1984 there should be increased returns of adults at 

 Holyoke. The return of sea lampreys at Holyoke in 

 1984 was not a record return, but this could be due 

 to the high discharge caused by the 50-yr flood that 

 occurred in early June 1984, when most sea lam- 

 preys are lifted. If the sea lamprey population in- 

 creases, the wound frequencies should increase on 

 host species of marine and anadromous fish. 



Sex Ratio 



Sex ratios for both years were skewed from 1:1 

 in favor of males, but the ratio was only significant 

 in 1982: in 1981, 56% were males (ratio: 1.3:1; x 2 

 = 3.4, P > 0.05; in 1982, 62% were males (ratio: 

 1.6:1; x 2 = H.6, P < 0.005, Table 1). Sex ratios also 

 changed during the spawning migration with the 

 proportion of males increasing late in the run. The 

 percent of males in the early and late periods were 

 55 and 59% in 1981 and 59 and 67% in 1982. The 

 increase in the proportion of males was not signifi- 

 cantly different from a 1:1 ratio in 1981, but the in- 

 crease was significant in 1982 (x 2 = 7.6:P < 0.01). 

 Applegate (1950) found that males in landlocked sea 

 lamprey populations increased to about 75% in the 

 late part of the run. The reason for this phenomenon 

 is unknown. 



Males are the most abundant sex in stable popula- 

 tions of sea-run and landlocked sea lampreys. 

 Beamish et al. (1979) reported 55% males (ratio: 

 1.36:1) in nearly mature adults in the St. John River 

 in 1974-77 (Table 1). Davis (1967), who collected 

 anadromous sea lampreys for 5 yr from Barrows 

 Stream, ME, reported a male:female ratio of 1.9:1; 

 however, the sample size was very small (N = 66). 

 Potter et al. (1974) found an excess of males in land- 



Table 1. — Mean total length and weight (SE in parenthesis), and 

 percent males in sea lampreys sampled at Holyoke Dam, Connec- 

 ticut River, compared with samples collected from the Mactaquac 

 Dam, St. John River. 



'249 males were weighed. 



2 155 females were weighted. 



3 Data from Beamish et al. (1979); ± 95% confidence limits in parenthesis. 



locked sea lamprey (ratio: 1.26:1). The sex ratio in 

 stable populations (where males are more abundant 

 than females) is different from the ratio in popula- 

 tions from the upper Great Lakes, where an excess 

 of females is typical of populations being eradicated 

 or controlled (Smith 1971). Sex ratios in sea lam- 

 preys also vary with cycles of abundance (Wigley 

 1959; Smith 1971), and temperature and nutrition 

 may differentially affect growth and survival of male 

 and female ammocoetes (Hardisty 1954). 



Total Length and Weight 



In 1981, 464 sea lampreys (0.9% of the number 

 lifted) were measured for total length; in 1982 the 

 number examined was 404 (1.5% of the number 

 lifted). There was no significant difference between 

 the mean length of males and females during either 

 year or for both years (Student's t-test: P > 0.05, 

 Table 1). Length of females and males ranged from 

 60 to 85 cm in both years. 



The similarity in mean total length of adults in the 

 consecutive spawning runs of 1981-82 suggests 

 relative stability of the sea lamprey population. This 

 differs greatly from the unstable sea lamprey 

 populations in the Great Lakes where body length 

 decreased from 1950's to 1960's— changes related 

 to decreases in food supply and changes in the en- 

 vironment (Smith 1971). 



The mean weight of females was not significant- 

 ly different from the mean weight of males (Stu- 

 dent's t-test: P > 0.05, Table 1). We determined the 

 length-weight relationship by using the regression 

 equations: log w = -3.42 ± (2.21) (log 1), (r 2 = 

 0.75, P < 0.01) for females and log w = -3.11 ± 

 (2.10) (log 1), (r 2 = 0.76, P < 0.01) for males. There 

 was no significant difference between the slopes of 

 the regression lines, consequently we combined 

 males and females (N = 404). Using the equation 

 y = b + mx or weight = b + (slope) (length), a highly 

 significant correlation (r 2 = 0.76, P < 0.01) was 

 found for the regression equation: weight = 521.9 

 + (0.23890) (length). The length-weight relationship 

 is linear, rather than sigmoid, as it is in most fishes. 

 Because the body is attenuate, the weight of sea lam- 

 preys does not increase as rapidly with length as it 

 does in most other fishes. This relationship is less 

 evident in females, possibly because of the additional 

 weight of their eggs. 



Generally, in landlocked populations, females are 

 slightly heavier than males because of their high 

 fecundity (Applegate 1950). We also found this was 

 true. Although the sea lampreys at Holyoke Dam 

 were similar in length to those in the St. John River, 



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