Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 4374
Title: Impact of Aeration and Alkalinity on the Water Quality and Product Quality of Transported Tilapia - A Simulation Study
Author: John Edwin Colt, Eric L. Kroeger
Publication Year: 2013
Journal: Aquacultural Engineering
DOI: 10.1016/j.aquaeng.2013.03.002
Keywords: water quality,transport,aeration,dissolved oxygen,carbon dioxide,un-ionized ammonia

 The impact of aerator type and alkalinity on water quality and product quality of Nile tilapia (Oreochrmis niloticus) were determined for simulated commercial hauling conditions. Three types of aerators were tested: pure oxygen aeration with a fine bubble diffuser (“Oxygen”), air aeration with medium bubble diffusers (“Air”), and a combination of both pure oxygen aeration and air aeration (“Mixed”). Simulated transport hauls were conducted at initial alkalinities of 1.74 ± 0.11 meq/L (“Low”) and 8.84 ± 0.55 meq/L (“High”).

The “Air” treatments resulted in lowest carbon dioxide concentration, and highest pH and un-ionized ammonia concentrations. At high alkalinities, the “Air” treatments were unable to maintain adequate dissolved oxygen levels. The “Mixed” treatment resulted in reduced carbon dioxide and dissolved oxygen concentrations. The “Oxygen” treatment resulted the highest dissolved oxygen, highest carbon dioxide, and lowest pH and un-ionized ammonia. The un-ionized ammonia concentrations were higher with the “High Alkalinity” treatments because of higher pHs. Significantly increased mortality was observed in the “Air” treatments in both the “Low-“ and “High-Alkalinity” treatments. Mortality in the “Oxygen” and “Mixed” treatments for both low and high alkalinities were comparable to that observed in commercial tilapia hauling using fine bubble diffusers and pure oxygen.

These results indicate that direct hauling mortalities will not be increased at high alkalinities, if pure oxygen aeration is used. The potential impact of water quality on survival and product quality may be less than from (a) physica

Theme: Recovery, Rebuilding and Sustainability of Marine and Anadromous Species
Foci: Maximize effectiveness and minimize impacts of artificial propagation in recovery, rebuilding and stock sustainability