30 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Of the 15 coefficients of correlation that could be 

 computed between abundance percentages among 

 the 6 principal species, 7 were significant (5 were 

 negative and 2 were positive). Additional sig- 

 nificant coefficients were obtained when time lags 

 of 1 to 3 years were established. With the white- 

 fish and walleyes a significant negative correlation 

 for 1929-38 was followed by a highly significant 

 positive correlation in 1939-47. Only a greatly 

 expanded knowledge of the natural history of 

 Green Bay fish can explain these interrelationships. 



Correlations between annual fluctuations in 

 abundance and production indicated that produc- 

 tion would have served as a reasonably dependable 

 indicator of the major changes of availability in 

 1929-49 for whitefish, lake herring, walleyes, yel- 

 low perch, and suckers, but would have been highly 

 misleading for lake trout. 



The abundance of fish and the intensity of fish- 

 ing exhibited highly significant positive correla- 

 tion for whitefish in the 1929-43 base period and 

 in 1929-49, and for walleyes in 1929-49. Our 

 knowledge of the fishery prompts us to view these 

 correlations as reflecting a true cause-and-effect 

 relation. The remaining coefficients fell short of 

 significance or had significant negative values 

 (lake trout in 1929-43 ; white and redhorse suckers 

 in 1929-49). These negative coefficients were ex- 

 plained as the result of heavy fishing for white- 

 fish and walleyes in which lake trout and suckers 

 were taken as incidental parts of the catch during 

 periods of low abundance of the latter two species. 



An outstanding feature of the data on fishing 

 intensity was the extremely great pressure directed 

 against most species during the last 2 or 3 years of 

 the 1929^9 period. The maximum levels (indices 

 give as percentages of the average 1929^3 inten- 

 sity) attained for the different varieties in recent 

 years were : Lake trout — 253 in 1948 ; whitefish — 

 407 in 1949 ; lake herring— 195 in 1948 ; walleyes— 

 615 in 1949 (possibly an underestimate) ; yellow 

 perch — 77 in 1949; white and redhorse suckers — 

 194 in 1949. Higher levels of fishing intensity 

 were reached in earlier years by only two species : 

 Lake herring — 220 in 1938; yellow perch — 190 in 

 1938. 



The upswing of production that carried the 

 annual take from the 21-year low of 1.4 million 

 pounds in 1944 to nearly 8 million pounds in 1918 

 and 1949 was made possible to a large degree by 

 the phenomenal increase in the abundance of 

 whitefish, lake herring, and walleyes and by an 

 enormous expansion of fishing activity (much of it 

 to be traced to fishermen who moved in from other 

 areas) . Although the cropping of this large sup- 

 ply of fish was desirable a dangerous situation has 

 been created. At such time as the abundance of 

 fish returns to a more nearly normal level the avail- 

 able supply may be inadequate to support profit- 

 able operations for all the fishermen in the bay. 

 Not only will the fishermen experience financial 

 difficulties, but there is a real threat of the enact- 

 ment of "protective" legislation that could all but 

 destroy the fishing industry. 



LITERATURE CITED 



Higgins, Elmer. 



193S. Shall our marine fish resource be squandered, 

 hoarded, or managed — and how? Trans. Third N. 

 Amer. Wildlife Conf., pp. 151-15S. 



Hile, Ralph. 



1937. The increase in the abundance of the yellow 

 pike-perch, Stizostedion vitreum (Mitchill), in Lakes 

 Huron and Michigan, in relation to the artificial prop- 

 agation of the species. Trans. Amer. Fish. Soc., 

 vol. 66 (1936), pp. 143-159. 



1950. Green Bay walleyes — a report on the scientific 

 investigation of the marked increase in abundance of 

 walleyes in Green Bay. The Fisherman, vol. 18, 

 No. 3, pp. 5-6. 



Hile, Ralph, Paul H. Eschmeyer, and George F. Lunger. 

 1951a. Decline of the lake trout fishery in Lake Michi- 

 gan. Fish. Bull. 60, U. S. Fish and Wildlife Service, 

 vol. 52, pp. 77-95. 

 1951b. Status of the lake trout fishery in Lake Supe- 

 rior. Trans. Amer. Fish. Soc, vol. 80 (1950) , pp. 278- 

 312. 

 Hile, Ralph, and Frank W. Jobes. 



1941. Age, growth, and production of the yellow perch, 

 Perca flavescens (Mitchill), of Saginaw Bay. Trans. 

 Amer. Fish. Soc, vol. 70 (1940), pp. 102-122. 

 Marr, John C. 



1951. On the use of the terms abundance, availability, 

 and apparent abundance in fishery biology. Copeia, 

 1951, No. 2, pp. 163-169. 



Milner, James W. 



1874. Report on the fisheries of the Great Lakes ; the 

 result of inquiries prosecuted in 1871 and 1872. Rept. 

 U. S. Comrnr. Fish, for 1872-73 (Part 2), pp. 1-78. 



