Application of polychaetes in (de)coupled integrated aquaculture: an approach for fish waste bioremediation

Abstract

Development of benthic components within integrated multi-trophic aquaculture (IMTA) systems warrants more attention, and the development of polychaetes as an extractive component in IMTA systems is ongoing. This study estimates the bioremediation potential of Capitella sp. and Ophryotrocha craigsmithi for coupled and decoupled salmon-driven IMTA. In coupled IMTA, polychaetes receive fresh faeces, while in decoupled IMTA, preservation of faeces is applied. Respiration and ammonia excretion rates were measured for polychaetes fed fresh, oven-dried or acidified salmon faeces, and combined with nutrients incorporated into tissue growth, to estimate nutrient requirements. Nutrient requirements were subsequently used to evaluate bioremediation potential. Metabolic rates were highest for O. craigsmithi and contributed notably to their overall nutrient requirement (20-30%). For the 2 polychaete species, nutrient requirements ranged from 5 to 26 mg C and from 2 to 6 mg N g-1 AFDW d-1. These requirements were comparable with or higher than other polychaete species, highlighting the potential for fish waste bioremediation by Capitella sp. and O. craigsmithi. Preserved diets reduced bioremediation potential 1.5 and 3-5 times for, respectively, Capitella sp. and O. craigsmithi. Assuming that polychaetes are efficient fish-faeces convertors, the bioremediation potential indicates that benthic cultivation units containing 65000-95000 ind. m-2 of Capitella sp. or 36000-194000 ind. m-2 of O. craigsmithi can convert the daily organic waste flux deposited below an average salmon farm. These densities were within ranges reported for wild populations, indicating that, based on the bioremediation potential, development of benthic IMTA with these 2 polychaete species seems realistic and efficient for waste conversion.

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

“…An alternative to cultivation of H. diversicolor with sludge collected from sea-based salmon aquaculture would be a direct integration of naturally under salmon farm occurring polychaetes species such as Capitella sp. and Ophryotrocha craigsmithi, building on research by Kinoshita et al (2008), Nederlof et al (2019), and Nederlof et al (2020). These species could be produced at high densities with a large biomass output (Tsutsumi et al, 2005) but, although initial efforts for a sea-based cultivation have been made, technical restraints persist and methods for cultivating and harvesting marine polychaetes beneath salmon farms have not been established (Jansen et al, 2019.…”

Life history traits for Ophryotrocha craigsmithi (Wiklund, Glover & Dahlgren, 2009), a candidate species in integrated multitrophic aquaculture

“…O. craigsmithi is not only among the smallest polychaetae candidate in our comparison between species in IMTA settings but also one of those reported to reach some of the highest densities under fish farms (Paxton and Davey, 2010;Eikje, 2013;Hamoutene et al, 2013). Furthermore, O. craigsmithi shows high carbon and nitrogen mitigation potential and high growth rates (Nederlof et al, 2020). Short generation time accompanied with semicontinuous reproduction would result in high population growth and allow for multiple harvests during a single fish production cycle that could increase the total yield for harvested polychaetes.…”

“…In addition to Ophryotrochas sp. high densities at fish farms, they have shown high carbon turnover rates and favorable protein and fatty acid profiles when fed with fish waste (Nederlof et al, 2019;Nederlof et al, 2020). Their nutritional value makes them attractive for the aquaculture feed industry as an ingredient in future feed formulations (Nederlof et al, 2019).…”

“…The demand for high-quality feed ingredients is increasing as the industry grow, and the need for these ingredients to be sustainably sourced is crucial for further expansion of the industry (Albrektsen et al, 2022). Combining the traits described above has led to the suggestion of farming O. craigsmithi in benthic IMTA systems (Fang et al, 2018;Jansen et al, 2019;Nederlof et al, 2020).…”

Seafood Waste Management Status in Bangladesh and Potential for Silage Production

“…Due to biological instability, high moisture content, high enzymatic activities, and rapid auto-oxidation, utilization of seafood waste is difficult. Thus, waste management and disposal in the seafood processing industry pose problems in terms of environmental protection and sustainability [31,37]. In less technology-intensive countries, seafood waste is usually used to produce animal feed ingredients such as fishmeal and silage [23,[38][39][40].…”