P.U.R.P

SOUTH COAST PURPLE URCHIN REMOVAL PROJECT

Overview

This pilot project aims to trial workflows to reduce purple urchin densities across a 1 acre site at San Miguel Island (see map below) and mobilize markets for the urchin harvested. The project includes analysis of how to grow the regional supply chains for purple urchin products, including ranched culinary formats, compost, mulch and soil amendments, as well as possible animal feeds. Modeled from efforts in Mendocino, commercial sea urchin divers strategically harvest urchin from urchin dense locations in hopes of catalyzing kelp growth. This project highlights and focuses on the opportunity for collaboration between scientists, fishermen, seafood industry and the greater blue economy. Project partners include:

Our study site, Tyler Bight at San Miguel Island was once an extensive kelp forest (grey areas) and highly productive fishing grounds. Now there is very little kelp (colored areas). Map courtesy of Kelpwatch

After our commercial divers harvested 3,000 lbs of purple urchin from our 1-acre site, we reduced grazing pressure on kelp enough for kelp to re-establish (see video below). A control site nearby was also monitored and did not show any kelp regrowth.

New kelp growth as of August 2025, video courtesy of Trent Petterson on the F/V Miss Marie

All of the purple urchin were crushed and dried in the sun, then ground into a soil amendment that is high in bio-available calcium and amino acids. We are investigating how to scale this supply chain to create market-support for purple urchin removal and kelp restoration, as well as utilize red urchin shell, a consistently available waste stream that can be diverted from the landfill.