Travis Wood, Southern Utah University
Biology
Speckled dace, Rhinichthys osculus, is a small minnow that occupies river systems in Utah, Arizona, and Nevada. These minnows prefer clean, faster-moving water with plenty of cover such as rocks or undercuts. The invasive crayfish Orconectes virilis inhabits areas where the Virgin spinedace is found and has a similar diet being an opportunistic feeder. I tested the hypothesis that the natural behavior of Virgin spinedace will be altered due to the presence of crayfish. I predicted that the spinedace would avoid the crayfish and stay out in the open exposing them to a higher risk of predation, since crayfish are a more aggressive organism and will try and eat virtually anything they come into contact with. The experimental trials were conducted (N=24) in Quail Creek, Utah. Large plastic bins with the front and back replaced with screen were used to allow water flow through our experimental chambers. Each bin was placed in the creek and had rocks, and an undercut bank to resemble the native habitat. Controls consisted of placing isolated Virgin spinedace in one of the bins to observe its behavior. In both controls and experimental trials, either 2 spinedace, or 5+ spinedace were added. In experimental trials, I introduced 2 crayfish into the experimental chambers with the Virgin spinedace and allowed them to acclimate for 10 minutes. After the 10 minute acclimation period, behavioral observations were made. Results indicated that when 2 spinedace were present along with the crayfish, they would stay out in the open and the crayfish would occupy the cover or undercut. When 5+ spinedace were present with crayfish, the spinedace displayed a mobbing or “strength in numbers” behavior where they would occupy the undercut and either clog it up with their presence so the crayfish would leave, or mob the crayfish to make them leave. This behavior was opposite of what I predicted would happen. Since this mobbing or “strength in numbers” behavior was not observed with the samples of just 2 spinedace, this may be a behavioral adaptation resulting from the presence crayfish. Further research can be done on the behavioral effects of various fish species in the presence of introduced or invasive species to determine if this behavior is seen in other fishes.