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Size Matters for Kelp Forest Reserves

Gary E. Davis, Peter L. Haaker, Daniel J. Kushner, Ian Taniguchi and Daniel V. Richards

US National Park Service, VENTURA, USA

Theme: TH2

Marine reserves that exclude fishing are widely proposed to restore depleted populations, sustain fisheries, and preserve biodiversity. Size of individual reserves is a critical factor for designing effective reserve networks, but little empirical evidence is available to determine minimum effective reserve size. Observations made annually since 1982 from a 12 ha reserve and surrounding areas at Anacapa and Santa Cruz Islands, California, indicate the reserve was too small to sustain a pink abalone (Haliotis corrugata) population, even in the absence of fishing in surrounding waters since 1996. Giant kelp (Macrocystis pyrifera), red sea urchin (Strongylocentrotus franciscanus), purple sea urchin (S. purpuratus), kelp bass (Paralabrax clathratus), California sheephead (Semicossiphus pulcher) and other components of kelp forests were able to persist at historic levels in the reserve for 20 years. Kelp forests adjacent to the reserve changed into urchin and brittle star barrens following El Niño events in 1982-83, 1986-87, and 1991-92, and have not yet returned to kelp forests. We suggest that this reserve is too small to sustain a kelp forest ecosystem, but may be near the minimum size for this system.