Effects of Niger Cake Inclusion in Fish Feed as a Major Protein Source on Cation Dynamics in Nile Tilapia-Lettuce Aquaponics System
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Date
2016-07
Authors
Aziz, Tiruken
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Publisher
Addis Ababa University
Abstract
In aquaponics system the survival of cultured organisms is exclusively dependent on dissolved ions generated by the fish wastes. In this system fish meal is mainly used as a major protein sources as a fish feed which is not affordable to developing countries despite its high cation compositions. Therefore, a study was conducted to investigate the cation dynamics in tilapia-lettuce aquaponics system by providing Niger cake in different proportions as replacement for fish meal in fish feed to compare its cation loading capacity with that of fish meal and a standard hydroponics. The experiment was done in five treatments with respect to the proportion of Niger cake; 0% (Control), 12.5% (TA), 25% (TB), 37.5% (TC), and 43% (TD) and each treatment in duplicates. One hydroponic treatment (H) was included in the experiment to check the performance of each treatment on cation dynamics with respect to lettuce. Water, fish and lettuce samples were collected from the system every week for cation analysis. Potassium was analyzed by Flame photometer; calcium using atomic absorption spectrophotometer and iron with spectrophotometer. The result of the experiment showed that higher Niger cake inclusion in the fish feed (43%), TD) resulted higher cation loading to the system than the control diet and less cation loading than the hydroponic solution. However, iron concentration in the aquaponics water showed significantly higher value than hydroponic solution (P>0.05). The lettuce cation content also showed that higher percentage of the alternative feed could provide higher concentration of calcium, iron and potassium than the control fish feed. Therefore, the higher percentage of alternative feed from plant sources such as Niger cake could provide higher cations for the cultured plants in an aquaponics system though these cations could not be comparable with the standard hydroponics. Key words Cation dynamics, Niger cake, Nile tilapia, Lettuce, Hydroponics, Aquaponics
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Keywords
Cation dynamics, Niger cake, Nile tilapia, Lettuce, Hydroponics, Aquaponics