Mating success and its consequences for population growth in an estuarine copepod

Abstract

We conducted experiments on mating success of the estuarine copepod Eurytemora affinis in the San Francisco Estuary, USA. The experimental approach was to isolate virgin pairs (one male and one female) in containers varying in volume from 0.03 to 32 l for 2, 4, or 8 h. Mating was considered successful if viable eggs were produced by individual females subsequently incubated for up to 5 d. The experimental data were analyzed by fitting a 3-parameter model to the data to determine the volume search rate of males. Mating frequencies indicated a volume search rate for E. affinis males of 7.2 ± 4.0 l h-1 (172 ± 96 l d-1, 95% CL), about 20-fold higher than that for Acartia hudsonica previously determined by a similar method. A simple population model showed that the critical population density needed to maintain the E. affinis population can be well below the seasonally low abundance of this copepod in the San Francisco Estuary. The low critical density may allow population persistence in an estuary without the production of resting eggs. © Inter-Research 2009.