California Department of Fish and Wildlife - Imperial Beach

Restoration Project

California Department of Fish and Wildlife - Imperial Beach

Restoration Objective:

Restoration was undertaken to restore a historical kelp bed.

Site Selection Criteria:

A site was selected at Imperial Beach where a Macrocystis bed was present up until the 1940s.

Cause Of Decline:

The Macrocystis bed at Imperial Beach disappeared in the 1940's. The causes of decline are unknown, but kelp harvesting and overgrazing by fish and sea urchins may have contributed.

Key Reasons For Decline:


Scientific Paper

Kelp Habitat Improvement Project. Annual Report 1

W.J. North

Site Observations:

Observation Date

1st Jan 1963 – 1st Jan 1967

Action Summary:

Treatment with quicklime was used to remove urchins at Imperial Beach and an adult Macrocystis transplant was introduced. During the winter of 1964-1965, four acres of bottom were treated with quicklime, and 40 adult kelp plants were transplanted to the region.

Lessons Learned:

This site was abandoned due to high recruitment and grazing by sea urchins.

Project Outcomes:

By fall 1967, only three plants remained and these were destructively grazed. Three juvenile plants were found, representing the second generation of kelp in the area. In spring and summer 1967, dense concentrations of urchins appeared at the borders of the region covered by seaweed.

Nature of Disturbance:

The young kelp plants attracted fish, and intense grazing occurred, gradually reducing transplant numbers.

Key Reasons For Decline:


Area of Restoration (Ha)


Indicator Data:


Ending Value:

Starting Value:

Adult Kelp Count