22 FISH PONDS ON FARMS. 
when nearing the destination to conform to that of the water in 
which the fish are to be liberated. During conveyance the water in 
the receptacles will be kept in motion and adequately aerated; but 
when standing still it must be artificially aerated by dipping out 
some water and pouring it back into the receptacle from a height. 
The ordinary 10-gallon can is employed by the Bureau of Fisheries 
for the transportation of small fish, but if the fish are too long for its 
diameter nothing is better than wash boilers. Any clean receptacle 
may be used, but those mentioned are the most convenient to handle. 
If the use of artificial food is not contemplated, the number of 
brood fish allotted to a pond must be apportioned to the natural food 
available for both the adults and the expected fry and fingerlings. 
Fifty of either species of black bass or 100 specimens of any of the 
smaller species are maximum numbers for an acre of water, where the 
offspring is to remain in the brood pond. These numbers should 
produce a much larger number of fry than the waters can sustain 
until mature, but allowance will have to be made for losses through 
cannibalism and the ordinary vicissitudes of their environment. 
Promiscuous collections of fish will invariably run about equally as 
to sex, and the numbers recommended will therefore give 25 and 50 
pairs, respectively. 
There are no external markings by which the sex of pond fishes 
can be positively determined, but the female black bass usually pre- 
sents a more mottled appearance than the male and her colors are 
brighter. 
SPAWNING SEASON. 
Black bass will nest in the spring when the water temperature 
rises above 60° F. Ordinarily 63° F. will bring about deposits of 
eggs, but if the season is a backward one, the fish may spawn at 58° 
F. On the other hand, an unusually advanced season may not bring 
results until the temperature exceeds 65° or 68° F. 
Suitable temperatures for spawning prevail in the more southerly 
States as early as February; in the latitude of Tennessee, in March; 
in southern Illinois, during April; in Iowa, during May; and in 
northern Minnesota, in June. The spawning season extends over 
two or more weeks, and is usually marked by two periods of intense 
activity, following a rise in temperature after several days of ab- 
normally cool weather. In the Southern States the nesting season 
is not so sharply defined, owing to the almost continuously favorable 
temperatures throughout the year, which cause rapid development 
of the ova. At the Texas station of the Bureau of Fisheries there 
regularly occurs a hatching period in February, one in April, and 
scattering hatches throughout the summer. The crappies, sunfishes, 
rock bass, and catfishes will spawn from one to two months later than 
