Other Game Fish 213 



moving tidal currents of the Sacramento-San Joaquin Delta 

 and also well up the Sacramento in more rapidly moving 

 waters. 



Its spawning activities, called "rock-fights" in the east 

 where the name "rock-fish" is current, involve large numbers 

 of individuals splashing about at the surface. Anywhere 

 from five to thirty appear, mill around for a few moments, 

 then all head up- or downstream and roll over on their 

 sides at about a 45-degree angle, throwing water in all di- 

 rections with their tails. These groups are usually composed 

 of one female and many males, the female being larger than 

 her consorts i and many such groups are in sight at one 

 time. That this is actually reproduction, and not courtship, is 

 proved by the fact that fertilized eggs can be collected from 

 the vicinity which are only one-sixteenth inch in diameter, 

 having not yet "water-hardened" — a process which, while 

 taking only one hour, swells them to about one-eighth inch 

 in diameter. 



The eggs sink but are what is called "semibuoyant," 

 meaning that they are so near the same specific gravity as 

 water that the slightest disturbance will lift them off the 

 bottom. They hatch in seventy hours at 60 degrees, in forty- 

 eight hours at 67 degrees. The young absorb the yolk-sac in 

 a week, and form scales when about half an inch long. They 

 grow rapidly, averaging four to five inches at the end of the 

 first year, fifteen inches at the third, twenty at the fifth, 

 thirty-two at the tenth, forty-two at the fifteenth. This is 

 when food is abundant and temperatures favorable, but it 

 appears that even under optimum conditions growth takes 

 place only between May and October, and that during the 

 remaining months of each year there is no increase in size. 

 They live to be at least twenty-five years old, and have been 

 known to reach a length of six feet and a weight of 125 



