency of the fish lift rather than a small popula- 

 tion (Fig. 2). After the flume and second lift were 

 added in 1975 and 1976, respectively, 22,000-53,000 

 adults have been passed upstream each year. The 

 53,000 counted in 1981 was the largest number ever 

 passed at Holyoke and the largest run documented 

 in any river. In 1981, 59% of the total run was lifted 



during the week of 24-30 May; and in 1982, 68% 

 were lifted during the week of 28 May-3 June. 

 Beamish (1980) reported that about 8,600 sea lam- 

 preys are lifted annually in the fish lift at Macta- 

 quac Dam. He estimated the spawning populations 

 in other northern streams at <8,000. 



The sea lampreys that reach Holyoke Dam are 

 only a portion of the total run, because several 

 tributaries below the dam support populations 

 (Whitworth et al. 1976). The sea lamprey popula- 

 tion may increase as adults gain access to additional 

 spawning and rearing habitat in headwater streams 

 by using fish passage facilities constructed for Atlan- 

 tic salmon, Salmo salar, and American shad (Mof- 

 fitt et al. 1982). Thus, the restoration program 

 designed primarily for Atlantic salmon and Ameri- 

 can shad is also restoring the sea lamprey to addi- 

 tional habitat. Since 1975, over 20,000 sea lampreys 

 have been passed each year at Holyoke Dam and 

 given access to new spawning and rearing habitat. 

 The estimated life span of sea lampreys in the St. 

 John River is estimated at 9-12 yr (Beamish and Pot- 

 ter 1975). Therefore, if the Connecticut River 

 population returns to their natal stream and has a 

 similar life cycle, and if the strength of the year 

 classes after 1975 was enhanced by the additional 

 rearing habitat above Holyoke, then beginning in 



60,000- 

 50,000- 

 40,000 



(Z 30,000 

 LU 



CD 



•^ 20,000 



600- 



not 



counted 



58 60 62 64 66 68-74 76 78 80 82 84 



YEAR 



Figure 2.— Number of adult sea lampreys lifted in the Holyoke fish lifts each year, 1958-84. 



478 



