Synthesis of habitat restoration impacts on young-of-the-year salmonids in boreal rivers

Abstract

supporting a shift towards self-sustainable schemes in fisheries management. These results imply that habitat restoration is a useful approach for improving the ecological and conservational status of salmonid populations in boreal rivers. To further improve the success rate, and thereby public acceptance, of restorations they need to be complemented by other management measures that enhance the potential for the recovery of threatened salmonid populations.

Immediate response of fish communities and water chemistry to causeway breaching and bridge installation in the Kaouk River estuary, British Columbia, Canada

“…Similarly, Pacific Staghorn Sculpins varied with breaching, but accounted for a smaller portion of the variation (14–23%). Long‐term monitoring of these and other estuary fish species is required, as their competition with juvenile salmon can depress salmon populations, and has negatively impacted the success of previous salmon restoration projects (Hyatt et al ; Gerwing & Plate ; Marttila et al ).…”

“…What is currently unknown is the long‐term impacts of causeway breaching, particularly if breaching of causeways has a detectable impact upon salmon populations throughout the watershed. Long‐term continuous monitoring at both the estuary and watershed scales is required for assessments of such trends (Marttila et al ). Continued monitoring (at least three more years) of fish communities and water chemistry in the Kaouk estuary will be conducted by the Ka:'yu:'k't'h'/Che:k'tles7et'h First Nations to elucidate long‐term trends associated with causeway breaching.…”

“…Future upstream restoration efforts may fail to improve salmon production if insufficient estuary habitat exists to support increasing populations of salmon. Further, downstream impediments can have strong negative impacts upon restoration success of upstream river reaches with regards to salmonid recovery (Marttila et al ). As such, estuary restoration may remove a potential bottleneck with regards to salmon survival, and represent an important step in watershed restoration (Elliott & Whitfield ; Marttila et al ).…”

“…Logistical constraints resulted in water chemistry not being monitored in every round; therefore, with only two temporal replicates (one before breaching and one after), we are not able to properly differentiate seasonal impacts from breaching impacts with regards to water chemistry using statistical modeling (BACI design). However, as water chemistry can have large impacts upon the success of restoration projects (Marttila et al ), water chemistry values must be examined in some manner. Long‐term monitoring will include water chemistry variables, addressing the sample size issue over time.…”

“…Therefore, success will be defined as observing juvenile salmon concurrently up and downstream of the causeway. Further, as other estuary fish species, such as Threespine sticklebacks ( Gasterosteus aculeatus ), can compete with juvenile salmon for prey, potentially impacting salmon populations (Hyatt et al ; Gerwing & Plate ; Marttila et al ), this project will also present baseline data of the entire estuary fish community. Finally, the success of restoration activities on fisheries production is influenced, in part, by water quality (Marttila et al ).…”