Abstract
The objective of the present work was to determine the effects of the interaction between feeding rate and area for periphyton in rearing aquaria for Nile tilapia. Twenty 25 L polyethylene outdoor aquaria were used to hold experimental fish. Three tilapia fingerlings (2.56 ± 0.14 g) were stocked in each aquarium for five weeks (12 fish m-2). There were two different feeding rates (full and full minus 30%) and two submerged areas for periphyton development (59.4% and 96.5% of the aquarium surface area; n = 5). Final body weight, specific growth rate and yield in the 96.5%-area aquaria of fish submitted to 30% less feed were significantly higher than in the 96.5%-area aquaria submitted to full feeding rates. Fish growth in the restricted-feed aquaria was favored by their better water quality (higher pH and lower total ammonia nitrogen). There were negative effects on final body weight, SGR, yield and feed conversion ratio of fish in full-feed aquaria when the area for periphyton increased from 59.4 to 96.5%. It was concluded that the combination of restricted feeding rates with large substrate areas for periphyton growth results in better water quality for fish culture than the adoption of each management alone.
Highlights
There is a consensus in aquaculture that natural feed has high nutritional value for fish, and that growth must be stimulated by producers through proper management (KNUCKEY et al, 2006)
One thousand male sex-reversed Nile tilapia, Oreochromis niloticus, fingerlings were obtained from a local fish producer and transported to LCTA facilities (Laboratório de Ciência e Tecnologia Aquicola, Departamento de Engenharia de Pesca, Centro de Ciências Agrárias, Universidade Federal do Ceará, Fortaleza, Ceará State, Brazil)
Except for the upper limit at 16:00 hours, which was observed solely at one day, the water temperature in the aquaria was within the proper range for tilapia growth (AZAZA et al, 2008)
Summary
There is a consensus in aquaculture that natural feed has high nutritional value for fish, and that growth must be stimulated by producers through proper management (KNUCKEY et al, 2006). In fish culture, such as tilapia culture, the main natural food items in ponds or aquaria are plankton (phytoplankton and zooplankton (EL-SAYED, 2006). Plankton alone is not capable of sustaining suitable fish growth rates in semi-intensive systems, even in high densities (NAYLOR et al, 2000). Animal Sciences of fish in semi-intensive systems require supplemental nutrient sources to achieve good productivity rates (TACON; DE SILVA, 1997). Fish producers offer agricultural by-products and/or incomplete artificial diets to animals (VAN EER et al, 2004)
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