Morphological Differences of Stream Fishes Above and Below Culverts

Fish passage structures such as road culverts may inhibit movement of fish, resulting in fragmentation and loss of habitat among populations of fish.  Road culvert design and placement can create different habitats (e.g., flow, depth, substrate) above and below the culvert.  In turn, these habitat differences can shape species assemblages or variation within a species.  Morphologies of species found in small, agricultural streams were examined above and below culverts.  Four culvert types (box, bottomless box, pipe arch, and bottomless pipe arch) at eleven sites in central Michigan were sampled in summer 2011; each site was sampled three times.  Fish in four 25-m reaches (two above and two below the culvert) were sampled by backpack electrofishing.  Each fish (>60-mm) was identified and photographed.  In the laboratory, box truss measurements were calculated using image analysis software.  Above and below culvert measurements differed for blacknose dace, central mudminnow, common shiner, and creek chub.  However, measurements varied by species, suggesting that certain morphological traits are more important for some species than others.