at MNPS overlapped at 30 to 35 mm (Fig. 12). Thus, length frequencies could not be used to separate 

 the species in earlier data. Data for the two species were combined. 



1 ooo zoo o 



FREQUENCY 



500 1 OOO 



FREQUENCY 



Figure 1 2. Length frequency distribution of sticklebacks. 



niackspotted and threespine sticklebacks were collected in all programs, but were only abundant in 

 impingement samples from fall through spring. Adults and young-of-the-year remain in the spawning areas 

 until late summer (Fitzgerald 1983), which may account for the low abundance of these fish during the 

 summer. Approximately 35% of all sticklebacks impinged at MNPS were taken in 1983 (Table 13). The 

 estimated impingment of sticklebacks in 1984 and 1985 was much lower, because sampling had been 

 eliminated at Unit 1. '['he estimated number of sticklebacks impinged ranged from 2,411 to 9,918 in the 

 period of two-unit operation prior to 1984, but no trend was apparent and, presumably, no impact had 

 resulted from MNPS operations. 



Sticklebacks were sufficiently abundant for time-series modeling in only impingement samples. The 

 R for the impingement time-series model was 0.82, demonstrating a good fit to the data. Cooling- water 

 flow, an annual periodic component, and a short term 4-mo cycle described impinged stickleback abundance. 

 A summary of this baseline model is presented in Appendix XVIII. 



37 



