Application of polychaetes in (de)coupled integrated aquaculture: production of a high-quality marine resource

Capitella sp. and Ophryotrocha craigsmithi received a diet of salmon feces to evaluatetheir potential to convert fish waste into valuable marine products, e.g. ingredients for fishfeed formulation. Production rate and body composition (focusing on fatty acid [FA] profiles)were determined for polychaetes fed fresh, acid-preserved or oven-dried salmon feces to evaluatetheir application in (de)coupled integrated multi-trophic aquaculture (IMTA) systems. Coupledproduction refers to direct integration of fish and polychaetes within the same (eco)system,while in decoupled production, units can be spatially or functionally separated. For decoupledproduction, preservation of fish waste is recommended. Although diets contained relatively lowpolyunsaturated FA (PUFA) levels (5−9% of total FAs), both species were rich in PUFAs (>30%of total FAs) and contained the essential FAs for fish. Feeding Capitella sp. the acid-preserveddiet enriched its FA profile. Accumulation of PUFAs, de novo synthesis and/or transfer via bacterialbiomass could have played a role in the upregulation of PUFA content. Amino acid profilesindicated that these polychaetes contained the amino acids essential for fish. Highest growth forboth species was observed when fed fresh feces, whereas preserved diets resulted in negativegrowth rates for O. craigsmithi, suggesting an important role of microbes in polychaete diets.Our results indicate that both species are potential valuable marine products. Given growth rateswith different diets, O. craigsmithi seems more suitable for integration in coupled systems, whileCapitella sp. is interesting for both coupled and decoupled integrated systems