FISHERIES IN MICHIGAN WATERS OF GREEN BAY 



29 



nance by whitefish, lake herring, and smelt lasted 

 2 to 4 years (lake herring once held first rank 

 for only 1 year). White and redhorse suckers 

 which exhibited little tendency toward periodic 

 fluctuations were dominant three times but never 

 in consecutive years. 



The total production (all species) stood at 2.3 

 million pounds in 1929, rose to 2.9 million pounds 

 in 1931, dropped to 1.4 million pounds in 1933, 

 and then increased to 4 million pounds in 1938. 

 The take continued to exceed 4 million pounds in 

 2 of the next 3 years (it was only 2.7 million pounds 

 in 1939) but 1942 saw the start of a decline that 

 carried the yield to the 21-year minimum of 1.4 

 million (1,379,000) pounds in 1944. Production 

 increased rapidly during the next 4 years, reach- 

 ing the 21-year peak of 7.9 million pounds in 1948. 

 The catch was only slightly below this figure in 

 1949 (7.8 million pounds) . The sharp rise to high 

 levels of production in recent years can be traced 

 largely to phenomenal increases in the take of 

 whitefish, lake herring, and walleyes. Production 

 attained the all-time recorded high for whitefish 

 in 1918 and for walleyes in 1949. The catch of 

 lake herring reached the 21-year maximum in 1918, 

 but still was far below the output for certain years 

 in 1891-1908. Also contributing to the increase 

 was the recovery of the smelt stock from the dis- 

 astrous 1943 mortality; the commercial take of 

 this species increased from less than 500 pounds 

 in 1944 to 1,050,000 pounds in 1949. 



The average annual production of 3,582,000 

 pounds for all species combined in 1929-49 was 

 3,503,000 pounds or 49.4 percent less than the 1891- 

 1908 mean of 7,085,000 pounds. Decline in the 

 take of lake herring alone (from 5,841,000 pounds 

 in 1891-1908 to 1,070,000 pounds in 1929-49— a 

 drop of 4,771,000 pounds) more than accounted for 

 the difference. For species other than the lake 

 herring the combined average output increased 

 from 1,244,000 pounds in 1891-1908 to 2,512,000 

 pounds in 1929-49 — a rise of 1,268,000 pounds or 

 102.9 percent. Comparisons of 1891-1908 and 

 1929-49 production figures throw doubt on the 

 validity of the commonly held belief that most or 

 all major declines in the production of individual 

 species have been the result of overfishing. If 

 we hold, for example, that the huge drop in the 

 average annual catch of lake herring was caused 



by overexploitation, we are sorely pressed to ac- 

 count for the increase in the output of whitefish, 

 a more valuable species always in high demand, 

 from an annual mean of 159,000 pounds in 1891- 

 1908 to 714,000 pounds in 1929^9. The sugges- 

 tion is offered that the principal effects of fishing 

 may lie in the disturbance of ecological relation- 

 ships among species, and that fishing pressure on 

 commercially exploited varieties may have oper- 

 ated so much to the advantage of the smaller, non- 

 commercial species that the latter now make up an 

 increased percentage of the total biological pro- 

 duction of fish. 



Statistics on distribution of the catch by month 

 and by quarter revealed pronounced differences 

 among the principal species with respect to sea- 

 sonal trends. Data on the catch by gear demon- 

 strated that all species were taken in quantity by 

 more than one type of gear and that the catches 

 of most gears are made up of several species. The 

 principal gears are gill nets (of three groupings 

 with respect to mesh size), pound nets, shallow 

 trap nets, and fyke and hoop nets. 



The fluctuations of abundance (as estimated 

 from the records of catch per unit fishing effort) 

 were considerable for all principal species. Least 

 variable were the abundance indices of yellow 

 perch and white and redhorse suckers. The abun- 

 dance of lake trout could have been described as 

 moderately steady were it not for the tremendous 

 decline after 1943 (believed to have been caused 

 by the sea lamprey). The most extensive fluctua- 

 tions in abundance occurred in the whitefish, lake 

 herring, and walleyes. The abundance indices of 

 these species were particularly high during the last 

 3 (whitefish, walleyes) or 5 (herring) years of 

 the period. Maximum levels attained (indices ex- 

 pressed as percentages of the average 1929-43 

 abundance) were: Whitefish— 275 in 1947; lake 

 herring— 367 in 1946; walleyes— 344 in 1949 (this 

 last figure may be an overestimate, see p. 22 ) . The 

 available evidence indicates that the attainment 

 of these high values was made possible by the 

 phenomenal strength of the 1943 year class of all 

 three species. The late development of the smelt 

 fishery and the disruption occasioned by the 1943 

 mortality have prevented the establishment of suit- 

 able norms for the estimation of fluctuations in 

 the abundance of that species. 



