WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



341 



The comparison of the relative abundance of whitefish in Lakes Michigan and 

 Huron in 1939 provides an explanation for the fact that the percentages for production 

 were the higher in Lake Michigan in that year despite a relatively more intensive fish- 

 ery in Lake Huron. The abundance of whitefish was below normal in 1939 in every 

 district of Lake Michigan. However, the percentage was below 50 in only two of the 

 eight districts (M-5 and M-7) and was below 60 in only three (M-5, M-6, and M-7). 

 In Lake Huron, on the other hand, the abundance of whitefish was less than 50 per- 

 cent of the 1929 "normal" in every district, and was so low as to suggest the virtual 

 disappearance of the species from the four most southerly districts. Thus it seems 

 that where the whitefish merely declined in abundance in Lake Michigan the species 

 approached extermination in most of Lake Huron. 



The possibility that abundance may have been above normal in 1929, the "normal" 

 year of reference for Lake Huron, does not affect the validity of the preceding state- 

 ment. If it is assumed, for example, that the abundance of whitefish in Lake Huron 

 was 50 percent above normal in 1929, hence that the percentages for 1939 should be 

 increased 50 percent, the following estimates are obtained of 1939 abundance as per- 

 centages of normal: 



District 

 H-l 

 H-2 

 H-3 



Abundance 



62 



64 

 9 



District 

 H-l 

 H-5 

 H-6 



Abundance 



10 



8 



15 



Even this increase leaves the percentages extremely low for the four southerly dis- 

 tricts, although the percentages for H-l and H-2 are raised to a point corresponding 

 roughly with the general level in Lake Michigan. 



The evidence that the use of deep trap nets in Lake Huron led to an excessively 

 great, and ultimately ruinous, expansion of .the whitefish fishery should not be taken 

 to signify that overfishing did not take place in Lake Michigan also. The capacity 

 for overfishing is not an exclusive characteristic of any one type of gear. Emphasis 

 has been placed on overfishing by the deep trap net merely because its extraordinary 

 efficiency made possible the extreme condition of overfishing observed in central and 

 southern Lake Huron. Obviously the removal of an equal quantity of whitefish by 

 any other gear would have proved equally disastrous. 



Although the maxima of production were relatively lower in Lake Michigan than 

 in Lake Huron, it must be considered probable that in some of the Lake Michigan dis- 

 tricts the catch of whitefish was sufficiently great to affect adversely the abundance of 

 the species in later years. In M— 1, for example, the high fishing intensity (tables 19 

 and 20) that made possible the production of roughly a million pounds of whitefish in 



* ? C 



DUO * O 



3 Q 



0. ^ 



I B 3 J / 9 J 5 



CALENDAR r £ A R 



Figures 13 to 20 show th? annua! fluctuations in the production (solid lines) and abundance (long dashes) of whitefish and in the intensity of the 

 whitefish fishery (short dashes) over the period, 1929-1939, in each of the eight statistical districts of Lake Michigan (see fig. 4). In each figure 

 the central horizontal line represents the average conditions for the 11 years, 1929-1939. 



Figure 13.— First district. M-l. 



