Chiba University - Tosa Bay

Restoration Project

Chiba University - Tosa Bay

Restoration Objective:

The aim of this study was to determine whether short stipe sporophytes of E. cava growing in warm waters in southern Japan become long stipe sporophytes after transplantation to a locality with lower temperature conditions for 2 years. The growth pattern of E. cava was also studied by monitoring the transplanted sporophytes.

Cause Of Decline:

Ecklonia cava is a large perennial kelp and forms a dense forest along the coast from central to southern Japan. The kelp forest plays an important role as nursery and breeding space for commercial fish, shellfish and other animals, and has high productivity. Recently, it has been reported that marine plant communities, including kelp forests, have disappeared or diminished along the Japanese coast. As an extreme example, 180 ha of E. cava forest disappeared in Tosa Bay, resulting in a collapse of the abalone fishery.

Key Reasons For Decline:


Scientific Paper

Growth of Ecklonia cava (Laminariales, Phaeophyta) sporophytes transplanted to a locality with different temperature conditions

Y. Serisawa, Aruga Yokohama, J. Tanaka
Phycological Research, Vol. 50.


Site Observations:

Observation Date

15th Nov 1995 – 15th Nov 1997

Action Summary:

Healthy juvenile sporophytes (< 1 year old) of Ecklonia cava with stipes <5cm long were collected from Tei in Tosa Bay in June 1995. Twenty-five sporophytes were attached individually to artificial slates (9 cm × 9 cm, 0.4 cm thick, composed of asbestos and cement) at the holdfast, using instant gel-type adhesive (Aron Alpha GEL-10) and kept in an indoor tank with flowing seawater (20°C, in darkness) for 1 day to confirm complete attachment. The slates with sporophytes were temporarily fixed for 5 months to concrete reefs, which were settled in advance at the sea bottom (9 m depth) close to the experimental site in Nabeta Bay, using water-resistant epoxy resin adhesive.

Lessons Learned:

Not focused on restoration

Project Outcomes:

Five Tei sporophytes and seven Nabeta sporophytes survived to the end of the study. The stipe length was consistently longer in Nabeta sporophytes than in Tei sporophytes after the second month of observation. After 2 years, the stipe of Nabeta sporophytes became longer and thicker than that of Tei sporophytes, reaching 25.6 ± 2.5cm in length.

Nature of Disturbance:

Some plates were detached from the experimental reefs by strong stormy waves during the winter of the first year.

Key Reasons For Decline:


Area of Restoration (Ha)


Indicator Data:


Ending Value:

Starting Value:

Adult Kelp Count