152 
PERCENTAGES OF INCREASE OR DECREASE BETWEEN 
1899 anp 1908 (ADJUSTED) 
Per cent.| Per cent. 
increase| decrease 
Fisheries products (pounds)....... 68 
(Black DASSe cate sue bole ove fore Cee 181 
Buttalo-fishy ier. oearsha:sietshst lena eaten tea katte ra 47 
MOUTH bs gibiciesa kaa Bi sAsicearay kira won eocente tet 46 
Cath Deel em Soo we: ole sto ce .eiatatanc a Un ace Aenea 13 
CrApDIer sy Siete telarte deal temseeke oleae 14 
Sheepsheda ss fais iisoiviess etemsiode Aes ©) sha tle epee 27 
IOUS Hiei cate Me tetetchs aves esn ve laich oval erele never teeter | ica Nee 30 
Pad dle-HShy os cc isis cssiets iors isieke sees 37 
Pe Gievereestete ete ratercicvege te at ee hacer tomene somatostatin Pepe tee 60 
UU BOM se eieleraisien manos ae Sela o Meta hongeameenen ats 25 
Suckers teeter tis octaees detache, sia tchtuawrea nieekcest: vers 28 
Sumiiphe sete 25 cosh icin ht ies bap tessa cree pa 110 
Walle yed) DIK s ica sie's.c. cuvieralste diu-c.0 feo ivepe' sears ont 67 
White, yellow, and rock bass................. 94 
Pere fra See oeeveetee tes 695 
All native fishes..............-+... 79 
Bottom=feed ers. ier leverciete s.0/s¥a:<.e's) cls istaliteremielelebaie 37 
per cent. per annum—a condition of things not easily understood except 
on the hypothesis that the resources of multiplication and subsistence 
opened up by the canal had enabled the native river fishes not only to 
sustain themselves but to increase in number in the face of the tremen- 
dous competition of a quantity of carp greater than that of all the other 
fishes of the river taken together. 
To what extent, if at all, it was the great and increasing quantity of 
organic material brought into the river by the canal which was the cause 
of increasing fish production, or whether the cause was mainly or wholly 
an expansion of the area of shallow water in which fishes could breed and 
feed to the best advantage, is a question to which we are unable to make 
definite answer ; but it is certain that it is now the area of available breed- 
ing and feeding grounds, and not the food supply, which is the limiting 
factor in the yield of the Illinois River fisheries. The raw materials of 
food sufficient for a much greater volume of plant and animal life than 
the river and its dependent waters now contain, are being continuously 
poured into the stream and worked up to the chemical conditions required 
for their assimilation; but they pass out of the river at its mouth in 
increasing quantities unassiniilated because, owing,to the progressive dik- 
ing of bottom-lands and draining of lakes, the productive area is steadily 
diminishing. From the report of Alvord and Burdick it appears that up 
to 1899 the area of the bottom-lands under completed levees was but 
9,100 acres; five years later it had risen to 21,500 acres; by 1908, the 
year when the fisheries data of the last national census were collected, to 
