Recruitment, survivorship, and age structure of a New York ribbed mussel population (Geukensia demissa) in relation to shore level - A nine year study

Age structure, recruitment, and survivorship of a Jamaica Bay, New York rib bed mussel (Geukensia demissa) population were studied over nine years at t wo shore elevations. Mussels were collected in November (following seasonal growth and recruitment) and March (to assay over-winter mortality). Larval recruits (0-class) averaged 55% of the population at the marsh edge compar ed with < 9% at the higher elevation (6 m upshore). High larval settlement at the edge apparently depletes the larval supply available for settlement within the marsh interior. At the edge, the population generally contained 7 monotonically decreasing age classes compared to 15-20 age classes at the interior site. At the interior site, most 0-class mussels may not directly settle into existing mussel aggregations, but instead immigrate over a per iod of two years following settlement. The linear survivorship curve at the edge reflects 40-50% mortality every yearn Over-winter mortality is sensit ive to winter ice conditions. Simulations of reproductive output based on s urvivorship and fertility data combined suggest that mussel cohorts living in the marsh may approach the lifetime reproductive output of marsh edge mu ssels after about 15 years, a life span which is not uncommon at higher sho re levels.