Culverts in paved roads as suitable passages for Neotropical fish species

Sergio Makrakis,Maristela Cavicchioli Makrakis,Ricardo Luiz Wagner,Theodore Castro-Santos,Maurício Spagnolo Adames

doi:10.1590/s1679-62252012000400009

Sergio Makrakis, Maristela Cavicchioli Makrakis + Show 3 more

Open Access

https://doi.org/10.1590/s1679-62252012000400009

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Abstract

Improperly installed or poorly maintained culverts can pose a serious threat to fish by disrupting their habitat and endangering spawning success. Road culverts that are not designed for fish passage frequently can become obstacles. This can be especially problematic for migratory species, but can lead to fragmentation of resident populations as well. This study evaluated 40 culverts of 29 sites within a 25-km radius from Toledo city, Paraná State, southern Brazil, with respect to their likely effects on movement of the local ichthyofauna. We collected data on the shape and length of culverts, culvert material, waterfall height, water column depth, slope, and estimated flow velocity. Culverts were categorized by level of barrier risk for upstream migration: high, medium, low, and impassable, as well as the type of barrier posed (fall height, depth, length and velocity). Most of culverts analyzed were considered potential barriers to fish movement, with 45% classified as impassible, 45% as high risk, 10% as medium risk, and no culverts as low risk. Brazilian culverts as fishways will require additional monitoring and studies to corroborate the premises proposed in the present study. Road culvert projects that are properly built and maintained will be able to simultaneously improve function of roadways and protect fish populations.

Highlights

Fish populations depend strongly on characteristics of the habitat where they live and perform biological functions
In order to define categories of culvert characteristics, we considered the high diversity of the fish species in Neotropical rivers and streams, mostly of small-sized species, and especially the high abundance of Siluriformes, which exhibit bottom swimming behavior and do not jump
Serious concerns proceed from the scenario envisioned in this study where the majority of culverts were considered barriers to fish movement; 45% are impassable, and another 45% have potentially high risk according to the criteria and approach used

Summary

Introduction

Fish populations depend strongly on characteristics of the habitat where they live and perform biological functions (reproduction, feeding, locomotion, etc.). Barriers to fish movement restrict the ability of them to access habitats, and can reduce their quality both upstream and downstream of the barrier (Morita & Yamamoto, 2002). Anthropogenic barriers are a primary factor affecting movements of fishes (Fullerton et al, 2010). Most road culverts are designed solely for the purpose of moving water beneath a roadway, with no consideration of effects on animal movement. Culverts are defined as a hydraulic structure to convey surface water runoff under highway, road, railroad, or other embankment (Clay, 1995). Shapes, and materials, and these factors, along with several others, affect their capacity and overall performance. Sizes and shapes may vary from small circular pipes to extremely large arch sections that are sometimes used in place of bridges (Ead et al, 2002). The most commonly used culvert shape is circular, but arches, boxes, rectangular and elliptical shapes are used, as well they may be simple, with only one or multiple culvert, over a culvert

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