Impacts of Highway Construction on Redd Counts of Stream-Dwelling Brook Trout

Abstract

Sedimentation during road construction is a human impact that threatens aquatic ecosystems. Despite a large body of literature on the effect of fine sediments on the initial developmental stages of fish, we do not know of any studies that have investigated the return of spawners to spawning grounds in streams impacted by sediment from road construction. The objective of this study was to quantify the return to spawning grounds of brook trout Salvelinus fontinalis at different stages of highway construction (before, during, and after construction). Redd counts were made at a fine spatial resolution (<0.5 m) over two consecutive years in 12 reaches distributed along a 115-km stretch of highway in the Laurentides Wildlife Reserve, Quebec. We found a significant decrease in redd counts in reaches affected by construction during the second year but no evidence of impacts in reaches affected by construction during the first year. A possible explanation is that sediment releases were well controlled during construction except after an extreme weather event occurring during the spawning season of the second year. However, we observed that a reach heavily impacted by sediments still supported high densities of spawners. Overall, we found a significant decrease in the absolute number of redd counts in the second year but strong consistency in the spatial distribution of the spawning sites, both within and among reaches and for all stages of highway construction and sediment loadings, which suggests that the return of spawners is more constrained by habitat variables than by sediment from highway construction.

Received March 30, 2012; accepted August 20, 2012

ACKNOWLEDGMENTS

We thank Y. Paradis for invaluable logistic and field support and E. Goupil and G. Pelletier for field assistance. We are grateful to L. Devine for comments on a previous version of the paper. We thank two anonymous reviewers as well as the Associate Editor and the Editor for their comments. Y. Bédard and M. Lafrance (Ministère des Transports du Québec [MTQ]) and the Société des établissements de plein air du Québec provided logistic support. This research was financed primarily by the MTQ. Additional funding came from grants from the Natural Sciences and Engineering Research Council of Canada to P. Magnan and M. A. Rodríguez and a grant from the Canada Research Chair Program to P. Magnan. Marc Pépino was supported by the MTQ and a fellowship from the Fondation de la faune du Québec.