94 Stephen J. Walsh and Brooks M. Burr 



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TOTAL LENGTH (mm) 



Fig. 4. Length-frequency distribution of 45 ammocoetes of Lampetra aepyptera 

 from Terrapin Creek, Graves County, Kentucky, 4 June 1980. Curves were 

 smoothed using sliding averages of 7 mm. Age classes are represented by 

 Roman numerals. 



1971; Potter and Bailey 1972; Rohde et al. 1976), difficulty arises in 

 discerning older age classes because there may be arrested growth of 

 larger ammocoetes, i.e., simultaneous occurrence of ammocoetes as 

 large or larger than transforming individuals in autumn collections. 

 Inadequate numbers of specimens from fall months prevented our test- 

 ing for a period of arrested growth for the Terrapin Creek population. 

 Transformers taken throughout the study period averaged 112 mm TL 

 (R = 95 - 125, N = 14); neotenic individuals averaged 103 mm TL (R = 

 75 - 129, N = 15). The largest ammocoetes from all collections averaged 

 111 mm TL (R = 102 - 135, N = 22). Assuming a March spawning 

 period, we estimate the duration of the larval stage in the Terrapin 

 Creek population to be 4.5 years. If a period of arrested growth occurs 

 in this population the length of the larval stage could be 5.5 years. A 

 larval life of 3 to 5.4 years for L. aepyptera has been suggested by others 

 (Hubbs 1971; Rohde et al. 1976; Seversmith 1953). Rohde et al. (1976) 

 and Rohde and Jenkins (1980) speculated that some individuals may 

 remain as larvae for over 6 years. 



When lengths (L) and weights (W) of ammocoetes were trans- 

 formed to log values and the line of best fit determined by least squares, 

 the regression equation was Log W = 1.95 + 0.352 Log L, r = 0.99). 

 Rohde et al. (1976) found that the weights of ammocoetes from Dela- 

 ware increased as the 2.73 power of length. When we compared the 

 linear regression for transformers and neotenic individuals combined, 

 we found a slightly higher slope than that for ammocoetes (Log W = 

 1.96 + 0.248 Log L, r - 0.92). 



Coefficient of condition values (K) were calculated for the Terrapin 



