SEA LAMPREY OF CAYUGA LAKE 



603 



cause of the relatively short time the nets were 

 fishing, it is believed that the data are not unduly 

 biased by attacks on trout in the nets. 



A total of 1,372 lake trout were examined for 

 lamprey scars and wounds. All were measured, 

 but to minimize injury from handling during warm 

 weather, only about 700 were weighed. Fork 

 length 9 was measured to the nearest 0.1 inch and 

 weight was measured on a Chatillon spring balance 

 to the nearest ounce. 



In this discussion, a wound is any place of lam- 

 prey attachment where the skin has been perfo- 

 rated and has not healed. Hemorrhaged blood 

 vessels and inflamed tissues produce a red appear- 

 ance. A scar is a wound that has healed. The 

 lacerated tissues have coalesced and the red 

 coloration has disappeared. The condition of 

 marks was rarely such as to make the classification 

 (scar or wound) questionable. That initial heal- 

 ing may take place within a few days was indicated 

 by observations on brook trout held in hatchery 

 troughs. 



Loss of body weight resulting from sea lamprey 

 attacks 



Before analysis to detect and measure possible 

 effects of sea lamprey attacks on the weight of lake 

 trout could be undertaken, it was necessary to 

 determine whether or not the length-weight rela- 

 tion differed between the sexes or from year to year. 

 For this purpose 19 unscarred males and 19 un- 

 scarred females were selected at random from 

 each of the collections made in 1949, 1950, and 

 1951. The analysis of covariance (after trans- 

 formation of lengths and weights to logarithms to 

 assure approximately linear regression) disclosed 

 no significant differences among the several 

 groups. Data for the sexes and the different 

 years of capture could accordingly be combined in 

 all further analyses. 



Relation between body weight and number of scars 

 and wounds. — Death is not inevitable to all lake 

 trout that are attacked by a sea lamprey. The 

 numerous trout that possess scars or wounds re- 

 sulting from sea lamprey attacks offer proof. 

 However, trout which have survived an attack 

 may or may not have suffered a setback in growth. 

 From the loss of blood alone it seemed likely that 



losses in body weight would result. Furthermore, 

 it was reasoned that any immediate weight loss 

 would be directly correlated with the number of 

 lamprey wounds, and a permanent weight loss 

 would be directly correlated with the number of 

 lamprey scars. 



Royce (1950) demonstrated that thinness was 

 not correlated with the number of lamprey attacks 

 on relatively large lake trout. The possibility re- 

 mained, however, that small lake trout might- 

 suffer adverse effects from lamprey attacks; con- 

 sequently the present study was restricted to lake 

 trout ranging from 9 to 22 inches in length. 



Lake trout whose lengths were within the size 

 range just mentioned were divided into three major 

 classes based on the number of scars borne by each 

 trout. Each class was subdivided into three 

 classes based on the number of wounds borne by 

 each trout (table 40). The major classes were as 

 follows: Trout without lamprey scars; trout with 

 one lamprey scar; and tiout with two or more 

 lamprey scars. Subclasses were: trout without 

 lamprey wounds; trout with one lamprey wound; 

 and trout witli two or more lamprey wounds. 

 Fifteen lake trout were taken at random from 

 each category to provide a total of 135 specimens 

 for the analysis. 



Table 40. — Mean adjusted weights and rank order of 

 weight classes of 9 groups of lake trout 



' The conversion formula for transforming fork length to total length is: 

 T= 1.082 F+0.045, where T equals total length and F equals fork length. 

 Initial study on the recovery and relative survival ol flngerling and yearling 

 lake trout stocked in Cayuga Lake, by William G. Bentley, M.S. thesis, 

 Cornell University, June 1950. 



The hypothesis that there was no difference in 

 weight among the scar classes or among the wound 

 subclasses was tested by an analysis of covariance. 

 The analysis for scars produced an F value that 

 was not significant, thus indicating that the null 

 hypothesis should be accepted (table 40). The 

 adjusted weights of the scar classes indicate that 

 lake trout with the highest incidence of lamprey 

 scars are the thinnest, but, as is shown by the scar- 

 class rank order, the trend is not consistent. 



