Biochemical composition of Hediste diversicolor (OF Müller, 1776) (Annelida: Nereidae) reared on different types of aquaculture sludge

Abstract

IntroductionSustainable growth of the salmon aquaculture industry is highly dependent on the availability of new feed resources as well as improved management and utilization of waste streams from production. Polychaetes are capable of recapturing and recycling valuable biomolecules contained in aquaculture sludge and at the same time constitute a possible resource for aquafeeds.Material and methodsIn this study, the potential of Hediste diversicolor (OF Müller, 1776) to recover nutrients and energy contained aquaculture sludge was evaluated. Hereby, the effect of two different diets, smolt and post-smolt sludge, and different feed levels on polychaete growth, and biochemical and elemental composition was assessed.Results and discussionSurvival ranged from 80-90%, independent of treatment. Specific growth rates at the highest feed levels were significantly higher than at the lowest feed levels and growth was not affected by the type of diet. Similarly, total lipid and total fatty acid content of polychaetes were positively correlated with feed level while the type of diet had a limited effect. Fatty acid composition of polychaetes reflected feed levels: in both diet groups, polychaetes at lower feed levels showed a higher percentage of saturated fatty acids; monounsaturated fatty acids increased with increased feed supply for smolt sludge-fed group and polychaetes fed post-smolt sludge showed increased polyunsaturated fatty acid content with increasing feed levels. Neither diet nor feed levels affected protein content and amino acid composition of polychaetes. In conclusion, H. diversicolor could be successfully cultivated on both smolt and post-smolt sludge and was rich in proteins and lipids as well as essential amino and fatty acids. The species can be considered a promising candidate for recycling valuable nutrients from different types of side streams salmon aquaculture.

Sludge from sea-based Atlantic salmon (Salmo salar L.) production: quantification, composition, and potential application in IMTA

“…As reported by Wang et al (2013), feed pellets have a higher nutritional value than salmon feces as they have a higher C, N, P, and lipid content. A smaller proportion of feed in sludge would explain the lower nutrient density of sludge collected in this trial compared to sludge from land-based aquaculture (Wang et al, 2019a, Anglade et al, 2023b, Anglade et al, 2023a. Additionally, feed spill in land-based aquaculture has been reported to be higher compared to sea-based aquaculture (Aas and Åsgård, 2017) which would also lead to a higher proportion of feed to feces in sludge and hence a higher nutritional value of sludge from land-based aquaculture.…”

“…Following an IMTA approach, nutrient-rich waste sludge from salmon aquaculture can be utilized by lower trophic organisms such as polychaetes, as demonstrated by several studies (Nederlof et al, 2019, Wang et al, 2019a, Anglade et al, 2023b. Whether the composition of the sludge collected in this study could be suited for it to be used as a diet for polychaetes H. diversicolor depends upon different factors.…”

“…In previous studies, the lipid content of H. diversicolor was strongly positively correlated with the lipid content of their diet. Since the lipid content of sludge collected in this study was similar or higher than that of sludge used by Wang et al (2019a) and Anglade et al (2023b), it can be considered appropriate for cultivation of the species. Although Anglade et al (2023b) reported no signi cant effect of a different ash content between smolt and post-smolt sludge on composition and growth on polychaetes, it should be considered whether the higher ash and associated salt content in sludge from sea-based aquaculture compared to sludge from land-based smolt and post-smolt production could affect digestibility in H. diversicolor.…”

“…Since the lipid content of sludge collected in this study was similar or higher than that of sludge used by Wang et al (2019a) and Anglade et al (2023b), it can be considered appropriate for cultivation of the species. Although Anglade et al (2023b) reported no signi cant effect of a different ash content between smolt and post-smolt sludge on composition and growth on polychaetes, it should be considered whether the higher ash and associated salt content in sludge from sea-based aquaculture compared to sludge from land-based smolt and post-smolt production could affect digestibility in H. diversicolor. In summary, sludge from sea-based production collected in this study is probable to be an appropriate diet and the application should be investigated further in laboratory trials.…”

“…Further, the P content of sludge was similar to that of salmon feces (Wang et al, 2013). N, protein, and AA content was lower than that of sludge from land-based salmon production (Wang et al, 2019a, Anglade et al, 2023bAnglade et al, , 2023a which can be explained by the changes in feed requirements for salmon and the correlated change in feces composition. In early life stages, salmon depend on a higher proportion of protein to support rapid growth and development (Nordgarden et al, 2002).…”