463 
times, both in the river and in the lakes, of surplus stocks of a size far 
more than sufficient to supply the immediate needs even of vastly richer 
bottom and shore populations than we found in 1914—1915. But though 
the river, at least in the region of low slope between Chillicothe and Ha- 
vana, could thus theoretically produce as large poundages of bottom and 
shore fauna as the lakes, or even larger, the figures for stocks on hand 
in the two years mentioned, as well as other evidence, tend rather to 
prove that the lakes are over their average acreage the better producers, 
and that their richest fauna is developed in the weedy littoral, where also 
occur the largest deposits of nitrogen; organic carbon, and other oxidiza- 
ble matters. 
As the margin between the bottom and shore fauna stocks on hand 
in 1914—1915, even in the most productive lake and river areas, and the 
food requirements, in kind, of a normal fish population, as of 1908 and 
neighboring years, seems clearly to be very much smaller than that be- 
tween the supplies and the needs of the bottom and shore fauna itself, 
it may be supposed that figures for stocks on hand after four or five 
months’ feeding by fishes can not be accepted as they stand, quite as 
confidently as plankton and nitrogen figures for use as an index of 
actual total productivity. If this is the case, and if it is also true, as we 
have reason to think, that the lakes rather than the river are not only 
the favorite feeding-grounds of the greater part of the large bottom- 
feeding fishes during the 9-months growing season but also the largest 
- producers of fish flesh, then we should expect that complete figures for 
total annual yield of bottom and shore invertebrates for the river and 
lake acreage in the Havana district would show a yet greater difference 
in favor of the lakes than is shown by the figures of stocks on hand as 
of July—October, 1914—1915. A further point in favor of the lakes 
is the fact that the very heavy bottom-fauna poundages of the river 
channel just above Havana consist largely of heavy-shelled snails, which 
we can not believe are easily made use of as food by any but the largest 
bottom-feeding fishes. Looked at in this way, the richest river valua- 
tions may represent accumulation in the presence of light feeding; while 
the lower poundages of bottom animals in the lakes opposite may be 
looked upon as residues from originally much larger stocks, fed down to 
a closer point than the river stocks, in consequence both of a relatively 
greater size-availability and of their location within the main-feeding 
range. 
FisH YIELDS 
On a plain acreage basis the total river acreage, at a gage of 10 feet, 
Beardstown*, between La Salle and Grafton, with equal productivity as- 
sumed in both river and lakes, should in 1908+ have supplied around 
18% of the total fish yield of that year, and the lakes about 82%. In 
* Gage selected by Alvord and Burdick as that prevailing on an average one 
half of the year, 1900—1913. 
+ Last year for which we have full figures for fish yields. 
