Stocking Density
Stocking density is a function of nutrient production and absorption. When integrating seaweeds into
recirculating IMTA aquaculture systems, the production of inorganic nutrients by the fed crop needs to be properly
coupled with the nutrient removal of the seaweeds (Figure 6.14). Nori, as previously mentioned, is one of
the most efficient seaweeds at removing inorganic nitrogen and phosphorous from the water. The production
of inorganic wastes by fish will be based on several factors including stocking density of fish and the amount of
feed they are given. Efficiency of inorganic nutrient removal by different species and water exchange rate also
need to be taken into account (Day, 2008). Day (2008) created predictive models that incorporate these parameters
and predict how much nori biomass is required. For example, a fish biomass of 5 kg require 1 kg of P. umbilicalis
to bring the ammoniumnitrogen level to below 25 μM. At a fish biomass of 40 kg, it is predicted that
you would need 6 kg of P. umbilicalis and the ammoniumnitrogen levels would be around 35 µM (Day, 2008).
Nutrient models such as these should play a large role in the determination of stocking density based on individual
systems.