California Department of Fish and Wildlife - San Diego

Restoration Project

California Department of Fish and Wildlife - San Diego

Restoration Objective:

The aim of this study was to determine the effects of artificial plants on the density of 3 sea urchin species in sea urchin-dominated areas and the survival of adult giant kelp transplanted into sea urchin-dominated areas. The study evaluated whether artificial plants could be used for protection and restoration of giant kelp forests in southern California.

Site Selection Criteria:

A site was selected in an urchin barren where Macrocystis beds had existed historically.

Cause Of Decline:

Forests of giant kelp (Macrocystis pyrifera) provide substrate, food and habitat for a wide variety of marine organisms, and support fisheries for fin fish, invertebrates and kelp. Forests of giant kelp also provide the basis for an alginate industry which has sales exceeding US$230 million annually. Sea urchins that live in forests of giant kelp typically feed on kelp debris that drifts down from the forest. However when sea urchins become abundant, they can have devastating effects on populations of marine plants, including giant kelps.

Key Reasons For Decline:


Scientific Paper

A new tool for kelp restoration

J.A. Vasquez, R.H. McPeak
California Fish and Game, Vol. 84.

Site Observations:

Observation Date

1st Jun 1995 – 10th Aug 1995

Action Summary:

Giant kelp transplants were secured to the substrate using 4 concrete nails, 4 tie-wraps, and 1 rubber band 1.2 cm wide per plant. Groups of 15 adult plants were collected at a depth of 12m off Point Loma. Transplants were < 1 year old, with holdfast diameters ranging from 18 to 111cm and averaging 8 fronds each. Two of these 15-plant groups were surrounded by 16 artificial plants each (constructed from cement bricks and plastic). The artificial plants were evenly distributed around the perimeter of the giant kelp group. All sea urchins had previously been removed from these experimental areas.

Lessons Learned:

While artificial plants were effective in preventing overgrazing, they could have a negative impact on natural settlement as they would disturb any emergent juveniles.

Project Outcomes:

All transplanted adult giant kelp survived in the experimental areas protected by artificial plants during the 70 days of the study period. The protected plants grew during the study and the mean number of stipes per plant increased significantly, from 8 to 14.

Key Reasons For Decline:


Area of Restoration (Ha)


Indicator Data:


Ending Value:

Starting Value:

Adult Kelp Count