Is fecundity modified by crowding in the copepod Centropages typicus?

Experiments were conducted to test the effect of overcrowdingon egg production rates in the copepod Centropages typicus.Fertility was not significantly reduced by the presence of otherconspecifics when the volume of water was the same for femalesincubated alone or in the presence of other females and males.There was no evidence of chemical cues affecting egg productionwhen females were kept in large (1 female in 100 ml sea waterSW] or small (1 female in 25 ml SW) volumes of water, withor without partitions, and in the presence or absence of foodor males. Also, spawning rate was not reduced when females wereincubated in flow-through experimental chambers which alloweddiffusion of pheromones between females incubated alone or inhigh densities (100 ind. in 50 ml SW). Only when females wereplaced at unnaturally high densities (1 female ml^–1) wasegg production significantly reduced, probably due to physicaldisturbance and increased number of collisions rather than chemicalcommunication among individuals. The results show that chemicalcues do not affect spawning behaviour when population densitiesare close to field conditions. By contrast, overcrowding inducedby swarming or aggregation may potentially limit reproductivesuccess due to reduced feeding, and production and cannibalismof eggs.