Freshwater Integrated Multi-Trophic Aquaculture (FIMTA): Developing aquaponics for cold temperate salmon, Salmo salar, hatchery systems and investigating the use of IMTA kelp biochar as a plant substrate

Abstract

Freshwater integrated multi-trophic aquaculture (FIMTA) integrates animal aquaculture with plant culture where wastes produced by fish are either converted by microbes and/or invertebrates, then consumed by plants, or directly consumed by plants. An experimental system tested 13 plant species and measured nutrient removal from sludge effluent collected from a commercial salmon hatchery using two techniques: the floating raft and the media-filled bed. Biochar, a stable form of carbon, was produced by the pyrolysis of IMTA-grown kelps and was tested as a substrate in both techniques. After rinsing, the biochar was suitable for seedling production and in the floating raft technique; however, it was unsuccessful in the media-filled beds presumably due to its high water retention. The development of FIMTA for salmon hatcheries will aid in the completion of IMTA from “egg to plate”, which can be useful for branding purposes, product diversification, wastes reduction, water reuse and improved societal acceptance. Importantly, reducing phosphorus levels in effluents can prevent eutrophication and help farmers meet water quality guidelines.