Reproduction and structure of the population of the Chaetognath Parasagitta friderici in Guanabara Bay (Brazil) based on short term sampling

the aim of this study was to describe the total density, densities of developmental stages and the reproduction period of parasagitta friderici. weekly samples were collected at one station in the channel of guanabara bay, rio de janeiro, during one year. three vertical hauls were made for each sample, and p. friderici was separated, the developmental stages were identified, and body length (bl), ovary length (ol) and seminal vesicle width (svw) were measured. throughout the year p. friderici was the most abundant chaetognath species occurring in all four developmental stages, the densities of which varied from week to week. higher densities of adults occurred in the spring, followed by peaks of juveniles in the summer. although p. friderici seems to reproduce continuously in guanabara bay, a reproductive peak was apparent during the spring. the intensification of reproduction during the spring, with juveniles occurring in the summer, seems to be related to the period of higher food supply during the rainy season and intrusions of the south atlantic central water.