62 Transactions of the Academy of Science of St. Louis 
the total of available forage. These forage forms are, of course, 
dependent on the plankton, ooze, and other microscopic sub- 
stances. A field examination of spawning facilities involves 
simply observing whether pools or riffles provide the desired 
depths and bottom composition, but post-season observations 
cannot detect a possible loss of 100 per cent of the eggs in a flood 
during the spawning season. 
The survival of the yearly hatch can be roughly learned by 
methodical collecting of fry or fingerlings in the summer from 
marginal weed beds in which most of these fish take refuge. 
After the iry emerge from the nest, the necessary physical cover 
and shelter must be supplied if these fish are to reach maturity. 
For larger fishes, debris, rocks, windfalls, and undercut banks 
supply suitable cover. The degree of sufficiency of cover can be 
mostly learned by observing its presence or absence and compar- 
ing this with a count of netted fishes removed from the available 
cover. The aforementioned types of cover still do not constitute 
serviceable cover if it is not in water of great enough depth. 
■ 
The Missouri Conservation Commission has been conducting 
such aquatic surveys by watersheds, mostly during the summer 
months beginning in 1939. These essential facts for fish produc- 
tion ascertained and consoUdated into an understandable whole 
will give the Missouri Conservation Commission an index to 
stream productivity and a guide by which it can initiate a plan- 
ned watershed and stream-improvement project to correct any 
deficiencies which are limiting fish production in the waters of 
the State. 
Survey data and their interpretation indicate that watershed, 
stream slope, and stream-bank erosion can be designated as the 
most in^ortant factors limiting production in the streams, for 
this condition in turn has limited several production factors 
within the streams themselves. The flushing of sediment and 
gravel into streams fills pools and channels with a result com- 
parable to shrinking the stream-length and restricting the extent 
of the aquatic medium; fish foods are buried or crushed by niov- 
mg gravel; spawn is buried or smothered by sediments; aquatic 
vegetation is destroyed; and cover or shelter for larger fishes 
IS obliterated. 
_ In attacking this problem the Missouri Conservation Com- 
niission IS looking for the cause in the watershed as well as the 
ettects in the stream, and a coordinated program including im- 
provements of both is under way. 
