of the years InvolTed. The median flow, therefore, is still less, 

 or very near 150 cubic feet per second. 



Assianing that the Trinity Rirer salmon population is at its 

 ■aximtm density under present conditions, and assuming that spawning 

 space is the dvterminlng factor, then, at a median spawning flow of 

 150 cubic feet per second, 5,647 nests would be ooeupied in the 

 river between Lewlston dam site and North Fork as determined by 

 application of formula previously described* 



EFFECTS CP HAIER DBVELOBJENT PIANS ON THE TRINITT RI7ER FISHEBT 

 AND SUGGESTED MEANS FOR FISHERT PROTECTION 



Resident game fishes will be least affected by the dam build- 

 ing program on the trinity River* Movements of these fish are limited 

 to short niigrations up the tributaries where they spawn* This movement 

 will not be Interfered with by dam construction except in the ease of 

 the brown trout which appears to maJce extensive migrations* This 

 species, however, shows reBiarkable powers of adjusting itself to chang- 

 ing conditions and should adapt to any reasonable set of conditions 

 which may result from dam construction* 



Steelhead trout help to maintain the heavily fished residen'^ 

 rainbow trout population of the Trinity River* Proposed dams will 

 block adult steelhead and will eliminate their construction to the 

 sports fishery above these structures* The reservoirs formed by the 

 dams will support resident trout to an unknown degree^ and will tend 

 to offset partially the loss of the steelhead fishery now existing 

 above the dam sites* Adult steelhead might be lifted over the dams 

 so that their progeny could be added to the resident fish population* 

 However, this addition to the resident population would be temporary* 

 Losses of seaward migrants in diversion structures would very likely 

 result in a net loss through such a program* 



The effect of the dam construction program on dace and sucker 

 populations cannot be stated at this time* The abundance of these 

 species will undoubtedly be affected. Whether they increase or de- 

 crease in numbers will be determined only after the stnictures are 

 built* If they increase or even maintain their present numbers, 

 they might sei^e as an important source of food for the resident 

 trout population* 



Management plans for the anadromous species are necessarily 

 based on three salient features of the water development plans i 

 (1) It is certain that the dams would be too high for economical 

 or practical construction of fish ladders over Hivai (2) as much 



56 



