Water Resources Research Act Program

Principal Investigators: Thomas McMahon

Abstract: Culverts are currently the most cost effective means of crossing streams for transportation. Forest roads used for recreation and timber practices routinely cross tributaries in headwater systems. Similarly, culverts are also commonly used in prairie systems where roads are maintained for transportation and agricultural purposes. The advantages of using culverts, in addition to material cost, can also include ease of installation, and wide-range applicability. However, it is widely known that road culverts can serve as obstacles migrant fish face in today's landscapes. The development of new roads, as well as the repair and upgrade of existing roads has led to substantial research addressing the effects culverts have on fish populations. The majority of this research has focused on salmonid species in mountain stream systems. While culverts do present a challenge to salmonid populations, road culverts are commonly used to cross streams in non-trout waters as well. The total effect road culverts have on species continuity in these warm-water systems remains largely unknown. This study proposes to investigate the effects road culverts have on prairie fish assemblages in the lower Yellowstone River drainage. Because many of the diverse number of fish species found in the tributaries of the lower Yellowstone River are considered poor swimmers, we would expect the passage limitations culverts present, to be at least similar to those affecting salmonid species. These can include excessive water velocities, drastic outlet drops, low-flow conditions during dry periods, lack of resting habitats both within the culvert and in the downstream plunge pool, and disorienting turbulent flows (Furniss et al. 1991). While these warm-water fish do not hold the same economic value that their salmonid relatives do, they do contribute to the overall biologic diversity of prairie systems, and also make up a large portion of the native fish found in Montana.