Bischoff, Adrian A. (2003) Experiments on growth and mortality of a marine polychaete of the genus Nereis. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 102 pp.

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Abstract

Nereis diversicolor, a detritivorous marine polychaete, was cultured, in a newly designed culture unit, to evaluate its potential for integrated aquaculture. The culture unit consists of a 75-litre tank, filled with 25 kg gravel (grain size 2-4 mm) and 25 litre brackish water. A continuous air and nutrient supply were connected to the culture unit. Solid waste (faeces and uneaten food), obtained from a recirculating aquaculture system for European Seabass (Dicentrarchus labrax), was used as solitary food source during growth experiments of Nereis diversicolor. Protein content of applied solid waste ranged from 100 to 360 gram dry weight per kg supplied waste and the amount of supplied protein per tank ranged from 1.61 to 8.19 gram dry weight per day. Supplied energy to the tanks ranged from 22.5 to 62.1 kJ per day. Three experiments with different stocking densities were executed. Each treatment (stocking density) consists of four replicates. All experiments were designed with a low stocking density, 188, 208 and 235 Individuals per m2, and a high stocking density, 376, 423 and 470 Individuals per m2. Water temperature and salinity during experiments was 18 ± 2°C and 16 ± 1‰, respectively. Culture of Nereis diversicolor within the newly developed system is possible. Average mortality ranged between 9 and 21% during all experiments. No relation between stocking rate and mortality and food composition and mortality was observed. During all experiments positive growth was observed. Average specific growth rates ranged from 0.67 to 1.87% wet weight per day. A relationship between specific growth rate and daily supplied energy per individual worm was detected. The average protein content of Nereis diversicolor reared under experimental conditions ranged from 575 to 640 gram per kg dry weight. Ten out of twenty-four cases showed a biomass loss during the experiments due to mortality. Within the newly developed culture unit the protein retention due to biomass increase ranged from 0.4 to 6.6 gram dry weight per m2, which represents 0.3 to 8.8% of supplied protein in the solid waste.

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