California Sea Grant College Program

The red abalone, Haliotis rufescens Swainson 1822, supports the only recreational free-dive abalone fishery in the United States. I examined annual survivorship of three size classes ( 178 mm) of red abalone from five sites in northern California and one site in southern California using capture-mark-recapture data. Survival was variable spatially and among size classes. Survivorship values were incorporated into a size based projection matrix model. Elasticity values were found to be greatest for the sub-legal red abalone 150 mm to 178 mm (maximum shell length) indicating that changes in the vital rates of this size class are most important to population growth. Current methods to describe the age-at-length relationship of red abalone are insufficient because shell lengths exceed those predicted by growth models. I evaluated the utility of analyzing atomic bomb generated radioisotope 14C in shell to validate this relationship.