Urchin Control
Project Lead:
Project Location: Bamfield, BC
Contact:​
Project Overview
Sea urchin densities have expanded in many areas around the world, following declines in natural urchin predators. In British Columbia, the hunting of sea otters and dramatic declines in sunflower stars following wasting disease outbreaks have led to sea urchin overpopulation. While sea urchins often scavenge a variety of foods, they are voracious kelp grazers and can remove large swaths of kelp forests in short periods of time, resulting in deforested areas known as “urchin barrens”. In B.C., there are three common urchin species: red urchins (Strongylocentrotus franciscanus), purple urchins (Strongylocentrotus purpuratus), and green urchins (Strongylocentrotus droebachiensi). Each of these species can form barrens, but red urchin barrens appear most wide-spread in B.C.
Photo: Urchin barren in Barkley Sound
In areas where urchins are overabundant, like Barkley Sound, urchin grazing limits restoration success. Urchins can quickly graze on newly outplanted kelp, undermining restoration efforts before the kelp has a chance to establish itself. Some intervention is needed to address urchin overabundance to ensure kelp restoration success. Intervention and mitigation strategies such as urchin exclusion (via cages or fences) or urchin removal (via harvesting, culling or relocation) offer potential means of alleviating grazing pressures. Yet their effectiveness likely depends on urchin densities and the intended scale of kelp-restoration efforts. Moreover, the optimal strategy will likely change over time or depending on context, making it important to provide managers with a roadmap for how to choose strategies adaptively as urchin abundance or site conditions change. A deeper insight of the role of urchin herbivory and mitigation efforts is necessary to predict and manage threatened kelp populations in BC.
Photo: KRI diver fixing an urchin fence at Hornby Island
PC: Rebecca Benjamin-Carey
Goals and Objectives
The overarching objective of this project is to empirically examine key aspects of urchin ecology and mitigation that will directly inform active kelp restoration efforts in Barkley Sound, British Columbia. Ultimately, we hope to determine the most effective urchin mitigation strategies under different contexts to protect vulnerable areas of kelp populations and ensure successful kelp restoration.
Photo: KRI diver Hannah Schriber collecting urchins from an experimental plot at Denman Island
PC: Rebecca Benjamin-Carey
Research Methods
While urchin grazing is known to be harmful to kelp, the extent to which local populations are grazing down kelp forests and the impact that they have on restoration efforts has yet to be assessed. Using exclusion fences, we are testing restoration success at dedicated field sites with and without the presence of urchins, quantifying survival rates of outplanted kelp and applying these findings to future restoration efforts. Given the grazing patterns of urchins, we assume that kelp restoration efforts will be more successful at sites with lower urchin densities or in regions where we can consistently exclude urchins from outplanted plots.
Photo: KRI diver and technician Clay Steell securing an urchin exclusion cage in Barkley Sound
PC: Dr. Lauren Dykman
We are also exploring alternative urchin management approaches, such as the utilization of natural fear cues to deter urchins from entering restoration sites. If effective, this approach could add a novel, behavior-based tool to the suite of techniques used for kelp forest restoration. We are also exploring sustainable urchin removal strategies by coordinating cultural harvests with local First Nations to provide a traditional food and restore local kelp forests in tandem.
Photo: A curious sea lion checking out a KRI diver as they repair an urchin exclusion fence at Denman Island
PC: Rebecca Benjamin-Carey
2023
Spring-Summer
Installed/ Trialed Urchin Exclusion Cages at Hornby Island
Monthly Monitoring of Kelp and Urchin Counts
Urchin Fear Cue Experiment in Barkley Sound
2024
Fall
2024
February
2024
Spring-Summer
Deploying Urchin Fences at Study Sites
Cultural Urchin Harvest in Barkley Sound
Continued Urchin Fence Exclusion at Denman Island
Urchin Removal Continues Around Outplanted Areas
2024
November
2025
Spring-Summer
2025
Spring-Summer