The abundance indices for the combined 

 districts (right-hand column of table 8; fig. 10) 

 which measure the general level of fishing suc- 

 cess give some indication of cyclic fluctuations. 

 The index stood at 121 in 1929, dropped to 90 in 

 1932, increased to 127 in 1934, declined (with 

 one exception to trend) to the 25-year minimum 

 of 78 in 1940, rose to 182 in 1945, fell away to 

 136 in 1949, increased to the 25 -year peak of 

 200 in 1952, and was 180 in 1953. The general 

 trend of availability has been upward since 1940. 

 Because of disturbing factors discussed earlier 

 in the section the significance of these fluctua- 

 tions is to a degree questionable. The common 

 use of nylon twine doubtless contributed strongly 

 to the high values of the index in the last 4 or 5 

 years of the period. 



States of Illinois, 1950-1953, and Wis - 

 consin, 1953 *. - -Since records of catch -per -unit- 

 effort are available for Wisconsin in only 1 year 

 (table 7) and for Illinois in only 4 (table 13), in- 

 dices of abundance have not been calculated for 

 either state. The actual poundages per lift of 

 10, 000 linear feet of chub gill nets, however, 

 permit comparisons of the quality of fishing in 

 various statistical districts. To facilitate these 

 comparisons for 1953 these poundages are re- 

 corded in figure 2 . 



The 1953 catch per lift of "chubs" (see 

 footnote 7) was lew in both of the Wisconsin 

 districts of Green Bay, W-l and W-2 (table 7). 

 Catches in the open lake, W-3 through W-6, 

 were larger than in Green Bay and in general 

 similar to those of contiguous waters of Michi- 

 gan (an exception need not be made for M-3, 

 since, as was explained earlier, the chub fish- 

 ing in the western part of that district was 

 assigned to M-2). Principal contrasts are pro- 

 vided by W-4 in which the catch of 354 pounds 

 per lift was lower than in M-5 (415 pounds) and 

 M-6 (407 pounds) and by W-6 where the take of 

 506 pounds exceeded the figures of 439 in M-7 

 and 447 in M-8. 



The catch of chubs per lift of 10, 000 

 linear feet of gill nets in Illinois (table 13) 

 ranged from 445 in 1951 to 583 in 1953. With- 

 out exception these averages were higher than 

 those of the adjacent Michigan district, M-8 

 (table 9). The 1953 catch per lift was also 



greater than that for the Wisconsin district 

 immediately to the north . 



The Wisconsin and Michigan records of 

 catch per lift in 1953 are believed to be compar- 

 able as measures of the availability of chubs . 

 The minimum legal mesh size was 2-1/2 inches 

 in both states and both had reasonably effective 

 enforcement of the law . Wisconsin and Michigan 

 regulations did differ as to maximum legal depth 

 (distance from float line to lead line) of chub 

 gill nets . In Wi sconsin these nets could not be 

 more than 35 meshes deep whereas in Michigan 

 the maximum legal depth was 11 feet. Despite 

 this difference in the regulations, the nets actu- 

 ally fished by Wisconsin and Michigan fishermen 

 were approximately the same. Operational dis- 

 advantages of deep gill nets prevented Michigan 

 fishermen from taking advantage of their more 

 liberal regulation . The relatively high catch per 

 lift in Illinois probably does not reflect a higher 

 abundance of chubs but resulted from the small 

 mesh size of nets fished by Illinois fishermen. 



If allowance is made for the small mesh 

 fished in Illinois, and if the detached waters of 

 Green Bay and districts M-3 and M-4 are ex- 

 cluded, it may be stated that the availability of 

 chubs varied only moderately in 1953 among 

 different areas of the main basins of Lake Michi- 

 gan. Major difference between districts in which 

 similar nets were fished was provided by W-4 

 (354 pounds per unit effort) and W-6 (506 pounds). 

 The unweighted mean of the catch per lift in Wis- 

 consin districts W-3 through W-6 was 429 pounds. 

 In Michigan the corresponding figure for M-2 and M- 

 through M-8 was 427 pounds. The situation in 

 1953 contrasts sharply with that in 1930-1932 

 when results of experimental fishing led Van 

 Oosten (1933) to state that, "Chubs were found 

 to be about 2.7 times as abundant in the Michigan 

 waters of Lake Michigan as in the Wisconsin and 

 Illinois waters of this lake." Van Oosten attributed 

 the lower abundance of chubs in Illinois and Wis- 

 consin to the more intensive fishing and the smaller 

 meshes in the nets fished along the west shore. 

 Although Van Oosten did not discuss production 

 statistics, it can be seen from table 2 that the 

 take was relatively light in Michigan in the years 

 of the Fulmar operations. In 1930-1932 Wisconsin 

 and Illinois catches were 6.2 times the Michigan 

 catch. Strong support of Van Qosten's explanation 



32 



