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 effects 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 the effects of culvert type (box, bottomless box, pipe arch, and bottomless pipe arch) on fish passage in an agricultural setting. The selected culverts were not 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 sampling 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, limited passage was assumed for at least one fish species during each season at a pipe arch culvert and for one species during summer at a box culvert. The best models from logistic regression revealed that culvert length had the largest effect on the proportion of Creek Chub Semotilus atromaculatus being found upstream out of the variables used. FishXing, a computer program used to predict fish passage through culverts, predicted that five culverts had passage-limiting flows to either Western Blacknose Dace Rhinichthys obtusus or Creek Chub during at least one season. However, all culverts were predicted to have some passable flows during each season (except one culvert during one season). Results suggest that even though culverts may not be obvious barriers, fish passage can still be limited. Received November 15, 2012; accepted March 12, 2013