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Effect of feeding strategies on the internal and external water quality impacts of intensive aquaculture.

Objectif

The aim of the research is to contribute to reducing the environmental impact of aquaculture through the reduction of ammonia concentration peaks on the water running through the fish farm.
Research was carried out in order to contribute to reducing environmental impact of aquaculture through the reduction of ammonia concentration peaks in the water running through the fish farm. Ammonia and urea are 2 major excretory products of fish.

The percentage of urea nitrogen excretion was in order of 20 to 25% of the total nitrogenous excretion in turbot, under laboratory conditions. In eel and seabass under farming conditions it ranged between 5 and 25%.
Excretion of nitrogenous compounds increases considerably when the feed is delivered in insufficient quantity, clearly because of proteins being utilized as energy sources. At the highest ratio levels, nitrogen excretion increases slightly and apparently more is excreted in the form of urea.
Also under field conditions 2 regression models were obtained, one applicable to ponds describing the existing relations among chlorophyll, ammonia, urea and pH, while the second, being applicable to raceways with high water refilling rates, describes the relations among total nitrogen, total phosphorus, soluble phosphorus, pH and temperature. About the chemical_physical focus of the pollutants, clear indications were given that the 30% of nitrogen and 40% of phosphorus which is present, was in the particulate form. This knowlwdge may help to chose dry treatment technology before release.
Ammonia and urea are 2 major excretory products of fish. It is generally accepted that ammonia is the dominant nitrogen waste, comprising from 60% to 90% of the nitrogen excreted. Ammonia is a toxic form of nitrogen that must be removed from the plant through a continuous refilling of water, calculated on the basis of the daily amount of excreted ammonia nitrogen. The rate of ammonia excretion by fish follows a daily cycle, scattered by the food distribution. Earlier studies demonstrated that, under laboratory conditions, the peaks of ammonia can be reduced with appropriate feeding strategies. On the basis of these assumptions, the scope of the research will be dual, as follows:
to develop a feeding protocol, in order to transfer to the field the laboratory acquired knowledge, related to the reduction of the daily ammonia peaks in water;
and to improve the basic knowledge about the influence of other environmental conditions (eg dissolved oxygen, water temperature, stresses, etc) on the ratio of excretion of the 2 chemical forms of excreted nitrogen: ammonia nitrogen and urea nitrogen.

The field application of findings from the first phase will lead, as an immediately applicative result, to a reduction of acute toxicity due to excreted ammonia, while the basic results obtained from the second phase will allow development of future strategies designed to reduce the toxicity of excreted nitrogen.

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Coordinateur

Universita degli Studi della Basilicata
Contribution de l’UE
Aucune donnée
Adresse
Via Nazario Sauro 85
85100 Potenza
Italie

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Participants (1)