An Evaluation of Bigmouth Buffalo (Ictiobus cyprinellus) and Common Carp (Cyprinus carpio) Association within the Qu'Appelle River System and its Implications for Species Conservation

Bigmouth buffalo (Ictiobus cyprinellus) is a fish species at risk in the Qu’Appelle River system of Saskatchewan, Canada. Little is known about their behaviours or how they have been impacted by the introduction of invasive common carp (Cyprinus carpio) into the system. As such, I had several main objectives within my study: 1) to determine the large-scale movements of bigmouth buffalo; 2) to assess whether bigmouth buffalo and common carp associate within Buffalo Pound Lake; 3) to determine which environmental factors (if any) affected the habitat selection of either species; and 4) to report other findings that may be relevant for species management. I captured and surgically implanted bigmouth buffalo and common carp with acoustic telemetry tags and recorded their movements. I then modeled my findings using R to determine association and the effect of environmental factors on their habitat selection. I found that bigmouth buffalo captured in Buffalo Pound Lake did not move throughout the Qu’Appelle River, and instead preferred to remain within the lake itself. Common carp left the lake during spawning to go upstream to a known spawning site, but bigmouth buffalo did not. I also discovered that outside of the May spawning period, the two species do not typically associate. Instead of spending more time in the shallows as we would expect, bigmouth buffalo were instead found in more open waters, while carp preferred the warm shallows. Even in the winter when overwintering space is limited, the two species did not associate. Both macrophyte presence and daily maximum noise had negative effects on habitat selection. Daily mean temperature did also have an effect, though this effect changed depending on the region of the lake. As temperature is consistent throughout the lake, it may be an indicator of some behavioural difference or instance of competition between the two species. Overall, I found that there is a possibility that competitive exclusion may be occurring. However, further research must be done to conclusively determine whether this is the case. Particularly as bigmouth buffalo are not recruiting as much and grow much slower than common carp do, which may lead to local extirpation once the population becomes too old.

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