WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



329 



Table 10. — Annual fluctuations in the abundance percentages for whitefish in the various districts and areas 



of Lake Huron, 1929-1939 



[Expressed as percentages of average 1929-1939 abundance. In the computation of percentages for areas of more than one district and for the 



entire lake, the abundance percentage for each district was weighted according to the percentage of the total 1929 



production contributed by that district] 



1 Year of introduction of the deep trap net. 



3 Years of greatest production by deep trap nets. 



Table 11. — Annual fluctuation in the catch of whitefish per unit of fishing effort of gill nets, deep trap nets, 

 and pound nets in the various districts of Lake Huron, 1929-1939 



these same decreases are apparent in the records of the actual catch per lift of deep 

 trap nets in these same districts (table 11). 



The history of the annual fluctuations in the abundance of whitefish in the years 

 subsequent to the decline that followed immediately upon the extensive use of the deep 

 trap net varied widely among the districts. 



In H-l, where the use of deep trap nets may be described as "moderate," the 

 abundance percentage for whitefish dropped to 85 in 1933, fluctuated irregularly in 

 1933-1937, and declined to a level of less than 60 percent in 1938 and 1939. Abundance 

 did not fall significantly below 80 before 1938. In H-2, the other district in which the 

 maxima of production and fishing intensity were relatively low, the sudden decline to 



