308 FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



earlier years of the fishery was greater than in 1891 and subsequent years. The 

 normal annual output of these earlier years most probably exceeded 5 million pounds. 

 The description of the fluctuations in the production of whitefish in the entire 

 lake before 1911 is made difficult by the lack of complete information in a number of 

 years. 13 Records of the total yield are available for only 11 years of the period, 1889- 

 1910. These catches exhibited considerable variation. The production was less than 



2 million pounds in 3 years (1894, 1895, and 1899), ranged between 2 and 3 million 

 pounds in 4 years (1892, 1893, 1896, and 1903), fell between 3 and 4 million pounds 

 in 2 years (1897 and 1908), and exceeded 4 million pounds in 1889 and 1890, the 

 earliest years of the period. The average for the 11 years was 2,813,000 pounds. 



The level of whitefish production for the entire lake was considerably lower in 

 the years, 1911-1926. The catch was greater than 2 million pounds in only 2 years 

 (1917 and 1918) of the 16, and in 10 years production was below iy 2 million pounds. 

 The 16-year average was 1,566,000 pounds. 



Improved catches in both Wisconsin and Michigan waters were responsible for an 

 uninterrupted period of 8 years, 1927-1934, in which the total catch of whitefish in 

 Lake Michigan did not fall below 2 million pounds. The production was more than 



3 million pounds in 5 of these years 11928-1932), was above 4 million pounds in 3 

 years (1929-1931), and exceeded 5 million pounds in 1930. The average for the 8-year 

 period was 3,717,000 pounds. The production in each of the 3 years, 1929-1931, was 

 greater than that recorded for any year of the period, 1890-1928, although a higher 

 yield was recorded for 1889 and there is evidence that the catch of whitefish in certain 

 years prior to 1889 may have been even greater. 



The average annual production of whitefish in Lake Michigan in the most recent 

 5-year period, 1935-1939, was 1,201,000 pounds. The catches in 1936, 1937, and 1939 

 were all below the smallest yield recorded for any year prior to 1936 except 1920; the 

 1939 record provides the second report of a total whitefish catch in Lake Michigan of 

 less than a million pounds. 



The grand average of 2,074,000 pounds for the years, 1889-1926, may perhaps 

 be accepted as the normal yield of whitefish for the entire lake. 



RECENT LARGE INCREASE IN THE PRODUCTION OF WHITEFISH 

 IN GREAT LAKES WATERS 



The preceding pages were devoted exclusively to a description of fluctuations in the 

 production of whitefish in the various waters of Lakes Huron and Michigan. A dis- 

 cussion of these fluctuations in terms of variations in the abundance of whitefish has 

 been avoided deliberately because of the many disturbing factors that render such in- 

 terpretations exceedingly unreliable. 



A fundamental difficulty in the use of the statistical data of the type given in 

 table 1 for estimations of fluctuations in the abundance of fish lies in the lack of 

 adequate information on the intensity of the fishery. It is known that in general 

 the fishing intensity of the early fishery was far less than that of the modern fishery— 

 that with the passage of the years the number of men and boats engaged in commer- 

 cial operations increased greatly. It is known too that certain technical develop- 

 ments such as the invention of power lifters, improvements in the efficiency of nets, 

 and the construction of faster and more cheaply operated craft, permitted an expan- 

 sion of fishing activity out of proportion to the mere increase in men and boats. 

 Because of the known increase in fishing intensity a given annual catch in the earlier 

 years of the fishery may be held to indicate a greater abundance of fish than an 

 equally large production a number of years later. 



Changes in fishery regulations also may affect production significantly. Increases 

 or decreases in the minimum legal mesh size, the imposition of a closed season, the 

 establishment or abandonment of a fishery for spawn, the closure of grounds or the 

 restriction of operations in certain areas, changes in the size limit of fish — all these 



13 Totals were omitted for all years in which records were lacking for either the State of Michigan or the State of Wisconsin waters. Certain of 

 the totals listed for Lake Michigan in table 1 do not include the production in Illinois and Indiana waters, but the omission of these catches most 

 probably had little effect on the values of the totals. (See appendix A.) 



