The triple bottom line impacts of O2 supplementation in recirculating aquaculture for food fish production
(Book - Regular Print)

Thesis,MSFS,Green Mountain College,2015

Includes bibliographical references.

The challenge to the food system is due to rising populations, increased urbanization, and the exportation of high animal protein western diets. Food fish show promise for relieving some of the supply issues surrounding high input animal protein food sources for humans, yet there are lingering concerns about aquaculture's sustainability. Some advances in aquaculture methods including recirculating aquaculture systems (RAS) have emerged, however, critical assessments are required to determine whether RAS can claim to be sustainable. Limiting factors exist that are preventing the advancement of high stocking density RAS into mainstream food production. One of these limiting factors is the need for O2 supplementation. With increased stocking densities, dissolved oxygen supplementation is required for exaggerated fish production. O2 supplementation in aquaculture typically occurs through the use of aeration mechanisms such as diffused air systems (regenerative blowers), mechanical aeration systems (paddle wheels), and water pump driven systems (venturis, degassing towers, spray fountains, and spray bars). O2 supplementation through paddle wheels and fountains is not possible in many RAS since many of these systems are too small. Regenerative blower systems are costly and operating costs vary depending upon location; air pumps may require rebuilding occasionally incurring more cost. Research conducted to study the effects of venturi/ vortex components in a RAS for O2 supplementation proved positive for the TBL of RAS. Off-gasses were expelled using venturi and vortex components while also increasing the dissolved oxygen in the solution. A single water pump drove the venturi/ vortex units. For optimum plant and fish growth, dissolved oxygen levels should be e5 mg/L. Actual stocking densities were 144 percent higher than the initial stocking density projections, and the dissolved oxygen level for the 42-day trial was 56.86 percent higher than the minimum required level of e5 mg/L. This in fact, could be a method of more sustainable RAS that adheres to the triple bottom line (TBL) of environmental stewardship, social equity, and economic viability. Sustainability within this analysis follows the TBL Aquaculture will be a vehicle to provide animal protein to the growing numbers of people around the world. This will require an increase in aquaculture production. This increase in production must correspond to the TBL in order to mitigate a corresponding increase in potential negative externalities.