Comparison of two methods for evaluating waste of a flow though trout farm

European water legislation enforces increasingly restrictive measures with regards to reduction of water consumption and waste emission in order to minimise the potential environmental impact of the agro industry sector. Fish farms are particularly concerned, but legislation covering effluent discharge varies significantly from country to country. However, recommendations and directives from institutional, national or regional bodies suggest the enforcement of increasingly strict waste reduction measures and the development of waste treatment. Before treatment, it is necessary to evaluate waste production in terms of composition and quantity. The waste quantification methods used today for fish culture systems are either based on direct measurements of nutrient and suspended solid fluxes or on indirect evaluation based on the digestibility coefficients of the feed constituents. The objective of the present study is to evaluate the waste of a freshwater flow through farm using both approaches and to discuss their applicability, drawbacks and advantages from the viewpoints of fish farmers and control authorities. Waste production on the farm was monitored during several 24 hour cycles in order to characterise the effluents of the system. The predictions and measurements for the total nitrogen (TN) parameter were well correlated, but measured and predicted suspended solids (SS) and total phosphorus (TP) values presented a weaker correlation coefficient. The hydrobiological method gives details on the N and P forms of waste but this method is heavy and it is difficult to obtain representative samples and flow rate measurements. The nutritional method is the simplest to use, provided that feed data are available. (C) 2007 Elsevier B.V. All rights reserved

The functional role of filter-feeders in IMTA system: development of a seabass-microalgae-oyster Crassostrea gigas ras-IMTA system

RésuméThe functional role of filter-feeders in IMTA system: development of a seabass-microalgae-oyster Crassostrea gigas ras-IMTA system. Aquaculture Europe 201

Efficiency and environmental performance of IMTA in marine and freshwater systems

RésuméEfficiency and environmental performance of IMTA in marine and freshwater systems. Aquaculture Europe 201

Aquaculture Multi Trophique Intégrée : le projet IMTA Effect

National audienc

Aquaculture Multi Trophique Intégrée : le projet IMTA Effect

National audienc

Dissolved nutrient release from solid wastes of southern bluefin tuna (Thunnus maccoyii Castelnau) aquaculture

© 2008 IngentaFinfish pens are point sources of dissolved nutrients released from fish metabolism or degradation of solid wastes. Nutrients leaching from uneaten feed and faeces are not usually quantified in mass budgets for these systems, leading to an overestimation of fish retention or deposition to the seabed. In this study, we investigated nutrient leaching from pellets and baitfish feed as well as faeces of southern bluefin tuna (Thunnus maccoyii) into seawater. Faeces were nitrogen depleted (51-54mg N g−1 dw) and phosphorus enriched (62-72 mg P g−1 dw) compared with feeds (83-111 mg N g−1 dw and 17-21 mg P g−1 dw). Less phosphorus was available for leaching from pellets and faeces of pellet-fed tuna (5-6%) than from baitfish and faeces of baitfish-fed tuna (17-21%). The proportion of soluble nitrogen in pellets (15%) was also lower than in baitfish and faeces (35-43%). Leaching loads for a feed conversion ratio of 5 were estimated as 22 and 26 kg N tonne−1 growth when baitfish or pellets were used as feed respectively. Phosphorus loads were estimated as 15 and 4 kg P tonne−1 growth respectively. More than 90% of nitrogen loads, and approximately 50% of phosphorus, are likely to be released into seawater before solid wastes reach the seafloor