40 



CALIFORNIA FISH AND GAME 



From the data presented in this paper it is evident that the yield 

 of fry from eggs hatched in gravel beds supplied with normal hatchery 

 water is far below that attained by the usual procedure of basket 

 hatching in flowing water. The experiments further show that mine 

 silt deposited on gravel spawning beds during either the early or later 

 stages of incubation results in negligible yields of fry and is therefore 

 a serious menace to natural propagation. 



From a practical standpoint this damage to spawning beds would 

 occur when mining silt enters a stream at times other than storm 

 periods when the water velocity is insufficient to carry the sediment 

 in suspension. It is a well known fact that the velocities necessary to 

 dislodge deposited particles are far greater than the velocities required 

 to carry the same particles in suspension. For this reason natural 

 stream turbidity is largely limited to those periods when storm water 

 causes erosion. During these periods stream flows in areas suitable for 

 steelhead, trout, or salmon spawning are sufficient to prevent bottom 

 deposits of natural erosion silt and damage to eggs in the gravel is 

 minimized. Thus, while mining silt may be natural material, its 

 presence in waterways during nonerosion periods results in bottom 

 deposition which is unnatural and damaging. 



From the data presented it is apparent that adequate control to 

 prevent the discharge of mining silt where spawning grounds may be 

 affected is essential to the preservation of normal fish populations, and 

 legislation to secure the necessary protection is therefore recommended. 

 This recommendation applies only to protection of spawning grounds, 

 as the studies did not include the effect of suspended silt on fry after 

 emergence above the gravel. However, irrespective of whether fry and 

 adult fish are injured by silt in suspension, the damage to domestic, 

 agricultural, industrial and recreational water uses from high tur- 

 bidity is sufficient to justify a reasonable but adequate control. To 

 secure such control, not only on mining but on pollution from varied 

 sources, the authors suggest that a state agency with authority to act 

 with respect to all water values and uses above mentioned would be 

 desirable. In this way the public could be assured of proper action 

 on complaints and violations rather than being referred from agency 

 to agency having different jurisdictions, as now happens. 



TABLE 4 

 Water Analyses 



