FRESHWATER INTEGRATED MULTI-TROPHIC AQUACULTURE (FIMTA): DEVELOPING AQUAPONICS FOR COLD TEMPERATE COMMERCIAL ATLANTIC SALMON Salmo salar HATCHERY SYSTEMS AND INVESTIGATING THE USE OF IMTA KELP BIOCHAR AS A PLANT SUBSTRATE  

Freshwater integrated multi-trophic aquaculture (FIMTA) applies the same principles as those used in marine IMTA (MIMTA), but in a freshwater setting. Aquaponics is a form of FIMTA that integrates recirculating aquaculture with plant culture, through a microbial link and in a symbiotic relationship. Wastes produced from the fish are either absorbed directly by the plants or converted by microbes and then consumed by the plants.

The development of our FIMTA system involved a two part investigation. The first part was to identify a suitable freshwater salmon hatchery. This was done with routine water testing at a number of sampling locations within eight hatcheries (4 flow-through and 4 recirculating). The data were used to select a hatchery for further development and also to create a software program that can be used by hatchery managers to quickly identify inadequacies in their water treatment systems and effluent discharge. The second part of the investigation was to collect effluent water from the selected hatchery and use it in a temperature and light controlled pilot scale FIMTA/aquaponic system to test potential plant species in terms of growth and nutrient removal capabilities.

The pilot scale system employed two common aquaponic techniques: the floating raft and the media filled bed. Biochar produced from IMTA grown kelps was used as a substrate and tested in both of these techniques. It was identified that, after rinsing, the kelp biochar was suitable for seedling production and for use in the floating raft technique; however, it was not successful in the media filled beds due to its high water holding capabilities.

A total of 13 plant species have been tested at temperatures of 10-15°C, as this is the optimal water temperature range for growing salmon in freshwater hatcheries. The ability of the system to remove nutrients from the collected salmon effluent has been varied depending on the species selected and the biomass they produced, and also due to the variability of nutrient levels in the collected effluent.

The development of FIMTA for commercial salmon hatcheries will aid in the completion of IMTA from egg to plate. Not only can this be useful for branding purposes, but it can also aid farmers in waste reduction, increased water reuse, increase product diversification and improvement of societal acceptance of the industry. In particular, reducing phosphorus levels in effluents can help farmers to meet water quality guidelines and prevent eutrophication in the environment.