Compiled by: Jay Warecki, Ph.D.
Director, Superior Aquaculture, LLC
(Report Released Sept., 2015)
- Fish Feed is normally the largest source of phosphorus to aquaculture systems.
- Approximately 70% of the phosphorus consumed can pass in feces. (Hakanson, et al. 1990)
- Similarly, Brown found that, “…the collected and dried waste from the raceways equaled 70.8% of the dry weight fed.” (Brown, 2010)
- Additionally, in many cases, only 50 % of the total nutrients fed are utilized by the fish.
- Superior Floating Raceways offer the ability to effectively capture and remove, either automatically or manually, some huge percentage of the nutrient-rich feces.
- Specially integrated sediment collection pods are available and recommended.
- Because phosphorus rapidly leaches from feces, the feces should be removed every 6-36 hours, depending upon load, feed qualities, temperature, pH, etc. (kabria, et al. 1997)
- Collected feces can be used in aquaponics, de-watered and fed to other animals, or used in fertilizers, mulch, etc.
- In addition to feces collection, the system also collects virtually all uneaten, settleable feed – which contains additional phosphorus.
- Uneaten feed and feces, “… are believed to contain most of their phosphorus in a water soluble, unstable form readily available to plants.” (Butz and Vens-Cappell, 1982)
- While soluble reactive phosphorus in the form of fish urine may be minor in comparison to feces, it should be mitigated as possible.
- When Superior Floating Raceways are used in a pond setting, the soluble reactive phosphorus from the urine can be absorbed by macrophytes, algae, and bottom sediments – which can be quite acceptable when within reason.
- However, Superior Raceways offer the farmer a means of collecting the dissolved fraction of P once it has been absorbed by the algae. The fact is that the raceways serve as excellent “traps” for both algae and valuable zooplankton.
- “The phosphorus collected in the raceways was actually greater (138%) than the total phosphorus fed in the fish feed.” (Brown, 2010) This was attributed to the phosphorus in the lipid-rich algae and valuable and zooplankton.
- Further reductions in raceway nutrient discharge can be achieved by the addition of in-line, small particle, collection modules – as commonly used in in-door RAS operations.
- Fish farm settling ponds offer opportunities for both increased levels of phosphorus extraction and potential production expansions.
To discuss your potential application or to view the “complete report”, give us a call or contact us by email.
Brown, Travis. 2010. Intensive Culture…in a Commercial-Scale, In-Pond Raceway. Ph.D. Dissertation, Auburn University.
Butz, I. & Vens-Cappell, 1982. Organic load from metabolic products of rainbow trout fed with dry food. In Albaster, J.S. (ed), Report of the EIFAC Workshop on Fish Farm Effluents, EIFAC Tech. Pap. 41:57-70.
Kibria, G.D. Nugegoda, R. Fairclough, & P. Lam. Hydrobiologia 357: 165-171, 1997. Kluwer Academic Publishers.