California Sea Grant College Program

On sandy beaches throughout California, we evaluated three stages of the life cycle of the grunion Leuresthes tenuis for their potential as possible indicators of local ecological health and condition. We examined spawning runs of the adults, embryonic development of the terrestrially incubating eggs, and the viability of hatchlings from multiple spawning runs and beaches over three years. We looked for characteristics that lead to strong runs and high embryo survival on grunion beaches and at changes over time through the season. Using this unique long-term dataset we may be able to assess the strength of the population of this species for the first time over its entire range. We predicted that assessment of differential success of grunion reproduction can provide new indicators for ecological health of sandy beaches. In addition we intend to provide increased scientific justification for establishing best management practices for sandy beaches, to restore and protect the sandy beach habitat for the benefit of wildlife and human visitors.