Surveys Show Kelp Forest Persists After Urchin Culling Ceases at Tankers Reef

In early 2021, the California Fish and Game Commission enacted a regulation allowing the unlimited take of sea urchins at Tankers Reef in Monterey, located just east of the commercial pier and offshore from Del Monte Beach. This three-year rule aimed to assess whether recreational divers could effectively reduce urchin densities to support kelp regrowth and whether they could collect, analyze, and communicate data in a scientifically rigorous manner useful to resource managers.

The regulation expired on April 1, 2024, and culling activities are no longer permitted. The coordinated culling efforts, led by the Giant Giant Kelp Restoration Project (G2KR), concluded in July 2023.

With continued funding from Seatrees, Reef Check monitors the Tankers restoration site twice a year (June and September) to evaluate the effects of the removal effort and now to study how the kelp forest can persist without ongoing urchin removal.

In 2024, Reef Check conducted four surveys at Tankers Reef—two at the restoration site (grid) and two at the control site. These surveys involved a total of 74 dives completed by 17 divers, including both staff and volunteers. Volunteers underwent restoration-specific training before each survey day. All surveys were conducted from a boat and required two days to complete.

The most recent surveys from September 2024 indicate that the kelp forest has persisted despite the cessation of coordinated culling efforts over a year ago (July 2023).

• Urchin densities at the restoration site currently average 3 urchins per m², compared to 5 urchins per m² at the control site.
• Giant kelp densities have remained stable since the fall 2023 surveys.
• Giant kelp stipe densities declined by nearly 45% in June 2024 but showed no further changes in the fall.

These findings suggest that the kelp forest has remained relatively stable, even without continued culling efforts. The fact that density of kelp individuals (plants) are stable while the numbers of stipes decreased suggest that some of the larger plants were lost over the winter 2023/24 and are being replaced by new smaller kelp plants in 2024.