SEA LAMPREY OF CAYUGA LAKE 



599 



in the weight-frequency graph, the largest of 

 which is composed of the transforming ammo- 

 coetes (believed to be only one age group). Since 

 age groups and I were established to be lacking 

 in the August collections, a justified assignment of 

 ages to the modes on the weight-frequency graph 

 is as follows: 0.013 ounce, age group II; 0.031 

 ounce, age group III; 0.066 ounce, age group IV; 

 0.101 ounce, age group V; 0.154 ounce, age group 

 VI; 0.172 ounce, age group VII (the transforming 

 ammocoetes). 



Table 36. — Weight-frequency distribution of ammocoetes 

 and transforming sea lampreys collected in Cayuga Inlet 

 during August 



[Weights are grouped by 0.25-gram intervals] 



Table 37. — Length-weight relationship of ammocoetes and 

 transforming sea lampreys from Cayuqa Inlet 



The distinctiveness of the modes in the weight- 

 frequency distribution (fig. 19) is striking. Even 

 more significant is the agreement between esti- 

 mates of age made independently from length and 

 weight distributions. From the data on the 

 length-weight relation of ammocoetes (table 37; 

 fig. 20) it is seen that modal lengths and modal 

 weights agree ; it may be concluded that the same 

 general groups of ammocoetes were identified by 

 the two methods. Although analyses of the 

 length and weight frequencies led to the same re- 

 sults, the weight-frequency method seems to be 

 the better because of greater precision in defining 

 age groups. 



AMMOCOETES 



The most questionable aspect in the interpreta- 

 tion of the length-frequency data on Cayuga Lake 

 ammocoetes concerns the validity of age group VI, 

 a group for which the mode was little apparent in 

 the August frequencies and whose size was slightly, 

 if at all, greater than that of transforming lam- 

 preys. Evidence that the VI group is valid was 

 obtained from experiments with marked speci- 

 mens. In this experiment a series of sea lamprey 



