410 



BULLETIN OF THE BUREAU OF FISHERIES 



(see Table 43) and the theoretical average weights of the fish of each age group are 



given below 



I The actual length of the 7-year herring taken in 1921. 



The total weight of the individuals of each age group of the sample, the percent- 

 age contributed by each age group to the combined sample, and the number of 

 pounds contributed by each age group to the commercial catch of 1920 are as follows: 



In 1920 all but the 2-year herring had been subjected in varying degrees to the 

 chemical pollution. Computations indicate that, as compared with the 3-year fish 

 taken in 1924 (Table 31), those of 1920 were 28.4 per cent below the normal weight. 

 In like manner the 4, 5, and 6 year fish of 1920 were found to be 21.6, 14.6, and 7.7 

 per cent, respectively, below normal weight. The loss to the fishermen in 1920 

 totaled 628,907 pounds, valued at (3.3 cents per pound. Table 64) $20,754, an average 

 loss in pounds of 20.5 per cent. By a process similar to that employed above, the 

 losses for the other years were computed as follows: 



' The financial losses for the years preceding 1920 are computed on the basis of 3 cents per pound; the average for 1920 and 1921 

 was 3.5 cents per poimd. According to Bay City fishermen the average price of herring is usually around 3.5 cents per pound- 

 in the fall of 1924 and of 1925 the price to the Bay City fishermen was 3.5 and 4 cents per pound. 



Adding together the annual losses computed for the years 1917 to 1923, inclusive, 

 we obtain the sum total of 4,450,224 pounds, with a value to the fishermen of 

 $135,753. This total is a rough estimate of the indirect losses suffered by the herring 

 industry of Saginaw Bay and is believed to have been occasioned by the pollution in 

 1915 to 1917 of the Dow chemical works. 



Not only were the herring mdirectly affected by this pollution but presumably 

 also the pickerel, perch, suckers, carp, and all the other species of fish that grow in 

 Saginaw Ba}^ The total damage done to these species involved greater financial 

 losses than those of the herring, for they yield the bulk of the commercial catches 

 of the bay and possess an average value greater than that of the herring. 



It must now be apparent that the indirect losses occasioned by a serious pollu- 

 tion may assume enormous proportions, as the effects of such a pollution are spread 

 over a series of year classes, each one of which at one time or another enters the 

 commercial catch and becomes one of its principal components for several con- 

 secutive yep,rs. 



