Prisoners Harbor | MARINe

Prisoners Harbor

Click here for Long-Term trends

Click here for Biodiversity Survey findings

Prisoners Harbor is located in the Northern Channel Islands, within the Channel Islands National Marine Sanctuary, on Santa Cruz Island, California. This site is located in an Area of Special Biological Significance (San Miguel, Santa Rosa, and Santa Cruz Islands ASBS) in Channel Islands National Park. The reef is only a few hundred meters from the Prisoners Pier. This site was established in the same location as one of the historic study sites used for a baseline study of the Southern California Bight (conducted by the Bureau of Land Management in 1978-79). This site receives roughly 200-300 visitors per year. The reef is difficult to access though due to an almost 2 m vertical rock at the beach intersection that is washed by waves on all but lowest tides.  Access is easier when the sand accumulates but that is rare. The moderately sloping site consists of moderately uneven terrain, containing few cracks and folds.

Prisoners Harbor biodiversity overview

Prisoners Harbor is dominated by consolidated sedimentary bedrock, and the area surrounding the site is comprised of a mixture of consolidated bedrock and sandy beach. The primary coastal orientation of this site is northeast, and is protected within the Prisoners Bay.

Long-Term Monitoring Surveys at Prisoners Harbor were established in 1994, and are done by Channel Islands National Park. Long-Term MARINe surveys currently target the following species: Chthamalus/Balanus (Acorn Barnacles), Mytilus (California Mussel), Hesperophycus (Olive Rockweed), Silvetia (Golden Rockweed), and Endocladia (Turfweed). In addition, motile invertebrates, mussel size structure, and water temperature are monitored at this site. Click here to view Long-Term trends at this site.

Prisoners Harbor long-term monitoring overview

Biodiversity Surveys were done in 2002, 2003, 2004, and 2022. The Biodiversity Survey grid encompasses two sections that are approximately 18 meters (along shore) x 5 meters (seaward), and 9 meters (along shore) x 5 meters (seaward). Click here to view Biodiversity Survey findings at this site.

For more information about Prisoners Harbor, please contact Stephen Whitaker (

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