WHITEFISH FISHERY OF LAKES HURON AND MICHIGAN 



339 



Michigan fishermen were able to abolish the net from their waters by law) ; (3) the 

 summer aggregation of whitefish occurs in shallower water in Lake Michigan than in 

 Lake Huron and hence the Lake Michigan fish never moved beyond the reach of pound 

 nets to the same degree as did those in Lake Huron; (4) the deep-water population of 

 whitefish available to the deep trap nets was less dense in Lake Michigan than in 

 Lake Huron, hence in contrast to the situation in Lake Huron the deep-trap-net lifts 

 did not alwavs average much larger than those of the pound nets. (See, for example, 

 M-l and M-2 for 1931, table 17.) 



Although the deep trap net usually took more whitefish per lift than did the pound 

 net in Lake Michigan, and from this point of view may be considered to have been very 

 effective and successful, in no district of the lake did the catch per lift of deep trap 

 nets approach the level that it attained in the four southerly districts of Lake 

 Huron (tables 11 and 17). The average catch per lift of deep trap nets in Lake Mich- 

 igan reached values of 257.5 pounds in M-2 in 1932 and 184.4 pounds in the same dis- 

 trict in 1931. Operations were limited, however, in M-2. In M-l and M-3, where deep- 

 trap-net operations were more extensive, the greatest average catches per lift were 131.7 

 pounds (M-l in 1930) and 164.9 pounds (M-3 in 1932). These values were far below 

 the greatest averages in the districts of central and southern Lake Huron (402.5 to 

 476.1 pounds per lift), but compared favorablv with the maxima in northern Lake 

 Huron (167.7 pounds per lift in H-l in 1930; 141.9 pounds per lift in H-2 in 1930). 

 The deep trap net was relatively unsuccessful in southern Lake Michigan also, for the 

 only significant operations with the gear (M-7 in 1934) yielded an average of 118.2 

 pounds of whitefish per lift. 



To be sure, the deep trap net was introduced into northern Lake Michigan after 

 the peak of abundance of the whitefish had passed. The examination of the abun- 

 dance percentages of table 21 suggests that if this gear had been fished in 1929, the 

 year of high abundance, the average catch per lift in that year most probably would 

 have exceeded the highest yields listed in table 17 for deep trap nets in each of the 

 northern districts. On the other hand, abundance percentages may not validly serve 

 as an exact index to the average size of a lift since the fluctuations in the catch per 

 lift of this gear did not always correspond with those in abundance subsequent to 1929. 

 For example, the average catch per lift of deep trap nets in M-l decreased in 1931 and 

 increased in 1932 despite the fact that abundance remained practically unchanged in 

 1931 and fell in 1932. Again, the highest yield (257.5 pounds per lift) of the northern 

 area occurred in a district (M-2) when abundance was normal (1932 1. 



As the average deep-trap-net lifts wen- small in comparison with those of central 

 and southern Lake Huron irrespective of how much abundance was above average, 

 the conclusion appears valid that in northern Lake Michigan as in northern Lake 

 Huron the deep trap net was far less successful than it was in central and southern 

 Lake Huron. 



The maximum and 1939 percentages of production, fishing intensity, and abun- 

 dance in table 18 have been computed with respect to average conditions in 1929-1939. 

 The corresponding estimates for Lake Huron (table 7) were made with reference to 



Table 18. — Maximum and 1939 production and abundance of whitefish and maximum and 1939 fishing 



intensity for whitefish 



[Expressed as percentages of the average 1929-1939 values in each statistical district of Lake Michigan] 



