IS FECUNDITY MODIFIED BY CROWDING IN THE COPEPOD CENTROPAGES TYPICUS

Experiments were conducted to test the effect of overcrowding on egg p roduction rates in the copepod Centropages typicus. Fertility was not significantly reduced by the presence of other conspecifics when the v olume of water was the same for females incubated alone or in the pres ence of other females and males. There was no evidence of chemical cue s affecting egg production when females were kept in large (1 female i n 100 ml sea water [SW] or small (1 female in 25 ml SW) volumes of wat er, with or without partitions, and in the presence or absence of food or males. Also, spawning rate was not reduced when females were incub ated in flow-through experimental chambers which allowed diffusion of pheromones between females incubated alone or in high densities (100 i nd. in 50 ml SW). Only when females were placed at unnaturally high de nsities (1 female ml(-1)) was egg production significantly reduced, pr obably due to physical disturbance and increased number of collisions rather than chemical communication among individuals. The results show that chemical cues do not affect spawning behaviour when population d ensities are close to field conditions. By contrast, overcrowding indu ced by swarming or aggregation may potentially limit reproductive succ ess due to reduced feeding, and production and cannibalism of eggs.