21 
Carp from Havana and points downstream showed no abnor- 
mality, excepting for a few individuals, perhaps one in a hundred, 
which supposedly had straggled downstream from Peoria Lake. At 
points between Peoria and Havana, intermediate percentages of 
"knothead" carp were found. At Pekin, for example, about 30 per 
cent of the knothead abnormality occurred. These percentages 
were based on carp averaging about 5 years of age, hence it seemed 
clear that carp did not migrate any considerable distances in the 
five years from the time the knothead characteristic was deter- 
mined in the fry stage until they were caught 5 years later, else 
the dividing line between knothead and normal carp would not be 
so clear-cut as it is between Peoria and Havana. Table I shows 
that the calculated average migration of a carp in five years 
is 17.9 miles. This figure was rather accurately predicted from 
a consideration of the distribution of knothead and normal carp 
in the Illinois River. 
The data on tagged carp have been arranged in Table IX, 
p. 22, to show,the rates of upstream and downstream migration. 
The rate of upstream migration shows a calculated migration con- 
‘stant of 0.24 miles in one day, while the downstream rate is 
0.07 miles per day. I regard these rates as significantly differ- 
ent. The greater downstream rate may be a reflection of the 
effects of drouth since fishes commonly exhibit an optimal stream 
size and move downstream in times of drouth. The data on tagged 
"fine fish" show upstream movements almost ten times as rapid as 
downstream. The reason for this difference from the behavior of 
carp is not clear. It may be supposed that "fine fish,” most of 
which are found in bottomliand lakes and other quiet waters, travel 
upstream willy-nilly when they find themselves in a current. 
Their rate of migration in lakes is only one-fourth their upstream 
rate. It must be remembered that any fish which shows a prefer- 
ential downstream movement under all conditions cannot long remain 
an Illinois fish and leave descendants to inhabit Illinois waters. 
Since these "fine fish" are not typical stream fishes, their reac- 
tions may be imperfectly adapted to stream life. This view seems 
to be supported by the low rates of migration found for typical 
stream fishes such as channel cat, common redhorse, black sucker, 
carp, and quillback. It appears that typical stream fishes are 
those which have a set of reactions which allow them to hold their 
place in a stream without crowding into the headwaters or being 
swept down to sea, 
While the evidence obtained by analysis of statistics 
presented here shows that the movements of fishes are random in 
nature, it is not incompatible with many kinds of observations 
which show that the movements of fishes are directed, i. e., not 
random. These scemingly opposite views may be readily harmonized 
by supposing that this randomness of fish movement appears only 
as a gross relationship covering long periods of time, while those 
observations tending to show that fish movements are directed 
commonly apply to much shorter periods of time. A great number 
of physical variables in water affect the movements of fishes, 
