Effects of diet and density on growth, survival and gametogenesis of Hediste diversicolor (O.F. Müller, 1776) (Nereididae, Polychaeta)

The effects of diet and density on growth, survival and gametogenesis of the common ragworm Hediste diversicolor (Nereididae, Polychaeta) were investigated with the aim of contributing to define their optimal ranges in the context of a commercial farming system. Two different experimental trials were set up: in the first one, juveniles of H. diversicolor, obtained from laboratory cultures established with specimens taken from the Venice Lagoon, were fed according to three different food regimes (two based on commercial feeds and one consisting of an homogenate of the brown alga Sargassum muticum); in the second trial the juveniles were maintained at different rearing densities (300, 1000 and 3000 ind. m−2). In both trials, the effects on growth, survival and gametogenesis were evaluated at various time-intervals during the eight-week period of the experiments. Results showed that H. diversicolor might be a promising species to be commercially exploited in an indoor farming system. In particular, high-protein diets permits elevated growth rates, earlier gametogenesis and sexual maturation. Both growth and survival rates were higher at the lowest densities, whereas the processes of gametogenesis and sexual maturation were not influenced by density.