Predation Pressure is Inversely Related to Abalone Recovery on the Channel Islands

Committee Members

• Dr. Jeremy Long, Chair (Biology)
• Dr. Luke Miller (Biology)
• Dr. Arielle Levine (Geography)

Abstract

Spatial heterogeneity in prey population recovery from disturbance can be driven and sustained by numerous factors, including life history traits, resource availability, and interspecific interactions. One such interaction is predation, because it can affect prey abundance and distribution, and it can vary spatially. 

However, few studies have assessed how predation may differ between locations at different points in their recovery status and how this might inform restoration approaches. For example, San Clemente and San Nicolas Island have differed in recovery of Black abalone, with no recovery at San Clemente Island and partial recovery at San Nicolas Island.

Here, we compared predation pressure on abalone between these two California Channel Islands using tethered juvenile Red abalone as a proxy. Community predation pressure was significantly higher on San Clemente Island than on San Nicolas Island. Consistent with these high predation rates, lined shore crab densities were elevated on San Clemente Island. While overall predation did not differ between the mid and low intertidal zones, shell remains of those predated indicated a potential difference in abalone predator composition between zones and islands. These observations suggest that location-specific predation pressure may help maintain spatial heterogeneity in natural prey recovery and present a challenge for reintroduction of abalone via translocation to San Clemente Island.