Watershed-scale effectiveness of floodplain habitat restoration for juvenile coho salmon in the Chilliwack River, British Columbia

Abstract

Although billions of dollars have been spent restoring degraded watersheds worldwide, watershed-scale studies evaluating their effectiveness are rare. To mitigate damage from past logging activities, the floodplain of the upper Chilliwack River watershed (∼600 km2) was extensively restored from 1996 to 2000 through off-channel habitat restoration. The contribution of restored habitat to watershed-scale production of wild coho (Oncorhynchus kisutch) smolts was estimated through an extensive mark–recapture program in 2002. 27%–34% of the production of the estimated 247 200 out-migrating coho smolts could be attributed to the 157 000 m2 of newly created habitat. Area-based habitat models from the literature performed reasonably well in predicting smolt production from restored habitat, providing an acceptable first-order approach for evaluating production benefits of restoration. The costs of smolt production integrated over 30 years ranged from US$0.69–US$10.05 per smolt, falling within the range of hatchery production costs reported elsewhere (typical cost of ∼US$1.00 per smolt) at the most cost-effective restoration sites. This study demonstrates that large-scale habitat restoration can effectively enhance fish production at a watershed scale, at a cost that may be comparable to hatchery smolt production.