Himalayan Blackberry (Rubus armeniacus) Effects on Fish Habitat: Impacts from Riparian Zones Inundated with Himalayan Blackberry
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Issue Date
2026
Editor
Authors
Leathem, Jason, Thomas
License
Subject
School of environment and sustainability
Abstract
This study compared the quality of fish habitat in small lotic reaches (channel width 1.5-5 m) having riparian zones inundated with invasive Himalayan blackberry (Rubus armeniacus) plants (test conditions) (3 sites) and reaches with a riparian zone consisting primarily of native vegetation (reference conditions) (5 sites). This thesis studied streams in the lower mainland of British Columbia near Coquitlam, Maple Ridge, and Mission to assess fish habitat quality indicators that included invertebrate drift input (allochthonous and total drift), temperature regulation (instream and riparian temperature), canopy cover, and instream complexity that provides rearing habitat for fish (large woody debris (LWD) habitat and residual pool habitat). I hypothesized that each fish habitat quality indicator would show lower quality in the test sites compared to the reference sites. My findings indicate that test sites had lower canopy cover, in comparison with reference sites made of natural vegetation from differing seral stages of growth (young to mature). Impacts were not detected when comparing invertebrate drift (both allochthonous and total), densities of LWD habitat, presence of residual pool habitat, depth of residual pool habitat, instream temperatures and riparian temperatures. Indicator variables assessed within this study exhibited a high degree of between-site variability both within and between the test and reference sites. Though the sample size was small within this study (3 test sites compared to 5 reference sites), trends in data were observed suggesting that test sites have lower LWD numbers, residual pool numbers, and produce slightly warmer instream temperatures, which aligned with historical literature. It is anticipated that Himalayan blackberry may have a large impact on fish habitat over an extended period due to its ability to inhibit seral growth of a riparian zone when it inundates an area (Feirke & Kauffman, 2003). This study is intended to assist environmental managers when considering habitat enhancements for sites with riparian zones inundated with Himalayan blackberry. Enhancements to these sites might improve instream temperature regulation, canopy cover, and instream complexity when a riparian zone is restored to its natural vegetation and allowed to mature.
Description
2026