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 (ϳ600 km 2 ) 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 m 2 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 ϳUS$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.Résumé : Bien que des milliards de dollars aient été dépensés à restaurer des bassins versants dégradés dans le monde entier, les études à l'échelle du bassin versant qui s'intéressent à l'efficacité de ces actions sont rares. Afin d'atténuer les dommages causés par les activités de coupe de bois passées, la plaine inondable du bassin versant du cours supérieur de la rivière Chilliwack (ϳ600 km 2 ) a fait l'objet d'une vaste restauration de 1996 à 2000 reposant sur la restauration d'habitats à l'extérieur du chenal. La contribution des habitats restaurés à la production de saumoneaux sauvages de saumons cohos (Oncorhynchus kisutch) à l'échelle du bassin versant a été estimée dans le cadre d'un vaste programme de marquage-recapture en 2002. De 27 % à 34 % de la production d'un total estimé de 247 200 saumoneaux cohos ayant migré vers la mer peut être attribuée aux 157 000 m 2 de nouveaux habitats créés. Les modèles d'habitat reposant sur la superficie recensés dans la littérature prédisent raisonnablement bien la production de saumoneaux d'habitats restaurés, fournissant une approche de premier ordre acceptable pour évaluer les avantages de la restauration en ce qui concerne la production. Les coûts de la production de saumoneaux intégrés sur 30 ans allaient de 0,69 $US à 10,05 $US par saumoneau, soit dans la fourchette des coûts de production en écloserie rapportés dans d'autres ouvrages (coût typique de 1,00 $US par saumoneau) pour les sites restaurés les plus efficaces en terme de coûts. L'étude démontre que la restauration d'habitats à grande échelle peut accroître efficacement la production de poissons à l'échelle du bassin versant à un coût qui pourrait se comparer à la production de saumoneaux en écloser...

Carbon dynamics of river corridors and the effects of human alterations

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“…The primary management implication to emerge from our study is the critical need to protect and restore the physical complexity of river corridors, including the lateral connectivity between channels and riparian areas. The importance of lateral connectivity and ecosystem integrity in riparian areas has previously been emphasized in many contexts, including enhanced flood controls (Opperman et al 2010), reduced nutrient loading to channels (Zhang and Mitsch 2007), protecting fish stocks (Ogston et al 2015), and reducing fine sediment concentrations in rivers (Fitzpatrick et al 2009). To these we can now add OC storage in riparian soil and biomass.…”

Review of Tools for Identifying, Planning, and Implementing Habitat Restoration for Pacific Salmon and Steelhead

“…Thus, unless traps are located in multiple locations in main stems, tributaries, and off-channel areas, traps and weirs are of limited utility for assessing reach conditions and identifying specific restoration opportunities, apart from indicating overall fish production from a watershed or tributary. When multiple traps are run and extensive smolt-trapping data are available for a variety of off-channel restoration or other restoration actions, they can provide useful information for predicting increases in fish due to restoration actions Ogston et al 2015).…”

Spatial Variability of Chinook Salmon Spawning Distribution and Habitat Preferences

“…For example, in our study, high-density spawning areas that exceed 2 km in length may be expanded or improved through restoration actions to increase spawning capacity. These reaches may also be used to identify restoration projects that target juvenile life stages as the reaches are likely to remain important spawning areas over time (Ogston et al 2014). Recent research suggests that spawning sites are associated with complex habitat types that support offspring after emergence (Falke et al 2013).…”