UBC Theses and Dissertations

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UBC Theses and Dissertations

Defining an historical baseline and charting a path to restoring habitat connectivity for salmonids in a highly urbanized landscape Finn, Riley


Loss of connectivity caused by anthropogenic barriers is a key threat for migratory freshwater species, barriers on streams can decrease the amount of habitat available for spawning and rearing. To set appropriate targets for restoration it is important to know how different populations have been impacted in terms of the location and extent of historically available habitat that has been lost or has become inaccessible. I mapped and predicted barriers to fish passage in streams and diking infrastructure to estimate the amount of floodplain and stream habitat that remains for 14 populations of salmon in the Lower Fraser River, British Columbia, Canada’s most productive salmon river. To place these estimates within a historical context, the floodplain area was estimated using vegetation records from the 1850’s, and lost streams were estimated. Accessibility to floodplain was poor across the entire region with only 15% of the historical floodplain remaining accessible. Linear stream habitat ranged in accessibility from 28-99% across populations. I used conservation planning software to maximize the amount and quality of stream habitat that can be restored across a range of budgets. An estimated 75% of habitat blocked by barriers could have access restored with an investment of 200 million dollars. With small budgets it was more efficient to remove a high number of culverts, but when budgets were larger, restoration included restoring passage past dams and flood infrastructure. The amount of habitat restored for each species varied depending on whether habitat quality was also prioritized, highlighting where restoration of freshwater habitat requires more than the removal of barriers.

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