importance of M-5 also decreased substantially 

 from second to fifth in rank and from 20 . 6 to 

 13.9 in percentage. The percentage decreased 

 sharply- -from 6.9 to 3. 4- -in M-4 but that small 

 district held last place in both periods. M-6 and 

 M-7 did not change ranking and experienced small 

 changes of percentages . 



The average annual number of intensity 

 units was higher in 1944-1953 than in 1929-1943 

 in every district but M-3 and M-4. The great- 

 est increases were in M-2 (1944-1953 average 

 of 33.1 units, 3.85 times the 1929-1943 mean 

 of 8.6) andM-8 (1944-1953 average of 30.4 

 units, 3.17 times the 1929-1943 figure of 9.6). 

 In the remaining districts the ratios of 1944- 

 1953 to 1929-1943 intensity were: M-7, 1.68; 

 M-6, 1.47; M-5, 1.03; M-4, 0.75; M-3, 0.48. 



The intensity indices for the combined 

 districts (right-hand column of table 17; fig. 10) 

 show alternating periods of above- and below- 

 average fishing pressure. The Index was 87 

 (actually 87. 1) in 1929, from which point it 

 dropped to only 44 in 1933. Fishing pressure 

 more than doubled in 1934 and again in 1935 to 

 reach an index value of 203 in the latter year . 

 The index was even higher in 1936 (209) and 

 continued well above 100 through 1939. The 

 drop to 41 in 1940 ushered in a 5-year period 

 in which the intensity index exceeded 50 only 

 once (1942) and a 7-year interval of values be- 

 low 100 . The increase that started in 1945 

 carried the index past the 15 -year base value in 

 1947 (115) . Intensity was consistently high- - 

 from 180 to 240- -in 1948-1953. 



Previous inquiries into factors control- 

 ling fishing intensity in the Great Lakes (Van 

 Oosten, Hile, and Jobes, 1946; Hile, 1949; 

 Hlle, Eschmeyer, and Lunger, 1951a, b; Hile, 

 Lunger, and Buettner, 1953) have shown the 

 problem to be extremely complicated . Although 

 a listing of the major factors would be simple, 

 it is difficult to obtain information on some 

 (particularly the economics of the fisheries), 

 and their interactions and effects are so varied 

 that analyses seldom lead to conclusive results. 



The fluctuations of fishing intensity for 

 chubs in Lake Michigan are better understood 

 in the light of their relation to those of other 



fisheries. Most chub fishermen have tradition- 

 ally directed nearly all of their fishing activity 

 toward the capture of lake trout and chubs . As 

 the lake trout fishery declined and disappeared 

 during the 1940's the fishermen turned more and 

 more to chub fishing, and finally most became 

 entirely dependent on chubs . The disappearance 

 of lake trout offers a simple explanation of the 

 recent upward trend and of the generally high 

 level of fishing intensity for chubs beginning 

 about 1948 . The only two districts that had lower 

 fishing intensity in 1944-1953 than in 1929-1943 

 (M-3 and M-4) also experienced such poor chub 

 fishing in recent years (in comparison with other 

 districts) that some fishermen either reduced or 

 abandoned fishing operations, and others moved 

 to better grounds. 



Although the recent high fishing intensity 

 for chubs can be explained easily as the result 

 of the decline of the lake trout, no similar gen- 

 eral explanation can be offered for fluctuations 

 in 1929-1943 before either the decline of trout 

 or the introduction of the more efficient nylon 

 netting (table 19) . High availability of chubs 

 might be expected to stimulate fishing intensity 

 and low availability to depress it; a significant 

 positive correlation (5 -percent level) occurred, 

 however, in only 2 districts (M-4 and M-5X 

 Since chubs were the principal alternative species 

 to the lake trout and since fishing for chubs and 

 trout are almost mutually exclusive (few chubs 

 are caught in trout nets and few legal-sized trout 

 in chub nets) fishing intensity for chubs should 

 be correlated negatively with the abundance of 

 trout and with the intensity of the lake trout 

 fishery. A significant negative correlation be- 

 tween the abundance of trout and fishing intensity 

 for chubs occurred in only 1 of 7 districts (M-7, 

 r -. -0.795, p<0.01); apparently the fluctuations 

 in availability of trout were not sufficient to pro- 

 duce the expected relationship . Fishing intensities 

 for lake trout and for chubs were correlated at 

 the 5-percent level in M-2 and M-4 and at the 

 1 -percent level in M-6, but not in the other 4 

 districts. The additional data of table 19 on 

 correlations between the abundance of chubs and 

 of lake trout and between fishing intensity for 

 trout and the abundance of that species give no 

 reason to question the conclusion that factors 

 controlling fishing intensity for chubs in 1929- 

 1943 were complex and variable. 



41 



