109 



Table 11. Estimates of numbers and biomass of total trout decreased 



42 and 28%, respectively, between 1970 and 1972. However, the biomass 



decrease was not significant on the basis of overlapping 80% confidence 



intervals. The number and biomass of rainbow trout showed the greatest 



decrease, 73 and 67%, respectively. Water withdrawals for irrigation have 



affected this stream in the past and may be partially responsible for these 



reductions. 



TABLE 11. Estimated trout populations for a 7590 ft section of Horse Prairie 

 Creek located two miles upstream of Clark Canyon Reservoir. 80% 

 confidence limit in parenthesis. 



July, 1970 May, 1972 



Species Size group (in ) Number Pounds Number Pounds 



Brown Trout > 6.0 345 365 230 294 



(±60) (±84) (±30) (±38) 



Rainbow Trout > 7.0 100 79 27 26 



(±35) (±27) (± 9) (± 9) 



TOTAL 445 444 257 320 



(±69) (±88) (±31) (±39) 



During the summer of 1969, about 1800 white suckers and 400 longnose 

 suckers greater than 7.8 inches were tagged in Clark Canyon Reservoir. In 

 the Spring of 1972, 6 tagged white suckers were recovered in Horse Prairie 

 Creek, approximately two miles upstream of the reservoir. In May of 1972, 

 in the same location in Horse Prairie Creek, 2813 white and 421 longnose 

 suckers were marked. During July, two marked suckers were recovered in 

 the reservoir, showing movement out of Horse Prairie Creek following spawning 



In one week in approximately 3000 feet of Horse Prairie Creek, 1,387 

 white and 345 longnose suckers were captured of which 70 white and 3 long- 

 nose suckers were marked. In a small stream such as this where a high 



