Aspects of the ecology of Mnemiopsis mccradyi Mayer in North Lake Worth, Florida

The abundance, biomass, and size class composition of Mnemiopsis mccradyi were monitored weekly from March 1994 to May 1995. Relationships between M. mccradyi abundance and several environmental variables were investigated, including water temperature, salinity, rainfall, density of specific M. mccradyi prey, and abundance of the predatory ctenophore Beroe ovata. The mean abundance from September to May was 14.8 ctenophores/m^3, while the mean from May to September was 0.3 ctenophores/m^3. Temperature observations indicated 26C (Sept-May) as optimal for population abundance, and 29-32C (May-Sept) as a possible upper temperature limit to larval development. Adults ctenophores dominated the population from May to September, while larvae and juveniles increased in number and biomass during the period of highest abundance. These results revealed two distinct seasons of M. mccradyi abundance based on ambient water temperature, and indicated that the dynamics of this population are attuned to the environmental conditions of a southern Florida estuary.