108 Barriers to Dispersion of River Fishes 
water communication, has no appreciable importance, is shown 
by the almost absolute identity of the fish faunze of Lake Winne- 
bago and Lake Champlain. While many large fishes range 
freely up and down the Mississippi, a majority of the species 
do not do so, and the fauna of the upper Mississippi has more 
in common with that of the tributaries of Lake Michigan than 
it has with that of the Red River or the Arkansas. The in- 
fluence of climate is again shown in the paucity of the fauna 
of the cold waters of Lake Superior, as compared with that 
of Lake Michigan. The majority of our species cannot endure 
the cold. In general, therefore, cold or Northern waters con- 
tain fewer species than Southern waters do, though the num- 
ber of individuals of any one kind may be greater. This is 
shown in all waters, fresh or salt. The fisheries of the Northern 
seas are more extensive than those of the tropics. There are 
more fishes there, but they are far less varied in kind. The 
writer once caught seventy-five species of fishes in a single 
Fic. 75.—Peristedion miniatum Goode and Bean, a deep-red colored fish of 
the depths of the Gulf Stream. 
haul of the seine at Key West, while on Cape Cod he obtained 
with the same net but forty-five species in the course of a week’s 
work. Thus it comes that the angler, contented with many 
fishes of few kinds, goes to Northern streams to fish, while the 
naturalist goes to the South. 
But in most streams the difference in latitude is insignificant, 
and the chief differences in temperature come from differences 
in elevation, or from the distance of the waters from the colder 
source, Often the lowland waters are so different in character 
as to produce a marked change in the quality of their fauna. 
These lowland waters may form a barrier to the free movements 
