AGE DETERMINATION FROM SCALES OF LAKE TROUT 



45 



4 5 6 7 8 9 



YEAR OF LIFE 



Figure 22. — Calculated lengths (sums of mean increments of growth in inches) of marked and unmarked lake trout of 

 year classes 1944-46, and of the older year classes (1938-43) from the wild stock, caught by 4'2-inch-mesh nets in north- 

 ernLake Michigan, areas 1-6. 



lake tiout (year classes 1944-46) caught by 2?^- 

 iiich-mesh nets in northern Lake Michigan were 

 also lower than those of marked lake trout caught 

 in the same nets. In fact, the differences between 

 their calculated lengths ranged from 0.4 inch at 

 formation of the first annulus to 1.1 inches at the 

 fifth annulus. The average difference was 0.2 

 inch greater than the average difference between 

 the groups of marked and unmarked lake trout 

 caught in large-mesh nets. The average annual 

 increment of growth in length for the fish from 

 small-mesh nets was 2.4 inches for both marked 



and unmarked lake trout but the marked fish were 

 already 0.4 inch longer than tiie luumirked fish at 

 formation of the first annulus (table 22, fig. 22). 

 Although marked and unmarked lake trout of 

 the same year classes caught by small-mesli nets 

 were somewhat smaller than those caught in the 

 large-mesh nets, the calculated lengths of the 

 unmarked fish retained about the same relative 

 position below those of the marked fish that the 

 unmarked fish had to the marked fish caught in 

 large-mesh nets. 



Table 22. — Calculated lettylhs (sums of mean increments of growth in inches) of marked and unmarked lake trout of year 



classes 1944-46 caught in Lake Michigan 

 [Increments of growth in parentheses] 



