Road crossings as barriers to small-stream fish movement
barriers, mark-recapture, fish movement, streams, culverts, upstream, water velocity, design, fish passage, critical levels
Journal or Book Title
Transactions of the American Fisheries Society
We used mark-recapture techniques to examine the effects of four types of roadcrossings on fish movement during spring base flows and summer low flows in small streams ofthe Ouachita Mountains, west-central Arkansas. We assessed movement for 21 fish species inseven familiars through culvert, slab, open-box, and ford crossings and through natural reaches.We detected no seasonal or directional bias in fish movements through any crossing type or thenatural reaches. Overall fish movement was an order of magnitude lower through culverts thanthrough other crossings or natural reaches, except no movement was detected through the slabcrossing. In contrast, open-box and ford crossings showed little difference from natural reachesin overall movement of fishes. Numbers of species that traversed crossings and movementswithin three of four dominant fish families (Centrarchidae, Cyprinidae, and Fundulidae) also werereduced at culverts relative to ford and open-box crossings and natural reaches. In spring,retention of fishes was consistently highest in stream segments upstream of crossings and lowestin downstream segments for all crossing types, a response attributed to scouring associated withspring spates. Water velocity at crossings was inversely related to fish movement; culvertcrossings consistently had the highest velocities and open-box crossings had the lowest. A keyrequirement for improving road crossing designs for small-stream fish passage will bedetermination of critical levels of water velocity through crossings.