22 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



followed more easily if reference is made to figures 

 9 to 14. 



Lake trout : During earlier years of the 1929^9 

 period, abundance was generally below the 15-year 

 (1929^13) mean but the trend was irregularly up- 

 ward (fig. 9). Sharp increases in 1936 and 1937 

 carried the index to the 21-year maximum of 157 

 in 1937. A decline to 94 in 1939 was followed by 

 a rise to a second peak of 138 in 1941. The suc- 

 ceeding years saw a pronounced downward trend 

 which culminated in an index of only 26 in 1947. 

 The rise to 44 in 1948 and 45 in 1949 still left the 

 abundance far below average. The recent decline 

 of the lake trout can be attributed primarily to the 

 depredations of the sea lamprey (Hile, Eschmeyer, 

 and Lunger 1951a). 



Whitefish : Van Oosten, Hile, and Jobes (1946) 

 believed that 1929 represented the peak year of a 

 period during which whitefish were abnormally 

 plentiful in Lake Michigan. In Green Bay the 

 1929 index stood at 180 (fig. 10) . From this value 

 the abundance declined to 66 in 1933, recovered 

 somewhat in 1934 (91 ) , and then declined to the 21- 

 year low (65) in 1937. After this year the avail- 

 ability of whitefish entered on a definite, though 

 slightly irregular, upward trend. Large increases 

 from 100 in 1945 to 148 in 1946 and the 21-year 

 maximum of 275 in 1947 were followed by sub- 

 stantial declines to 221 in 1948 and 158 in 1949. 



Lake herring : The abundance was consistently 

 below average in 1929-33 (range from 57 in 1933 

 to 91 in 1931 — see fig. 11). A sharp increase to 



197 in 1934 was followed by a long decline (inter- 

 rupted by a small rise in 1940) that led to the 21- 

 year low of 51 in 1942. Small increases in 1943 

 and 1944, a phenomenal jump from 82 to 306 in 

 1945, and yet another increase to 367 in 1946, 

 raised the level of abundance to the 21-year high. 

 The subsequent downward trend which carried 

 the percentage to 203 in 1948 was halted by a rise 

 to 228 in 1949. 



Walleye: From the 21-year minimum of 54 in 

 1929 the abundance of walleyes (fig. 12) rose to 



198 in 1933 and then fell away to the same mini- 

 mum of 54 in 1939 (interruption to the decline 

 in 1930). The following years saw a highly ir- 

 regular but definite upward trend. The increases 

 were so large after 1946 that a level of 344 was 

 reached by 1949. 



The data on the catch of walleyes per lift (table 

 14) together with our knowledge of changes that 

 have taken place in the types of trap nets fished 

 in Green Bay give us reason to suspect that the 

 abundance of walleyes during the last few years, 

 particularly in 1947-49, may have been overesti- 

 mated. The catches per lift of fyke nets in these 

 3 years indicate a great abundance of walleyes 

 (catches from 150 to 206 percent of the 1929-43 

 mean) and the pound-net records for 1948 and 

 1949 support a similar view (lifts 147 and 142 

 percent of 1929^3 mean). These 1947-49 fig- 

 ures were relatively far lower, however, than those 

 for trap nets in which the average lift ranged from 

 30 to 56 pounds as compared with a 15-year aver- 

 age of 8. To some extent this relatively greater 

 increase in the catch of trap nets may have re- 

 flected especially heavy concentrations of fish on 

 trap-net grounds (as compared with pound- net 

 and fyke-net grounds) during the years of high 

 abundance of walleyes. Much of the exceptional 

 success of trap nets, however, is believed to have 

 resulted from the introduction (especially by Lake 

 Huron fishermen who moved into the area) of 

 larger nets better suited to the taking of walleyes 

 than the gear employed by local operators in 

 earlier years. 



Yellow perch : During the years 1929^2, fluctu- 

 ations in the abundance of yellow perch (fig. 13) 

 were largely without trend and relatively limited 

 (ranged from 82 in 1936 to 114 in 1937), but dur- 

 ing the later years the variations were wide. After 

 dropping from 110 in 1942 to 63 in 1944 the abun- 

 dance index jumped suddenly to the 21-year peak 

 of 150 in 1945 only to fall away to the 21-year low 

 of 49 in 1949. 



White and redhorse suckers : The fluctuations in 

 abundance of suckers (fig. 14), much like those of 

 yellow perch, were without clear-cut trends. The 

 index was low (63) in 1929, but during the next 

 17 years it varied irregularly within the range of 

 71 ( 1939 ) to 131 ( 1935 ) . The level of availability 

 was again low (60 or 61) during the last 3 years, 

 1947-49. 



Smelt: As stated earlier, late development of 

 the fishery and the effects of the 1943 epidemic 

 have prevented the establishment of "normal" 

 standards from which to estimate annual fluctua- 

 tions in the abundance of smelt; nevertheless, a 

 good idea of the extent of these fluctuations is to 



