Species Interactions 



Two minnow complexes were identified and compared in Beaver Creek. 

 The creek chub complex consisted of the creek chub, fathead minnow and 

 sand shiner, while the flathead chub complex consisted of the flathead 

 chub {Htjbop6li> gfiacifxA) , silver minnow {Hijbognathti6 ahgijhxtif,) and the 

 plains minnow (//. placld^A] . The percent composition of these two 

 complexes in Beaver Creek for 1977 and 1978 is shown in figures 22 and 

 23, respectively. 



Although the percentages of each complex vary somewhat between 

 years, the association between the two is similar. The flathead chub 

 complex dominates the lower portions of the creek while the creek chub 

 complex is dominant in the upper reaches. Section 24 appears to be the 

 transition zone for the complexes with the creek chub complex showing 

 dominance upstream from this section. Together, the complexes generally 

 dominate the fish numbers throughout the creek. In areas not dominated 

 by the complexes, goldeye tend to be abundant in the lower reaches, 

 replaced by white suckers upstream. The flathead chub complex prefers 

 turbid waters which flow over silty, pebbly substrates and the creek 

 chub complex chooses clearer water and can withstand mucky habitats with 

 extensive rooted vegetation (Brov/n 1971 and Baxter and Simon 1970). 



Sauger show close association with the flathead chub complex but 

 walleye are associated with both complexes. Sauger are found as far 

 upstream as section 21, which is about where the flathead chub complex 

 begins to lose dominance. Considering the piscivorous nature of sauger 

 and walleye, these complexes probably represent important forage bases. 



Goldeye {Hiodon alofiOldeA] are abundant in Beaver Creek. Although 

 little information is available concerning competition of goldeye, 

 walleye and sauger for food, space, shelter, and spawning sites, the 

 possibility may exist and may limit walleye and sauger numbers. Spawning 

 for goldeye occurs at temperatures between 10-12. 80C (59-550F), 

 corresponding to the spawning period of sauger and walleye. Although 

 goldeye generally spawn in pools and backwaters, competition for space 

 is likely to occur. Goldeye feed extensively on the water surface 

 for insects so competition for food is unlikely. Large numbers of 

 goldeye could prey heavily on walleye fry. Creek chubs are the only 

 other piscivore present in large numbers in Beaver Creek. 



The goldeye and flathead chub complex are predominantly downstream. 

 In contrast, the creek chub and fathead minnow are generally most corrmon 

 in the upstream sections. The white sucker is cormion throughout the 

 drainane. Game fish compose a small percent of fish species present. 



Beaver Creek Tributaries 



Aquatic invertebrates and fish populations were sampled in three 

 tributaries to Beaver Creek (Figure 2). Water chemistry measurements are 



-62- 



