SIMoN
  Sanctuary Integrated Monitoring Network
Monitoring Project

Persistence and Recovery of Abalone Populations in Central California

Principal Investigator(s)

  • Fiorenza Micheli
    Stanford University

Funding

  • Stanford Research Incentive Award
  • Monterey Bay Sanctuary Foundation
Start Date: January 01, 1972
End Date: December 31, 2009

An understanding of the processes that allow populations and communities to persist and recover following disturbance is critical to many important questions in ecology and conservation biology. Marine protected areas (MPAs) represent a powerful approach to conserving and promoting recovery of marine species and habitats impacted by fishing and other human activities. However, certain scenarios may prevent recovery or lead to further declines, even within MPAs. These include: extreme population reductions prior to protection; protection of unsuitable or degraded habitats; and intervening natural disturbances, such as extreme weather events, predation or disease outbreaks.

We investigated patterns and processes of persistence and recovery of depleted invertebrate populations, red (Haliotis rufescens) and black (H. cracherodii) abalone, in central California. Abalone densities, size structure, and predation mortality were compared along a time-series of no take and de facto reserves (sites where access is limited by private property) established in central California between 1931 and 1997 and protected for varying lengths of time. Longterm persistence was examined within a permanent site established buy John Pearse (UC Santa Cruz) and colleagues within a no-take marine reserve in 1972 (the Hopkins Marine Life Refuge).

Protection from human harvesting resulted in greater proportions of large individuals within intertidal but not subtidal habitat. Red abalone shows remarkably low fluctuations in densities and size structure over a 30 year period. Intense predation by sea otters in the subtidal habitat, combined with high recruitment rates may underlie these patterns.

Summary to Date

Abalone densities, size structure, and predation mortality were compared along a time-series of no take and de facto reserves (sites where access is limited by private property) established in central California between 1931 and 1997 and protected for varying lengths of time.

Longterm persistence was examined within a permanent site established within a no-take marine reserve in 1972. Protection from human harvesting resulted in greater proportions of large individuals within intertidal but not subtidal habitat. Red abalone shows remarkably low fluctuations in densities and size structure over a 30 year period. Intense predation by sea otters in the subtidal habitat, combined with high recruitment rates may underlie these patterns.

Monitoring Trends

  • Larger individuals of black abalone were found within marine reserves
  • Greater black abalone densities were found at sites south of Monterey bay (Pebble beach, Carmel Point, Point Lobos, Yankee Point and Soberanes Point) than within Monterey bay (Cannery Row, Hopkins Marine Life Refuge and Point Pinos)
  • No significant differences in black abalone abundances were found between marine reserves and open-access sites
  • No significant variation in red abalone densities, size structure and mortality rates were found over three decades (1972-2003) within the Hopkins Marine Life Refuge

Discussion

In January 2009, black abalone (Haliotis cracherodii) was listed by NOAA's Fisheries Service as an endangered species under the Endangered Species Act. The final ruling was published in the Federal Register, volume 74 no. 9., pages 1937-1946.

Study Methods

Black and red abalone (and red and purple sea urchins) were counted within 7-9 belt transects (30 x 2 m) at intertidal and subtidal (5-20 m depth) locations within 8 intertidal and 6 subtidal sites. Substrate type and rugosity was characterized along each transects. Locations of transects were recorded using a hand held GPS. Within the Hopkins Marine Life Refuge, red abalone densities and sizes were monitored every 3-4 months within a 40 x 40 m permanent plot established by John Pearse et al. in 1972. Mortality rates were estimated by removing all visible abalone shells from the permanent plot at monthly intervals. Abalone recruitment is quantified using collectors (plastic crates filled with boulders, checked monthly).

Documents

  • Micheli et al. (2008)
    Persistence of depleted abalones in marine reserves of central California
    330 KB PDF