149 
yield of the river fisheries rose from 6,037,378 pounds to 12,605,691 * 
pounds—with an average annual yield of approximately 8,900,000 pounds ; 
and between 1900 and 1908 inclusive it rose from 11,899,865 pounds to 
21,583,000 * pounds, with an annual average of approximately 15,000,000 
pounds. The increase for the five years immediately preceding the open- 
ing of the sanitary canal was thus about 9 per cent. per annum, that for 
the 8-year period following the opening was about 3.5 per cent. per annum, 
and the estimated decline for the next four years based upon statistics of 
production at Havana was at the rate of 15 per cent. per annum. The 
fisheries at this point yielded in fact 25 per cent. less in 1912 than they 
did in 1896; the gain made in the course of this period of sixteen years 
was more than lost before its close. 
There are four factors to which this rise and fall of production may 
be attributed: 1, the opening of the ‘sanitary canal and the diversion 
of nearly all the Chicago sewage from lake to river; 2, the rapid multipli- 
cation of the European carp, which by 1908 yielded 64 per cent. of the 
whole product of the river fisheries; 3, the great stimulus to fishing 
which this enormous increase of the carp produced; and 4, the rapid 
progress of reclamation operations from 1908 onward. The first three 
of these factors tended to increase the actual yield, but the last, a cause 
of decline, has more than overbalanced their joint effect. It is difficult 
to isolate these various factors’ in a way to distinguish their separate 
shares in this stimulus to production or the reverse, but something may 
be done in this direction by an examination of such statistics as are 
available. 
The principal multiplication of carp came between 1894 and 1897, 
when this fish rose in ratio from 9.6 per cent. to 56.5 per cent. of the 
entire catch from the river; and the carp continued in about this ratio 
of abundance until 1903, when it stood at 54.9 per cent. Our next data 
are those for 1908, when the entire catch from the river, as given by the 
U. S. Bureau of Fisheries, was 24,000,000 pounds, of which 64.4 per 
cent. were carp, the total yield of both carp and other fishes being more 
than twice that reported for any preceding year. The year 1908 was, 
however, so exceptionally favorable for fishing that its totals are mis- 
leading; but the rise in ratio of carp to other fish seems nevertheless 
correct. 
It is evident that it is to the increase of carp more than to the influx 
- of Chicago sewage that we must attribute the rise in production after 
1894. From that year to 1899 (the period of rapid multiplication of 
carp) the fisheries’ yield of the river increased 2.1 times, while by 1907, 
seven years after the opening of the canal, it had risen only to 14,739,000 
pounds—an additional gain of 17 per cent. 
This latter increase may have been due to a greater food supply 
derived from the sewage, or it may have been simply a consequence of 
the growth of the fishing industry, which was greatly stimulated by the 
increase of the carp supply. 
* The mean of the estimates of the U. S, Fish Commission and of the Illinois 
Fishermen’s Association. 
