"WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



367 



may be expected to capture 113 illegal whitefish to only 78 in large-mesh nets. The 



release of undersized fish by large-mesh nets is, therefore, 100 X 



113.4 — 77.9 



or 31.3 



113.4 



percent. This percentage of release is more reliable than the release of 25.9 percent 

 computed from the average catches of the two groups of nets without consideration of 

 the effects of locality, depth, and time. 



That the undersized whitefish, as well as the lake trout commonly taken with 

 them, do escape from the pots of impounding nets with the larger meshes is further 

 suggested by the progressive increase in the average sizes of these fish with each in- 

 crease in the size of mesh (table 38). 



The controversy concerning the proper size of mesh in the pots of impounding nets 

 does not, however, revolve so much around the release of undersized fish as around 

 the escape of legal-sized fish, both whitefish and lake trout. It is not believed that 

 any legal-sized whitefish can go through meshes smaller than 4H inches as found in 

 use (the minimum size required by Michigan's law), but it is most probable that some 

 legal-sized lake trout escape as is suggested by the larger average size of these fish in 

 the bigger-meshed nets (table 38). 



Table 38. — Average size of whitefish and lake trout taken from Lakes Huron and Michigan in 1931 and 1932 

 in impounding nets with different sizes of mesh in the pot 



Additional information on this question of escapement is provided by the length 

 and weight frequencies of the whitefish and lake trout gilled in the different sizes of 

 mesh (tables 39, 40, 41, and 42). Table 39 shows that all of the whitefish gilled in 

 meshes smaller than 3 inches were undersized. Presumably, then, no legal-sized white- 

 fish can escape through these meshes. It was not until a mesh of 3% to 3 15 16 

 inches (about 4 to 4 7/16 inches as manufactured) was used that legal-sized white- 

 fish were gilled in any numbers, although 91 percent of the gilled fish were still below 

 the 2-pound legal limit. Even the largest meshes for which data are adequate (4 to 

 4 7/16 inches) did not permit many of the smaller fish to escape as 79 percent of the 

 gilled individuals in these meshes were undersized, and the average weight of all fish 

 was noticeably less than 2 pounds (1 pound, 11 ounces). 



It is of interest to note from the frequencies that the bulk of the gilled whitefish 

 varied from 1 to 2 pounds in weight in meshes of 3 to 3 15/16 inches and from 1 to 2 1 /! 

 pounds in the larger meshes — a range of onlv 1 or iy± pounds. The corresponding 

 range in length of these fish (table 40) was $y 2 inches (15 - 18V 2 ; 15% _ 19; 16 - 19V 2 

 inches). 



The progressive increase in the average weight of the undersized gilled whitefish, 

 as well as in the average length (table 40), with each increase in the size of mesh 



