The trout is a slim fish in the salmon family. In the nature, trouts can be found in the sea as well as in freshwater. The trout-meat is highly appreciated and trouts are raised in freshwater dams along many streams in Jutland. The trouts raised in farms are usually delivered to freezing and filleting factories for further processing to the consumer market, to further growth in sea-farms and to “put and take” lakes mostly in Germany.
 

Process description

The present data refer to trouts (200 to 500 g) produced in Danish trout farms in 2000 for freezing and filleting for the consumer market. The trouts are produced in many different ways depending on local conditions, but the general processes are following: 1) young trouts produced in a hatchery are put into a dam 2) in the dam the trouts are fed with trout feed for a period of 12-18 months, 3) the trouts are caught and transported alive in water tanks to the trout slaughterhouse.

Freshwater from local streams is used in the dams. Groundwater or dam water is applied in hatchery depending on the quality of stream water. Vaccination, medicine and helping agents are applied to keep eggs and fish free of diseases. Electric aeration systems are usually applied to maintain sufficient oxygen in the water. Water from the dams is cleaned and re-circulated more or less depending on local conditions and emission limits from the authorities.

Data collection and treatment

Data on feed and helping agents consumption as well as emissions to water are derived from literature (Miljøstyrelsen, 2001). Data on electricity consumption are partly based on literature (Landbrugs- og fiskeriministeriet, 1998) and partly based on data collection from 10 farms located in Mid-Jutland. The data collected from farms are based on farmer’s 2000 records.

Average data have been determined for all parameters and furthermore the range of electricity consumption and emissions to water has been determined for the most varying parameters.


Technical scope 

All production processes in hatchery as well as in trout dams are included. Consumption of stream water has not been considered because water is returned to the streams. Consumption of freshwater for hatchery has not been considered because the amount is small. Generation of solid waste from e.g. packaging has not been considered. Medicine is not included.
 

Representativity 

Data on feed and helping agents consumption are derived from 388 farms representing all trout farms in Denmark. Data on electricity consumptionare derived from 10 farms representing 2.5% of the Danish farms. Data on emissions to water are based on at least 900 measurements in 150 farms and representing about 40% of trout farms in Denmark. Feed consumption per kg of trout produced varies only slightly and is considered representative to all Danish trout farms. Data on electricity, medicine and helping agents consumption as well as emissions to water vary significantly from farm to farm 1) due to different quality and availability of stream water 2) due to different recirculation and treatment of dam water. In summary, the data are derived from large samples of farms and provide a very representative national average. However, due to the large variation, the data are not representative to most individual farms.
 

Validation

The measured data on emissions to water have been compared with data determined by mass balance (Miljøstyrelsen, 2001) The measured data are somewhat lower than data determined by mass balance. The reason may be that emissions determined by mass balance do not take absorption in dam’s sludge and evaporation from dam’s surface into account. The measured data are derived from a large number of samples (more than 900) and are considered more reliable than data based on mass balance.
 

Inputs and outputs

The table below shows exchanges (inputs and outputs) associated with trout production. Data are provided per kg of living trout at the gates of the trout farms.

1) Electricity consumption is to a large extend determined by the degree of recirculation and treatment of dam water. The electricity consumption range from almost zero at farms with no water treatment to about 3 kWh per kg trout at farms with comprehensive water treatment.
2) Emissions of BOD, total P and total N to aquatic recipients are also determined very much by the degree of recirculation and water treatment. The emissions range from almost zero output at farms with 100% recirculation of dam water to about 100 g BOD, 3 g total P and 35 g N per kg trout at farms with no water treatment. The latter data are based on mass balance calculations (Miljøstyrelsen, 2001). 

References:

Landbrugs og fiskeriministeriet (1998). Projekt Bæredygtigt Dambrug. Rapport fra Landbrugs- og Fiskeriministeriet, Strukturdirektoratet. In Danish.

Miljøstyrelsen (2001). Punktkilder - Det nationale program for overvågning af vandmiljøet - Orientering fra miljøstyrelsen Nr. 13. In Danish.
 

Administrative information

Data URL: http://www.lcafood.dk/database/processes/aquaculture/troutproduction.html
Version no.: 1.00
Authors: Erik Olesen, Højmarklaboratoriet a/s and Per H. Nielsen 2.-0 LCA consultants.
Data entry: Data have been entered in this format by Erik Olesen and Per H. Nielsen.
Data completed: July 2003.