Population characteristics and trophic interactions between Pacific mole crabs and Redtail surfperch on northern California sandy beaches

A network of marine protected areas (MPAs) was established to protect northern California coastal habitats in December 2012. Populations of two indicator species, Amphistichus rhodoterus (redtail surfperch) and Emerita analoga (pacific mole crabs) were characterized within MPAs and reference sites to provide baseline ecological information for this region. Data were gathered using a series of simple field surveys (hook and line fishing surveys for A. rhodoterus along with core and transect surveys for E. analoga). Relative abundance, lengths, and sex ratios of A. rhodoterus did not differ between MPAs and their respective reference sites, whereas condition (overall health) increased in a north to south trend. Although based on a limited number of tag returns, movement of A. rhodoterus within northern California appears to be relatively local. Relative swash zone abundance of E. analoga did not differ between the MPA studied and its respective reference sites. Abundance and biomass of small-sized (\u3c10 \u3emm) E. analoga greatly increased during the summer months, likely due to recruitment to northern California beaches. A similar trend occurred for medium and large-sized crabs during spring months, likely due to the timing of reproduction in this region. Both species serve as good indicator species for the northern California region. However, future monitoring for E. analoga should be based on timing of reproduction and recruitment