Fish Passage Through Culverts In Central Michigan Warmwater Streams

Road culverts can alter stream flow, remove fish habitat, and limit fish movement.  Little is known about the impacts of culverts on fish movement in low order, low gradient streams in an agricultural setting.  Eleven sites on first and second order streams in central Michigan were examined for effects of culvert type on fish passage in an agricultural setting.  None of the selected culverts were obvious barriers to fish passage as none were perched above the stream.  Four reaches (two upstream and two downstream of a culvert) were sampled three times in spring, summer, and fall 2011 at each site.  Mark-recapture was used to observe fish movement and the probability of fewer fish being found upstream of a culvert relative to downstream was modeled with logistic regression.  Based on recapture movements, one culvert was assumed to have limited passage for at least one fish species during each season and another for one species during summer.  The best models from logistic regression revealed that culvert length had the largest impact on the proportion of creek chubs being found upstream out of the variables used.  Results suggest that even though culverts may not be obvious barriers, limited fish passage can still occur.