Abstract
Organic wastes can be recycled in an ecologically sound way in fishponds by applying integrated agriculture and aquaculture systems (IAA). This kind of waste recycling can help to protect the environment from pollution and improve fishpond yields. Additionally, IAA provides an opportunity for diversification of the output from two or more existing subsystems leading to higher overall farm economic returns. This study explored the potential application of amaranth wastes (AW) as a dietary ingredient for tilapia in a tilapia-amaranths integrated system (ITA). An experimental diet (AD) contained 10% (based on the control diet, CD) inclusion of AW collected from a nearby vegetable market. The experiments included triplicate treatments with; (i) fish fed on AD, where the pond water was used for irrigating the amaranth plants (IAA-fish), and (ii) fish fed on CD, where no pond water was used for irrigating the amaranth plants (non-IAA fish). 90 days after fish stocking, eighteen 4 m2 amaranth plots were prepared and treated with (i) tap water without fertilization (control amaranths), (ii) water from IAA-fish pond and organically fertilized (IAA amaranths), and (iii) tap water and inorganically fertilized (non-IAA amaranths). The use of AW improved the fish feed conversion ratio. The overall net income from ITA was 3.2, 2.3, 2.6, and 1.8 higher than from non-IAA amaranths, IAA-amaranths, non-IAA fish, and IAA fish sub-systems respectively.
Highlights
The urgent need for increasing protein production per unit area of farmed land is a priority worldwide [1]
Anti-nutritional factors, and mineral composition of amaranth waste (AW) used in the experimental diet are shown in DM stands for dry matter, CP for crude protein, CL for crude lipid and CF for crude fibre
The results demonstrate that the inclusion of AW in the fish feed does not compromise, but rather improves the feed utilization efficiency by the fish
Summary
The urgent need for increasing protein production per unit area of farmed land is a priority worldwide [1]. Capture fisheries have been one of the major animal protein sources for many people in East Africa [2]. With the current declining wild fish yields and growing population, fish protein is increasingly becoming scarcer. Recent studies suggest that almost half of the African fish stocks are overexploited or fully exploited [3]. Despite the dominance of capture fisheries in total fish production in the continent, the promise of aquaculture as the new frontier in fish production holds strong. About one-sixth of the total production of food fish in Africa in 2016 came from aquaculture [4]. The fish supply deficit in most African countries presents significant prospects for aquaculture development [5]
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