174 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



cisely the period of incubation of any eggs treated in pond-culture. 

 With some kinds, under extreme conditions of temperature and other 

 less understood factors, wide variations are found. Bass eggs require 

 from 7 days to 3 weeks for hatching, but usually from 8 to 10 days — 

 governed mostly by the temperature of the water. Eggs artificially 

 impregnated, in an experimental way, hatch in from 70 hours to 4 

 days at a temperature of 63° F., or somewhat over. 



When the fry leave the eggs, they remain on the nest till the sac is 

 absorbed, this depending, as with other fishes, on the period of incu- 

 bation, modified by the temperature or condition of the atmosphere; 

 usually a fifth less time being required to absorb the sac than for hatch- 

 ing the eggs. When the sac is absorbed, the fry rise from the nest 

 and form a school which hovers over the nest usually from two to four 

 days, settling back at night, except in extremely warm weather, when 

 they may scatter in a few hours. A sudden fall of temperature may 

 cause the school to settle back and remain a day or two longer on the 

 nest. The tactics of the parents change and they no longer stand 

 guard over the nest, but circle around the school, whipping back truants 

 and driving off intruders. When the school rises and iiunger begins 

 to be felt, the fry separate and are driven, for protection, by the parent 

 fish into shoal water or into the thick grasses; there they are deserted, 

 and dispersing, they seek the minute Crustacea, larvte, and insects. 



Black-bass fry do not average one-fourth of an inch in length and 

 are almost colorless for the first three to five days, when the pigment 

 forms along the back, making them appear quite dark when viewed 

 from above, though it is difiicult to distinguish the color of an indi- 

 vidual fish when caught on a net of bolting-cloth. 



Very young rock bass seem occasionally to attach themselves to the 

 sides and bottom of the nests and to submerged plants. This action 

 has not been noticed with black bass, possibly because their nests, 

 being in deeper water, are more difficult of observation. 



POOD OF THE YOUNG. 



Just how much food to give the young bass fry is as difficult to 

 determine as with any other young fish. They are very greedy, and, if 

 acceptable food is given them, ajipear to be hungry nearly all the time, 

 and it is more than probable that the troubles caused by overfeeding 

 other fishes would show themselves in the bass if they were overfed. 

 Bass, like the trout, are given about 1 J per cent of their weight in food 

 per day. This ratio will maintain black-bass fry in a healthy growing 

 state, and ])robably less will be found to answer with rock-bass fry. 

 Compared with other fishes reared in troughs, especially some of the 

 trout, bass are easily managed. Healthy fry have been carried at 

 Keosho for four months with a loss of only 2 per cent. When first 

 brought into the troughs, they can not be induced to take the prepared 

 food, as they are wild and must be tamed or domesticated. They are 



