FISH-SCRAP FERTILIZER INDUSTRY OF ATLANTIC COAST. 9 
that of the migration of birds ; the latter may be described as an up 
and down migration, or what amounts to the same thing, an off and 
on shore migration. The former is seasonal, while the latter may be 
seasonal, diurnal, or irregular. Fish migrate for various reasons : 
(1) To find water ,of an agreeable temperature and depth: (2) to 
find water of an agreeable temperature and depth in which food can 
be acquired; and (3) to spawn. By noting the temperature of the 
water of the various regions in which the menhaden have shown 
themselves, at the time of their appearance and of their departure, 
correlating figures have been obtained which are taken to indicate 
the extremes of temperature agreeable or bearable to the menhaden. 
The temperature thus indicated as most agreeable is 60° to 70° 
Fahrenheit. Where the temperature of the water in the spring 
reaches 50° F., the fish are likely to appear: and when it falls to that 
temperature in the autumn, they are equally apt to disappear. Ap- 
parent exceptions to the latter have been observed; it is believed, 
however, that the exceptional cases were caused by the detentions of 
the fish against their will by the contour of the coast line, or other 
such causes. This is taken as the lower limit of temperature bear- 
able to the menhaden, while the upper limit is believed to be 75° 
to 80° F. Thus, the coolness of the night, or a cold wind lowering 
the temperature of the surface water, causes the schools to disap- 
pear beneath the surface. 
Sensitiveness to temperature change, hypothesized for the men- 
haden, is not peculiar to that fish. On the contrary, the supposition 
of this sensitiveness is based on the definite knowledge that that 
characteristic is possessed by other fish. 
Since menhaden disappear, from northern waters during the winter 
to return again during the summer, it becomes necessary to account 
for their movements in the interim. Three courses are open to them : 
(a) To migrate to southern waters; (b) to hibernate in waters of 
great depth and low temperature; (e) to migrate abatically. or off- 
shore,- until waters of congenial temperature are reached. 
The first suggestion is in conformity with the prevailing beliefs 
of the fishermen. They picture the northern migration as a move- 
ment of the whole body of fish, swimming at a great rate of speed, 
feeding as they advance and increasing in fat, the larger and stronger 
pushing on farther north while the smaller and weaker are left 
behind and tarry in the more southern regions : that in the fall they 
return, growing thinner as they advance, due to the development 
of the roe ("the fat all goes into the roe"), and that they remain 
south during the winter. This belief is logical to the extent at least 
that during the spring the schools frequently are seen actually swim- 
ming north and in the fall south. And it is known that they are to 
be seen in Florida waters during the winter. 
5781°— 13 2 
