364 Intinois NaruraAL History Survey BULLETIN 
from 23.0 to 30.6 inches. Of the stur- 
geons taken in this section of the net, 76.2 
per cent were of commercial sizes (25 
inches or more fork length); of those 
sturgeons taken in the section with 114- 
inch mesh, 61.2 per cent were of commer- 
cial sizes. 
The number and percentages of the 
fishes that were gilled in the experimental 
floats are listed in table 29. None of the 
five saugers taken during the experiment 
was gilled. In the section with the 114- 
inch-mesh inner net, +.2 per cent of the 
fish were gilled; in the section with the 
2-inch-mesh inner net, 5.6 per cent were 
gilled. 
Discussion 
During the past 50 years, there have 
been increasing numbers of sport fisher- 
men in Illinois and other states. Many 
of these fishermen view with suspicion the 
operations of commercial fishermen. Some 
even believe that commercial fishermen 
have been responsible for the decline of 
sport fish populations in certain localities. 
Their beliefs probably have developed as 
a result of hearsay, casual contact with 
the commercial fish industry, and lack of 
realization that many _ environmental 
changes have taken place in the past cen- 
tury and that some of these have had an 
effect on the fishery of the Mississippi 
River and other waters. 
The effect of commercial fishing devices 
of illegal mesh size on certain sport fishes 
was demonstrated by Bennett (1948:411) 
in his study at Fork Lake, a small artifi- 
cial lake of 1.38 acres stocked with blue- 
gills and largemouth bass. After nearly 
31 years of being cropped heavily with 
small-mesh wing nets, Fork Lake still 
contained a large population of fish. If it 
was not possible in a 1.38-acre lake to re- 
duce a sport fish population to a low level 
by concentrated effort with commercial 
gear of a mesh smaller than legal size, 
then it certainly does not appear logical 
that commercial fishermen, using nets of 
legal-size mesh, could remove enough 
sport fishes from the Mississippi River to 
affect the sport fishery, even if it were 
lawful to keep the sport fish taken in com- 
mercial devices. 
It was demonstrated in the survey of 
Vol. 26, Art. 4 
1944 and 1946 reported here that com- 
mercial fishing devices can be fished on a 
selective basis. Of the fishing devices 
tested in the survey, basket traps and 
floated trammel nets were found to be the 
ones most selective for commercial species. 
Other devices were found to be quite se- 
lective when fished for a particular species 
of fish. The type of fishing device, the 
mesh size, and the fishing site influenced 
the species composition of the catch. 
Missouri statutes no longer specify 
minimum size limits for any commercial 
fish, except catfish. Illinois and Iowa still 
have minimum size limits on certain com- 
mercial species. Analysis of data from 
the Mississippi River survey of 1944 and 
1946 indicates that, where minimum size 
limits of commercial fish are necessary, 
sizes of fish caught can be controlled by 
using nets of certain mesh sizes. The use 
of mesh size as a means of controlling the 
size of fish in the commercial catches re- 
duces the labor of complying with the law 
by eliminating the necessity for measur- 
ing the fish in the catches. 
Practices and policies of fish manage- 
ment for the Caruthersville-Dubuque sec- 
tion of the Mississippi River should not 
eliminate either sport fishing or commer- 
cial fishing. Prohibitive measures aimed 
at either kind of fishing affect the best use 
of the fishery. Too frequently, laws gov- 
erning this dynamic river fishery tend to 
be static and thereby defeat their original 
purpose to benefit the fishery. Laws es- 
tablished to aid in the management of the 
river fishery should not be adopted with 
an attitude of permanency. These laws 
should be changed whenever scientific 
findings indicate they are no longer useful. 
Summary 
1. Data on fishing with various types 
of commercial fishing devices were col- 
lected during a fish survey of the Missis- 
sippi River between Caruthersville, Mis- — 
sourl, and Dubuque, Iowa, in 1944 and 
1946. Particular emphasis was placed on 
determining the selectivity and effective- 
ness of the commercial fishing devices of 
various mesh sizes used on the river. 
2. During the survey, the following 
types of commercial fishing devices were 
used: seines, trammel nets, basket traps, 
