Variability in Growth and Age Structure Among Populations of Ribbed Mussels, Geukensia demissa (Dillwyn) (Bivalvia: Mytilidae), in Jamacia Bay, New York (Gateway NRA)

Growth rates, body weight, density and biomass of ribbed mussels, Geukensia demissa (Dillwyn), were determined at Spartina alterniflora marsh-flat sites in Jamaica Bay, New York (Lower Hudson Estuary). Cumulative growth and annual growth increments varied but rates were lower at sites within the central bay relative to peripheral sites. Local variability both in size at Ring-1 and size-specific annual growth rates probably account for the variability in cumulative length. No pattersn were noted in frequency distributions of shell size but congruence in age structure was observed among neighboring sites in some areas of the bay. Mussel densities were greater within Jamaica Bay than at most other locations reported in the literature and estimated biomass values were lower. Growth rates of Jamaica Bay mussels were lower than other populations in the northeastern American coast. Four hypotheses that may account for observed Geukensia growth rates in Jamaica Bay are presented and discussed: higher population density, higher vertical marsh levels, variability in phtyoplankton quality and/or quantity, long-term sublethal chemical pollution.