The aquaculture industry is incredibly efficient and necessary to increase the world's food supply. However, aquaculture is often met with much skepticism, particularly involving its effect on the environment. Aquaponics is a form of aquaculture that combines the hydroponic growth of plants and herbs with fish. Utilizing the nutrient rich fish effluent in a dosed re-circulating system limits most negative environmental effects aquaculture can impose on the environment while producing a secondary crop. These systems are designed to raise large quantities of fish in relatively small volumes of water by utilizing bio-filters to treat the water and then reuse it. The fish effluent provides 10 of the 13 essential nutrients to the plants with only Ca, K, and Fe needing supplementation.
We attempted to replicate Dr. James Rakocy's ("godfather of aquaponics," US Virgin Islands scientist) aquaponic system set-up in order to test the feasibility of growing 2-year post-smolt Atlantic salmon in an aquaponics system. Two additional objectives were: to analyze which plants among spinach, arugula and oregano grew best in the system, and to determine the optimum plant to fish stocking density ratio.The specific growth rate (SGR) for the 2 - year post- smolt Atlantic salmon over a five week time period was 1.97%/day, and among the highest for freshwater salmonids.
The Atlantic salmon performed well in the system and provided nutrients in excess to the 0.04m2 of hydroponic plants. Oregano grew significantly better in the system when analyzed by height. Upon visual analysis arugula was clearly the fastest growing plant with the most biomass. The feeding rate ratio calculated was 196.5g/m2/day compared to the 60-100g/m2/day optimum described by Dr. James Rakocy, indicating that the plant ratio could have been doubled and nutrients were readily available.
Overall, the 2-year post-smolt Atlantic salmon grew very well in the l5°C water system and all plants experienced posi¬tive linear growth, with oregano being significantly higher than both spinach and arugula, but arugula having the highest biomass.