PS 76-170
Competitive interactions between native benthic fish, native crayfish, and invasive rusty crayfish for shelter
Invasive crayfish are a major concern in aquatic ecosystems and can have devastating impacts on both plant and animal communities. The rusty crayfish (Orconectes rusticus), is a common invasive in the Great Lakes region and has had detrimental impacts in both lake and stream ecosystems through destruction of macrophyte beds, outcompeting native crayfish for shelters which often increases susceptibility to fish predation), and hybridizing with native crayfish producing competitively superior individuals. Although many species are outcompeted by the rusty crayfish some species seem to be able to coexist. In this study, we used an artificial stream to investigate the competitive superiority between the invasive rusty crayfish, native crayfish (O. obscurus) and central mottled sculpin (Cottus bairdi) fishes for shelter. The following combinations were tested: 10 O. obscurus + 10 C. bairdi, 10 O. rusticus + 10 C. bairdi, and 10 O. obscurus + 10 O. rusticus. Only 10 pvc shelters were used to limit shelter availability. During each 24-hour trial, shelters were monitored for species occupancy at dawn, afternoon, and dusk.
Results/Conclusions
Our results show that invasive rusty crayfish occupied significantly more shelters than the native crayfish (P = 0.0042). However, combinations of both invasive and native crayfish with the central mottled sculpin showed that neither crayfish displayed competitive superiority over this benthic fish (P > 0.05). Overall, this suggests that the rusty crayfish may be able to outcompete native O. obscurus for shelter but may not decrease shelter use for native benthic fishes. O. obscurus is a species of concern in Ohio and rarely occupy streams where O. rusticus are found. Although some native crayfish can co-exist with this invasive, it is likely that O. obscurus cannot; however, more studies are necessary to test this question. While O. rusticus did not outcompete C. bairdi for shelter, shelter competition experiments with other native benthic fishes should be completed to assess if this invasive has negative impacts on fish assemblages as a whole.