FISHERIES EST MICHIGAN WATERS OF GREEN BAY 



25 



Table 21. — Fluctuations in fishing intensity for the prin- 

 cipal commercial species in Green Bay, 1929-49 



[Expressed as percentages of the 1929-43 mean] 



' Probably too low; see footnote 14. 



Table 22. — Correlation between indices of abundance and 

 of fishing intensity for six principal species in Green 

 Bay, 1929-43 and 1929-49 



Over the base period 1929-43 only whitefish 

 exhibited a significant positive correlation be- 

 tween abundance and fishing intensity. The cor- 

 relation for lake trout was significant but negative, 

 and among the remaining species the values of r, 

 all positive, were far below the level of significance 

 (r= ±0.514 at p = 0.05 and -i/=13). The addition 

 to the base period of 6 years' data brought about 

 several changes in the relationship. In 1929-49 

 the value of r for whitefish continued to be positive 

 at a high level of significance, but the correlation 

 between abundance and fishing intensity for lake 

 trout, although still negative, was no longer sig- 

 nificant. At the same time a highly significant 

 positive correlation for the walleye and a signifi- 

 cant negative correlation for suckers appeared. 

 In lake herring and yellow perch the values of the 

 coefficient continued to fall short of significance. 



Although an abundance of fish normally would 

 be expected to stimulate fishing operations 15 and 

 a scarcity to depress them, those studies that have 

 been made of the relation between availability 

 and fishing pressure for individual species have 

 failed to reveal a consistent relation between the 

 two (Van Oosten, Hile, and Jobes 1946 ; Hile 1949 ; 

 Hile, Eschmeyer, and Lunger 1951 a and 1951 b). 

 Even where the data have favored the assumption 

 of a cause-and-effect relationship, the correlation 

 has at times been negative. In State of Michigan 

 waters of Lake Superior, for example, the evidence 

 indicates that fishermen increased fishing pressure 

 as the abundance of lake trout declined in order 

 to maintain production at an economically satis- 

 factory level (Hile, Eschmeyer, and Lunger 

 1951b) . In shallow-water fisheries where several 

 species are usually taken together the situation be- 

 comes extremely complicated, for it is the total 

 catch of a number of species that determines the 

 financial returns to the fishermen. Our under- 

 standing of the economic, biological, and other 

 factors that may influence fluctuations of fishing 

 intensity does not justify a detailed consideration 

 of the problem at this time. The remainder of this 

 section will be restricted, therefore, to comments 

 on certain relationships between abundance and 

 fishing intensity in northern Green Bay for which 

 satisfactory explanations can be advanced. 



The fluctuations in the intensity of the fishery 

 for lake trout in the Michigan waters of Green 

 Bay were treated by Hile, Eschmeyer, and Lunger 

 (1951a) who explained the negative correlation 

 between fishing pressure and the abundance of lake 

 trout on the basis of the following points: Lake 

 trout and whitefish are commonly taken together 

 in large-mesh gill nets, with the whitefish normally 

 making up the bulk of the catch ; the fishing inten- 

 sity for whitefish has been correlated closely with 

 the availability of that species and the fishing 

 pressure on lake trout accordingly has tended to 

 fluctuate with the availability of whitefish; the 

 abundance indices of lake trout and whitefish have 

 been correlated negatively, however, and as a result 

 a negative correlation has existed between abun- 



15 Excessively high abundance can lead to a glutting of the 

 market with an accompanying collapse of prices and thus depress 

 fishing intensity. Severe market gluts are not common with most 

 Great Lakes species, and when they do occur they usually are so 

 short-termed as to have no great effect on the total annual fishing 

 intensity. 



