38 



Table 1/ 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



-Relation between total length (inches) and weight (ounces) of lake trout from northern Lake Michigan, also lengths 

 and toeights calculated with the length-weight equation 



[Based principally on lake trout recaptured from the 1944-46 plantings of marked fish. See text for details] 



lengths where averages are based on one or a few 

 fish. Other factors that possibly could have con- 

 tributed to the discrepancies include: annual and 

 seasonal fluctuations in condition; sex and state of 

 gonads (of the larger, mature fish); and gear selec- 

 tion. " It may, accordingly be held valid to use 

 the equation to describe the general length-weiglit 

 relation and thus estimate weight when length only 

 is known or length when weight only is available. 



The calculated weights (table 17) show that lake 

 trout would be expected to attain the weight of 1 

 pound at 15.1-15.2 inches, 2 pounds at about 18.9 

 inches, and 3 pounds at 21.5-21.6 inches. The 

 length corresponding to I/2 pounds, the minimum 

 weight at which lake trout may be taken legally in 

 the State of Michigan, was 17M inches. 



To test whether the equation representing the 

 length-weight relationship of the lake trout in the 

 sample was also representative of younger fish, 



" See Farran (1936) and Deasonand Hile (1947) for discussions of the efTects 

 of gill-net selectivity on the estimation of the length-weight relation. 



calculations of weight were compared with the 

 weights of the control groups reared in ponds at 

 Marquette, Mich. (Shetter 1951). The lengths at 

 which tlie comparisons were made are average 

 lengths at capture of the fish in the control groups. 

 Lengths overlapping those of the lake-reared fish 

 up to 10.7inciies are also inclmled in the tabulation. 



