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Increasing the natural food to promote sustainable and ecological production in the carp farming. Coordination (NatKa)
Project
Project code: 2815NA069, 5654
Contract period: 01.02.2016
- 31.01.2019
Budget: 198,332 Euro
Purpose of research: Applied research
Keywords: Carp, Cyprinus carpio
Ecological approaches for maximal use of natural forage productivity and reducing resources for fish nutrition are a major goal for the future of green pisciculture. Despite the fact that availability of natural food organisms is the most important advantage of traditional earth pond rearing of carp, raising the intrinsic production is widely overseen today. Environmental conditions have profoundly changed, requiring novel methods to achieve higher bio-nutritional growth. In this project, our aim is to lower the amount of crop feeding and to increase the natural food in carp diet to improve meat and water quality by simple and cheap measures under high ecological conscience with a reduction of costs. Hence, we focus on experimental field approaches with high practical value to find effective measures enabling common earthen carp ponds to produce greater amounts of natural fish dietary organisms from early spring throughout the year. In specially designed experimental settings using distinct replicate enclosure lots, water and soil treatments as well as special fertilisation regimes are tested. Also, green manuring by winter crop sowing and input of plant-derived structures to elevate zoobenthic production are evaluated with respect to water quality enhancement. In addition, combinatory approaches in experimental and full sized ponds including green fertilization are performed and a monitoring programme is conducted to explore locally distinct trophic patterns in running pond systems. Pivotal feature of our evaluation is the measurement of microbial activity in soil and water in response to treatments, since bacteria in mud and water substantially affect water parameters crucial for trophic interactions. Besides trophically important soil and water parameters like phosphorous and nitrogen, we monitor algae and zooplankton production, microfauna onset and composition and abundance of the most important food organisms for carp.
The present study focused on the evaluation of various means to enhance naturale forage production in order to elevate the intrinsically produced fish yield in typical carp pond culture, increase sustainability and product quality. In special experiments inside carp ponds and smaller delimited units therein, the effects of organic fertilization and other management measures were tested for an increase in invertebrate carp food organism density under analysis of water and pond bottom chemistry. It could be shown, that targeted administration of organic substances such as animal manure and plant material can effectively increase natural yield an in nutrient-poor ponds.
Bioavailable phosphorus in particular was identified as a limiting factor in the ponds investigated.
The pond bottom as a nutrient reservoir is decisive for the growth of nature. Its available phosphorus content (P2O5-CAL), together with other parameters such as pH and microbial activity, is a measure of pond fertility. The occurrence of natural forage organisms showed a clear dependence on basic nutrient supply and the resulting primary production (phytoplankton). In a pond with a nutrient-rich pond bottom (P2O5-CAL 23.8 mg/100 g soil), no significant increase of phyto- and zooplankton as well as benthic nutrients could be achieved by the application of different organic fertilizers in fish-free units. However, the effect on planktonic and benthic living nutrients is sometimes different, especially with regard to bottom dwelling oligochaete worms, which respond well to organic fertilization also in nutrient-rich ponds. In ponds with nutrient-poor pond bottoms (P2O5-CAL 13.4 mg/100 g soil), organic fertilisation with horse and chicken manure (3t/ha) increased the nutrient density and the average fish yield in the experimental units could be increased by about 200 kg/ha. With regard to zooplankton biomass, a positive trend could be observed in the P and N dense organic fertiliser substrates, with different organic substrates having different effects on nutrient biomass production, especially in terms of effect continuance. Green manuring by autumn sowing proved to be an adequate means to increase the early occurrence of rotifers. Rye is suitable for this in winter-dry ponds. In waterlogged ponds, the gradual administration of horse manure should be used from April onwards. No negative effects on the environment were detected as a consequence of fertilization. In particular, also with fish stocking, neither in the pond water nor in the pond soil a measurable enrichment of nitrogen and phosphorus compounds or organic material were found at the end of the production period. High pH values in ponds could be significantly reduced by straw fertilization. The stocking with carp and mechanical aeration and circulation of the pond water favours the microbial activity and microbial biomass in the pond bottom. In addition, the circulation of pond water promoted soil-living carp food organisms and primary production of microalgae. Neither the single draining of ponds in winter or in the following summer, nor soil calcification carried out during this process produced a reduction of the organic substance content of the pond soil. The winter drainage nevertheless led to a significant reduction in the volume of pond sludge, which is not reversible after rewetting and is retained after re-impounding. The reduction of the sludge layers is initially caused by a compaction of the structure of the organic matter and the mineral components of the soil. The degradation of organic matter therefore requires regular and repeated drainage phases. In this study, we were able to demonstrate that the natural yield of carp ponds can be increased to varying degrees, but still efficiently, by various sustainable and economically and ecologically compatible measures (and their combination in practice). In order to estimate the need for fertilisation in a pond and as a basis for decisions on the choice of organic fertiliser and its use, it is helpful to determine some basic parameters, such as the available phosphorus content of the pond bottom. There is a need for further research in this area.
Section overview
Subjects
- Pond fisheries
Framework programme
Federal Organic Farming Scheme and other forms of sustainable agriculture (BÖLN)
