Growth, survival and fatty acids profile of Polychaete, Nereis diversicolor (Müller, 1776) cultured using waste water of great sturgeon, Huso huso (Linnaeus, 1758), culture at different densities in an integrated farming system

Growth and survival of Polychaete, Nereis diversicolor fed on waste water of great sturgeon, Huso huso at different densities were studied. The study aimed to assess the efficacy of feeding of N. diversicolor with waste water derived from different densities of great sturgeon culture as well as to find a balance between fish density and growth of the worm. The worms (0.2-0.3 kg m-2) with an initial mean weight of 0.05 g were fed for 55 days with waste water of great sturgeon at densities of 2-3, 3-4 and 4-5 kg m-2 fish. A group of worms fed with fish feed was considered as the control. The obtained results showed that the biomass and average weight of the harvested worms were significantly higher at the density of 3-4 kg m-2 fish than in the other two treatments (p<0.05). Also, worms fed with fish feed (control group) showed higher survival rate and biomass production than the treatments. Some fatty acids were abundant in worms from the treatments, specifically 14:0, 16:0, C18:1n9c, 20:1, 22:1n-9, 18:3n-3, 20:2, 20:5n-3 (EPA) and 22:6n-3 (DHA), but were significantly lower than the control worms. The results demonstrate that production of N. diversicolor using fish waste water was highly efficient and can offer a sustainable solution to remove organic load in the aquaculture waste waters. Also, production of N. diversicolor via this method as an alternative source of fatty acids and protein for H. huso production could achieve multiple aims such as retention of valuable lipids from the H. huso waste water.