36 Fish Cultural Association. 
middle of July, when their impetus is apparently checked, and 
their movements for thirty or forty days seem to be local 
only. During this period the temperature at Portland varies 
from 60 deg. to 70 deg., this being the height of midsummer. 
The monthly means for July and August, 1876, were 66 deg. 
7 m., and 63 deg. g m. The same months at New London 
are placed at 73 deg. and 73 deg. 3 m.; at Norfolk, 84 deg. 
1 m.; June, July, and August, at Jacksonville, average above 
85 deg., and we have no satisfactory evidence that the men- 
haden are seen there in midsummer. At Key West the low- 
est monthly. mean is in December, at 66 deg. 4 min., in an 
unusually cold winter. 
IV. PREFERRED RANGE OF TEMPERATURE. 
These facts seem to indicate that under ordinary circum- 
stances the menhaden prefers a temperature of 60 deg. to 70 
deg. Fahrenheit. When the rising temperature of spring has 
passed the limit of 50 deg. to 51 deg., the fish are certain to 
appear; and when the falling temperature of autumn reaches 
that point their departure is equally sure, though a few indi- 
viduals may linger in water not congenial to them. The 
opposite limit seems to be marked by the line 80 deg., or 
perhaps 75 deg. 
An easterly or northerly wind, lowering temporarily the 
surface temperature, causes the school to sink below the sur- 
face. The chill of night also drives them down. 
These. conclusions ‘are! not to;bei regarded as final. The 
movements of the fish about Cape Hatteras are very puzzling, 
and need to be interpreted by a series of careful temperature 
observations. 
